XX/XY Chimerism in Internal Genitalia of a Virilized Heifer

Abstract

Five DSD heifers underwent genetic analysis in the present study. We cytogenetically analyzed in vitro cultured leukocytes and searched for SRY, AMELX/AMELY and ZFX/ZFY genes in leukocytes and hair follicles, finding that four of the studied heifers were freemartins (XX/XY leukocyte chimerism). The fifth case had an underdeveloped vulva localized ventrally and cranially to the mammary gland, a normal female sex chromosome complement (60,XX) in the leukocytes, and a lack of Y-chromosome-derived genes in the leukocytes and hair follicles. Postmortem anatomical examination of this heifer revealed the presence of normal ovaries with follicles, uterus, and oviducts, but molecular detection of the SRY, ZFX, ZFY,AMELX, and AMELY genes in these organs indicated the presence of a cell line carrying the Y chromosome. Further analysis of twelve microsatellite markers revealed the presence of additional variants at six loci in DNA samples derived from the reproductive organs; XX/XY chimerism was thus suspected in these samples. On the basis of the detection of AMELY (Y-linked) versus AMELX (X-linked) and SOX9 (autosomal) versus AMELY genes by droplet digital PCR (ddPCR), the Y/X and Y/autosome ratios were evaluated; they indicated the presence of XX and XY cell lines in the reproductive tissues. Our study showed that XX/XY chimerism can be present in the internal reproductive organs of the virilized heifers with a normal female set of sex chromosomes (60,XX) and a lack of Y-chromosome-derived genes in the leukocytes. The etiology of this phenomenon remains unknown.

Sexing of Embryos at the Time of Twin Reduction: A Clinical Approach

“…Although XX/XY chimeras have been described in both bull and heifer calves from single births [ 66 , 67 , 68 ], the single-born freemartin remains unknown [ 14 , 69 ]. Determining the level of XX/XY chimerism in males born after a reduction in their female co-twins may help clarify this point.…”

A crazy ants’ crazy form of reproduction: Causes and consequences

“…When cells are similarly exchanged between male and female embryos, it leads to a condition called 'freemartinism', resulting in infertile embryos with the XX/XY genotype. Freemartins have been observed in cattle and less frequently in humans (Szczerbal et al 2022).…”