Figure 2
From: MAX controls meiotic entry in sexually undifferentiated germ cells
Max conditional knockout in sexually undifferentiated germ cells induces meiotic onset. (A) The mating scheme to generate Max conditional-knockout mice. Male and female Maxfl/fl embryos with CreERT2 cDNA were designated MC and FC, while male and female embryos without the cDNA were designated M and F, respectively. (B) Plots of the intensity of individual MAX staining signals in germ and somatic cells at E11.5 from tamoxifen-administered Maxfl/fl mouse embryos with and without the Cre transgene. MAX protein signal intensity was quantified using ImageJ software, as in Fig. 1C. (C) Examination of the effect of Max disruption on the expression of meiosis-related genes. Sycp3, Meiosin, and Stra8 mRNA levels in germ cells from M, MC, F, and FC embryos at the indicated days were quantified by quantitative PCR. Data were normalized to the β-actin expression levels. A short vertical line within the dots represents the mean. Student’s t-tests were conducted, *P < 0.05. (D) Double immunostaining of germ cells subjected to Max gene disruption and their control counterparts. Fetal female and male embryos with or without CreERT2 cDNA were treated with tamoxifen at E8.5 and then sectioned genital ridges from embryos at either E11.5 or E13.5 were subjected to immunostaining of MAX (magenta) and SYCP3 (green), and counterstained with DAPI (blue). Each germ cell is indicated by an arrowhead. Yellow arrowheads indicate germ cells that completely lost the MAX protein signal. PL, preleptotene; eL, early leptotene. (E) Scatter plot representing the intensity of the MAX and SYCP3 staining signals in individual male and female germ cells at E11.5 and E13.5. Proportions of germ cells with a lower MAX protein signal than somatic cells are shown. (F) Proportions of germ cells in meiotic prophase l in gonads from F (n = 3305 total cells) and FC (n = 4456 total cells) embryos at E14.5. Germ cells were classified into four stages (preleptotene, leptotene, zygotene, and pachytene) by the SYCP3 staining pattern. The differences in the proportions between F and FC mice at each stage were examined statistically by Student’s t-test, *P < 0.05.
