EFNB1 and cardiac hypertrophy: An intriguing finding from our study is the physiological cardiac hypertrophy of the heart between P20 and P60, which, from a CM lateral standpoint, does not rely on a classical myofibril addition in the CM but, at least in part, on an ephrin-B1-dependent- (1) crest maturation through SSM swelling at the CM surface and (2) lateral stretching of the CM.