Connexin30 mutations responsible for hidrotic ectodermal dysplasia cause abnormal hemichannel activity

Clouston syndrome or hidrotic ectodermal dysplasia (HED) is a rare dominant genodermatosis characterized by palmoplantar hyperkeratosis, generalized alopecia and nail defects. The disease is caused by mutations in the human GJB6 gene which encodes the gap junction protein connexin30 (Cx30). To gain insight into the molecular mechanisms underlying HED, we have analyzed the consequences of two of these mutations (G11R Cx30 and A88V Cx30) on the functional properties of the connexons they form. Here, we show that the distribution of Cx30 is similar in affected palmoplantar skin and in normal epidermis. We further demonstrate that the presence of the wild-type protein (wt Cx30) improves the trafficking of mutated Cx30 to the plasma membrane where both G11R and A88V Cx30 co-localize with wt Cx30 and form functional intercellular channels. The electrophysiological properties of channels made of G11R and A88V Cx30 differ slightly from those of wt Cx30 but allow for dye transfer between transfected HeLa cells. Finally, we document a gain of function of G11R and A88V Cx30, which form functional hemichannels at the cell surface and, when expressed in HeLa cells, generate a leakage of ATP into the extracellular medium. Such increased ATP levels might act as a paracrine messenger that, by altering the epidermal factors which control the proliferation and differentiation of keratinocytes, may play an important role in the pathophysiological processes leading to the HED phenotyp

Variability and Phylogeny of the L1 Capsid Protein Gene of Human Papillomavirus Type 5: Contribution of Clusters of Nonsynonymous Mutations and of a 30-Nucleotide Duplication

AbstractWe analyzed the variability and established the phylogeny of the L1 capsid protein gene of 33 isolates of human papillomavirus type 5 (HPV5) obtained from epidermodysplasia verruciformis patients from different continents. By comparing the sequences of a 419-bp fragment with those published for two Japanese isolates, we found 12.9% variable nucleotide positions, defining 25 variants with mutation rates ranging from 0.2 to 8.8%. Such a high intratypic diversity is unusual among HPVs. Nine of the 139 encoded amino acids were variable and 12 protein variants were identified. Fifteen of the 16 substitutions observed were clustered in two short regions. A 9-amino-acid insert, already reported for the Japanese HPV5b isolate, was found within one of the regions in five isolates. Our data support that the insert arose from the duplication of a 30-nucleotide sequence. Phylogenetic trees distributed the DNA variants into three subtypes (a to c) with a divergence higher than 4.5% and allowed the recognition of European and African lineages. By contrast with the trees based on the HPV5 E6 gene, HPV5a DNA variants and the HPV5b variants lacking the insert constituted a single group in the L1 amino acid tree, probably reflecting different levels of structural constraints for the HPV5 L1 and E6 proteins. In that respect, the short variable L1 sequences should represent less constrained regions

Two New Loci for Autosomal Recessive Ichthyosis on Chromosomes 3p21 and 19p12-q12 and Evidence for Further Genetic Heterogeneity

Autosomal recessive ichthyosis (ARI) includes a heterogeneous group of disorders of keratinization characterized by desquamation over the whole body. Two forms largely limited to the skin have been defined: lamellar ichthyosis (LI) and nonbullous congenital ichthyosiform erythroderma (NCIE). A first gene for LI, transglutaminase TGM1, has been identified on chromosome 14, and a second one has been localized on chromosome 2. In a genomewide scan of nine large consanguineous families, using homozygosity mapping, two new loci for ARI were found, one for a lamellar form in a 6-cM interval on chromosome 19 and a second for an erythrodermic form in a 7.7-cM interval on chromosome 3. Linkage to one of the four loci could be demonstrated in more than half of 51 consanguineous families, most of them from the Mediterranean basin. All four loci could be excluded in the others, implying further genetic heterogeneity in this disorder. Multipoint linkage analysis gave maximal LOD scores of 11.25 at locus D19S566 and 8.53 at locus D3S3564