Fig. 10

Midbrain-hindbrain boundary gene expression is disrupted in prim5 brd2aMO morphants. In situ hybridization to RNA of MHB genes in wildtype uninjected (WT), brd2aMO1-injected (brd2aMO), and control MO-injected (MOc), embryos. For each target gene, a total of 30 embryos and three clutches per treatment were analyzed per treatments. In situ results for eng2a (A–C lateral view; D–F dorsal view), pax2a (G–I lateral view; J–L dorsal view), and wnt1 (M–O lateral view; P–R dorsal view). The hindbrain half of the MHB expression domain of both eng2a and pax2a is reduced in intensity or absent in brd2aMO morphants (arrows in B,E and H,K). Penetrance and expressivity of eng2a and pax2a phenotypes are analyzed in S) and T), respectively. Expression levels were scored as 1 (normal), 2 (reduced), or 3 (absent), and numbers of embryos in each category were evaluated statistically. brd2aMO1 morphants show a higher percentage of category 2 and 3 mutant phenotypes, while WT and MOc embryos show predominantly category 1 normal phenotypes for both eng2a and pax2a (p < 0.0001, chi square contingency), indicating that normal levels of Brd2a are necessary for the proper expression of these genes at MHB.