Generation of a Conditional Allele of the Transcription Factor Atonal Homolog 8 (Atoh8)

Abstract

Atonal Homolog 8 (Atoh8) is a basic helix-loop-helix (bHLH) transcription factor that is highly conserved across species and expressed in multiple tissues during embryogenesis. In the developing pancreas, Atoh8 is expressed in endocrine progenitors but declines in hormone-positive cells, suggesting a role during early stages of the endocrine differentiation program. We previously generated a whole-body Atoh8 knockout but early lethality of null embryos precluded assessment of Atoh8 functions during organ development. Here we report the generation of a conditional Atoh8 knockout mouse strain by insertion of two loxP sites flanking exon 1 of the Atoh8 gene. Pancreas-specific Atoh8 knockout (Atoh8 Δpanc) mice were obtained by mating this strain with a Pdx1-Cre transgenic line. Atoh8 Δpanc mice were born at the expected mendelian ratio and showed normal appearance and fertility. Pancreas weight and gross pancreatic morphology were normal. All pancreatic cell lineages were present, although endocrine δ (somatostatin) cells were modestly augmented in Atoh8 Δpanc as compared to control neonates. This increase did not affect whole-body glucose tolerance in adult knockout animals. Gene expression analysis in embryonic pancreases at the time of the major endocrine differentiation wave revealed modest alterations in several early endocrine differentiation markers. Together, these data argue that Atoh8 modulates activation of the endocrine program but it is not essential for pancreas formation or endocrine differentiation in the mouse. Given the ubiquitous expression pattern of Atoh8, the availability of a mouse strain carrying a conditional allele for this gene warrants further studies using temporally regulated Cre transgenic lines to elucidate time or cell-autonomous functions of Atoh8 during development and in the adult.

Zebrafish atoh8 mutants do not recapitulate morpholino phenotypes

“…Despite its involvement in a range of biological processes, the phenotypic consequences of loss of Atoh8 appear to be mild. Pancreatic differentiation and physiology was largely normal in embryos with conditional removal of Atoh8 exon 1 in Pdx1-expressing pancreatic progenitors, although several lineage markers had altered expression levels, and a modest increase in somatostatin-producing (δ) cells was detected [ 16 ]. Mice with global deletion of either exon 1 or exon 2 of Atoh8 were viable with no structural abnormalities found, notwithstanding gene expression changes in lung mesenchyme [ 10 ].…”

Murine transcription factor Math6 is a regulator of placenta development

“…3 ). Unfortunately, it was not possible to detect the Math6 protein in our tissue samples by immunostaining and Western blot because of the lack of a specific antibody against murine Math6 24 . Our results reveal a strong Math6 expression in all placental layers and a variety of cells at day E10.5 (Fig.…”

Understanding human fetal pancreas development using subpopulation sorting, RNA sequencing and single-cell profiling

“…With regard to genes involved in morphogenesis, the expression of the RhoGAP STARD13 in these populations suggests a conservation of its role in tip cell morphogenesis (Petzold et al, 2013). Only a few markers were specific to the B population, notably the proneural gene ATOH8, which represses the NEUROG3-induced differentiation program in the mouse (Ejarque et al, 2016). Its absence in population C suggests an expression at the early phase of NEUROG3 expression, or even earlier.…”