The skin protects the body against environmental insults and to function properly, epidermal keratinocytes maintain a perfect balance between proliferation and differentiation. Alteration of this balance leads to disorders. Some of these diseases are linked to connexin (Cx) mutations. Connexins are widely expressed in all layers of the epidermis but exact roles of connexins in the epidermis are not known. Analysis of disease mutations can be invaluable for understanding connexin function. Connexin mutations causing skin disorders acquired novel properties and some resulted in active hemichannels that caused release of signaling molecules into the extracellular space and alteration of calcium (Ca2+) mechanisms in adjacent cells. Ca2+ plays roles in keratinocyte proliferation and differentiation and alteration of Ca2+ in the epidermis causes skin disorders. Changes in extracellular Ca2+ levels influence keratinocyte intercellular Ca2+ signals and affect their cellular events. Here it is proposed that aberrant hemichannel activities of Cx26 mutations can alter the epidermal Ca2+ balance by releasing metabolites into the extracellular space and interfere with keratinocyte differentiation programs . For this, normal human keratinocyte cell lines transfected with mutant Cx26 will be used to analyze cellular events, changes in metabolites level and Ca2+ metabolism in cells. Further, keratinocytes with mutant Cx26 will be grown to 3D structures that mimic the normal epidermis and effects of mutant channels on cells in 3D configuration and on Ca2+ signaling will be characterized. The ultimate aim is to understand roles of Cx26 in the skin and its disease. This proposal provides an integration opportunity for the applicant to the host organization in order for her to create her own research laboratory and to transfer her knowledge, research and teaching experiences acquired in USA to the host country and research communities in Europe while retaining her partners in USA.