No abstract

Background Alterations in autophagy have been reported in hypertrophic cardiomyopathy (HCM) caused by Danon disease, Vici syndrome or LEOPARD syndrome, but not in HCM caused by mutations in genes encoding sarcomeric proteins, which account for most of HCM cases. MYBPC3, encoding cardiac myosin-binding protein C, is the most frequently mutated HCM gene. Methods and Results We evaluated autophagy in HCM patients carrying MYBPC3 mutations and in a Mybpc3-targeted knock-in (KI) HCM mouse model, as well as the effect of autophagy modulators on the development of cardiomyopathy in KI mice. Microtubule-associated protein 1 light chain 3 (LC3)-II protein levels were higher in HCM septal myectomies than in non-failing control hearts and in 60-week-old KI than wild-type (WT) mouse hearts. In contrast to WT, autophagic flux was blunted and associated with accumulation of residual bodies and glycogen in hearts of 60-week-old KI mice. We found that Akt-mTORC1 signaling was increased, and treatment with 2.24 mg/kgxd rapamycin or 40% caloric restriction for 9 weeks partially rescued cardiomyopathy or heart failure and restored autophagic flux in KI mice. Conclusions Altogether, we found that i) autophagy is altered in HCM patients with MYBPC3 mutations, ii) autophagy is impaired in Mybpc3-targeted KI mice and iii) activation of autophagy ameliorated the cardiac disease phenotype in this mouse model. We propose that activation of autophagy might be an attractive option alone or in combination with another therapy to rescue HCM caused by MYBPC3 mutations.

Developmental eyelid closure is an evolutionarily conserved morphogenetic event requiring proliferation, differentiation, cytoskeleton reorganization, and migration of epithelial cells at the tip of the developing eyelid. Many signaling events take place during eyelid closure, but how the signals converge to regulate the morphogenetic process remains an open and intriguing question. Here we show that mitogen-activated protein kinase kinase kinase 1 (MAP3K1) highly expressed in the developing eyelid epithelium, forms with c-Jun, a regulatory axis that orchestrates morphogenesis by integrating two different networks of eyelid closure signals. A TGF-α/EGFR-RhoA module initiates one of these networks by inducing c-Jun expression which, in a phosphorylation-independent manner, binds to the Map3k1 promoter and causes an increase in MAP3K1 expression. RhoA knockout in the ocular surface epithelium disturbs this network by decreasing MAP3K1 expression, and causes delayed eyelid closure in Map3k1 hemizygotes. The second network is initiated by the enzymatic activity of MAP3K1, which phosphorylates and activates a JNK-c-Jun module, leading to AP-1 transactivation and induction of its downstream genes, such as Pai-1 . MAP3K1 inactivation reduces AP-1 activity and PAI-1 expression both in cells and developing eyelids. MAP3K1 is therefore the nexus of an intracrine regulatory loop connecting the TGF-α/EGFR/RhoA-c-Jun and JNK-c-Jun-AP-1 pathways in developmental eyelid closure.