Titin in the pregnant uterus – a loss of function approach to smooth muscle biomechanics and mechanosignaling

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Titin is the largest known protein in mammals. Its function has been primarily analyzed in heart and skeletal muscle, where it determines the proper assembly and spacing of the sarcomere - the main contractile unit of striated muscle - as well as the elastic properties of the myofilament. Mutations in the titin gene have been recognized as the most common cause of inherited heart disease.In smooth muscle, researchers have struggled to characterize titin expression, localization, and function. Although preliminary data suggests an interaction with α-actinin and myosin filaments, the role of titin in smooth muscle is only poorly understood.Recently, we have generated smooth muscle specific titin knockout mice and uncovered an embryo implantation defect in deficient mothers. The resulting mislocalization and crowding mimics the phenotype of mice with a defect in the lysophosphatidic acid receptor 3 and phospholipase A2 alpha, which link to G-protein coupled receptor signaling, calcium mobilization, and the arachidonic acid pathway. Accordingly, we propose that smooth muscle titin determines the mechanical, metabolic, and signaling properties of the muscular wall of the uterus. Our preliminary analysis suggests that smooth muscle titin contributes to the peristaltic movement of the pregnant uterus as a prerequisite for proper implantation. Here, we will study the molecular, cellular, and functional basis of the phenotype and characterize smooth muscle titin expression on the RNA and protein level, including its localization and the smooth muscle titin interactome. We will determine the elastic and contractile properties of wildtype and titin-deficient uterus rings and investigate if titin based signaling contributes to the implantation phenotype. The proposed work could provide novel insights into the development of ectopic pregnancies and implantation defects.