Genetic control of apoptosis during neural crest development: BMP4, msx and Slug

CELESTE TRÍBULO; MANUEL J. AYBAR; SARA S. SÁNCHEZ; ROBERTO MAYOR

Homerton College, Cambridge, Inglaterra.

Congreso; 9th International Xenopus Conference; 2002

Programmed cell death (apoptosis) is a normal physiological phenomenon known to play an important role in morphogenesis associated with normal embryonic development. Apoptosis serves multiple functions during development, including: removal damaged, misplaced, abnormal or excess cells; sculpting structures during morphogenesis; controlling cell number; etc. Studies in chick have shown that regions from where neural crest cells migrate are separated by stripes where all presumptive neural crest cells undergo apoptosis. It has been demonstrated that BMP4, through activation of msx family genes, can induce apoptosis to these neural crest cells. On the other hand, there are evidences in C. elegans, which suggest that a Slug family gene, called ces-1, can block the programmed cell death in specific cells. Recently, an apoptotic program was identified in Xenopus which high levels of cell death were detected in the region of the neural crest. We propose that apoptosis in Xenopus neural crest could be regulated by BMP4/Xmsx-1 with an apoptotic function and XSlug with a survival activity. Cell death was analyzed by whole-mount in situ DNA end-labeling technique (the TUNEL protocol), as well as by serial sections of paraffin-embedded TUNEL-stained embryos. We detected apoptosis in the region of prospective neural crest and in the migrating neural crest, confirmed previous results. Comparison between apoptosis patterning and genes expression, done by in situ hybridization, showed that the genes analyzed (XSlug, Xmsx-1, BMP4) have expression in the neural crest and are co-localized with apoptosis patterning. With the aim to elucidate if the suggested genes could participate on the regulation of apoptosis in the Xenopus neural crest, we carried out gain of function and loss of function approaches. Also, we achieved caps experiments. In both of them, gain of function of XSlug or loss of function of BMP4 and Xmsx-1 showed a decrease of apoptosis. Taken together, our results suggest that, during neural crest development, BMP4 and Xmsx-1 promote apoptosis while XSlug act like an apoptosis repressor.