Effect of the blood chimerism in the reproductive tract: preliminary results in eight twin foals

DEMYDA-PEYRÁS, S.; MORENO-MILLÁN, M.; HIDALGO, M.; ANAYA, G.; MOLINA, A.

Berna

Conferencia; 21st Annual ESDAR Conference; 2017

VetSuisse University Bern

Chimerism is a genetic condition in which an individual carries two or more cell lines with different genetic background. In mammals, this pathology was described in two forms: 1) true chimerism, which originated from an early fusion of two embryos, 2) blood chimerism, which is produced by the placental fusion between fetuses. This condition was barely reported in horses since twinning is a rare condition. Therefore, its reproductive effect is still not clear. In this study we analysed 8 foals (3 pairs of Pura Raza Española (PRE) and 1 pair of Criollo Argentino (CRA)) derived from twin delivers. Animals, which ranged from 6 months to 1 year at the moment of the analysis, were cytogenetically characterized using classic and molecular methods. Karyotyping and C-banding were performed on metaphases obtained from whole blood cultures. Additionally, 7 STR markers (five located in ECAX and 2 located in ECAY) were determined in DNA obtained from blood and hair follicles separately. Karyotype showed two different cell lines only in 6 of the individuals (2 PRE and 1 CRA pairs). C-banding determined that those differences were located in the sex pair (64,XX/64,XY). Those results were confirmed by molecular analysis, showing results compatible with blood chimerism in 6 individuals. The remaining pair was characterized as normal twin brothers. Internal and external reproductive organs were characterized as normal and in agreement with the age of the foals. Those findings suggest that blood chimerism has no effect on the development of the reproductive tract of horses, and agree with previous studies that suggested that only true chimerism can affect their fertility. This report also showed that blood chimerism is not present in all the foals delivered after twin pregnancies.