Role of DeltaNp63 during epidermis development in Xenopus laevis

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

Hotel Panamericano, Buenos Aires

Congreso; 4th International Meeting of the Latin American Society of Developmental Biology; 2008

Latin American Society of Developmental Biology

The p63 gene is a transcription factor structurally conserved among a wide range of organisms. In mammals p63 has two promoters that generate two types of protein isoforms, TAp63 and DNp63. The TA isoforms are able to activate transcription of specific target genes and induce apoptosis. The DN isoform lacks the NH2-terminal transactivation domain and can function as a dominant negative protein. It was shown that the DN isoform has an anti-apoptotic role. Also in mammals, epidermal development requires the transcription factor p63 and in zebrafish, the DNp63 isoform is a direct target of BMP and is required for epidermal proliferation. In Xenopus, only a cDNA corresponding to mammals DNp63gamma has been cloned and its role in development and apoptosis remains unknown. The ectoderm patterning has been suggested to be under the control of BMP4 that can induce epidermal fate and inhibit the formation of neural tissue. However, target genes regulated by BMP4 and their roles during the specification of epidermis are less understood. We have analyzed the participation of DNp63 in Xenopus epidermal development and its role as an antiapoptotic factor. The expression pattern of DNp63 was examined  and compared with FoxD3, Sox2 and XK81A expression in gastrula and neurula stage and the main expression of DNp63 is located in the epidermis. Then, we decreased the levels of BMP4 as much in whole embryos as in ectodermal explants and we found a decrease in DNp63 expression. Also, we performed gain of function experiments of DNp63 and we observed an increase of epidermal markers and a decrease of neural crest and neural plate markers. Then, we proceeded to analyze the participation of DNp63 in the apoptotic process. We overexpressed DNp63 in whole embryos and in animal caps and in both experiments, the TUNEL analysis showed that DNp63 produced a decrease of apoptosis. Finally, we analyzed whether DNp63 was able to regulate the transcription of some factors of the apoptotic pahtway. Taken together, our results suggest that DNp63 is regulated by BMP4 and participates in the epidermis specification. On the other hand, DNp63 is acting as an antiapoptotic factor regulating the transcriptions of some apoptotic and anti-apoptotic factors probably in such a way that allow the development of the epidermal cells.