ins encoding soluble Wnt antagonists. Moreover, activation of the Wnt pathway by wnt3a or the GSK-3 inhibitor 6-bromoindirubin-3′-oxime leads to self-renewal and pluripotency. Expression levels of Wnt3a and FZD7 in ESCs is 946128-88-7 site higher than those in differentiated cell types. Knockdown of FZD7 also leads to obvious changes in the typical morphology of ESCs and decreases in Oct4 expression, implying that the Wnt3a/FZD7 pathway is important for ESC maintenance. In addition, TCF3, one of the key Wnt-activated transcriptional regulators, is proposed to regulate the expression of key ESC transcription factors including Oct4 and Nanog, and co-occupies almost all promoter regions occupied by ESC-specific transcription factors. -Catenin is reported to form a complex with Oct4 in a TCF-independent manner to enhance ESC pluripotency. However, -catenin is also suggested to be unimportant for pluripotent stem cell self-renewal and expansion, indicating that the effect of -catenin may be context-dependent. The secretin receptor is a family of GPCRs that interact with secretin, the gastrointestinal peptide hormone. Secretin is a member of the secretin-glucagon family and regulates the secretion of bicarbonate ions into the duodenum from the epithelia lining the pancreatic and biliary ducts. In addition to regulating water homeostasis, secretin is reported to have pleiotropic effects in several organ systems and has been termed a neuroendocrine hormone. Vasoactive intestinal peptide and the pituitary adenylyl cyclase activating polypeptides belong to the secretin peptide family and display pleiotropic functions. The physiological actions of these widely distributed peptides are reported to be through the PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19809023 stimulation of three common GPCRs: Vasoactive intestinal polypeptide receptor 1, VPAC2 and phosphatase of activated cells 1 receptor. VPAC1, VPAC2 and PAC1R preferentially activate adenylyl cyclase and increase intracellular cAMP, thereby regulating stem cell maintenance. GPCRs IN SOMATIC REPROGRAMMING TO PSCs The iPSC field advanced significantly in 2006 when Takahashi and Yamanaka discovered that retroviral transduction of only four genes-Sox2, Oct4, c-Myc, and Klf4-was sufficient to induce pluripotency in somatic cells through somatic reprogramming to PSCs. Importantly, iPSCs provide an alternative to the use of human embryos, overcoming ethical issues. In addition, iPSC technology allows the use of patientspecific somatic cells to generate therapeutic iPSCs, overcoming the potential for immune rejection. In human cells, rehttp://bmbreports.org G protein-coupled receptors in stem cell maintenance and somatic reprogramming to pluripotent or cancer stem cells Hye Yeon Choi, et al. programming using the additional factors Nanog and Lin28 to replace c-Myc and Klf4 dramatically reduces the time required to generate iPSCs. To avoid genetic modification and to improve the efficiency of iPSC generation and differentiation, iPSC production technology was advanced using techniques that avoided stable integration of foreign genetic material into the host genome. Treatment of synthetic compounds such as valproic acid favors the maintenance and induction of the pluripotent state, enhancing somatic reprogramming to PCSs. The goal of patient-specific iPSC therapy is to prepare somatic cells from patients, reprogram and differentiate them to replace diseased cells, and successfully transplant them back into the same patients without immune problems. Because pluripotent