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Neuronal ceroid lipofuscinoses
Handbook of Clinical Neurology, Vol. 113 (3rd series) Pediatric Neurology Part III O. Dulac, M. Lassonde, and H.B. Sarnat, Editors © 2013 Elsevier B.V. All rights reserved
Chapter 173
Neuronal ceroid lipofuscinoses 1
BRIGITTE CHABROL1*, CATHERINE CAILLAUD2 AND BERGE MINASSIAN3 Reference Center for Hereditary Metabolic Illnesses, Hoˆpital Timone Enfants, Marseilles, France
2 3
Laboratoire de Biochimie et Gntique Molculaire, Facult de Mdecine Cochin, Paris, France
Division of Neurology, Department of Paediatrics, Hospital for Sick Children, University of Toronto, Toronto, Canada
INTRODUCTION Neuronal ceroid lipofuscinoses (NCL) represent a group of autosomal recessive neurodegenerative disorders, presenting with myoclonic epilepsy, psychomotor delay, progressive loss of vision and early death. Four main clinical forms have been delineated (infantile, late infantile, juvenile, and adult), but many other variants have also been described. The NCL often present as progressive myoclonic epilepsy (PME), occurring in previously normal children and worsening gradually, but myoclonus may be mild and may not be the presenting feature. These disorders are characterized by the presence of autofluorescent lipopigments exhibiting particular ultrastructural features on electron microscopy depending on the clinical form: granular osmiophilic deposits (GROD), curvilinear profiles, and fingerprints bodies, either alone or in association (Goebel and Wisniewski, 2004). The identification of the deficient protein and/ or the genetic defect is required for a specific diagnosis, which is necessary for a reliable genetic counseling in atrisk families. The global incidence of neuronal ceroid lipofuscinoses is 1/12 500 in Anglo-Saxon countries. It has not clearly been estimated in France, but the late infantile form is predominant (80%), as in other southern European countries.
CLINICAL FORMS AND ASSOCIATED GENES CLNI locus CLINICAL FORMS The CLN1 gene is mainly associated with the classical infantile form (Santavuori–Haltia disease), which begins
between 3 and 18 months of age with hypotonia and irritability, and the baby becomes difficult to comfort. Myoclonic jerks start early, followed by generalized epileptic seizures. Hand-wringing or knitting automatisms are common, which, along with the slowing of head growth and developmental regression, raise the comparatively optimistic differential diagnosis of Rett syndrome, but unlike the latter CLN1 does not stabilize, continuing instead to deteriorate until death by 10 years of age (Mole et al., 2005). Rapid visual impairment occurs with early optic atrophy and macular degeneration. Then, the clinical presentation is completed with spastic tetraplegia, blindness, severe and constant microcephaly, and pharmacoresistant epileptic seizures. Death occurs in the first decade of life (Santavuori et al., 1973). One of the earliest signs found on electroencephalogram (EEG) is the lack of occipital attenuation on eye opening and closure, followed by loss of stage II sleep spindles, and then the EEG becomes practically flat (“vanishing” EEG). Electroretinogram (ERG) is almost always extinguished before 11 months of age. The visual evoked potentials (VEP) are abolished by 40 months. Magnetic resonance imaging (MRI) shows early severe cerebral and cerebellar atrophy and a very particular hyposignal of the hypothalamus and basal ganglia. White matter lesions, seen as T2 hypersignals, are first periventricular and then extend peripherally. Magnetic proton resonance spectroscopy shows an important decrease in N-acetylaspartate (NAA) that expresses neuronal loss and an N-acetylglucosamine peak due to increased intracerebral dolichol. Cortical hypoperfusion is disclosed by SPECT (single photon emission computed tomography), first in fronto-occipital areas, before MRI changes. Electron microscopy (on skin, rectal, conjunctival, or muscle
*Correspondence to: Brigitte Chabrol, Centre de Re´fe´rence des Maladies Me´taboliques de l’Enfant, Hoˆpital d’Enfants, CHU de la Timone, Marseille (13), France. E-mail: [email protected]
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B. CHABROL ET AL. delayed latency, followed by decrease in amplitude extinction by the age of 3–4 years. The amplitude of the cortical somesthetic evoked potentials (SEP) is also highly increased. MRI shows rapid cerebellar atrophy, preceding cortical atrophy, and a hypersignal in the periventricular white matter. Curvilinear bodies are found on electron microscopy (Fig. 173.2A). Patients with protracted or juvenile forms involving the CLN2 gene have also been reported (Wisniewski et al., 1999).
CLN2 GENE AND TRIPEPTIDYL PEPTIDASE I The CLN2 gene consists of 13 exons and encodes a lysosomal pepstatin-insensitive protease, called tripeptidyl peptidase I (TPPI) (Sleat et al., 1997). Around 100 mutations have been described for the CLN2 gene. Fig. 173.1. Skin electron microscopy of CLN 1 shows characteristic granular osmiophilic deposits (GROD).
CLN3 locus CLINICAL FORMS
biopsy) shows characteristic granular osmiophilic deposits (GROD) (Fig. 173.1).
CLN1 GENE AND PALMITOYL PROTEIN THIOESTERASE The CLN1 gene encodes a protein called palmitoyl protein thioesterase (PPT), whose role is to remove palmitate from thioacylated proteins (Vesa et al., 1995). All Finnish patients carry the R122W mutation. More than sixty other mutations have been found.
CLN2 locus CLINICAL FORMS The CLN2 gene is usually associated with the classical late infantile form (Jansky–Bielschowsky disease). It starts between 2 and 3 years of age with generalized epileptic seizures, myoclonias, and/or atypical absences, followed by psychomotor regression, ataxia, and hypotonia. Loss of vision is rapid and complete, with thinning of retinal vessels and pale macula, associated with optic nerve atrophy by the age of 4–5 years. Neurological deterioration progresses over a few months, and death occurs between 10 and 15 years in a bedridden state (Williams et al., 1999). A very particular EEG response is seen on low frequency photic stimulation, with polyphasic spike and slow wave complexes that are synchronous with photic stimulations and exhibit maximal amplitude in the posterior regions. Visual evoked potentials (VEPs) have characteristic amplitude and morphology consisting of a spike followed by a high amplitude slow wave (giant responses). The ERG firstly shows
The CLN3 gene is mainly associated with the juvenile form (Spielmeyer–Vogt–Sj€ogren disease or Batten disease). This form begins between 4 and 9 years of age with mild and isolated deterioration of visual acuity and diffuse pigmentary retinopathy with tapetoretinal degeneration. Ocular pathology is initially a pigmentary retinopathy often misdiagnosed as retinitis pigmentosa or cone dystrophy. Neuropsychological difficulties appear afterwards, mainly consisting of memory testing alterations, behavioral changes, and decreased academic performance. After 2–5 years, generalized, complex partial, and more rarely myoclonic seizures start. Behavioral psychiatric disturbances such as self-mutilation, violent outbursts, and agitation have been reported, associated with pyramidal, cerebellar, and mainly extrapyramidal signs. After 10 years, pigment aggregates are found in the retina and the macula. The early visual impairment and the prolonged evolution are characteristic of this form, sometimes called the chronic juvenile form (Jarvela et al., 1997). EEG changes are variable and nonspecific, the VEPs have decreased amplitude at the beginning and are abolished 10 years after. ERG amplitude is also diminished before total extinction. MRI shows cortical lesions by the age of 9 years and cerebellar lesions around 13 years (Fig. 173.2B). Thalamus and basal ganglia hyposignals are found in T1 and T2. SPECT shows hypoperfusion predominating in the posterior cerebral regions but the pattern is different from that of the early infantile form. This particular NCL can be diagnosed through the identification of vacuolated blood lymphocytes. Furthermore, electron microscopy shows characteristic fingerprints. Atypical juvenile
NEURONAL CEROID LIPOFUSCINOSES
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Fig. 173.2. CLN 2 (A) Skin electron microscopy shows characteristic curvilinear bodies. (B) Brain MRI shows cortical and cerebellar atrophy.
forms have also been reported, presenting with either delayed onset or a protracted course (Lauronen et al., 1999).
CLN3 GENE AND CLN3P PROTEIN The CLN3 gene is composed of 15 exons and encodes a transmembrane protein called CLN3P or Battenine. The function of this protein is not clearly understood, but it might be a palmitoyl protein delta-9 desaturase (Narayan et al., 2006). About 60 mutations have been identified. A 1.02 kb deletion removing exons 7 and 8 is particularly common in most populations (70–90 % of the alleles).
6 years. Ultrastructural findings reveal the presence of mixed deposits, associating both curvilinear and fingerprint bodies.
CLN5 GENE AND PROTEIN The CLN5 gene, composed of four exons, encodes a lysosomal protein which is both a soluble and a transmembrane protein of unknown function. In Finland, where this clinical form was first individualized, most patients carry a 2 bp deletion, but another less frequent mutation (W75X) has also been reported (Holmberg et al., 2000).
CLN5 locus CLINICAL FORMS The CLN5 gene is responsible for a late infantile form mostly seen in Finland (Finnish variant) and presenting clinical criteria close to the classical form. Concentration and learning difficulties are observed from 4–5 years of age, followed by visual failure. Epilepsy and myoclonus are frequent at 7–8 years. Ataxia appears by the age of 7–10 years and a rapid clinical deterioration is then observed. Around 10 years, patients lose the ability to walk, they become spastic and are bedridden up to the age of 20–30. VEP, ERG, and SEP show the same abnormalities as those described in the classical late infantile form. MRI T2 hypersignals are found by the age of
CLN6 locus CLINICAL FORMS The CLN6 gene is involved in the Indo-European variant of the late infantile form. Indeed, this form (also called Lake and Cavanagh disease or early juvenile form) seems to be more frequent in Indo-Pakistani or south European patients. The clinical pattern is very close to the classical late infantile form, with psychomotor deterioration starting with ataxia at 4 years, seizures at 5 years, myoclonus around 5–6 years, visual impairment at 5–7 years, and loss of ability to walk at 7 years. Ultrastructural features usually associate curvilinear and fingerprint deposits.
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CLN6 GENE AND PROTEIN The CLN6 gene, consisting of seven exons, was localized to the 15q21-23 chromosomal region (Wheeler et al., 2002). It encodes a transmembrane protein of unknown function. Around 70 mutations have been described on this gene.
CLN7 locus (MFSD8 gene) The MFSD8 gene has recently been involved in Turkish NCL patients presenting a late infantile form and either curvilinear or fingerprint deposits (Siintola et al., 2007). This gene, now called CLN7 (the previous CLN7 gene described in Turkish patients has disappeared from the nomenclature, as it was similar to CLN8), is localized at 4q28.1-q28.2 and encodes a transmembrane protein. More than 30 mutations have been described on this gene.
CLN8 locus CLINICAL FORMS The CLN8 gene is associated with two different forms of neuronal ceroid lipofuscinoses. (1) Progressive epilepsy with mental retardation, or northern epilepsy. This particular clinical presentation has been individualized in patients originating from north-east Finland. It starts in early infancy and its progression extends into adulthood. The beginning is marked by febrile seizures (not always present), generalized tonic-clonic attacks occurring in childhood, recurring at puberty, and decreasing in adulthood. A slow cognitive regression is noted. Motor abnormalities and visual impairment appear after puberty. Deposits found on electron microscopy associate curvilinear and fingerprint bodies. (2) Turkish late infantile variant. This form, reported in Turkish patients, is very close to the classical late infantile form with an onset marked by psychomotor regression around 3–4 years with ataxia, epilepsy at 4 years, visual impairment at 5 years, and loss of ability to walk by the age of 5–6 years. Initially linked to a potential CLN7 locus, this variant is finally due to mutations in the same gene as northern epilepsy (CLN8) (Ranta et al., 2004).
CLN8 GENE AND PROTEIN The CLN8 gene consists of three exons and encodes a transmembrane protein of unknown function. Finnish patients with northern epilepsy all carry the R24G mutation. Other mutations have been described in Turkish and Italian patients.
CTSD or CLN10 locus CLINICAL FORMS Rare congenital forms of neuronal ceroid lipofuscinosis have been described that are characterized by microcephaly at birth, absence of psychomotor skills, and rapid death. None of the genes presented above has been implicated to date in the occurrence of this variant. As a cathepsin D-deficient ovine model has been reported to present a disease close to the congenital NCL, the CTSD gene was suspected to be a candidate gene in humans. Disease-causing mutations were found in some patients with congenital forms, but also with late infantile forms, confirming the role of the CTSD gene in the pathogenesis of NCL (Steinfeld et al., 2006).
CTSD GENE OR CLN10 The cathepsin D gene, also called CLN10, includes 9 exons. Seven mutations have been reported to date on the CTSD gene. Other genes Novel genes have recently been involved in NCL (Anderson et al., 2013). Mutations have been found in the potassium channel related gene KCTD7 or CLN14 gene in patients of different origin, presenting with early-onset progressive myoclonic epilepsy. Some patients with juvenile NCL have mutations in the ATP13A2 or CLN12 gene. In the autosomal recessive adult forms of NCL, mutations have been reported either in the progranulin gene (GRN or CLN11 gene) or in the cathepsin F gene (CTSF or CLN13 gene). Some patients with autosomal dominant form called Parry disease, differing by the absence of myoclonus epilepsy and ataxia, have mutations in the DNAJC5 or CLN4 gene encoding a cysteine-string protein alpha.
PATHOPHYSIOLOGY Neuronal ceroid lipofuscinoses are characterized by cortical and cerebellar atrophy with loss of pyramidal neurons and Purkinje cells associated with significant reactive astrogliosis. The pathology predominates on pyramidal neurons located between layers III and V of the cerebral cortex, layer IV representing the major receptive zone of the excitatory stimuli originating from thalamic sensory-motor pathways. Neuronal death could be linked to excitotoxicity phenomena and to the impairment of GABAergic inhibiting neurons. Moreover, storage material has been found in astrocytes from hippocampus mossy fibers known to play a role in epileptogenesis. In the juvenile form, neuronal loss is observed with predilection in the basal ganglia.
NEURONAL CEROID LIPOFUSCINOSES A lysosomal accumulation of autofluorescent lipopigments can be found in neurons. These deposits present different structures according to the clinical type (GROD, curvilinear and fingerprint bodies) and their composition includes either saposins A and D (infantile forms) or mitochondrial ATP synthase subunit c (other forms). The diversity of proteins involved in NCL (at least 10, and may be more) and of their subcellular localization suggests that they can play an essential role not clearly understood, in a common functional pathway of neural cells (Cooper et al., 2006).
PRE- AND POSTNATAL DIAGNOSIS Postnatal diagnosis of the index case As the CLN1 and CLN2 genes encode lysosomal enzymes, diagnosis of classical infantile and late infantile forms can be performed by using, respectively, palmitoyl protein thioesterase and tripeptidyl peptidase I enzymatic assays, followed by the characterization of the mutation(s) on the corresponding genes. For the CLN2 gene, two common mutations can be tested first, but complete sequencing of the gene is necessary if these abnormalities are not present in the patient. For the other clinical forms, diagnosis only relies on mutation analysis. For the juvenile form, the common deletion of 1.02 kb is studied first, as most patients hold this mutation in a homo- or heterozygous state. For the late infantile variants, many loci need to be tested: CLN5, CLN6, CLN7 (MFSD8), and CLN8. It is important to note that such studies are usually performed after neuropathological analyses permitting to definitely confirm NCL and to target the genes to be tested.
Prenatal diagnosis A prenatal diagnosis is currently possible for all forms of NCL if the enzyme deficiency and/or the mutation(s) have been previously characterized in the index case. Samples from parents also need to be studied in order to confirm the segregation of the deleterious alleles. Prenatal diagnosis can be performed either early, on chorionic villi, or possibly later, on cultured amniotic cells. It will be based on enzymatic assay and mutation(s) detection for the CLN1 and CLN2 genes, and on molecular study alone for the other genes.
TREATMENT Based on the hypothesis of peroxidation abnormalities, some authors have proposed the use of antioxidants (vitamin E, selenium) with no clear benefit. Recently, polyunsaturated fatty acid supplementation has been suggested. Myoclonic movements can be treated by diazepines (diazepam, clobazam, clonazepam) or valproate.
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Lamotrigine is particularly effective in such diseases, while carbamazepine, phenytoin, and vigabatrin often worsen the symptoms. In the forms where myoclonias appear first, it is possible to use piracetam, which is well tolerated and effective at high doses, or levetiracetam. In juvenile forms with psychiatric symptoms, neuroleptics (haloperidol) can be used. Nursing has considerable importance, and gastrostomy ensures correct nutritional status is achieved in the advanced forms. The importance of pain secondary to retractions should not be underestimated and it should be treated efficiently, particularly in the early infantile form. Bone marrow transplantation was tried without success in late infantile and juvenile forms (one case each) (Lonnqvist et al., 2001). Different research teams are now developing gene transfer approaches using viral vectors, mainly AAV (adenoassociated virus) administered via the intracerebral route in animal models of classical infantile or late infantile forms (Griffey et al., 2006).
REFERENCES Anderson WA, Goebel HH, Simonati A (2013). Human pathology in NCL. Biochem Biophys Acta (in press, http://dx.doi.org/10.1016/j.bbadis.2012.11.014). Cooper JD, Russell C, Mitchison HM (2006). Progress towards understanding disease mechanisms in small vertebrate models of neuronal ceroid lipofuscinosis. Biochim Biophys Acta 1762: 873–889. Goebel HH, Wisniewski KE (2004). Current state of clinical and morphological features in human NCL. Brain Pathol 14: 61–69. Griffey MA, Wozniak D, Wong M et al. (2006). CNS-directed AAV2-mediated gene therapy ameliorates functional deficits in a murine model of infantile neuronal ceroid lipofuscinosis. Mol Ther 13: 538–547. Holmberg V, Lauronen L, Autti T et al. (2000). Phenotypegenotype correlation in eight patients with Finnish variant late infantile NCL (CLN5). Neurology 55: 579–581. Jarvela I, Autti T, Lamminranta S et al. (1997). Clinical and magnetic resonance imaging findings in Batten disease: analysis of the major mutation (1.02-kb deletion). Ann Neurol 42: 799–802. Lauronen L, Munroe PB, Jarvela I et al. (1999). Delayed classic and protracted phenotypes of compound heterozygous juvenile neuronal ceroid lipofuscinosis. Neurology 52: 360–365. Lonnqvist T, Vanhanen SL, Vettenranta K et al. (2001). Hematopoietic stem cell transplantation in infantile neuronal ceroid lipofuscinosis. Neurology 57: 1411–1416. Mole SE, Williams RE, Goebel HH (2005). Correlations between genotype, ultrastructural morphology and clinical phenotype in the neuronal ceroid lipofuscinoses. Neurogenetics 6: 107–126. Narayan SB, Rakheja D, Tan L et al. (2006). CLN3P, the Batten’s disease protein, is a novel palmitoyl-protein Delta-9 desaturase. Ann Neurol 60: 570–577.
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Ranta S, Topcu M, Tegelberg S et al. (2004). Variant late infantile neuronal ceroid lipofuscinosis in a subset of Turkish patients is allelic to Northern epilepsy. Hum Mutat 23: 300–305. Santavuori P, Haltia M, Rapola J et al. (1973). Infantile type of so-called neuronal ceroid-lipofuscinosis. 1. A clinical study of 15 patients. J Neurol Sci 18: 257–267. Siintola E, Topcu M, Aula N et al. (2007). The novel neuronal ceroid lipofuscinosis gene MFSD8 encodes a putative lysosomal transporter. Am J Hum Genet 81: 136–146. Sleat DE, Donnelly RJ, Lackland H et al. (1997). Association of mutations in a lysosomal protein with classical late-infantile neuronal ceroid lipofuscinosis. Science 277: 1802–1805. Steinfeld R, Reinhardt K, Schreiber K et al. (2006). Cathepsin D deficiency is associated with a human neurodegenerative disorder. Am J Hum Genet 78: 988–998.
Vesa J, Hellsten E, Verkruyse LA et al. (1995). Mutations in the palmitoyl protein thioesterase gene causing infantile neuronal ceroid lipofuscinosis. Nature 376: 584–587. Wheeler RB, Sharp JD, Schultz RA et al. (2002). The gene mutated in variant late-infantile neuronal ceroid lipofuscinosis (CLN6) and in nclf mutant mice encodes a novel predicted transmembrane protein. Am J Hum Genet 70: 537–542. Williams RE, Gottlob I, Lake BD et al. (1999). Classic late infantile NCL. In: HH Goebel, SE Mole, BD Lake (Eds.), The Neuronal Ceroid Lipofuscinoses (Batten Disease). IOS Press, Amsterdam, pp. 37–54. Wisniewski KE, Kaczmarski A, Kida E et al. (1999). Reevaluation of neuronal ceroid lipofuscinoses: atypical juvenile onset may be the result of CLN2 mutations. Mol Genet Metab 66: 248–252.
Chapter 173
Neuronal ceroid lipofuscinoses 1
BRIGITTE CHABROL1*, CATHERINE CAILLAUD2 AND BERGE MINASSIAN3 Reference Center for Hereditary Metabolic Illnesses, Hoˆpital Timone Enfants, Marseilles, France
2 3
Laboratoire de Biochimie et Gntique Molculaire, Facult de Mdecine Cochin, Paris, France
Division of Neurology, Department of Paediatrics, Hospital for Sick Children, University of Toronto, Toronto, Canada
INTRODUCTION Neuronal ceroid lipofuscinoses (NCL) represent a group of autosomal recessive neurodegenerative disorders, presenting with myoclonic epilepsy, psychomotor delay, progressive loss of vision and early death. Four main clinical forms have been delineated (infantile, late infantile, juvenile, and adult), but many other variants have also been described. The NCL often present as progressive myoclonic epilepsy (PME), occurring in previously normal children and worsening gradually, but myoclonus may be mild and may not be the presenting feature. These disorders are characterized by the presence of autofluorescent lipopigments exhibiting particular ultrastructural features on electron microscopy depending on the clinical form: granular osmiophilic deposits (GROD), curvilinear profiles, and fingerprints bodies, either alone or in association (Goebel and Wisniewski, 2004). The identification of the deficient protein and/ or the genetic defect is required for a specific diagnosis, which is necessary for a reliable genetic counseling in atrisk families. The global incidence of neuronal ceroid lipofuscinoses is 1/12 500 in Anglo-Saxon countries. It has not clearly been estimated in France, but the late infantile form is predominant (80%), as in other southern European countries.
CLINICAL FORMS AND ASSOCIATED GENES CLNI locus CLINICAL FORMS The CLN1 gene is mainly associated with the classical infantile form (Santavuori–Haltia disease), which begins
between 3 and 18 months of age with hypotonia and irritability, and the baby becomes difficult to comfort. Myoclonic jerks start early, followed by generalized epileptic seizures. Hand-wringing or knitting automatisms are common, which, along with the slowing of head growth and developmental regression, raise the comparatively optimistic differential diagnosis of Rett syndrome, but unlike the latter CLN1 does not stabilize, continuing instead to deteriorate until death by 10 years of age (Mole et al., 2005). Rapid visual impairment occurs with early optic atrophy and macular degeneration. Then, the clinical presentation is completed with spastic tetraplegia, blindness, severe and constant microcephaly, and pharmacoresistant epileptic seizures. Death occurs in the first decade of life (Santavuori et al., 1973). One of the earliest signs found on electroencephalogram (EEG) is the lack of occipital attenuation on eye opening and closure, followed by loss of stage II sleep spindles, and then the EEG becomes practically flat (“vanishing” EEG). Electroretinogram (ERG) is almost always extinguished before 11 months of age. The visual evoked potentials (VEP) are abolished by 40 months. Magnetic resonance imaging (MRI) shows early severe cerebral and cerebellar atrophy and a very particular hyposignal of the hypothalamus and basal ganglia. White matter lesions, seen as T2 hypersignals, are first periventricular and then extend peripherally. Magnetic proton resonance spectroscopy shows an important decrease in N-acetylaspartate (NAA) that expresses neuronal loss and an N-acetylglucosamine peak due to increased intracerebral dolichol. Cortical hypoperfusion is disclosed by SPECT (single photon emission computed tomography), first in fronto-occipital areas, before MRI changes. Electron microscopy (on skin, rectal, conjunctival, or muscle
*Correspondence to: Brigitte Chabrol, Centre de Re´fe´rence des Maladies Me´taboliques de l’Enfant, Hoˆpital d’Enfants, CHU de la Timone, Marseille (13), France. E-mail: [email protected]
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B. CHABROL ET AL. delayed latency, followed by decrease in amplitude extinction by the age of 3–4 years. The amplitude of the cortical somesthetic evoked potentials (SEP) is also highly increased. MRI shows rapid cerebellar atrophy, preceding cortical atrophy, and a hypersignal in the periventricular white matter. Curvilinear bodies are found on electron microscopy (Fig. 173.2A). Patients with protracted or juvenile forms involving the CLN2 gene have also been reported (Wisniewski et al., 1999).
CLN2 GENE AND TRIPEPTIDYL PEPTIDASE I The CLN2 gene consists of 13 exons and encodes a lysosomal pepstatin-insensitive protease, called tripeptidyl peptidase I (TPPI) (Sleat et al., 1997). Around 100 mutations have been described for the CLN2 gene. Fig. 173.1. Skin electron microscopy of CLN 1 shows characteristic granular osmiophilic deposits (GROD).
CLN3 locus CLINICAL FORMS
biopsy) shows characteristic granular osmiophilic deposits (GROD) (Fig. 173.1).
CLN1 GENE AND PALMITOYL PROTEIN THIOESTERASE The CLN1 gene encodes a protein called palmitoyl protein thioesterase (PPT), whose role is to remove palmitate from thioacylated proteins (Vesa et al., 1995). All Finnish patients carry the R122W mutation. More than sixty other mutations have been found.
CLN2 locus CLINICAL FORMS The CLN2 gene is usually associated with the classical late infantile form (Jansky–Bielschowsky disease). It starts between 2 and 3 years of age with generalized epileptic seizures, myoclonias, and/or atypical absences, followed by psychomotor regression, ataxia, and hypotonia. Loss of vision is rapid and complete, with thinning of retinal vessels and pale macula, associated with optic nerve atrophy by the age of 4–5 years. Neurological deterioration progresses over a few months, and death occurs between 10 and 15 years in a bedridden state (Williams et al., 1999). A very particular EEG response is seen on low frequency photic stimulation, with polyphasic spike and slow wave complexes that are synchronous with photic stimulations and exhibit maximal amplitude in the posterior regions. Visual evoked potentials (VEPs) have characteristic amplitude and morphology consisting of a spike followed by a high amplitude slow wave (giant responses). The ERG firstly shows
The CLN3 gene is mainly associated with the juvenile form (Spielmeyer–Vogt–Sj€ogren disease or Batten disease). This form begins between 4 and 9 years of age with mild and isolated deterioration of visual acuity and diffuse pigmentary retinopathy with tapetoretinal degeneration. Ocular pathology is initially a pigmentary retinopathy often misdiagnosed as retinitis pigmentosa or cone dystrophy. Neuropsychological difficulties appear afterwards, mainly consisting of memory testing alterations, behavioral changes, and decreased academic performance. After 2–5 years, generalized, complex partial, and more rarely myoclonic seizures start. Behavioral psychiatric disturbances such as self-mutilation, violent outbursts, and agitation have been reported, associated with pyramidal, cerebellar, and mainly extrapyramidal signs. After 10 years, pigment aggregates are found in the retina and the macula. The early visual impairment and the prolonged evolution are characteristic of this form, sometimes called the chronic juvenile form (Jarvela et al., 1997). EEG changes are variable and nonspecific, the VEPs have decreased amplitude at the beginning and are abolished 10 years after. ERG amplitude is also diminished before total extinction. MRI shows cortical lesions by the age of 9 years and cerebellar lesions around 13 years (Fig. 173.2B). Thalamus and basal ganglia hyposignals are found in T1 and T2. SPECT shows hypoperfusion predominating in the posterior cerebral regions but the pattern is different from that of the early infantile form. This particular NCL can be diagnosed through the identification of vacuolated blood lymphocytes. Furthermore, electron microscopy shows characteristic fingerprints. Atypical juvenile
NEURONAL CEROID LIPOFUSCINOSES
1703
Fig. 173.2. CLN 2 (A) Skin electron microscopy shows characteristic curvilinear bodies. (B) Brain MRI shows cortical and cerebellar atrophy.
forms have also been reported, presenting with either delayed onset or a protracted course (Lauronen et al., 1999).
CLN3 GENE AND CLN3P PROTEIN The CLN3 gene is composed of 15 exons and encodes a transmembrane protein called CLN3P or Battenine. The function of this protein is not clearly understood, but it might be a palmitoyl protein delta-9 desaturase (Narayan et al., 2006). About 60 mutations have been identified. A 1.02 kb deletion removing exons 7 and 8 is particularly common in most populations (70–90 % of the alleles).
6 years. Ultrastructural findings reveal the presence of mixed deposits, associating both curvilinear and fingerprint bodies.
CLN5 GENE AND PROTEIN The CLN5 gene, composed of four exons, encodes a lysosomal protein which is both a soluble and a transmembrane protein of unknown function. In Finland, where this clinical form was first individualized, most patients carry a 2 bp deletion, but another less frequent mutation (W75X) has also been reported (Holmberg et al., 2000).
CLN5 locus CLINICAL FORMS The CLN5 gene is responsible for a late infantile form mostly seen in Finland (Finnish variant) and presenting clinical criteria close to the classical form. Concentration and learning difficulties are observed from 4–5 years of age, followed by visual failure. Epilepsy and myoclonus are frequent at 7–8 years. Ataxia appears by the age of 7–10 years and a rapid clinical deterioration is then observed. Around 10 years, patients lose the ability to walk, they become spastic and are bedridden up to the age of 20–30. VEP, ERG, and SEP show the same abnormalities as those described in the classical late infantile form. MRI T2 hypersignals are found by the age of
CLN6 locus CLINICAL FORMS The CLN6 gene is involved in the Indo-European variant of the late infantile form. Indeed, this form (also called Lake and Cavanagh disease or early juvenile form) seems to be more frequent in Indo-Pakistani or south European patients. The clinical pattern is very close to the classical late infantile form, with psychomotor deterioration starting with ataxia at 4 years, seizures at 5 years, myoclonus around 5–6 years, visual impairment at 5–7 years, and loss of ability to walk at 7 years. Ultrastructural features usually associate curvilinear and fingerprint deposits.
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CLN6 GENE AND PROTEIN The CLN6 gene, consisting of seven exons, was localized to the 15q21-23 chromosomal region (Wheeler et al., 2002). It encodes a transmembrane protein of unknown function. Around 70 mutations have been described on this gene.
CLN7 locus (MFSD8 gene) The MFSD8 gene has recently been involved in Turkish NCL patients presenting a late infantile form and either curvilinear or fingerprint deposits (Siintola et al., 2007). This gene, now called CLN7 (the previous CLN7 gene described in Turkish patients has disappeared from the nomenclature, as it was similar to CLN8), is localized at 4q28.1-q28.2 and encodes a transmembrane protein. More than 30 mutations have been described on this gene.
CLN8 locus CLINICAL FORMS The CLN8 gene is associated with two different forms of neuronal ceroid lipofuscinoses. (1) Progressive epilepsy with mental retardation, or northern epilepsy. This particular clinical presentation has been individualized in patients originating from north-east Finland. It starts in early infancy and its progression extends into adulthood. The beginning is marked by febrile seizures (not always present), generalized tonic-clonic attacks occurring in childhood, recurring at puberty, and decreasing in adulthood. A slow cognitive regression is noted. Motor abnormalities and visual impairment appear after puberty. Deposits found on electron microscopy associate curvilinear and fingerprint bodies. (2) Turkish late infantile variant. This form, reported in Turkish patients, is very close to the classical late infantile form with an onset marked by psychomotor regression around 3–4 years with ataxia, epilepsy at 4 years, visual impairment at 5 years, and loss of ability to walk by the age of 5–6 years. Initially linked to a potential CLN7 locus, this variant is finally due to mutations in the same gene as northern epilepsy (CLN8) (Ranta et al., 2004).
CLN8 GENE AND PROTEIN The CLN8 gene consists of three exons and encodes a transmembrane protein of unknown function. Finnish patients with northern epilepsy all carry the R24G mutation. Other mutations have been described in Turkish and Italian patients.
CTSD or CLN10 locus CLINICAL FORMS Rare congenital forms of neuronal ceroid lipofuscinosis have been described that are characterized by microcephaly at birth, absence of psychomotor skills, and rapid death. None of the genes presented above has been implicated to date in the occurrence of this variant. As a cathepsin D-deficient ovine model has been reported to present a disease close to the congenital NCL, the CTSD gene was suspected to be a candidate gene in humans. Disease-causing mutations were found in some patients with congenital forms, but also with late infantile forms, confirming the role of the CTSD gene in the pathogenesis of NCL (Steinfeld et al., 2006).
CTSD GENE OR CLN10 The cathepsin D gene, also called CLN10, includes 9 exons. Seven mutations have been reported to date on the CTSD gene. Other genes Novel genes have recently been involved in NCL (Anderson et al., 2013). Mutations have been found in the potassium channel related gene KCTD7 or CLN14 gene in patients of different origin, presenting with early-onset progressive myoclonic epilepsy. Some patients with juvenile NCL have mutations in the ATP13A2 or CLN12 gene. In the autosomal recessive adult forms of NCL, mutations have been reported either in the progranulin gene (GRN or CLN11 gene) or in the cathepsin F gene (CTSF or CLN13 gene). Some patients with autosomal dominant form called Parry disease, differing by the absence of myoclonus epilepsy and ataxia, have mutations in the DNAJC5 or CLN4 gene encoding a cysteine-string protein alpha.
PATHOPHYSIOLOGY Neuronal ceroid lipofuscinoses are characterized by cortical and cerebellar atrophy with loss of pyramidal neurons and Purkinje cells associated with significant reactive astrogliosis. The pathology predominates on pyramidal neurons located between layers III and V of the cerebral cortex, layer IV representing the major receptive zone of the excitatory stimuli originating from thalamic sensory-motor pathways. Neuronal death could be linked to excitotoxicity phenomena and to the impairment of GABAergic inhibiting neurons. Moreover, storage material has been found in astrocytes from hippocampus mossy fibers known to play a role in epileptogenesis. In the juvenile form, neuronal loss is observed with predilection in the basal ganglia.
NEURONAL CEROID LIPOFUSCINOSES A lysosomal accumulation of autofluorescent lipopigments can be found in neurons. These deposits present different structures according to the clinical type (GROD, curvilinear and fingerprint bodies) and their composition includes either saposins A and D (infantile forms) or mitochondrial ATP synthase subunit c (other forms). The diversity of proteins involved in NCL (at least 10, and may be more) and of their subcellular localization suggests that they can play an essential role not clearly understood, in a common functional pathway of neural cells (Cooper et al., 2006).
PRE- AND POSTNATAL DIAGNOSIS Postnatal diagnosis of the index case As the CLN1 and CLN2 genes encode lysosomal enzymes, diagnosis of classical infantile and late infantile forms can be performed by using, respectively, palmitoyl protein thioesterase and tripeptidyl peptidase I enzymatic assays, followed by the characterization of the mutation(s) on the corresponding genes. For the CLN2 gene, two common mutations can be tested first, but complete sequencing of the gene is necessary if these abnormalities are not present in the patient. For the other clinical forms, diagnosis only relies on mutation analysis. For the juvenile form, the common deletion of 1.02 kb is studied first, as most patients hold this mutation in a homo- or heterozygous state. For the late infantile variants, many loci need to be tested: CLN5, CLN6, CLN7 (MFSD8), and CLN8. It is important to note that such studies are usually performed after neuropathological analyses permitting to definitely confirm NCL and to target the genes to be tested.
Prenatal diagnosis A prenatal diagnosis is currently possible for all forms of NCL if the enzyme deficiency and/or the mutation(s) have been previously characterized in the index case. Samples from parents also need to be studied in order to confirm the segregation of the deleterious alleles. Prenatal diagnosis can be performed either early, on chorionic villi, or possibly later, on cultured amniotic cells. It will be based on enzymatic assay and mutation(s) detection for the CLN1 and CLN2 genes, and on molecular study alone for the other genes.
TREATMENT Based on the hypothesis of peroxidation abnormalities, some authors have proposed the use of antioxidants (vitamin E, selenium) with no clear benefit. Recently, polyunsaturated fatty acid supplementation has been suggested. Myoclonic movements can be treated by diazepines (diazepam, clobazam, clonazepam) or valproate.
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Lamotrigine is particularly effective in such diseases, while carbamazepine, phenytoin, and vigabatrin often worsen the symptoms. In the forms where myoclonias appear first, it is possible to use piracetam, which is well tolerated and effective at high doses, or levetiracetam. In juvenile forms with psychiatric symptoms, neuroleptics (haloperidol) can be used. Nursing has considerable importance, and gastrostomy ensures correct nutritional status is achieved in the advanced forms. The importance of pain secondary to retractions should not be underestimated and it should be treated efficiently, particularly in the early infantile form. Bone marrow transplantation was tried without success in late infantile and juvenile forms (one case each) (Lonnqvist et al., 2001). Different research teams are now developing gene transfer approaches using viral vectors, mainly AAV (adenoassociated virus) administered via the intracerebral route in animal models of classical infantile or late infantile forms (Griffey et al., 2006).
REFERENCES Anderson WA, Goebel HH, Simonati A (2013). Human pathology in NCL. Biochem Biophys Acta (in press, http://dx.doi.org/10.1016/j.bbadis.2012.11.014). Cooper JD, Russell C, Mitchison HM (2006). Progress towards understanding disease mechanisms in small vertebrate models of neuronal ceroid lipofuscinosis. Biochim Biophys Acta 1762: 873–889. Goebel HH, Wisniewski KE (2004). Current state of clinical and morphological features in human NCL. Brain Pathol 14: 61–69. Griffey MA, Wozniak D, Wong M et al. (2006). CNS-directed AAV2-mediated gene therapy ameliorates functional deficits in a murine model of infantile neuronal ceroid lipofuscinosis. Mol Ther 13: 538–547. Holmberg V, Lauronen L, Autti T et al. (2000). Phenotypegenotype correlation in eight patients with Finnish variant late infantile NCL (CLN5). Neurology 55: 579–581. Jarvela I, Autti T, Lamminranta S et al. (1997). Clinical and magnetic resonance imaging findings in Batten disease: analysis of the major mutation (1.02-kb deletion). Ann Neurol 42: 799–802. Lauronen L, Munroe PB, Jarvela I et al. (1999). Delayed classic and protracted phenotypes of compound heterozygous juvenile neuronal ceroid lipofuscinosis. Neurology 52: 360–365. Lonnqvist T, Vanhanen SL, Vettenranta K et al. (2001). Hematopoietic stem cell transplantation in infantile neuronal ceroid lipofuscinosis. Neurology 57: 1411–1416. Mole SE, Williams RE, Goebel HH (2005). Correlations between genotype, ultrastructural morphology and clinical phenotype in the neuronal ceroid lipofuscinoses. Neurogenetics 6: 107–126. Narayan SB, Rakheja D, Tan L et al. (2006). CLN3P, the Batten’s disease protein, is a novel palmitoyl-protein Delta-9 desaturase. Ann Neurol 60: 570–577.
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Ranta S, Topcu M, Tegelberg S et al. (2004). Variant late infantile neuronal ceroid lipofuscinosis in a subset of Turkish patients is allelic to Northern epilepsy. Hum Mutat 23: 300–305. Santavuori P, Haltia M, Rapola J et al. (1973). Infantile type of so-called neuronal ceroid-lipofuscinosis. 1. A clinical study of 15 patients. J Neurol Sci 18: 257–267. Siintola E, Topcu M, Aula N et al. (2007). The novel neuronal ceroid lipofuscinosis gene MFSD8 encodes a putative lysosomal transporter. Am J Hum Genet 81: 136–146. Sleat DE, Donnelly RJ, Lackland H et al. (1997). Association of mutations in a lysosomal protein with classical late-infantile neuronal ceroid lipofuscinosis. Science 277: 1802–1805. Steinfeld R, Reinhardt K, Schreiber K et al. (2006). Cathepsin D deficiency is associated with a human neurodegenerative disorder. Am J Hum Genet 78: 988–998.
Vesa J, Hellsten E, Verkruyse LA et al. (1995). Mutations in the palmitoyl protein thioesterase gene causing infantile neuronal ceroid lipofuscinosis. Nature 376: 584–587. Wheeler RB, Sharp JD, Schultz RA et al. (2002). The gene mutated in variant late-infantile neuronal ceroid lipofuscinosis (CLN6) and in nclf mutant mice encodes a novel predicted transmembrane protein. Am J Hum Genet 70: 537–542. Williams RE, Gottlob I, Lake BD et al. (1999). Classic late infantile NCL. In: HH Goebel, SE Mole, BD Lake (Eds.), The Neuronal Ceroid Lipofuscinoses (Batten Disease). IOS Press, Amsterdam, pp. 37–54. Wisniewski KE, Kaczmarski A, Kida E et al. (1999). Reevaluation of neuronal ceroid lipofuscinoses: atypical juvenile onset may be the result of CLN2 mutations. Mol Genet Metab 66: 248–252.