Elimination of XX cells in the testes of heterosexual bovine twins with XX/XY chimerism

Abstract

In five heterosexual male bovine twins and three freemartins, all not older than three months, XX/XY chimerism in the blood and gonads has been found. One heterosexual male bovine triplet showed at the age of 18 or 22 months XX/XY chimerism in the blood but not in the testes. In another male co-twin of a freemartin, XX/XY chimerism has been detected in the blood and the testes (at biopsy) at the age of two months. In the same animal, the blood chimerism was still present at the age of 18 months, whereas the chimerism of the testes had vanished at that time. Therefore, it can be concluded that, in the course of time, the XX cells of the testes have been eliminated. This elimination, which possibly occurs in embryonic life, partially explains why male co-twins of freemartins do not have malformations of the genital organs and are fertile. Possibly, the XY cells of the testes have an eliminating influence against neighbouring cells with an XX karyotype. The eliminating effect could be directed at the two active X chromosomes of these germ cells. The hypothesis would also account for the observation that blood lymphocytes with an XX karyotype, which have, according to the Lyon hypothesis, only one active X chromosome, are not eliminated with time.

Possibilities for Genetic Manipulation of Sex Ratio in Livestock

“…Ohno et aL (1962) reported XX as well as XY chromosome-bearing cells in the testes of 1-day-old Holstein heterosexual twin bull calves. The presence of XX cells in testes of older affected bulls was reported by Teplitz et al (1967), Weiss and Hoffman (1969) and Lodja (1972), hut Weiss and Hoffmann (1969) reported that the ratio of XX to XY cells declined with advancing age. Whether XX cells are capable of meiotic division in the testicular environment of the heterosexual twin bull is a subject of controversy.…”

“…There is some tendency for a positive association of ratio of XX to XY cells across tissues (Ohno et al, 1962;Teplitz et al, 1967;Dunn et al, 1968). For leucocytes and lymphocytes, the ratio of XX to XY cells also is repeatable across time (Teplitz et aL, 1967;Weiss and Hoffmann, 1969).…”

Germ cells in natural and experimental chimeras in mammals

“…However, these observations have not been confirmed in the more recent studies by Dunn, Kenney, Stone & Bendel (1968) and Evans, West & Ford (personal communication) who were not able to discover either mitotic or meiotic X X metaphase plates in the testes of bulls born from heterosexual pregnancies. Weiss & Hoffmann (1969) described recently chimerism of leukocytes and of the gonadal tissue in several pairs of unlike-sexed bovine twins. However, in view of the fact that chimerism of the gonads was assessed on the basis of examination of cells grown in tissue cultures, the opinion of the present author, contrary to that of Weiss & Hoffmann, is that these findings provide evidence for chimerism of the somatic tissue rather than of the germinal tissue.…”