Attenuation of Wnt/b-catenin activity reverses enhanced generation of cardiomyocytes and cardiac defects caused by the loss of emerin

Mutations in EMD, encoding emerin cause skeletal muscle and heart defects in patients with X-linked Emery– Dreifuss muscular dystrophy (X-EDMD) but the underlying mechanisms leading to cardiac defects are poorly understood. Here, we investigated the role of emerin in controlling cardiomyocyte proliferation and cardiac remodeling and explored its function in regulation of the Wnt/b-catenin pathway. We observed a remarkable increase of cardiomyocytes in emerin-null adult mice accompanied with decreased numbers of multinucleated cells. Depletion of emerin in mouse ES cell-derived cardiomyocytes by shRNA caused hyperactivation of Wnt/ b-catenin signaling, increased proliferation and abrogated timely cardiac differentiation. Likewise, emerin-null mice exhibited increased Wnt/b-catenin signaling, cardiac dysfunction and perturbed hypertrophic re-modeling following pressure overload. Pharmacological inhibition of b-catenin normalized proliferation and differentiation of ES cell-derived cardiomyocytes while inactivation of a single allele of b-catenin efficiently rescued cardiac dysfunction in emerin-null mice. We conclude that emerin constrains b-catenin signaling in the heart providing tight control of cardiomyocyte numbers. Enhanced Wnt/b-catenin signaling seems to con-tribute tocardiacdefectsobserved inX-EDMD.Hence, therapeutic inhibitionofWnt/b-cateninsignalingmightbe beneficial for X-EDMD patients