Fig. 3

arnt1/2 mutants show decreased etsrp, tal1 and lmo2 expression in the lateral plate mesoderm at the 4- to 6-somite stages. Whole-mount in situ hybridization for etsrp, tal1 and lmo2 expression was performed on 4- to 6-somite stage embryos that were the offspring of an arnt1bcm2/+;arnt2bcm3/+ adult zebrafish. (A) Expression of etsrp was observed in the anterior and posterior lateral plate mesoderm (ALPM and PLPM) in 93% of embryos. (B) Limited or no expression of etsrp was observed in 7% of embryos, consistent with the expected Mendelian ratio of 6.25% for arnt1bcm2/+;arnt2bcm3/+ (arnt1/2 mutants). (C) Expression of tal1 was observed in the ALPM and PLPM in 93% of embryos. (D) Limited or no expression of tal1 was observed in 7% of embryos, consistent with the expected Mendelian ratio of 6.25% for arnt1/2 mutants. (E) Expression of lmo2 was observed in 89% of embryos. (F) Limited or no expression of lmo2 was observed in 11% of embryos, which is slightly more than the expected Mendelian ratio of 6.25% for arnt1/2 mutants. We genotyped a subset of each group of embryos (see Tables S2-S4) and observed a correlation between number of mutant alleles and expression of etsrp, tal1 and lmo2 genes. Spearman correlation, etsrp, r=−0.9, P<0.001; tal1, r=−0.6, P<0.005; lmo2, r=−0.2, P<0.01. All embryos are oriented with dorsal towards the top. Fractions in the bottom right corners refer to the number of embryos with the indicated phenotype over the total number of embryos examined. Scale bars: 100 μm.