Investigating the Role of Extracellular Matrix in Down Syndrome Associated Cardiac Phenotypes.

PROJECT SUMMARY Congenital heart defects (CHD) affect ~1% of all births and are the leading cause of morbidity and mortality in infants. Notably, over 50% of Down Syndrome (DS) infants, the most prevalent autosomal abnormality caused by trisomy 21 (T21), are born with a CHD, with septal defects most common. The pathways that contribute to cardiac defects in T21 are poorly understood. The critical region of human chromosome 21 associated with CHD harbors genes coding for extracellular matrix (ECM) as well as cell-ECM and cell-cell adhesion proteins, among others. Using T21 hiPSCs derived from DS individuals, our preliminary data show increased ECM, tissue stiffening, and altered ECM-cell interactions in iPSC derived cardiomyocytes compared to isogenic controls. We also observe precocious differentiation including changes in cell cycle, contractility, and nuclear morphology. Based on compelling preliminary data, we hypothesize that disruption of ECM during heart development leads to downstream effects on cell signaling and to cytoskeletal reorganization that impacts nuclear architecture and gene expression programs. We will test this hypothesis using 3D cardiac models, providing a unique opportunity to investigate critical pathways at the molecular, cellular, and tissue level. In Aim 1 we test the idea that a maladaptive ECM-integrin circuit impacts costamere formation and downstream signaling in cardiac models. In Aim 2 we will test the idea that ECM alterations can impact nucelar architecture and genome organization through cytoskeltal reorganization. Understanding mechanobiological regulation of heart development in T21 will fill a major knowledge gap and is expected to reveal new molecular mechanisms that contribute to CHD. More broadly, this work has the potential to identify therapeutic modalities that minimize DS- associated phenotypes as well as provide a broader solution to a range of diseases involving ECM alterations including age-related degeneration, fibrosis, and cancer. The fellowship training plan capitalizes on the well-established expertise of the Boyer lab in cardiac gene regulatory mechanisms and Dr. Boyer’s extensive mentorship experience, as well as the input of leading experts in the fields of nuclear architecture, cell adhesion and ECM. Dr. Boyer’s lab at the Massachusetts Institute of Technology in both the Biology and Biological Engineering Departments is an ideal research and training environment, facilitating ample opportunities for collaboration and the ability to pursue creative and challenging projects. This project will allow me to develop new skills and expertise that will provide the strongest foundation for my development as an independent researcher.