Fig. 3

A The sex ratio of offsprings derived from blm^+/− incrosses suggests a role for Blm in zebrafish sex determination and/or gonad differentiation. Data from two incrosses combined is shown. (For individual incrosses, see Supp Fig. 2A). B Complete lack of females among blm^−/− mutant fish in the absence of a functional Tp53 indicates that the effect of Blm is Tp53-independent. (Pairwise p values were calculated with Chi-square test; ns not significant. Data from two incrosses combined are shown. For individual incrosses, see Supplementary Fig. 2B). C The number of GFP-positive germ cells (GCs) in the gonad of blm^+/+ and blm^+/− individuals was substantially higher than that of their blm^−/− siblings. All individuals were on a Tg(ddx4:egfp) background at the age of 1-month post-fertilization (scale bar: 100 μm). D Gonadal GC counts of different blm genotypes as determined on a Tg(ddx4:egfp) background at the size of 5–6 mm. While GC counts of heterozygous blm^+/− individuals were similar to those of wild types, homozygous blm^−/− individuals showed significantly lower numbers (p = 2.5e-03; Welch t-test). E The ratio of fertilized embryos in a total of 51 crosses using males of different blm genotypes. F, G Toluidine Blue staining of testis sections from wild-type (F) and blm^−/− mutant (G) fish. Asterisks denote spermatozoa clusters of normal densities. Homozygous mutant blm^−/− testes showed a drastic reduction of mature spermatozoa (scale bar: 50 μm). Labels: Fe female, M male, GC germ cell.