XX/XY Chimerism in Internal Genitalia of a Virilized Heifer
2022
Izabela Szczerbal | Joanna Nowacka-Woszuk | Monika Stachowiak | Anna Lukomska | Kacper Konieczny | Natalia Tarnogrodzka | Jakub Wozniak | Marek Switonski
Five DSD heifers underwent genetic analysis in the present study. We cytogenetically analyzed in vitro cultured leukocytes and searched for <i>SRY</i>, <i>AMELX</i>/<i>AMELY</i> and <i>ZFX</i>/<i>ZFY</i> 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 <i>SRY</i>, <i>ZFX</i>, <i>ZFY,</i><i>AMELX,</i> and <i>AMELY</i> 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 <i>AMELY</i> (Y-linked) versus <i>AMELX</i> (X-linked) and <i>SOX9</i> (autosomal) versus <i>AMELY</i> 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.
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