Figure 1.
Fertility of male offspring resulting from various crosses.
The female parents are shown from left to right and male parents from top to bottom. The circles symbolize genomes (chrX sticking out), intersubspecific hybrids have the circles split in halves; the pictures of sperm cells within the circles indicate the degree of fertility. Except for the (PWD×B6)F1 hybrids, all males carry sperm; female offspring from all indicated crosses are fertile.
Table 1.
The effect of Prdm9 dosage on hybrid sterility.
Table 2.
Effects of Prdm9 alleles and dosage on reciprocal hybrids.
Table 3.
Overview of male reproductive phenotypes.
Table 4.
Males differing by the Prdm9 allele, its dosage, or background divided into classes according to fertility.
Figure 2.
Sex body formation in the Prdm9PWD/− F1 hybrid male.
Surface-spread nuclei of adult testicular cells treated with a hypotonic solution were indirectly labeled using antibodies marking the synaptonemal complex (anti-SYCP1 and anti-SYCP3) to discern the stage of primary spermatocytes and the phosphorylated form of the histone variant H2AX (anti-γH2AX) to visualize the sex body and then observed under a fluorescent microscope. Left, pachytene carrying a sex body (67 cases found per total of 100 nuclei from four biological replicates); right, pachytene without a sex body (33/100 nuclei).
Figure 3.
Expression of Prdm9 and Morc2b in prepubertal hybrid testis.
Real-time qRT-PCR was performed using RNAs of 14-day-old F1 intersubspecific hybrids of the indicated Prdm9 genotypes (maternal/paternal); −, null. The animals carrying genotypes labeled by the same color were littermates. The columns indicate mRNA expression (mean ± standard deviation) relative to β-actin mRNA for five amplicons in Prdm9 (arranged from the 5′ to 3′ of the gene) and one in Morc2b (orange); the asterisks mark significantly different values (*, p<0.05; **, p<0.01); the expression of Prdm9 was similar in all except the Prdm9PWD/− F1 hybrids.