Connexin30 mutations responsible for hidrotic ectodermal dysplasia cause abnormal hemichannel activity

• Published in: Human molecular genetics Vol. 13; no. 16; pp. 1703 - 1714
• Main Authors: Essenfelder, Guilherme Munhoz, Bruzzone, Roberto, Lamartine, Jérôme, Charollais, Anne, Blanchet-Bardon, Claudine, Barbe, Michael T., Meda, Paolo, Waksman, Gilles
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 15.08.2004; Oxford Publishing Limited (England)
• Subjects: Adenosine Triphosphate - metabolism; Animals; Biological and medical sciences; Connexin 30; Connexins - genetics; Connexins - metabolism; Dermatology; DNA Primers; Ectodermal Dysplasia - genetics; Electrophysiology; Epidermis - metabolism; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Hair and nails disorders; HeLa Cells; Humans; Immunohistochemistry; Ion Channels - genetics; Ion Channels - metabolism; Medical sciences; Microinjections; Molecular and cellular biology; Mutagenesis, Site-Directed; Mutation - genetics; Nucleic Acid Amplification Techniques; Oocytes - metabolism; Transfection; Xenopus; Hidrotic ectodermal dysplasia; Genetics; Dermoskeleton; Skin disease; Mutation; Genetic disease
• ISSN: 0964-6906; 1460-2083; 1460-2083
• DOI: 10.1093/hmg/ddh191

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 phenotype.