Pax4 is not essential for beta-cell differentiation in zebrafish embryos but modulates alpha-cell generation by repressing arx gene expression

Djiotsa, Joachim, Verbruggen, Vincianne, Giacomotto, Jean, Ishibashi, Minaka, Manning, Elisabeth, Rinkwitz, Silke, Manfroid, Isabelle, Lvoz, Marianne L. and Peers, Bernard (2012) Pax4 is not essential for beta-cell differentiation in zebrafish embryos but modulates alpha-cell generation by repressing arx gene expression. BMC Developmental Biology, 12 37.1-37.16. doi:10.1186/1471-213X-12-37

Author Djiotsa, Joachim
Verbruggen, Vincianne
Giacomotto, Jean
Ishibashi, Minaka
Manning, Elisabeth
Rinkwitz, Silke
Manfroid, Isabelle
Lvoz, Marianne L.
Peers, Bernard
Title Pax4 is not essential for beta-cell differentiation in zebrafish embryos but modulates alpha-cell generation by repressing arx gene expression
Journal name BMC Developmental Biology   Check publisher's open access policy
ISSN 1471-213X
Publication date 2012-12-17
Sub-type Article (original research)
DOI 10.1186/1471-213X-12-37
Open Access Status DOI
Volume 12
Start page 37.1
End page 37.16
Total pages 16
Place of publication London, United Kingdom
Publisher BioMed Central
Subject 1309 Developmental Biology
Formatted abstract
Background: Genetic studies in mouse have demonstrated the crucial function of PAX4 in pancreatic cell differentiation. This transcription factor specifies beta- and delta-cell fate at the expense of alpha-cell identity by repressing Arx gene expression and ectopic expression of PAX4 in alpha-cells is sufficient to convert them into beta-cells. Surprisingly, no Pax4 orthologous gene can be found in chicken and Xenopus tropicalis raising the question of the function of pax4 gene in lower vertebrates such as in fish. In the present study, we have analyzed the expression and the function of the orthologous pax4 gene in zebrafish.

Results: pax4 gene is transiently expressed in the pancreas of zebrafish embryos and is mostly restricted to endocrine precursors as well as to some differentiating delta- and epsilon-cells but was not detected in differentiating beta-cells. pax4 knock-down in zebrafish embryos caused a significant increase in alpha-cells number while having no apparent effect on beta- and delta-cell differentiation. This rise of alpha-cells is due to an up-regulation of the Arx transcription factor. Conversely, knock-down of arx caused to a complete loss of alpha-cells and a concomitant increase of pax4 expression but had no effect on the number of beta- and delta-cells. In addition to the mutual repression between Arx and Pax4, these two transcription factors negatively regulate the transcription of their own gene. Interestingly, disruption of pax4 RNA splicing or of arx RNA splicing by morpholinos targeting exon-intron junction sites caused a blockage of the altered transcripts in cell nuclei allowing an easy characterization of the arx- and pax4-deficient cells. Such analyses demonstrated that arx knock-down in zebrafish does not lead to a switch of cell fate, as reported in mouse, but rather blocks the cells in their differentiation process towards alpha-cells.

Conclusions: In zebrafish, pax4 is not required for the generation of the first beta- and delta-cells deriving from the dorsal pancreatic bud, unlike its crucial role in the differentiation of these cell types in mouse. On the other hand, the mutual repression between Arx and Pax4 is observed in both mouse and zebrafish. These data suggests that the main original function of Pax4 during vertebrate evolution was to modulate the number of pancreatic alpha-cells and its role in beta-cells differentiation appeared later in vertebrate evolution.
Keyword Insulin
mRNA export
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Institute for Molecular Bioscience - Publications
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 8 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 6 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Wed, 25 Feb 2015, 11:26:11 EST by Anthony Yeates on behalf of Institute for Molecular Bioscience