Prohibitin1 acts as a neural crest specifier in Xenopus development by repressing the transcription factor E2F1

Abstract

SUMMARYProhibitin 1 (phb1), which was initially described as an inhibitor of cell proliferation, is a highly conserved protein found in multiple cellular compartments. In the nucleus it interacts with the transcriptional regulators Rb and E2F1 and controls cell proliferation and apoptosis. Here we unravel an unexpected novel function for phb1 in Xenopus cranial neural crest (CNC) development. Xphb1 is maternally expressed; zygotically expressed neurula stage transcripts accumulate in the CNC and the neural tube. Knockdown of Xphb1 by antisense morpholino injection results in the loss of foxD3, snail2 and twist expression, whereas expression of c-myc, AP-2 and snail1 remains unaffected. Xphb2, its closest relative, cannot substitute for Xphb1, underlining the specificity of Xphb1 function. Epistatic analyses place Xphb1 downstream of c-myc and upstream of foxD3, snail2 and twist. To elucidate which subdomain in Xphb1 is required for neural crest gene regulation we generated deletion mutants and tested their rescue ability in Xphb1 morphants. The E2F1-binding domain was found to be necessary for Xphb1 function in neural crest development. Gain-and loss-of-function experiments reveal that Xphb1 represses E2F1 activity; suppression of E2F1 through Xphb1 is required for twist, snail2 and foxD3 expression in the CNC. With the Xphb1 dependency of a subset of CNC specifiers downstream of c-myc, we have identified a new branching point in the neural crest gene regulatory network.

Peter Pan functions independently of its role in ribosome biogenesis during early eye and craniofacial cartilage development in Xenopus laevis

“…We also found c-Myc to be upstream of Slug, FoxD3 and Twist (Fig. 7F,H), as shown previously by others (Bellmeyer et al, 2003;Schneider et al, 2010). Co-injection of c-Myc RNA (0.25-0.5 ng) together with PPan MO did not rescue the effects of PPan depletion on NC marker gene expression (Fig.…”

Apoptosis in amphibian development

“…Inhibition of Prohibitin1 resulted in the loss of expressions for several genes whereas other genes were not affected. E2F1-binding domain was necessary for the action of Xphb1 in development of neural crests [40].…”

“…Its gene Xphb1 was maternally and zygotically expressed. In neurula transcripts, it accumulated in the neural tube and the neural crests [40]. Inhibition of Prohibitin1 resulted in the loss of expressions for several genes whereas other genes were not affected.…”

“…At stage 57, muscle cells began to be altered [40,51] and fast muscular fibres were deleted first [59]. At stage 62, TUNEL positive cells of muscle were detached from the extracellular matrix and died [60] and finally caudal muscles were removed [53,69].…”

Prohibitin is required for transcriptional repression by the WT1–BASP1 complex

“…8 Here we report that BASP1 interacts with the transcriptional corepressor and tumor suppressor prohibitin. Prohibitin acts as a corepressor for several transcription factors including E2F, 15-20 Rb, 21 estrogen receptor, ER 22-24 and androgen receptor AR 25, 26 . We demonstrate that prohibitin forms an integral component of the WT1-BASP1 repressor complex and that it functions to recruit ATP-dependent chromatin remodeling complexes to WT1-dependent promoters.…”