The hos encodes the SWI/SNF chromatin remodeling complex subfamily gene smarce1, resulting in a frame shift and premature stop of smarce1 translation. (A) Integrated genetic and physical map of the hos locus on zebrafish chromosome 3. The hos mutation interval is flanked by the microsatellite markers Z9964 and Z9016 and was further defined using custom-made microsatellite markers (TD). The final hos interval encodes one full open reading frame, zebrafish smarce1, and an additional partial open reading frame, zebrafish prkcb1. Sequencing of both genes reveals a point mutation of thymine to cytosine at the splice donor site of intron 8 of the smarce1 gene. (B) Sequencing results showing a point mutation of thymine to cytosine at a splice donor site (intron 8) of smarce1 in hos. (C) Amplified smarce1 targeting intron 8 by RT-PCR, indicating an intron inclusion resulting from the point mutation. (D) Schematic description of translational premature stop codon (*) by the hos point mutation. (E) Smarce1 protein sequence alignment of homozygous hos mutant, wild-type zebrafish, mouse, and human nearby mutation site (dr: Danio rerio; mm: Mus musculus; hs: Homo sapiens). (F) Relative smarce1 mRNA expression in hos embryo and heart compared to that in wt at 96 hpf (n = 3). (G) Smarce1 protein levels are not detectable in hos embryo and heart compared to that in wt controls at 96 hpf.
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