Further studies on the cell populations of an intersex horse.

This study delves into the cellular composition of a hermaphrodite horse, exploring whether the equine subject is mosaic or a chimera. The findings suggest that the horse might be a chimera, featuring cell types having different sexual characteristics due to factors like double fertilization or blastocyst fusion.

Research Methodology and Findings

• The researchers embarked on this study by examining an intersex horse that displayed variations in chromosome constitution across its cell types. The objective was to ascertain whether the horse was a mosaic (single individual with different genetic populations) or a chimera (single individual formed from different zygotes).
• Cells from the horse’s gonadal tissue and peripheral blood were cultured, revealing a preponderance of 64/XX and 64/XY cells, typically representing female and male chromosome constitution respectively. However, 64/XX cells were found to be dominant in both the gonadal tissue and peripheral blood.
• The occurrence of drumstick-bearing polymorphonuclear neutrophils in the intersex horse was the same as in standard mares, suggesting a striking similarity between them.

Further Discoveries

• Blood type analysis of the intersex horse occurred through the use of 17 naturally occurring agglutinins and hemolysins, substances that promote clumping or destruction of red blood cells.
• The analysis showed partial agglutinations with three antibodies (anti-A, anti-F, and anti-I), all linked with the A blood grouping system. It also showed a degree of red blood cell destruction (hemolysis) with anti-Fr(3).
• The above findings pointed towards a phenomenon known as erythrocyte chimerism, which suggests an exchange of blood cell precursors within the uterus. This phenomenon has also been observed in other domestic animals.

Conclusions and Implications

• The presence of both XX and XY cells in the gonadal cultures, even in the apparent absence of germ cells, suggests that the intersex horse could be a wholebody chimera. This could be due to double fertilization or fusion of early-stage embryos (blastocyst fusion).
• Such outcomes contribute to the understanding of sexual development and cell differentiation in mammals, particularly horses. They also underscore the genetic complexity that can occur even within one individual.