Identifying a distinct developmental module in the zebrafish dentition

In the zebrafish pharynx, the first three teeth to form, 3V1, 4V1, and 5V1, have distinct adult and embryonic morphologies, suggesting that these teeth may form using different developmental pathways. Previous studies of gene expression profiles and mutant phenotypes in 3V1, 4V1, and 5V1 have identified four genes that might be involved in dissociating these tooth modules: pitx2b, eve1, pbx1a, and pbx1b. To determine how the developmental roles of these four genes differ across 3V1, 4V1, and 5V1, and obtain a better understanding of how these three teeth develop, I performed CRISPR/Cas9– mediated knockouts in each of these genes, or analyzed embryos from a stable transgenic mutant line where available, and observed the resulting tooth germs and mineralized tooth structures via fluorescence and confocal microscopy. Preliminary results implicate pitx2 as being required for tooth mineralization, offer a possible role for pbx1a, pbx1b,
and eve1 in distinguishing the developmental pathway of 3V1, and suggest that 3V1 constitutes a distinct developmental module within the early ventral dentition.