Abstract
Simple SummaryThe disorders of sex development (DSDs) are congenital conditions characterized by inconsistency among chromosomal, gonadal, and anatomical sex development. Reproduction and prolificacy are two main parameters in the sheep industry; thus, DSDs in sheep are very detrimental. Interestingly, no DSDs-associated gene mutations have been reported in sheep so far, probably due to the fact that affected animals are not detected and studied. With the aim to deepen the knowledge about DSDs in sheep and improve diagnostic tools, screening of a sheep farm aimed to detect and study DSDs in ovine species has been started, and the actual findings relative to the first two sheep flocks analysed are reported here. In our opinion, this study demonstrates that, despite the low number of studies on ovine DSDs, if compared with other species, this problem is actually present and needs more attention.The Disorders of Sex Development (DSDs) are congenital conditions characterized by inconsistency among chromosomal, gonadal, and anatomical sex development. The aim of this research is to report the clinical and cytogenetic findings of four DSD cases and 13 couples of heterosexual twins in sheep. To this purpose, C- and R-banding techniques were used, and the analyses of the SRY (Sex Determining Region Y) and AMEL (Amelogenin) genes were carried out. Moreover, morphopathological analyses were performed in one case. The four DSD sheep cases were registered as females at birth, and for none of them it was possible to establish whether the subjects were born from heterosexual multiple births. Three of the four cases were diagnosed as XX/XY blood lymphocyte chimaeras, while the fourth case was diagnosed as a 54, XY SRY-positive DSD sheep. None of the heterosexual twins showed XX/XY blood chimaerism. This finding suggests that the blood chimaeric cases detected could also be due to a zygote/embryo fusion. Moreover, no gene variants involved in sheep DSD are known, the identification of which would be very useful for the sheep industry.
Highlights
One of the main causes of subfertility or sterility in livestock is Disorders of Sex Development (DSDs), congenital conditions in which there is an inconsistency among chromosomal, gonadal, and anatomical sex development [1,2].The study of livestock affected by these disorders allows the discovery of new causative mutations and the development of new diagnostic tools to identify and eliminate them from breeding populations.Animals 2019, 9, 776; doi:10.3390/ani9100776 www.mdpi.com/journal/animalsit provides the opportunity to improve the understanding of mammalian sexual development and differentiation.Sheep DSD cases reported in the literature are mainly linked to XX/XY lymphocyte cell chimaerism caused by blood mixing through vascular anastomosis developed between heterosexual twins during multiple pregnancies [3]
This paper reports the first results obtained from an initial screening of two sheep farms aimed to detect and study DSD in ovine species
As many as four cases of DSD were detected in only two farms, and of these, three chimaerisms were found in one and a case of XY SRY-positive intersex was found in the other
Summary
Sheep DSD cases reported in the literature are mainly linked to XX/XY lymphocyte cell chimaerism caused by blood mixing through vascular anastomosis developed between heterosexual twins during multiple pregnancies (freemartin syndrome) [3]. This finding is of great interest, because freemartin syndrome in sheep is not as frequent in the case of multiple births with lambs of different sex. Some studies based on pedigree analysis showed a familial tendency toward vascular anastomoses at the early stage in gestation, supposing the existence of a single dominant gene influencing this trait [4,7,8] The knowledge of this percentage in those populations and breeds that are in selection for litter size is of great interest
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