Fig. 2

The fh227 allele is accurately mapped to chromosome 12 and egr2b using gDNA extracted from fixed tissue. Dorsal view of mbp expression in 5 dpf zebrafish using WISH and the mbp riboprobe shows phenotypically normal expression (purple) of mbp along the pLLNs (arrowheads) (A) compared to severely reduced mbp expression along the pLLN (arrowheads) in egr2b^{fh227/ fh227} mutants (B). (C) When the ratio of variant to reference alleles in the mutant pool is compared to the sibling pool and graphed across the whole genome for egr2b^fh227, a clear spike on chromosome 12 is observed (box). This spike indicates genotypic linkage to the trait used to sort the mutant and sibling pools. (D) When looking at chromosome 12, egr2b^fh227 is linked to a single region centered ∼10 Mb (arrow). (E) Linkage map of the egr2b^fh227 allele showing the 21 different homozygous, nonsynonymous, protein-coding SNPs in the single chromosome 12 region linked to the decreased mbp expression in the PNS which was used to sort the mutant and sibling pools. The single introduced stop is the mutation responsible for the egr2b^fh227 mutant phenotype.