Reproduction Abstracts

Background: Turner syndrome in human arises from the loss of genetic material from a sex chromosome, resulting in the 45,XO genotype, with the remaining X chromosome being maternally-inherited (Xm) or paternally-inherited (Xp). As the gene dosage and expressions of Xp and Xm chromosomes are epigenetically different, this study aims to investigate the different influences of Xm and Xp on placental phenotype, using a mouse model.

Methods: 14 placentas from pre-term MF1 mice (3XX, 3XY, 5XmO, and 3XpO) at 18.5 days post-coitum were isolated, formalin-fixed, paraffin-embedded, and sectioned. To examine the placental morphological differences, sections were stained histologically (H&E, PAS, and Azan) and immunohistochemically (CDX2, CK19, fibronectin, laminin, and pecam-1). Student’s t-test was used to analyse various comparison parameters, including the size of the placenta and its constituent layers; as well as the estimates of cell density, and CDX2-positive and glycogen cell numbers in the junctional zone (Jz).

Results: WT (XX and XY) placentas are quite similar to each other. XpO placentas are significantly different from the other three genotypes, especially in the Jz, where there is pronounced lateral Jz hyperplasia (P=0.038), with increased numbers of CDX2-positive (P=0.0092) and glycogen cells (P=0.017). XmO placentas exhibit large morphological variations, with mixed characteristics between WT and XpO placentas.

Discussion: Our findings show that XmO placentas are less phenotypically abnormal, suggesting that they may function better than XpO placentas. This may help explain the findings from previous literature documenting that XmO mice foetuses are more viable than XpO foetuses, and that most of the human 45,XO foetuses surviving to birth have Xm.