Figure 1. The skywarp mutation.

a, Schematic of the skywarp (swp) mutation, a C to G transversion 3 bp proximal to exon 5 predicted to damage the intron 4 3′ splice site leading to skipping of exon 5. b, Schematic of the Snrnp40^swp mutant protein. c, RT-PCR amplification across exon 5 of Snrnp40 mRNA from splenocytes of the indicated genotypes. d, Immunoblot analysis of FLAG-tagged wild-type Snrnp40 and Snrnp40^swp expression in HEK 293T cells. Co-transfected GFP was used as a transfection efficiency control and GAPDH was used as an internal control. e, Immunoblot analysis of endogenous Snrnp40 in lysates of splenocytes from mice of the indicated genotypes. f, Schematic of the rplc allele generated by CRISPR-Cas9 gene targeting. The original swp single base substitution was recreated in cis with a synonymous marker mutation (C to T) 11 bp downstream from the swp mutation. g, Lymphocyte and monocyte counts from hematological analysis of the blood (n=6 mice per genotype; ****P<0.0001, unpaired, two-tailed Student’s t-test). h, Ratio (Snrnp40^swp/rplc to Snrnp40^swp/+) of the number of each cell type in the blood (n=8 mice per genotype; ****P<0.0001, unpaired, two-tailed Student’s t-test). i, Frequency of each cell type among total white blood cells in the blood (n=6 mice per genotype; *P=0.018, **P=0.0041, ****P<0.0001, unpaired, two-tailed Student’s t-test). Data are representative of two (c,d), three (h), four (g), or six (e,i) independent experiments (mean ± s.d. in g-i). The gel (c) and blots (d,e) were cropped to show relevant bands and their original images are presented in the Source Data.