[The role of actin cytoskeleton in regulating the deployment process of mouse cardiac second heart field progenitor cells].

The vertebrate heart tube originates from cardiogenic mesodermal cells in the early embryo, and subsequently elongates by progressive addition of second heart field (SHF) progenitor cells from adjacent pharyngeal mesoderm and splanchnic mesoderm. Insufficient addition of SHF cells to the heart tube causes the failure of maximal elongation of the heart tube, which results in a series of developmental defects including the most common congenital birth defects, such as right ventricular dysplasia and outflow tract septation, and alignment anomalies. SHF cells form an atypical, apicobasally polarized epithelium which is characterized by apical monocilia, and dynamic actin-rich basal filopodia. In this review, we summarize recent research progresses of actin cytoskeleton in the deployment process of mouse SHF progenitor cells, and reveal the significance of actin cytoskeleton in SHF development, especially in the deployment of SHF cells to the outflow tract, to provide theoretical reference for elucidating and understanding the biological characteristics of SHF deployment.

ERα inhibited myocardin-induced differentiation in uterine fibroids.

Uterine fibroids, also known as uterine leiomyomas, are a benign tumor of the human uterus and the commonest estrogen-dependent benign tumor found in women. Myocardin is an important transcriptional regulator in smooth and cardiac muscle development. The role of myocardin and its relationship with ERα in uterine fibroids have barely been addressed. We noticed that the expression of myocardin was markedly reduced in human uterine fibroid tissue compared with corresponding normal or adjacent myometrium tissue. Here we reported that myocardin induced the transcription and expression of differentiation markers SM22α and alpha smooth muscle actin (α-SMA) in rat primary uterine smooth muscle cells (USMCs) and this effect was inhibited by ERα. Notably, we showed that, ERα induced expression of proliferation markers PCNA and ki-67 in rat primary USMCs. We also found ERα interacted with myocardin and formed complex to bind to CArG box and inhibit the SM22α promoter activity. Furthermore, ERα inhibited the transcription and expression of myocardin, and reduced the levels of transcription and expression of downstream target SM22α, a SMC differentiation marker. Our data thus provided important and novel insights into how ERα and myocardin interact to control the cell differentiation and proliferation of USMCs. Thus, it may provide potential therapeutic target for uterine fibroids.