Fig. 2

The herzschlag mutation is an allele of the ttna gene. (A) Microsatellite mapping with SSLP markers on zebrafish chromosome 9 shows a linkage between the herzschlag mutant locus and a ~1 Mbp region including the titin gene cassette. Flanking markers showed minimal recombination between the AB/TB and WIK polymorphic backgrounds in ~200 meioses. (B) Resolution of SSLP markers used for microsatellite mapping. AB/TB genetic markers (white arrows) migrate faster than WIK markers (gray arrows), and thus a double band indicates a recombination event between the marker and the mutation, while a single lower band indicates no recombination. (C) The outcome of a complementation cross between herzschlag and the known heart-isoform-specific ttna mutant pickwick demonstrates that the two mutations fail to complement. The phenotype of the heteroallelic mutant (top) is indistinguishable from the pickwick mutant phenotype (pik), displaying pericardial edema, reduced heartbeat, small head and eyes, but with normal locomotion. The complementation cross produced this mutant phenotype with the expected Mendelian ratios (D), whether hel males and pik females were used, or vice versa (206 embryos out of n=822 total offspring from four individual crosses).