06-P030 Unfolded protein response leading to cataractogenesis in a microphthalmia cataract mouse mutant

Abstract

nectin-1 gene are responsible for a rare human syndrome characterized by ectodermal dysplasia (ED). The nectin-1 (N1) null mutant mice have a mild defect in skin, (Wakamatsu etal., 2007), but no severe phenotypes were reported, suggesting the compensation by other nectins. In this study, we tested this hypothesis by generating N1 and N3 compound mutant mice.We observed coexpression of N1 and N3 in the inner root sheath of hair follicles and in the suprabasal layer of epidermis.All compound mutants showed severe skin abnormality and reduced hair follicles at post natal day 10. Histological analysis indicated that the compound mutant skin was eosinophilic and the nuclei in the basal cell layer exhibited abnormal shapes and arrangement. Their hair follicles were smaller than wild type and had lost their typical structure. Immunohistochemical analysis revealed that the basal cell layer marker laminin, as well as filaggrin and loricrin were severely reduced in the mutant skin, and that keratin14 was reduced while the expression keratin 10 was normal. The cell junction molecules E-cadherin, ZO-1, and DSG were reduced or mislocalized, and the expression of p63 and Ki67 were severely reduced in the mutant skin. Similar gene expression alterations were also observed in the mutant hair follicles.These results indicate that N1 and N3 have important functions in the control of epidermal homeostasis and hair formation and that they are functionally redundant in these processes. Down syndrome is characterised by trisomy of chromosome 21, and has been linked to overexpression of a number of genes located in the Down Syndrome Critical Region on chromosome 21. DYRK1A is one of the genes in the DSCR and DYRK family members have been shown to play a critical role in the development of the nervous system in worms, mouse and drosophila. Overexpression of active GFP-DYRK1A in HeLa cells causes centrosome duplication and defects in mitotic spindle structure, consistent with a role in mitotic function. To date, there is no clear definition of how DYRK1A functions in cycling cells or in neurogenesis and constitutes an important biological and medical question.We are examining the role of DYRK1A in cell division and in neurogenesis in cultured cells and in the developing spinal cord.We use HeLa cells to probe the subcellular details of DYRK1A function and a novel imaging-based assay that monitors cells within the early chick spinal cord as they form mitotic spindles, transit mitosis and give rise to neurons or neural progenitors.We have shown that the endogenous DYRK1A and the overexpression of kinase and carboxy terminus domains localise to centrosomes. We have also found that depleting DYRK1A by siRNAs causes a loss of metaphase cells, an increase in sub-G1 cells, and delocalization of PLK1 from the midbody. Having shown a requirement for DYRK1A in mitosis, we aim to understand the link between a fundamental requirement in cell division and the fundamental processes of cell differentiation.A novel syndrome causing hereditary birth def...