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Fig. 2 The sk29 locus encodes smarcc1a. (A) Schematic depicting meiotic map of the sk29 critical interval. The sk29 mutation is flanked by SSLP markers z10632 and z6293 on chromosome 16 and is tightly linked to SSLP marker z1215 (no recombinants out of 2350 meioses). Additional SNP and SSLP markers (ensembl.org/Danio_rerio) near the sk29 mutation are indicated with numbers of recombinants (r) out of 2350 meioses. (B) cDNA from sk29 mutants contains a C to T transition at position 1942 of the smarcc1a open reading frame (arrows), resulting in a premature stop codon. (C) Zebrafish smarcc1a encodes a 1089 amino acid protein with several conserved motifs and approximately 74% overall similarity to human SMARCC1. The SMART domain classification program63 identifies Chromo64 and SANT26 domains within residues 211-258 and 613-661, respectively. Pfam classification65 identifies a SWIRM domain66 within residues 444-532. The smarcc1ask29 nonsense mutation changes Gln648 (CAA) to a stop codon (TAA), disrupting the SANT domain. (D–G) The sk29 mutation causes a strong reduction in levels of smarcc1a transcripts. Lateral views, anterior to the top. (D, F) Whole-mount in situ hybridization indicates that the smarcc1a expression pattern is not spatially restricted in wild-type. (E, G) smarcc1a transcripts are dramatically reduced in smarcc1ask29 mutants at the 10 and 21 somite (som) stages. (H–K) The sk29 mutation causes a strong reduction in levels of Smarcc1 protein. (H, I) Lateral views, anterior to the right, dorsal to the top. (J, K) Lateral views, anterior to the left, dorsal to the top. Whole-mount immunostaining shows presence of Smarcc1 protein throughout the wild-type embryo at 16 som (H) and within the wild-type heart at 36 hpf (J, arrowhead). Smarcc1 immunostaining is dramatically reduced in sk29 mutants at 16 som (I) and 36 hpf (K).