Fig. 11

brd2aMO morphants show mostly normal expression of nearby markers in midbrain and hindbrain. In situ hybridization to midbrain (Otx2) and hindbrain (krox20, HoxA2b, HoxB1a) markers in wildtype uninjected (WT), brd2aMO1-injected (brd2MO), and control MOc or brd2aMO1mis5-injected embryos (MOc or mis5), using a total of three clutches and 15–30 embryos per treatment. In situ results for krox20 (A–C lateral view; D–F dorsal view), Otx2 (G–I dorsal view), HoxA2b (J–L lateral view), and HoxB1a (M–O lateral view) are shown. Expression of Otx2, HoxA2b, and HoxB1a is normal (H, K, N), while expression of krox20 is often reduced in intensity or absent medially in brd2aMO morphants (B, E). Penetrance and expressivity of the krox20 phenotype are shown in P). Expression phenotypes for krox20 were scored as 1 (normal), 2 (reduced), or 3 (absent medially), and numbers of embryos in each category were evaluated statistically. brd2aMO morphants show a higher percentage of category 2 and 3 mutant phenotypes, although differences from controls tested just below statistical significance (p = 0.0550, chi square contingency). Expression of markers on either side of anterior hindbrain r1 (Otx2, HoxA2b) remains within normal boundaries, as does expression of r4 HoxB1a marker between r3 and r5, indicating lack of expansion into eng2a- or krox20-vacated territory, respectively. Slightly reduced expression of these markers is occasionally observed.