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PANK2 gene analysis confirms genetic heterogeneity in neurodegeneration with brain iron accumulation (NBIA) but mutations are rare in other types of adult neurodegenerative disease
Neuroscience Letters 407 (2006) 162–165
PANK2 gene analysis confirms genetic heterogeneity in neurodegeneration with brain iron accumulation (NBIA) but mutations are rare in other types of adult neurodegenerative disease M.M. Matarin a , A.B. Singleton a , H. Houlden b,∗ a
Molecular Genetics Unit, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, United States b Department of Molecular Neuroscience, Institute of Neurology, Queen Square, London, WC1N 3BG, England, United Kingdom Received 16 June 2006; received in revised form 12 August 2006; accepted 14 August 2006
Abstract Mutations in the pantothenate kinase 2 gene (PANK2) are the cause of pantothenate kinase associated neurodegeneration (PKAN), an autosomal recessive (AR) disorder characterized by motor symptoms as such as dystonia or parkinsonism, mental retardation, retinitis pigmentosa and iron accumulation in the brain. As many neurodegenerative conditions have similar clinical features we screened a number of adult and childhood onset movement disorders for PANK2 mutation. This included cases with neurodegeneration and brain iron accumulation, corticobasal degeneartion, progressive supranuclear palsy (PSP), Parkinson’s disease (PD), multiple system atropy, giant axonal neuropathy (GAN), neuroaxonal dystrophy (NAD), Guam dementia and HARP syndrome (pallido-pyramidal syndrome and hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa and pallidal degeneration). From our series of patients one patient with PKAN and a progressive severe dystonic syndrome, cerebellar ataxia, retinitis pigmentosa and eventual anarthria had a novel combination of two compound heterozygote mutations identified in the PANK2 gene, G → A transition at base 1238 (G411R) and a C → A transition at base 1184 (A395E). In the patient with HARP syndrome two compound heterozygote mutations (Met327Thr and IVS5–1 G to T) in the PANK2 gene were found. No other mutations were found in any of the other patient groups, suggesting that PANK2 mutations are not associated with the aetiology of these adult degenerative conditions and confirms the genetic heterogeneity in neurodegeneration with brain iron accumulation. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: PANK2; Neurodegeneration; PKAN; NBIA; Mutation
Neurodegeneration with brain iron accumulation (NBIA) refers to a heterogeneous group of disorders with a rare inherited neurodegenerative disorder characterized by early onset extrapyramidal disorder with rapid progression, intellectual impairment and often either pigmentary retinopathy or optic atrophy. This group were previously referred to as having Hallervorden-Spatz syndrome. The most prevalent form of NBIA is called pantothenate kinase associated neurodegeneration (PKAN) and is due to mutations in the pantothenate kinase 2 gene (PANK2) gene on chromosome 20p13-p12.3 [16,21]. Other forms of NBIA include infantile and adult neuroaxonal dystrophy (NAD), aceruloplasmineamia and neuroferritinopathy [4]. A number of mutations and mutation types have now been identified throughout PANK2. Preliminary evidence suggests
∗
Corresponding author. Tel.: +44 207 938 3611x4285; fax: +44 207 278 5616. E-mail address: [email protected] (H. Houlden).
0304-3940/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2006.08.030
patients with two loss of function alleles present with early severe disease and that age at onset correlates with pantothenate kinase residual activity [3,12,2]. There are a proportion of patients with a typical phenotype for PKAN without PANK2 mutations, although large genomic rearrangements, duplications and deletion in PANK2 cannot be excluded [3,12,2]. The clinical and radiographic features of PKAN patients with PANK2 mutation suggests the presence of a mutation in the PANK2 gene is usually associated with the classical early onset disease with extrapyramidal features and the presence of the ‘eye of the tiger’ magnetic resonance imaging (MRI) sign [3,12,2,17]. Neuropathologically, PKAN is characterized by lateral degeneration of the globus pallidus and substantia nigra pars reticulata with deposition of iron in the affected regions and more widely distributed neuronal axonal spheroids [14,15]. There are atypical cases of PKAN, many with adult-onset cases, a more slowly progressive course, parkinsonism, dystonia, dysarthria and psychiatric manifestations have also been
M.M. Matarin et al. / Neuroscience Letters 407 (2006) 162–165
described [3,6,18,20,13,10,5]. The ‘eye of the tiger’ sign on MRI is not pathognomonic of PKAN and some patients with PANK2 mutations do not have this sign or may only have it transiently [8,1]. The ‘eye of the tiger’ sign has also been reported in corticobasal degeneration and progressive supranuclear palsy (PSP), late onset diseases known to have Tau associated pathology and genetic aetiology [19], and one assymptomatic individual has been reported with this sign for at least a 2-year period [9]. Given the wide clinical spectrum of PKAN, the age of onset being up to 30 years with some patients still walking in their 50s and the overlap in imaging studies, many other neurodegenerative conditions could potentially have PANK2 mutations as a cause for their disease [3,12,2]. In this article, we sequenced the PANK2 gene in a number of patients with NBIA and other neurodegenerative conditions that present with similar clinical features. Patients and families in the study were recruited with their prior consent and ethical approval to carry out this study. The clinical details of the individuals are given in Table 1, clinical details of the patient with HARP syndrome have been previously reported [5]. Two patients with pallido-pyramidal syndrome were cousins. Genomic DNA was extracted from peripheral blood with family consent, exons 1–7 of the PANK2 (longest transcript) were analyzed by polymerase chain reaction (PCR) amplification (ABgene Thermo-start DNA polymerase kit) followed by PCR cleanup (Millipore PCR purification 96 well plates) direct DNA sequencing (BigDye terminator sequencing reagent, Applied Biosystems and Abgene dye terminator removal 96 well plates). A total of 11 primers (Sigma-Genosys custom primers, UK) were designed to amplify the seven exons of PANK2 [21]. Sequencing reaction was performed and analyzed on an ABI 3100 automated sequencer (Genescodes, VA). In our series of patients the progressive supranuclear palsy and corticobasal ganglionic degeneration (CBD) patients were negative for exons 9–13 of the Tau gene. The patients with Parkinson’s disease (PD) were early onset (<55) with a dominant family history and negative for the Parkin and alpha-synuclein genes. The cases with giant axonal neuropathy (GAN) were negative for the Gigaxonin gene mutations. In one patient with PKAN (Family 1) and a progressive severe dystonic syndrome, cerebellar ataxia, retinitis pigmentosa and eventual anarthria a
163
novel combination of two compound heterozygote mutations were identified in the PANK2 gene, G → A transition at base 1238 (G411R) and a C → A transition at base 1184 (A395E). The clinical details of Family 1 are given below. In the patient with HARP syndrome (Family 2) two compound heterozygote mutations (M327T and IVS5–1 G to T) in the PANK2 gene were found. These mutations were not identified in 100 aged control individuals. No other mutations were found in any of the other patients with NBIA or the other neurodegenerative conditions. The Parkinson’s disease patients were not screened for LRRK2 gene mutations but in future studies these cases should be screened and excluded [11]. This proband was the product of a normal pregnancy, delivery and early development. There were no other medical problems, no family history and the parents were not related. At the age of 18 months she developed poor balance, at 2 years clumsy upper limbs with a tremor and at the age of 4–5 years night blindness and decreased peripheral fields. She was stable until 12 years old when her walking deteriorated with gross cerebellar ataxia in her upper and lower limbs. Due to ataxia she was unable to walk from the age of 14 years. She had reduced visual acuity at 6/18, reduced visual fields, slow saccadic pursuit, reduced vertical movements and gross ataxic nystagmus. There was a salt and pepper retinopathy and blurred pink discs. From her early teens she suffered from severe dystonic posturing and spasms in all four limbs. Her head tended to turn upwards, face had blepharospasm and she frequently blinked. There was also severe orol-lingular-buccal spasms that were particularly distressing and caused frequent biting of the lips which often became infected. Her tone was increased, she had brisk reflexes and extensor planters. Extensive biochemical blood and urine investigations were carried out and were normal apart from 15% acanthocytes seen on the blood film. Acanthocytes are a frequent finding in patients with classical PKAN and dystonia [3], they can also be found in other similar neurological disorders such as neuroacanthocytosis and abetalipoproteinemia. Muscle biopsy was normal. Electroencephalogram (EEG) revealed excess of intermediate slow components and a relative poverty of rhythmic EEG components for her age. The electroretinogram (ERG) was consistent
Table 1 Neurodegenerative diseases analysed Diagnosis
N
Family history
Pathologically confirmed
Mutation
NBIA HARP CBD PSP Familial PD GAN NAD Guam dementia MSA PPS
10 1 2 2 20 3 4 2 2 2
No No No No Yes, AD all cases No No Yes, AD/AR cases No Yes, AR
4 0 2 2 7 2 4 2 2 0
F1-(G411R, A395E) F2-(M327T, IVS5–1 G > T) 0 0 0 0 0 0 0 0
PPS, pallido-pyramidal syndrome; N, individual; NBIA, neurodegeneration and brain iron accumulation; HARP, hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa and pallidal degeneration; CBD, corticobasal ganglionic degeneration; PSP, progressive supranuclear palsy; PD, Parkinson’s disease; GAN, giant axonal neuropathy; NAD, neuroaxonal dystrophy; MSA, multiple system atrophy; F,: family; AD, autosomal dominant; AR, autosomal recessive.
164
M.M. Matarin et al. / Neuroscience Letters 407 (2006) 162–165
Fig. 2. PANK2 amino acid changes the individual from Family 1 with the alignment of the amino acid sequences for PANK1, PANK2 and PANK3 from human and mouse. This shows that the mutations are conserved across the PANK sequences and also across species, data not shown but also conserved across Drosophila melanogaster, C. elegans and S. cerevisiae PANK2 sequences.
Fig. 1. Axial T2-weighted MRI scan of the patient (Family 1) with compound heterozygous PANK2 mutations. This shows the bilateral ‘eye of the tiger’ sign: marked hypointensity in the globus pallidus (white arrow) with a high signal in the anteromedial region (black arrow).
with gross loss of function in the outer retinal layer, particularly the peripheral parts. MRI brain showed the ‘eye of the tiger sign’ typical of iron deposition in the globus pallidus (Fig. 1). From her early teens she rapidly developed speech and swallowing problems with striatal dysarthria and eventual anarthria. Numerous therapeutic treatments were tried with limited success for her dystonia including tetrabenazine, diazepam, sinemet, baclofen and botulinum toxin injections. She died from a chest infection at the age of 22 years. Mutations in the PANK2 gene can cause a movement disorder with a wide selection and severity of clinical features. As there is significant overlap with other neurodegenerative disorders we screened the PANK2 gene in a variety of these degenerative conditions where the aetiology was unknown. Based on this small series these data confirm that the PANK2 gene is not associated with the aetiology of PD [7] and also suggests that the PANK2 gene is unlikely to be associated with the other neurodegenerative conditions analysed here. This study also confirms the genetic heterogeneity in NBIA. One out of the 10 NBIA cases screened had two compound heterozygous PANK2 mutations: the G411R mutation which is the commonest PANK2 mutation seen in PKAN and can present as both typical and atypical PKAN and the A395E mutation which has not previously been identified. These mutations are likely pathogenic being highly conserved across different species (Fig. 2) which would indicate they should cause a severe pattern of disease as in the case we present. In comparison the patient with HARP syndrome (Family 2) had two compound heterozygous PANK2 mutations, one conserved in species M327T and the other a splice site mutation IVS5–1 G to T. She had a much milder mainly dystonic phenotype and at the age of 32
years was still mobile and walking to football matches with her father [5]. These data show that the patients phenotype is difficult to predict based on the PANK2 mutation(s), although the large number of mutations now reported may help the clinician advise on the patients prognosis by drawing comparison [2]. In conclusion, this study reveals the PANK2 gene is unlikely to be associated with PD or a number of other neurodegenerative disorders. In the PKAN cases with PANK2 mutations there is a variable phenotype that can in some cases be indicated by the severity of the mutations present. A proportion of NBIA patients are caused by PANK2 mutations but there is still evidence from this and other studies for the existence of one or more other genes. Acknowledgements We are grateful to The Medical Research Council and the Mason Medical Research Foundation for supporting this work. We also thank the families for their assistance. References [1] F.A. Baumeister, D.P. Auer, K. Hortnagel, P. Freisinger, T. Meitinger, The eye-of-the-tiger sign is not a reliable disease marker for Hallervorden-Spatz syndrome, Neuropediatrics 36 (2005) 221–222. [2] M.B. Hartig, K. Hortnagel, B. Garavaglia, G. Zorzi, T. Kmiec, T. Klopstock, K. Rostasy, M. Svetel, V.S. Kostic, M. Schuelke, E. Botz, A. Weindl, I. Novakovic, N. Nardocci, H. Prokisch, T. Meitinger, Genotypic and phenotypic spectrum of PANK2 mutations in patients with neurodegeneration with brain iron accumulation, Ann. Neurol. 59 (2006) 248–256. [3] S.J. Hayflick, S.K. Westaway, B. Levinson, B. Zhou, M.A. Johnson, K.H. Ching, J. Gitschier, Genetic, clinical, and radiographic delineation of Hallervorden-Spatz syndrome, N. Engl. J. Med. 348 (2003) 33–40. [4] K. Hortnagel, N. Nardocci, G. Zorzi, B. Garavaglia, E. Botz, T. Meitinger, T. Klopstock, Infantile neuroaxonal dystrophy and pantothenate-kinaseassociated neurodegeneration: locus heterogeneity, Neurology 63 (2004) 922–924. [5] H. Houlden, S. Lincoln, M. Farrer, P.G. Cleland, J. Hardy, R.W. Orrell, Compound heterozygous PANK2 mutations confirm HARP and Hallervorden-Spatz syndromes are allelic, Neurology 25 (2003) 1423–1426. [6] J. Jankovic, J.B. Kirkpatrick, K.A. Blomquist, P.J. Langlais, E.D. Bird, Late-onset Hallervorden-Spatz disease presenting as familial parkinsonism, Neurology 35 (1985) 227–234. [7] T. Klopstock, M. Elstner, C.B. Lucking, B. Muller-Myhsok, T. Gasser, E. Botz, P. Lichtner, K. Hortnagel, Mutations in the pantothenate kinase gene PANK2 are not associated with Parkinson disease, Neurosci. Lett. 379 (2005) 195–198.
M.M. Matarin et al. / Neuroscience Letters 407 (2006) 162–165 [8] N. Kumar, C.J. Boes, D. Babovic-Vuksanovic, B.F. Boeve, The “eye-ofthe-tiger” sign is not pathognomonic of the PANK2 mutation, Arch. Neurol. 63 (2006) 292–293. [9] J.C. Martinez-Castrillo, J. Masjuan, B. Pilo, P. Simal, J. MartinezSanmillan, Eye-of-the-tiger sign in an asymptomatic patient, Mov. Disord. 20 (Suppl.) (2005) S40. [10] A.P. Nicholas, K.S. Earnst, D.C. Marson, Atypical Hallervorden-Spatz disease with preserved cognition and obtrusive obsessions and compulsions, Mov. Disord. 20 (2005) 880–886. [11] C. Paisan-Ruiz, S. Jain, E.W. Evans, W.P. Gilks, J. Simon, M. van der Brug, A. Lopez de Munain, S. Aparicio, A.M. Gil, N. Khan, J. Johnson, J.R. Martinez, D. Nicholl, I.M. Carrera, A.S. Pena, R. de Silva, A. Lees, J.F. Marti-Masso, J. Perez-Tur, N.W. Wood, A.B. Singleton, Cloning of the gene containing mutations that cause PARK8-linked Parkinson’s disease, Neuron 44 (2004) 575–577. [12] M.T. Pellecchia, E.M. Valente, L. Cif, S. Salvi, A. Albanese, V. Scarano, U. Bonuccelli, A.R. Bentivoglio, A. D’Amico, C. Marelli, A. Di Giorgio, P. Coubes, P. Barone, B. Dallapiccola, The diverse phenotype and genotype of pantothenate kinase-associated neurodegeneration, Neurology 64 (2005) 1810–1812. [13] D. Saleheen, A. Nazir, S. Khanum, S.R. Haider, P. Frossard, A novel mutation in a patient with pantothenate kinase-associated neurodegeneration, CMAJ 173 (2005) 578–579. [14] F. Seitelberger, Neuropathological conditions related to neuroaxonal dystrophy, Acta Neuropathol. (Berl) 5 (Suppl.) (1971) 17–29.
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[15] K.F. Swaiman, Hallervorden-Spatz syndrome and brain iron metabolism, Arch. Neurol. 48 (1991) 1285–1293. [16] T.D. Taylor, M. Litt, P. Kramer, M. Pandolfo, L. Angelini, N. Nardocci, S. Davis, M. Pineda, H. Hattori, P.J. Flett, M.R. Cilio, E. Bertini, S.J. Hayflick, Homozygosity mapping of Hallervorden-Spatz syndrome to chromosome 20p12.3-p13, Nat. Genet. 14 (1996) 479–481. [17] M. Thomas, S.J. Hayflick, J. Jankovic, Clinical heterogeneity of neurodegeneration with brain iron accumulation (Hallervorden-Spatz syndrome) and pantothenate kinase-associated neurodegeneration, Mov. Disord. 19 (2004) 36–42. [18] T.D. Taylor, M. Litt, P. Kramer, M. Pandolfo, L. Angelini, N. Nardocci, S. Davis, M. Pineda, H. Hattori, P.J. Flett, M.R. Cilio, E. Bertini, S.J. Hayflick, Genetic heterogeneity in patients with pantothenate kinase-associated neurodegeneration and classic magnetic resonance imaging eye-of-the-tiger pattern, Mov. Disord. 21 (2006) 252–254. [19] J.J. Zarranz, J.C. Gomez-Esteban, B. Atares, E. Lezcano, M. Forcadas, Taupredominant-associated pathology in a sporadic late-onset HallervordenSpatz syndrome, Mov. Disord. 21 (2006) 107–111. [20] Y.H. Zhang, B.S. Tang, A.L. Zhao, K. Xia, Z.G. Long, J.F. Guo, S.K. Westaway, S.J. Hayflick, Novel compound heterozygous mutations in the PANK2 gene in a Chinese patient with atypical pantothenate kinaseassociated neurodegeneration, Mov. Disord. 20 (2005) 819–821. [21] B. Zhou, S.K. Westaway, B. Levinson, M.A. Johnson, J. Gitschier, S.J. Hayflick, A novel pantothenate kinase gene (PANK2) is defective in Hallervorden-Spatz syndrome, Nat. Genet. 28 (2001) 345–349.
PANK2 gene analysis confirms genetic heterogeneity in neurodegeneration with brain iron accumulation (NBIA) but mutations are rare in other types of adult neurodegenerative disease M.M. Matarin a , A.B. Singleton a , H. Houlden b,∗ a
Molecular Genetics Unit, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, United States b Department of Molecular Neuroscience, Institute of Neurology, Queen Square, London, WC1N 3BG, England, United Kingdom Received 16 June 2006; received in revised form 12 August 2006; accepted 14 August 2006
Abstract Mutations in the pantothenate kinase 2 gene (PANK2) are the cause of pantothenate kinase associated neurodegeneration (PKAN), an autosomal recessive (AR) disorder characterized by motor symptoms as such as dystonia or parkinsonism, mental retardation, retinitis pigmentosa and iron accumulation in the brain. As many neurodegenerative conditions have similar clinical features we screened a number of adult and childhood onset movement disorders for PANK2 mutation. This included cases with neurodegeneration and brain iron accumulation, corticobasal degeneartion, progressive supranuclear palsy (PSP), Parkinson’s disease (PD), multiple system atropy, giant axonal neuropathy (GAN), neuroaxonal dystrophy (NAD), Guam dementia and HARP syndrome (pallido-pyramidal syndrome and hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa and pallidal degeneration). From our series of patients one patient with PKAN and a progressive severe dystonic syndrome, cerebellar ataxia, retinitis pigmentosa and eventual anarthria had a novel combination of two compound heterozygote mutations identified in the PANK2 gene, G → A transition at base 1238 (G411R) and a C → A transition at base 1184 (A395E). In the patient with HARP syndrome two compound heterozygote mutations (Met327Thr and IVS5–1 G to T) in the PANK2 gene were found. No other mutations were found in any of the other patient groups, suggesting that PANK2 mutations are not associated with the aetiology of these adult degenerative conditions and confirms the genetic heterogeneity in neurodegeneration with brain iron accumulation. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: PANK2; Neurodegeneration; PKAN; NBIA; Mutation
Neurodegeneration with brain iron accumulation (NBIA) refers to a heterogeneous group of disorders with a rare inherited neurodegenerative disorder characterized by early onset extrapyramidal disorder with rapid progression, intellectual impairment and often either pigmentary retinopathy or optic atrophy. This group were previously referred to as having Hallervorden-Spatz syndrome. The most prevalent form of NBIA is called pantothenate kinase associated neurodegeneration (PKAN) and is due to mutations in the pantothenate kinase 2 gene (PANK2) gene on chromosome 20p13-p12.3 [16,21]. Other forms of NBIA include infantile and adult neuroaxonal dystrophy (NAD), aceruloplasmineamia and neuroferritinopathy [4]. A number of mutations and mutation types have now been identified throughout PANK2. Preliminary evidence suggests
∗
Corresponding author. Tel.: +44 207 938 3611x4285; fax: +44 207 278 5616. E-mail address: [email protected] (H. Houlden).
0304-3940/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2006.08.030
patients with two loss of function alleles present with early severe disease and that age at onset correlates with pantothenate kinase residual activity [3,12,2]. There are a proportion of patients with a typical phenotype for PKAN without PANK2 mutations, although large genomic rearrangements, duplications and deletion in PANK2 cannot be excluded [3,12,2]. The clinical and radiographic features of PKAN patients with PANK2 mutation suggests the presence of a mutation in the PANK2 gene is usually associated with the classical early onset disease with extrapyramidal features and the presence of the ‘eye of the tiger’ magnetic resonance imaging (MRI) sign [3,12,2,17]. Neuropathologically, PKAN is characterized by lateral degeneration of the globus pallidus and substantia nigra pars reticulata with deposition of iron in the affected regions and more widely distributed neuronal axonal spheroids [14,15]. There are atypical cases of PKAN, many with adult-onset cases, a more slowly progressive course, parkinsonism, dystonia, dysarthria and psychiatric manifestations have also been
M.M. Matarin et al. / Neuroscience Letters 407 (2006) 162–165
described [3,6,18,20,13,10,5]. The ‘eye of the tiger’ sign on MRI is not pathognomonic of PKAN and some patients with PANK2 mutations do not have this sign or may only have it transiently [8,1]. The ‘eye of the tiger’ sign has also been reported in corticobasal degeneration and progressive supranuclear palsy (PSP), late onset diseases known to have Tau associated pathology and genetic aetiology [19], and one assymptomatic individual has been reported with this sign for at least a 2-year period [9]. Given the wide clinical spectrum of PKAN, the age of onset being up to 30 years with some patients still walking in their 50s and the overlap in imaging studies, many other neurodegenerative conditions could potentially have PANK2 mutations as a cause for their disease [3,12,2]. In this article, we sequenced the PANK2 gene in a number of patients with NBIA and other neurodegenerative conditions that present with similar clinical features. Patients and families in the study were recruited with their prior consent and ethical approval to carry out this study. The clinical details of the individuals are given in Table 1, clinical details of the patient with HARP syndrome have been previously reported [5]. Two patients with pallido-pyramidal syndrome were cousins. Genomic DNA was extracted from peripheral blood with family consent, exons 1–7 of the PANK2 (longest transcript) were analyzed by polymerase chain reaction (PCR) amplification (ABgene Thermo-start DNA polymerase kit) followed by PCR cleanup (Millipore PCR purification 96 well plates) direct DNA sequencing (BigDye terminator sequencing reagent, Applied Biosystems and Abgene dye terminator removal 96 well plates). A total of 11 primers (Sigma-Genosys custom primers, UK) were designed to amplify the seven exons of PANK2 [21]. Sequencing reaction was performed and analyzed on an ABI 3100 automated sequencer (Genescodes, VA). In our series of patients the progressive supranuclear palsy and corticobasal ganglionic degeneration (CBD) patients were negative for exons 9–13 of the Tau gene. The patients with Parkinson’s disease (PD) were early onset (<55) with a dominant family history and negative for the Parkin and alpha-synuclein genes. The cases with giant axonal neuropathy (GAN) were negative for the Gigaxonin gene mutations. In one patient with PKAN (Family 1) and a progressive severe dystonic syndrome, cerebellar ataxia, retinitis pigmentosa and eventual anarthria a
163
novel combination of two compound heterozygote mutations were identified in the PANK2 gene, G → A transition at base 1238 (G411R) and a C → A transition at base 1184 (A395E). The clinical details of Family 1 are given below. In the patient with HARP syndrome (Family 2) two compound heterozygote mutations (M327T and IVS5–1 G to T) in the PANK2 gene were found. These mutations were not identified in 100 aged control individuals. No other mutations were found in any of the other patients with NBIA or the other neurodegenerative conditions. The Parkinson’s disease patients were not screened for LRRK2 gene mutations but in future studies these cases should be screened and excluded [11]. This proband was the product of a normal pregnancy, delivery and early development. There were no other medical problems, no family history and the parents were not related. At the age of 18 months she developed poor balance, at 2 years clumsy upper limbs with a tremor and at the age of 4–5 years night blindness and decreased peripheral fields. She was stable until 12 years old when her walking deteriorated with gross cerebellar ataxia in her upper and lower limbs. Due to ataxia she was unable to walk from the age of 14 years. She had reduced visual acuity at 6/18, reduced visual fields, slow saccadic pursuit, reduced vertical movements and gross ataxic nystagmus. There was a salt and pepper retinopathy and blurred pink discs. From her early teens she suffered from severe dystonic posturing and spasms in all four limbs. Her head tended to turn upwards, face had blepharospasm and she frequently blinked. There was also severe orol-lingular-buccal spasms that were particularly distressing and caused frequent biting of the lips which often became infected. Her tone was increased, she had brisk reflexes and extensor planters. Extensive biochemical blood and urine investigations were carried out and were normal apart from 15% acanthocytes seen on the blood film. Acanthocytes are a frequent finding in patients with classical PKAN and dystonia [3], they can also be found in other similar neurological disorders such as neuroacanthocytosis and abetalipoproteinemia. Muscle biopsy was normal. Electroencephalogram (EEG) revealed excess of intermediate slow components and a relative poverty of rhythmic EEG components for her age. The electroretinogram (ERG) was consistent
Table 1 Neurodegenerative diseases analysed Diagnosis
N
Family history
Pathologically confirmed
Mutation
NBIA HARP CBD PSP Familial PD GAN NAD Guam dementia MSA PPS
10 1 2 2 20 3 4 2 2 2
No No No No Yes, AD all cases No No Yes, AD/AR cases No Yes, AR
4 0 2 2 7 2 4 2 2 0
F1-(G411R, A395E) F2-(M327T, IVS5–1 G > T) 0 0 0 0 0 0 0 0
PPS, pallido-pyramidal syndrome; N, individual; NBIA, neurodegeneration and brain iron accumulation; HARP, hypoprebetalipoproteinemia, acanthocytosis, retinitis pigmentosa and pallidal degeneration; CBD, corticobasal ganglionic degeneration; PSP, progressive supranuclear palsy; PD, Parkinson’s disease; GAN, giant axonal neuropathy; NAD, neuroaxonal dystrophy; MSA, multiple system atrophy; F,: family; AD, autosomal dominant; AR, autosomal recessive.
164
M.M. Matarin et al. / Neuroscience Letters 407 (2006) 162–165
Fig. 2. PANK2 amino acid changes the individual from Family 1 with the alignment of the amino acid sequences for PANK1, PANK2 and PANK3 from human and mouse. This shows that the mutations are conserved across the PANK sequences and also across species, data not shown but also conserved across Drosophila melanogaster, C. elegans and S. cerevisiae PANK2 sequences.
Fig. 1. Axial T2-weighted MRI scan of the patient (Family 1) with compound heterozygous PANK2 mutations. This shows the bilateral ‘eye of the tiger’ sign: marked hypointensity in the globus pallidus (white arrow) with a high signal in the anteromedial region (black arrow).
with gross loss of function in the outer retinal layer, particularly the peripheral parts. MRI brain showed the ‘eye of the tiger sign’ typical of iron deposition in the globus pallidus (Fig. 1). From her early teens she rapidly developed speech and swallowing problems with striatal dysarthria and eventual anarthria. Numerous therapeutic treatments were tried with limited success for her dystonia including tetrabenazine, diazepam, sinemet, baclofen and botulinum toxin injections. She died from a chest infection at the age of 22 years. Mutations in the PANK2 gene can cause a movement disorder with a wide selection and severity of clinical features. As there is significant overlap with other neurodegenerative disorders we screened the PANK2 gene in a variety of these degenerative conditions where the aetiology was unknown. Based on this small series these data confirm that the PANK2 gene is not associated with the aetiology of PD [7] and also suggests that the PANK2 gene is unlikely to be associated with the other neurodegenerative conditions analysed here. This study also confirms the genetic heterogeneity in NBIA. One out of the 10 NBIA cases screened had two compound heterozygous PANK2 mutations: the G411R mutation which is the commonest PANK2 mutation seen in PKAN and can present as both typical and atypical PKAN and the A395E mutation which has not previously been identified. These mutations are likely pathogenic being highly conserved across different species (Fig. 2) which would indicate they should cause a severe pattern of disease as in the case we present. In comparison the patient with HARP syndrome (Family 2) had two compound heterozygous PANK2 mutations, one conserved in species M327T and the other a splice site mutation IVS5–1 G to T. She had a much milder mainly dystonic phenotype and at the age of 32
years was still mobile and walking to football matches with her father [5]. These data show that the patients phenotype is difficult to predict based on the PANK2 mutation(s), although the large number of mutations now reported may help the clinician advise on the patients prognosis by drawing comparison [2]. In conclusion, this study reveals the PANK2 gene is unlikely to be associated with PD or a number of other neurodegenerative disorders. In the PKAN cases with PANK2 mutations there is a variable phenotype that can in some cases be indicated by the severity of the mutations present. A proportion of NBIA patients are caused by PANK2 mutations but there is still evidence from this and other studies for the existence of one or more other genes. Acknowledgements We are grateful to The Medical Research Council and the Mason Medical Research Foundation for supporting this work. We also thank the families for their assistance. References [1] F.A. Baumeister, D.P. Auer, K. Hortnagel, P. Freisinger, T. Meitinger, The eye-of-the-tiger sign is not a reliable disease marker for Hallervorden-Spatz syndrome, Neuropediatrics 36 (2005) 221–222. [2] M.B. Hartig, K. Hortnagel, B. Garavaglia, G. Zorzi, T. Kmiec, T. Klopstock, K. Rostasy, M. Svetel, V.S. Kostic, M. Schuelke, E. Botz, A. Weindl, I. Novakovic, N. Nardocci, H. Prokisch, T. Meitinger, Genotypic and phenotypic spectrum of PANK2 mutations in patients with neurodegeneration with brain iron accumulation, Ann. Neurol. 59 (2006) 248–256. [3] S.J. Hayflick, S.K. Westaway, B. Levinson, B. Zhou, M.A. Johnson, K.H. Ching, J. Gitschier, Genetic, clinical, and radiographic delineation of Hallervorden-Spatz syndrome, N. Engl. J. Med. 348 (2003) 33–40. [4] K. Hortnagel, N. Nardocci, G. Zorzi, B. Garavaglia, E. Botz, T. Meitinger, T. Klopstock, Infantile neuroaxonal dystrophy and pantothenate-kinaseassociated neurodegeneration: locus heterogeneity, Neurology 63 (2004) 922–924. [5] H. Houlden, S. Lincoln, M. Farrer, P.G. Cleland, J. Hardy, R.W. Orrell, Compound heterozygous PANK2 mutations confirm HARP and Hallervorden-Spatz syndromes are allelic, Neurology 25 (2003) 1423–1426. [6] J. Jankovic, J.B. Kirkpatrick, K.A. Blomquist, P.J. Langlais, E.D. Bird, Late-onset Hallervorden-Spatz disease presenting as familial parkinsonism, Neurology 35 (1985) 227–234. [7] T. Klopstock, M. Elstner, C.B. Lucking, B. Muller-Myhsok, T. Gasser, E. Botz, P. Lichtner, K. Hortnagel, Mutations in the pantothenate kinase gene PANK2 are not associated with Parkinson disease, Neurosci. Lett. 379 (2005) 195–198.
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