Fig. 5. had encodes the zebrafish Na,K ATPase 1B1 isoform. (A) Linkage analysis shows 98 recombinants to z5508, 41 recombinants to z3705 and no recombinants to Z6384 of LG1 in 848 meiosis. (B) Schematic cDNA and genomic structures of zebrafish Na,KATPase 1B1. Dark boxes depict transmembrane domains (TM1-TM10). Arrows indicate positions of primers (5F and 5R) used for PCR analysis. Four exons (depicted by blue-boxes, labeled as exon A-D) were amplified from the genomic DNA using the 5F and 5R primers. A deletion at the 3' boundary of exon C (red bar) was detected in had mutants. (C) Genomic sequence of 1B1 between the 5F and 5R primer sequences. The 2 bp-insertion is shown in blue and sequences deleted in had are shown in red. (D) RT-PCR analysis shows two alternative splicing variants (arrows) in had mutants. (E) Predicted structure of the Na,K-ATPase 1B1 protein. Amino acids encoded by exon B are shown in green and those encoded by exon C are in yellow. The purple region represents sequences between TM7 and TM8, which include crucial elements for the interaction of the and ß subunits. (F) The 1B1 isoform is highly expressed in the two-day old wild-type embryonic heart, but is not detectable in had mutant heart. Arrows point to the heart.