During early Xenopus laevis development, cells respond differentially to fibroblast growth factor (FGF) as time changes. This change in response to a signal as a function of time is called ‘competence’. However, the same cells may respond differently to similar regional cues if found in a new time setting. Cells located in a given place and time respond to regional external signaling cues in a process called ‘induction’. In the absence of XLPOU91 activity, the cues driving proper embryonic cell fates are lost.ĭuring early embryonic development, cells must sense the dimension of time. Thus, XLPOU91 epistatically lies upstream of chch/ Sip1 gene expression, regulating the competence transition that is critical for neural induction. Ectopic Sip1 or chch expression rescues the morphant phenotype. Churchill ( chch) and Sip1, two genes regulating neural competence, are not expressed in XLPOU91 morphant embryos. The initial expression of mesoderm and endoderm markers is normal, but neural induction is abolished. In morphant ectoderm explants, mesoderm responsiveness to FGF is extended from blastula to gastrula stages. XLPOU91 knockdown induces high levels of Xbra expression, with blastopore closure being delayed to later neurula stages. Ectopic XLPOU91 expression in Xenopus embryos inhibits FGF induction of Brachyury ( Xbra), eliminating mesoderm, whereas neural induction is unaffected. A Xenopus Oct3/4 homologue gene, XLPOU91, regulates mesoderm to neuroectoderm transitions. At blastula stages, FGF induces mesoderm, but at gastrula stages FGF regulates neuroectoderm formation. In Xenopus laevis, cellular responsiveness to fibroblast growth factor (FGF) changes during development. Cellular competence is defined as a cell's ability to respond to signaling cues as a function of time.
0 kommentar(er)
