Fig. 3. The nz171 mutation affects the zebrafish rad21 gene. (A) nz171 maps to a region on chromosome 16 containing rad21. Schematic of chromosome 16 from the centromere `southwards', cM (centiMorgans) indicated as per the MGH Meiotic Mapping Panel (http://zebrafish.mgh.harvard.edu/). SSLP markers determined to be `north' of the mutation are indicated in green and `south' markers in red. Right, expansion of the interval shown as mapped on the Heat Shock Meiotic panel (Woods et al., 2000) on which nearest north and south markers are shown. The rad21 gene is shown in blue. (B) Schematic representation of the rad21 gene, coding region shaded gray. A truncated protein is produced as a result of the Gly-277-STOP mutation in exon 8 (asterisk). (C) Rad21 protein is not present in nz171 homozygote embryos. Immunoblot showing Rad21 protein and -tubulin loading control. Positive control is 5 µg protein isolated from HT29 colon carcinoma cells. (D-F) rad21 transcription in wild-type and nz171 embryos. (D) RT-PCR with rad21-specific primers indicates rad21 transcript is maternally inherited in zebrafish embryos. PCR products separated by agarose gel electrophoresis. (E,F) Expression pattern of rad21 in whole-mount wild-type and nz171 embryos at stages indicated (anterior to the left). rad21 transcript is undetectable in nz171 mutants (E, lower panels). (F) Lateral (left) and dorsal (right) views of anterior regions showing specific wild-type expression of rad21 (mhb, midbrain-hindbrain boundary; mc/ba, mandibular cartilage/branchial arches; ov, otic vesicle; t, telencephalon; pf, pectoral fin).