Emery-Dreifuss muscular dystrophy (EDMD) is a heterogeneous late-onset disease involving skeletal muscle wasting and heart defects caused, in a minority of cases, by mutations in either of two genes encoding the inner nuclear membrane (INM) proteins, emerin and lamins A/C. Nesprin-1 and -2 are multi-isomeric, spectrin-repeat proteins that bind both emerin and lamins A/C and form a network in muscle linking the nucleoskeleton to the INM, the outer nuclear membrane, membraneous organelles, the sarcomere and the actin cytoskeleton. Thus, disruptions in nesprin/lamin/emerin interactions might play a role in the muscle-specific pathogenesis of EDMD. Screening for DNA variations in the genes encoding nesprin-1 (SYNE1) and nesprin-2 (SYNE2) in 190 probands with EDMD or EDMD-like phenotypes identified four heterozygous missense mutations. Fibroblasts from these patients exhibited nuclear morphology defects and specific patterns of emerin and SUN2 mislocalization. In addition, diminished nuclear envelope localization of nesprins and impaired nesprin/emerin/lamin binding interactions were common features of all EDMD patient fibroblasts. siRNA knockdown of nesprin-1 or -2 in normal fibroblasts reproduced the nuclear morphological changes and mislocalization of emerin and SUN2 observed in patient fibroblasts. Taken together, these data suggest that EDMD may be caused, in part, by uncoupling of the nucleoskeleton and cytoskeleton because of perturbed nesprin/emerin/lamin interactions.

No abstract

Spinal muscular atrophies (SMA, also known as hereditary motor neuropathies) and hereditary motor and sensory neuropathies (HMSN) are clinically and genetically heterogeneous disorders of the peripheral nervous system. Here we report that mutations in the TRPV4 gene cause congenital © 2009 Nature America, Inc. All rights reserved.Correspondence should be addressed to M.A.-G. (michaela.auergrumbach@medunigraz.at).. METHODS: Methods and any associated references are available in the online version of the paper at http://www.nature.com/ naturegenetics/. Accession codes. GenBank: human TRPV4 cDNA, NM_021625; human TRPV4, NP_067638 IsoA. Pfam: ankyrin repeat, PF00023.Note: Supplementary information is available on the Nature Genetics website. AUTHOR CONTRIBUTIONS: M.A.-G., S.U., J.S., M.E.M., A.H.C., K.J.D., C.M.A.v.R.-A., N.E.A., H.L., B.S.-W., R.P., C.L., G.W.P., H.J.S., H.K. and T.R.P. recruited the study participants, acquired clinical data, conducted neurological and neurophysiological evaluations and performed linkage analysis. M.A.-G, C.G., L.P. and C.F. carried out the Affymetrix array linkage studies and identified the mutations. A.O., Z.B. and B.T. designed, carried out and analyzed the electrophysiological and Ca 2+ -imaging studies. E.F. conducted immunofluorescence and immunohistochemistry studies. H.S. conducted fluorescence-activated cell sorting (FACS) and biotinylation studies. A.K. performed structural biology and biocomputing analyses. A.H.C., M.E.M. and H.K. participated in the data analysis and reviewed the manuscript. M.A.-G. and C.G. analyzed the data, designed and supervised the study and wrote the manuscript. Supplementary Fig. 1) and observed linkage to three chromosomal regions with log 10 of odds (lod) scores >2 for several SNP markers, including the chromosome 12q23-24 region (data not shown). We constructed haplotypes by including additional distantly related family members (right branch of the pedigree; Supplementary Fig. 1). The genetic interval transmitted with the disease resides between SNPs rs2374688 and rs35426 (Chr. 12: 106,197,054,429 bp; Supplementary Table 1) and overlaps with the intervals reported for risk of congenital distal SMA, SPSMA and HMSN2C 2-4 . Europe PMC Funders GroupIn an affected individual from family FAM_1, we began sequencing all protein-coding exons and exon-intron boundaries of 19 genes but initially observed only known SNPs (Supplementary Table 2). However, sequencing of all protein-coding exons of TRPV4 (transient receptor potential vanilloid 4; chr. 12: 108,705,277-108,755,595; reverse strand) revealed a heterozygous C-to-T nucleotide change at position 943 in exon 6 (Supplementary Fig. 2a), which is predicted to cause the substitution of arginine with tryptophan at position 315 of TRPV4 (R315W). We then screened DNA samples from additional families showing one of the phenotypes described above, including two families previously reported 1,3,4 . All affected individuals from the chromosome 12q23-24-linked family (here called FAM_2) described by...

Hereditary sensory and autonomic neuropathy type I (HSAN-I) is an axonal peripheral neuropathy associated with progressive distal sensory loss and severe ulcerations. Mutations in the first subunit of the enzyme serine palmitoyltransferase (SPT) have been associated with HSAN-I. The SPT enzyme catalyzes the first and rate-limiting step in the de novo sphingolipid synthesis pathway. However, different studies suggest the implication of other genes in the pathology of HSAN-I. Therefore, we screened the two other known subunits of SPT, SPTLC2 and SPTLC3, in a cohort of 78 HSAN patients. No mutations were found in SPTLC3, but we identified three heterozygous missense mutations in the SPTLC2 subunit of SPT in four families presenting with a typical HSAN-I phenotype. We demonstrate that these mutations result in a partial to complete loss of SPT activity in vitro and in vivo. Moreover, they cause the accumulation of the atypical and neurotoxic sphingoid metabolite 1-deoxy-sphinganine. Our findings extend the genetic heterogeneity in HSAN-I and enlarge the group of HSAN neuropathies associated with SPT defects. We further show that HSAN-I is consistently associated with an increased formation of the neurotoxic 1-deoxysphinganine, suggesting a common pathomechanism for HSAN-I.

Recently, two missense mutations (N88S, S90L) in the Berardinelli-Seip congenital lipodystrophy gene have been identified in autosomal dominant distal hereditary motor neuropathy and Silver syndrome. We report the phenotypic consequences of the N88S mutation in 90 patients of 1 large Austrian family and two unrelated German families. Variation in the clinical and electrophysiological phenotype enabled us to distinguish six subtypes. In 4.4%, the disorder was not penetrant. Twenty percent of the patients were subclinically affected; some of these patients could only be detected by pathological nerve conduction studies. A distal hereditary motor neuropathy type V phenotype characterized by predominant hand muscle involvement was found in 31.1%, whereas 14.5% showed typical Silver syndrome with amyotrophy of the small hand muscles and spasticity of the lower extremities. Moreover, the phenotype present in 20% was compatible with Charcot-Marie-Tooth disease. In 10%, the clinical diagnosis of pure or complicated hereditary spastic paraparesis was made. Electrophysiological studies showed an axonal neuropathy but also chronodispersion of compound motor action potentials and conduction blocks. Sensory nerve conduction studies were rarely pathological. Our study indicates that the dominant N88S mutation in the Berardinelli-Seip congenital lipodystrophy gene 2 leads to a broad spectrum of motor neuron disorders.