Aging is an inevitable and natural process of life that is characterized by impaired body functions and increased susceptibility to both physical and mental disease. Age-related disease has grown into a major societal and economic problem as life expectancy continues to increase. Developing therapies that delay the onset of age-related disease represents a pressing biomedical research and public health need. Progeria is caused by a rare de novo mutation in the lamin A gene. Lamin A is a structural protein in the nuclear lamina that functions to tether transcriptionally inactive heterochromatin to the nuclear periphery. The symptoms of progeria mimic various age-related pathologies, including vision loss, musculoskeletal degeneration, liver steatosis, atherosclerosis, hair loss and hardened skin. Progeria thus provides a unique model for understanding the biology of aging. Despite the known molecular cause of progeria, the exact biological mechanism of how a mutation in lamin A gives rise to aging-like symptoms in various tissues is not understood. Using computational approaches, we identified a unique link between lamin and CpG islands (CGIs). CGIs are DNA elements with unusually high frequencies of the Cytosine-phosphate-Guanine dinucleotide that are primarily associated with gene promoters. Our results demonstrate that silent genes lacking CGIs (CGI-) form heterochromatin and localize to the nuclear periphery, and that lamin proteins interact primarily with the promoters of silent CGI- genes. Genes containing CGIs (CGI+) associate primarily with euchromatin, even when silent. A growing body of evidence suggests that aging-associated changes in nuclear lamina and chromatin architecture disrupt gene regulation that leads to tissue-specific degenerative disease. The overarching goal of this proposal is to begin defining how lamin A regulates gene expression. We will test the hypothesis that the progeria lamin A mutation selectively disrupts CGI- gene regulation in a tissue-specific manner using a unique resource, progeria patient iPS cells. Gene expression and cellular abnormalities associated with progeria and aging will be characterized in normal and progeria iPS cells differentiated into cardiomyocytes and hepatocytes. We will also characterize gene regulation and cellular properties in differentiated normal and progeria iPS cells into which we have introduced or corrected the progeria lamin A mutation using CRISPR- Cas9 genome editing. Finally, we will conduct a large-scale meta-analysis of publicly-available genome-scale datasets generated under different aging contexts to determine if the expression and epigenetic regulation of CGI- genes is selectively disrupted during aging. The studies we propose uniquely analyze gene regulation and chromatin architecture from the perspective of CGI elements, which are often overlooked. Our studies will thus provide new and fundamental insights into progeria, aging, and aging-associated degenerative diseases.
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