DESCRIPTION (provided by applicant): The long term goal of this Program is to elucidate the manner in which disruption of normal cohesin function results in the multisystem developmental disorder Cornelia de Lange syndrome (CdLS) and to identify downstream effectors of cohesin function that are important in the pathogenesis of more common isolated birth defects of the types (e.g. congenital heart defects, cleft palate, diaphragmatic hernias, limb defects) seen in constellation in CdLS. The PI (Dr. Krantz) and Project Leaders (Dr. Lander and Dr. Dorsett) of this Program established a successful collaboration since the Pi's discovery of the first CdLS gene (NIPBL) and the initial implication of cohesin in human developmental disorders. At the inception of this Program the role of NIPBL and cohesin in mammalian development was largely unknown. Dr. Dorsett's discovery that the NIPBL ortholog in Drosophila (nipped-b) was a key regulator of gene expression, prompted the initial hypothesis that disruption of cohesin's non-canonical role in gene regulation was the underlying mechanism involved in causing CdLS. This Program Project has built, and will continue to build, on the diverse, but complementary, strengths, experience and resources available to the project leaders. A three-pronged approach to studying this gene and pathway in humans (Project I), mouse and zebrafish (Project II) and Drosophila (Project III) has led to significant discoveries into how cohesin and its regulators function, the identification of novel CdLS genes, the characterization of a group of developmental disorders collectively termed "cohesinopathies", as well as the establishment of valuable resources including the only Nipbl mutant mouse model, multiple mutant Drosophila lines and the world's largest repository of cohesin mutant human cell lines and clinical information. In this renewal our collaborative team will use innovative approaches to continue to synergistically characterize the function, interactions and role of the structural and regulatory cohesin proteins involved in CdLS, and their downstream targets, in causing syndromic and isolated human structural birth defects. This Program is supported by a data- and resource-sharing core that will fuel all three Projects and an administrative core to oversee, facilitate and optimize the interactions of all Projects. RELEVANCE: CdLS is a multisystem developmental disorder caused by mutations in structural and regulatory cohesin genes. Recent discoveries have identified a non-canonical role of cohesin as a critical regulator of gene expression, disruption of which results in significant developmental consequences. This Program outlines a plan to characterize cohesin's function in gene regulation, identify its effector genes and evaluate their role in causing isolated birth defects of the types seen in CdLS.