Insights into molecular and functional mechanisms behind inherited heart and skin disorders.

Abstract

Desmosomes are macromolecular, dynamic and adaptable complexes that connect intermediate filaments of neighboring cells in a variety of tissues, generating a large mechanically resilient structure. The importance of maintaining desmosome homeostasis for tissue integrity and optimal organ function has been revealed through the identification of desmosome-associated disorders and mechanistic studies into desmosome regulation. This thesis focuses on inherited skin and heart conditions linked to mutations in desmosomal genes or in genes believed to be implicated in desmosome regulation. Part of this thesis is focused on the molecular analysis and identification of novel desmosomal mutations in patients clinically diagnosed with Arrhythmogenic Right Ventricular Cardiomyopathy, and the genetic diagnosis of patients with hypotrichosis, hypotrichosis and PPK or acral peeling skin syndrome. Patients were analysed using a number of different genetic techniques including custom capture array, HaloPlex targeted resequencing, exome capture and Sanger sequencing. Both novel and previously reported mutations were identified in DSP, DSC2, DSG2, PKP2, DSG4 or CSTA in patients diagnosed with these disorders. The molecular mechanisms behind mutations in the protease inhibitors cystatin A and calpastatin, leading to the skin disorders exfoliative ichthyosis and PLACK syndrome, were also investigated. In vitro analysis, using siRNA-mediated knockdown in the immortalised keratinocyte cell line HaCaT, demonstrated that these mutations, affecting the structure and function of the protease inhibitors, lead to deficient intercellular adhesion, possibly through the indirect regulation of desmosomal complexes through their target proteases.