Mutations in the retinal guanylate cyclase (RETGC-1) gene in dominant cone-rod dystrophy

The dominant cone-rod dystrophy gene CORD6 has previously been mapped to within an 8 cM interval on chromosome 17p12-p13. The retinal- specific guanylate cyclase gene (RETGC-1), which maps to within this genetic interval and previously was implicated in Leber's congenital amaurosis, was screened for mutations within this family and in a panel of small families and individuals with various cone and cone- rod dystrophy phenotypes. A missense mutation (E837D) was identified in affected members of the CORD6 family, as well as a second missense mutation (R838C) in three other families with dominant cone-rod dystrophy. RETGC-1 is only the fourth gene to be implicated in cone-rod dystrophy and this is the first report of dominant mutations in this gene.      

The neuroprotective agent sipatrigine (BW619C89) potently inhibits the human tandem pore-domain K(+) channels TREK-1 and TRAAK

We have cloned and functionally expressed the human orthologue of the mouse TRAAK gene. When cDNA for hTRAAK is expressed in either Xenopus oocytes or HEK293 cells it forms a K(+)-selective conductance and hyperpolarises the resting membrane potential. Quantitative mRNA expression analysis using Taqman revealed that hTRAAK mRNA is predominantly present in the central nervous system where it exhibits a regionally diverse pattern of expression. Like the related channel TREK-1, the activity of TRAAK was potentiated by arachidonic acid. The neuroprotective agent sipatrigine (10 microM) inhibited both hTREK-1 (73.3+/-4.4%) and hTRAAK (45.1+/-11.2%) in a reversible, voltage-independent manner. Inhibition of both channels was dose-dependent and for TREK-1 occurred with an IC(50) of 4 microM. The related compound lamotrigine, which is a better anticonvulsant but weaker neuroprotective agent than sipatrigine, was a far less effective antagonist of both channels, producing <10% inhibition at a concentration of 10 microM.     

Identification of a novel mutation R42P in the gap junction protein beta-3 associated with autosomal dominant erythrokeratoderma variabilis

We report a missense mutation in the gap junction protein beta-3 (encoding Connexin 31), which was detected in only the affected members of a family in which the autosomal dominant skin disease erythrokeratoderma variabilis was segregating. The nucleotide change results in an arginine to proline substitution in codon 42. This residue is positioned on the first transmembrane/first extracellular domain of the gap junction protein with the mutation replacing a negatively charged residue with a nonpolar residue. This change may disrupt the conformation of the protein and voltage gating polarity leading to impaired channel function.     

High allele loss rates at I7q I2-q2I in breast and ovarian tumors from BRCAI-linked families

Loss of heterozygosity (LOH) was evaluated in 174 breast and ovarian tumors derived from 94 families with at least 3 first-degree relatives affected with either of these cancers. By linkage analysis 26 families were identified as having a high posterior probability of being due to BRCAI (the breadovarian cancer susceptibility locus on 17q 12–21) with lod scores varying from 0.5 1 to 9.49. Tumor genotypes were determined at at least 2 constitutionally heterozygous markers flanking BRCA I in a total of 58 tumors from these families. These tumors were derived from 52 patients, the BRCAI mutation carrier status of which was evidenced by DNA sequencing in 20, and inferred by reconstructing haplotypes in the remainder. LOH was detected in 50 (86%) tumors. and invariably involved the wild-type allele. Where informative, this allele was of paternal origin in 33 cases and of maternal origin in I0 cases. These results strongly suggest that BRCA I is a tumor suppressor gene and that LOH is greatly favored to fully inactivate it. © 1995 Wiley-Liss, Inc.     

Acral peeling skin syndrome associated with a novel CSTA gene mutation

Acral peeling skin syndrome (APSS) is a rare autosomal recessive condition, characterized by asymptomatic peeling of the skin of the hands and feet, often linked to mutations in the gene TGM5. However, more recently recessive loss of function mutations in CSTA, encoding cystatin A, have been linked with APSS and exfoliative ichthyosis. We describe the clinical features in two sisters with APSS, associated with a novel large homozygous deletion encompassing exon 1 of CSTA.