Flounder (Paralichthys olivaceus) FoxD1 and its regulation on the expression of myogenic regulatory factor, MyoD

It has been reported that FoxD1 plays important roles in formation of several different tissues, such as retina and kidney in vertebrates. The function of FoxD1 in muscle development is, however, unclear although it is expressed in muscle cells in zebrafish. Muscles are the major tissue in fish, which serves as a rich protein source in our diet. To further understand the function of FoxD1 in fish muscle development, here we isolated and characterized the FoxD1 gene from flounder (Paralichthys olivaceus), a valuable sea food and an important fish species in aquaculture in Asia. We analyzed its expression pattern and function in regulating myogenic regulatory factor, MyoD, one of the earliest marker of myogenic commitment. In situ hybridization revealed that FoxD1 was expressed in the tailbud, adaxial cells, posterior intestine, forebrain, midbrain and half of the retina in flounder embryos. Functional studies demonstrated that when flounder FoxD1 was over-expressed in zebrafish by microinjection, MyoD expression was decreased, suggesting that FoxD1 may be involved in myogenesis by regulating the expression of MyoD.     

PV.1 Suppresses the Expression of FoxD5b during Neural Induction in Xenopus Embryos

Suppression of bone morphogenetic protein (BMP) signaling induces neural induction in the ectoderm of developing embryos. BMP signaling inhibits eural induction via the expression of various neural suppressors. Previous research has demonstrated that the ectopic expression of dominant negative BMP receptors (DNBR) reduces the expression of target genes down-stream of BMP and leads to neural induction. Additionally, gain-of-function experiments have shown that BMP downstream target genes such as MSX1, GATA1b and Vent are involved in the suppression of neural induction. For example, the Vent1/2 genes are involved in the suppression of Geminin and Sox3 expression in the neural ectodermal region of embryos. In this paper, we investigated whether PV.1, a BMP downstream target gene, negatively regulates the expression of FoxD5b, which plays a role in maintaining a neural progenitor population. A promoter assay and a cyclohexamide experiment demonstrated that PV.1 negatively regulates FoxD5b expression.