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. 2020 Oct 23;6(43):eabb6606. doi: 10.1126/sciadv.abb6606

Fig. 3. CAST/EiJ Prdm9-null females are fertile.

Fig. 3

(A) Immunofluorescence staining of histology sections from 3-week postpartum ovaries in wild-type and Prdm9−/− females of different genetic backgrounds. DDX4 (red, also known as MVH) marks oocytes. DNA is stained with 4′,6-diamidino-2-phenylindole (DAPI) (blue). Arrowheads indicate primordial follicles. Scale bars, 100 μm. Note the oocyte depletion in Prdm9−/− mice in the B6 and C3H genetic backgrounds, in contrast to survival of oocytes in wild-type and Prdm9−/− mice in the CAST genetic background. (B) Pups produced by CAST.Prdm9−/− female mice. (C) Reproductive productivity of wild-type and Prdm9−/− females in different genetic backgrounds. P values were calculated using the Mann-Whitney U test with Bonferroni correction for multiple testing. NS, not significant. (D) Coimmunolabeling detection of MLH1 foci (red) in pachytene oocyte chromatin spreads, also labeled with antibody against SYCP3 (blue) in wild-type and Prdm9−/− CAST females. Scale bars, 10 μm. (E) Violin plot with dots showing numbers of MLH1 foci per oocyte (error bars, SEM). The genotypes of mice tested are indicated below the graphs. P values were calculated using the Mann-Whitney U test with Bonferroni correction for multiple testing. (F) Scheme of construction of B6CASTF2.Prdm9−/− female cohorts used for SNP array genotyping [Giga Mouse Universal Genotyping Array (GigaMUGA)]. Seventy-five F2 females were generated by crossing B6CASTF1.Prdm9−/− and B6CASTF1.Prdm9+/− females with B6CASTF1.Prdm9+/− males. Eight-week-old B6CASTF2.Prdm9−/− females were phenotyped for oocyte quantity and genotyped. (G) Quantitative trait locus (QTL) mapping, with the total number of ovarian follicles (refer to Materials and Methods for details) per B6CASTF2.Prdm9−/− female as the phenotype. QTL (pink) reached significance on chromosome 5, with a peak at ~100.4 Mb (1.5 LOD drop: 72.9 to 127.65 Mb, mm10). (H) Genotype effects of the chromosome 5 QTL. CAST alleles affect oocyte number positively, as highlighted by CC (violet) and BC (orange) lines, relative to B6 homozygotes (BB, green). CC, homozygous CAST; BB, homozygous B6; BC, heterozygous CAST/B6. Photo credit: Catherine Brunton and Tanmoy Bhattacharyya, The Jackson Laboratory.