Isl1 and Wntbeta-catenin regulation of cardiac progenitor cells

描述（由申请人提供）：尽管心血管生物学取得了几十年的进展，但心脏病仍然是发达国家的主要死亡原因。最近，基于心脏祖细胞（CPCs）的治疗已成为一种有前景的潜在心脏治疗方法。然而，我们不知道CRC自我更新、增殖和分化的机制，这是心脏再生治疗的先决条件。我最近的研究结果表明，规范的Wnt信号是CRC扩展所必需的。为了寻找Wnt/p-catenin信号的下游介质，我对具有和不具有组成性活性Wnt/p-catenin信号的小鼠胚胎的crc进行了表达阵列分析。这项研究揭示了几个在结直肠癌发展中起关键作用的基因，这些基因受到p-catenin的负面影响，包括Isietl、心肌和Smyd1。值得注意的是,| 3 -

DESCRIPTION (provided by applicant): Despite decades of progress in cardiovascular biology, heart disease remains the leading cause of death in the developed world. Recently, therapies based on cardiac progenitor cells (CPCs) have emerged as promising potential cardiac therapeutics. However, we do not know the mechanisms underlying CRC self renewal, proliferation and differentiation, a prerequisite for cardiac regenerative therapy. My recent findings suggest that canonical Wnt signaling is required for CRC expansion. To search for downstream mediators of Wnt/p-catenin signaling, I performed expression array analyses of CRCs from mouse embryos with and without constitutively active Wnt/p-catenin signaling. This search revealed several genes with pivotal roles in CRC development that are negatively affected by p-catenin, including Isietl, Myocd and Smyd1. Notably, |3- catenin stabilization severely downregulated isietl, a temporal marker of undifferentiated CRCs that is required for normal cardiogenesis. /s/ef t-deficiency increased the number of CRCs and suppressed their cardiac differentiation. To understand how cellular decisions are implemented by Isietl and Wnt/p-catenin signaling, I have begun to identify the critical downstream pathways that affect CRC maintenance and differentiation. I found that Isietl loss-of-function severely compromised expression of Myocd, a gene required for smooth muscle differentiation. Interestingly, Isietl did not affect expression of Smyd1, an essential gene for cardiomyocyte differentiation, suggesting an Isietl-independent regulation of Stnydl by Wnt/p-catenin signaling. Among the genes upregulated by p-catenin, I found that Bhlhb2, a transcriptional repressor with a novel role in cardiogenesis, is expressed specifically in the cardiac region. Importantly, increased Bhihb2 \e\/e\s in CPCs resulted in downregulation of Smyd1, raising the possibility that Wnt/pcatenin signaling may regulate Smyd1 expression through Bhlhb2. Taken together, these findings set the stage for a mechanistic exploration of the role of Wnt/p-catenin signaling and Isietl in understanding maintenance and differentiation of CRCs that will facilitate future cell-based heart therapeutics. The specific aims of this proposal are (1) To test whether Isietl affects the self-renewal, proliferation, and differentiation of CRCs; (2) To determine if Isietl is an essential effector for Wnt/p-catenin signaling-mediated expansion of CRCs; (3) To investigate if Isietl and Wnt/p-catenin signaling directly activate Myoccf and Bhlhb2, respectively, to affect CRC fates. These studies will lay the foundation for understanding the molecular mechanisms of CRC maintenance and differentiation.