Two Novel Cases of Autosomal Translocations in the Horse: Warmblood Family Segregating t(4;30) and a Cloned Arabian with a de novo t(12;25).

The article discusses the discovery of two new autosomal translocations or chromosome rearrangement in horses. These findings provide significant insights into equine genetics and reproductive issues and underline the need for regular genetic screening of animals used for breeding and those produced through assisted reproductive technologies.

Case 1: Translocation t(4p;30) in a Breeding Stallion

• The researchers identified a breeding stallion with a balanced autosomal translocation labelled t(4p;30). This means that parts of chromosomes 4 and 30 had switched places, potentially affecting genes located in these areas.
• Despite this chromosomal anomaly, the stallion had been able to produce both normal offspring and others with congenital abnormalities.
• The researchers found that among the stallion’s nine offspring that appeared normal, four had normal karyotypes (chromosome arrangements), four carried the balanced t(4p;30) translocation like their father, and one possessed an unbalanced translocation that resulted in three copies of 4p chromosome segment (tertiary trisomy).
• The investigators argue that the unbalanced form of t(4p;30) translocation can be tolerated, leading to viable offspring with congenital abnormalities, as opposed to most known equine autosomal translocations that typically result in embryonic death.

Case 2: Translocation t(12q;25) in Cloned Arabian Stallions

• The second case involves two cloned Arabian stallions that were created via somatic cell nuclear transfer from the same genetic donor. These stallions were examined due to fertility issues.
• A balanced translocation t(12q;25) was found in one clone, implying a switching of chromosome parts between chromosomes 12 and 25. But the other clone did not exhibit this translocation.

Conclusions and Implications

• The findings highlight the utility and importance of regular cytogenetic screening of breeding animals and those generated through assisted reproductive technologies. Such screening would help identify potential genetic abnormalities that could affect an animal’s health or fertility.
• These particular instances of translocation offer valuable contributions to molecular studies exploring the points where translocations occur (breakpoints) and the genetic consequences of these changes within the horse species.