Hereditary motor and sensory neuropathy-Lom (HMSNL) in an Italian gypsy family

Abstracts assigned. Genes and ESTs (expressed sequence tag) localised on chromosome 5, are actually mapped on the YACs contig.

NAO3 Hereditary motor and sensory neuropathy-Lom (HMSNL) in an Italian gypsy family Adriana Trogua, Mariangela Zanetti a, Cristina Bergonzoni ~, Stefano Stilli b, Marcello Villanova~'g, Patrizia Sabatelli a, Peter Yanakiev ~, Luba Kalaydjievat~ Luciano Merlini g

'~Clinica ORL, Universitgt di Bologna, bPaediatric Orthopaedic Department, lstituto Ortopedico Rizzoli, Bologna, "Institute of Neurological Sciences, University of Siena, alstituto di Citomorfologia Notvnale e Patologica C.N.R. Bologna, ~Neuromuscular Unit, Laboratory of Molecular Pathology, Medical University, Sofia, Bulgaria, JCentre for Human Genetics, Edith Cowan University, Perth, Australia, UNeuromuscular Unit, lstituto Ortopedico Rizzoli, Bologna, Italy HMSNL is an autosomal recessive demyelinating neuropathy associated with deafness which has been recently mapped to chromosome 8q24. An Italian gypsy family, apparently non-consanguineous, presented with 4 out of 5 children with feet deformity and hand weakness in the first decade of life. The three oldest cases aged 15, 13 and 11 years, showed distal wasting and weakness, which were more marked in the oldest sibling. They also had talipes cavus equinovarus. The youngest child, aged 7 years, was considered normal by the parents, but showed mild distal weakness in the 4 limbs. The parents were clinically normal. Median motor nerve conduction velocity was normal in the parents and markedly reduced in the children ranging from 6 to 15 m/s with distal latency of 8.8 to 13.6 ms. Sural nerve biopsy in the 13-year-old boy showed severe loss of myelinated fibres. The remaining axons were of very small size and had a thin myelin sheath. Several poorly developed onion bulb-like formations were observed. Electron microscopy showed that onion bulbs were composed of arranged Schwann cell processes enclosing one or more axons. Sometimes only basal laminae were observed. Numerous axons of myelihated and unmyelinated fibres contained irregularly oriented neurofilaments and neurotubules. Many capillaries showed endothelial hyperplasia associated with thickness or reduplication of the basement membrane. Hearing loss had been noted by the parents in the oldest sibling. The youngest had a pure sensorineural loss with the others showing a mixed pattern bilaterally with loss of stapedial reflex. Waves I-III-V and interpeak latencies were increased in all four siblings. The family shows evidence of linkage to the 8q24 region where the HMSNL gene has been placed. The genetic analysis of 7 polymorphic markers spanning the HMSNL region showed that all 4 affected siblings in our family are homozygous for the same haplotype. It is identical to the common HMSNL haplotype found in Bulgarian Gypsy HMSNL alleles for 6 of the markers. One marker displays a rare allele which is found only in a subset of Gypsy HMSNL patients, probably as a result of the divergence of Gypsy groups carrying the disease gene.

NAO4 Giant axonal neuropathy: clinical study and genetic mapping C. Ben Hamida a, L. Cavalier b, S. Belal ~, H. Sanhaji ~, N. Nadal b, C. Barhoumi ~, N. Mrissa~, N. Maarzouki ~, J.-L. Mandel b, M. Ben Hamida a, M. Koenigb, F. Hentati a

~'iztboratoire de Neuropathologie et Neurobiologie Moleculaire, lnstitut National de Neurologie, la Rabta 1007, Tunis, Tunisia, blnstitut de Genetique et de Biologie Moleculaire et Cellulaire, CNRS - INSERM - ULP, lllkirch, France Giant axonal neuropathy (GAN) is a rare autosomal recessive disorder described as a symmetrical distal neuropathy, with peripheral axons dilated by accumulation of l 0 nm neurofilaments (NF) and a severe course of the disease. The observation of kinky or curly hairs is not a constant finding. We studied three consanguineous non-related Tunisian families with 12 patients sharing a slow course of the disease. By linkage analysis we localised the GANI locus in a 3 cM interval flanked by two linked markers

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(two point lod-score calculation between the linked haplotype and the disease locus was 14.2 at O, max = 0), showing a genetic homogeneity in the 3 families.

NAO5 Cloning of the gene for autosomal dominant cerebellar ataxia with progressive macnlar dystrophy (SCA7) reveals a highly unstable CAG repeat expansion Gilles David a, Nacer Abbasa, Giovanni Stevanin~, Alexandra Durra'b, Gael Yvert¢, Geraldine Cancel ~, Chantal Weber~, Georges Imbertc, Frederic Saudou~, Eric Antonioua, Harry Drabkin J, Robert Gemmill a, Paola Giunti~, Ali Benomart, Nick Wood ~, Merle Ruberg~, Yves Agid ~'b, Jean-Louis Mandel c, Alexis Brice ~'b

~INSERM U289, H@ital de la Salp~tribre, Paris, France, ~'Federation de Neurologie, H3pital de la SalpOtri~re, Paris. France, "IGBMC, lllkireh, France, dUniversity of Colorado Health Sciences Center, Denver, USA, elnstitute of Neurology, London, UK, tService de Neurologie, HOpital des Specialites, Rabat, Morocco The gene for spinocerebellar ataxia 7 (SCA7) has recently been mapped to chromosome 3p12-p13. We have identified by positional cloning a novel gene of unknown function containing a CAG repeat that is expanded in SCA7 patients. On normal alleles, CAG repeat size range from 7 to 17 repeats, whereas on mutated alleles they range from 38 to 130 repeats, surpassing the 121 repeat allele observed in HD, the largest reported until now. Gonadal instability in SCA7 is greater than that observed in any of the seven known neurodegenerative diseases caused by translated CAG repeat expansions, and is markedly associated with paternal transmissions, which account for most of the juvenile cases. SCA7 is the first such disorder in which the degenerative process affects the retina in addition to other brain structures, enlarging the spectrum of neuronal loss in this growing class of diseases. Haplotype studies should show whether certain alleles are predisposed to expansion, as in SCA3/ MJD. Finally, the genetic homogeneity of ADCA II and the facility with which the expansion can be detected by routine methods now permit reliable diagnosis.

Keywords: Spinocerebellar ataxia 7; Trinucleotide repeat expansion; Cloning

NAO6 Expression and mitochondrial Iocalisation of frataxin, the Friedreich's ataxia gene product P. Cavadini a, C. DiBlasi b, S. Baratta ~, S. DiDonato~, M. Morab, F. Taronf'

~'Department of Biochemistry and Genetics and ~'Neuromuscular Disease, lstituto Nazionale Neurologico 'C. Besta', Milan, Italy Friedreich's ataxia (FA) is the most common hereditary ataxia (1:50000). The disease gene (X25; Campuzano et al., 1996) encodes a 210-aa protein, termed frataxin, whose physiological role is presently unknown. To gain insights into the pathogenic mechanism leading to FA, we have expressed the HAl-epitope-tagged frataxin cDNA in transfected mammalian cells (CMT4). Experiments were performed with both an anti-HAl monoclonal antibody and two different anti-frataxin polyclonal antibodies. Western blot analysis of transiently transfected cells showed a larger band of -30 kDa and a smaller band of ~21 kDa. Interestingly, immunofluorescence analysis of transfected cells revealed that the signal pattern of frataxin was similar to that of two mitochondriaspecific probes, CPT-I1 and SSBP, thus indicating a mitochondrial localisafion of frataxin. Immunofluorescence analysis with anti-frataxin polyclonal antibodies confirmed the characteristic 'mitochondrial' pattern also in human fibroblasts and skeletal muscle fibres. Immunocytochemistry results were confirmed by immunoprecipitation experiments in transfected cells radiolabeled with [35S]methionine in the presence and in the absence of an inhibitor of mitochondrial import. Analysis of the immunoprecipitated protein revealed a single larger band when the ceils were grown in the presence of the inhibitor and two bands when the cells were grown in