SMN gene deletions in adult-onset spinal muscular atrophy.
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Biomedical subjects
Publications and source records attributed to A Munnich.
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Stargardt disease (STGD) and late-onset fundus flavimaculatus (FFM) are autosomal recessive conditions leading to macular degenerations in childhood and adulthood, respectively. Recently, mutations of the photoreceptor cell-specific ATP binding transporter gene (ABCR) have been reported in Stargardt disease. Here, we report on the screening of the whole coding sequence of the ABCR gene in 40 unrelated STGD and 15 FFM families and we show that mutations truncating the ABCR protein consistently led to STGD. Conversely, all mutations identified in FFM were missense mutations affecting uncharged amino acids. These results provide the first genotype-phenotype correlations in ABCR gene mutations.
PURPOSE: To report the identification of two novel RDS mutations in the peripherin/RDS gene of two unrelated French patients affected by autosomal dominant retinitis pigmentosa (ADRP). METHODS: Fifty-eight unrelated patients affected by ADRP were analyzed. Our diagnostic for RP were bilateral fundus involvement, concentric depression of the visual field and severe involvement on electroretinogram. Transmission of the trait was unambiguous. Our strategy was to analyze the coding sequence of the gene using a combination of single-strand conformation polymorphism (SSCP) and direct sequence analysis of the exons of the gene. Exons that displayed conformational polymorphisms were sequenced on an automated DNA sequencer. RESULTS: The sequence analyses revealed two previously unreported missense mutations: Cys165Tyr and Phe211Leu in exons 1 and 2, respectively. None of the 70 controls analyzed carried these base changes. Cosegregation of the base substitution with the disease could be tested in both families presenting the Cys165Tyr and Phe211Leu mutations. CONCLUSIONS: Several lines of evidence support the idea that these base substitutions are disease-causing mutations. To the best of our knowledge, no peripherin/RDS gene analysis has been previously reported in ADRP in France.
Comparative genomic hybridization on a microarray (microarray-CGH) allows to detect genomic chromosome imbalances. In order to assess its value to detect small chromosome imbalances observed in a clinical setting, using a DNA chip available commercially (Spectral Genomics, Houston, Texas, USA), we studied the DNA of 9 patients carrying a well characterized chromosome imbalance and the DNA of 11 patients where cytogenetic techniques such as high resolution banding karyotype, FISH using subtelomeric probes and comparative genomic hybridization on metaphase chromosomes conclude to a normal and/or balanced karyotype. A result was obtained for 19/20 patients. Failure of hybridization was observed for one patient. For all the other cases the sex of patients was correctly identified. Microarray-CGH was able to correctly diagnose the chromosome imbalance in 6/8 patients carrying such a defect i.e 9/11 imbalances (deletion or duplication) were detected. No chromosome imbalance was observed in 11 patients considered normal and/or balanced using cytogenetic techniques. Several clones were found to be polymorphic and required FISH studies to eliminate duplication or deletion. In conclusion, we think that this commercially available DNA chip might be useful to screen for chromosome imbalances. However, technical improvements are still necessary before using it in a clinical setting. Also, further studies are necessary to assess its sensitivity and specificity.
The availability of more and more reliable obstetrical echographies makes now possible to screen fetuses for microphtalmies and anophtalmies. More over, by mean of linkage studies with DNA markers within a family, we can identify the women who will transmit X-linked diseases, and realize a prenatal diagnosis. This technology can be applied to the following ophthalmological diseases: the X-linked retinoschisis, the choroideremia, the ocular albinism, the Noorie disease, and recently the retinoblastoma. From now on, the use of such a technology which makes it possible to detect ophthalmological diseases in the fetuses, is posing ethical problems especially in case of diseases without any survival prognosis involvement.
Hirschsprung disease (HSCR, aganglionic megacolon) is a frequent congenital malformation regarded as a multigenic neurocristopathy. Four susceptibility genes have recently been identified in HSCR, namely the RET proto-oncogene, the glial cell line-derived neurotrophic factor (GDNF), the endothelin B receptor (EDNRB) and the endothelin-3 genes (EDN3). Homozygosity for EDN3 mutations has been previously shown to cause the Shah-Waardenburg syndrome, a combination of HSCR with features of the Waardenburg syndrome. Here, we report on heterozygous EDN3 missense mutations in isolatec HSCR. The present data give further support to the role of the endothelin signaling pathway in the development of neural crest-derived enteric neurons. They also suggest the possibility that either recessive or weakly penetrant dominant alleles could occur at the EDN3 locus, depending on the nature of the mutation.