Identical action of Y chromosome and sxr factor in early testicular development in the mouse.

Abstract

The Sxr (sex reversed) factor in the mouse described by Cattanach et al. (1971) causes sex reversal of genetic female mice, thus producing XX males. Its primary effect is induction of testicular development in XX embryos. In the present study, the early steps of testicular development in sex reversed XX and in XY mouse embryos are examined. The embryos are bred from male carriers of the Sxr mutation. After determination of the sex chromosomes from chromosomal spreads, the appearance of testis cords is evaluated in sex reversed XX embryos and their XY littermates at 12 1/2 and 13 days of pregnancy. In sex reversed XX embryos testis cords appear at the same stage of development as in XY embryos. From day 13 to 17 of pregnancy, the volume of the testis anlage is determined by planimetry in sex reversed XX and in normal XY embryos from separate litters. No significant difference is found in the growth rate of XX and XY testes. Measurements of the diameter of the testis cords also indicate the same developmental pattern in both groups. Thus, during induction of a testis the Sxr factor perfectly imitates the Y chromosome in all parameters investigated.