Comparative FISH mapping of 32 loci reveals new homologous regions between donkey and horse karyotypes.

The research focused on the mapping of 32 genetic loci from horse and cattle onto donkey chromosomes, identifying new homologous regions between donkey and horse karyotypes. The study was able to point out, to a certain extent, the genetic rearrangements between the two species, contributing to our understanding of their evolution and divergence from a common ancestor.

Objective of the Research

• The study sought to map 32 loci including specific genes, microsatellites, and anonymous BAC clones from horse and cattle on donkey chromosomes to draw comparisons between the karyotypes of the two species.

Findings of the Comparative FISH mapping

• Out of the 32 loci mapped, 13 markers were also mapped for the first time in the horse, providing new data.
• This new information, alongside pre-existing data, presents a more comprehensive comparative status between the horse and donkey karyotypes.
• It was observed for the first time that there’s a correlation between eleven equine acrocentric autosomes and donkey chromosomes.
• The study identified at least 20 chromosome rearrangements, including inversions, fusions, and fissions, differentiating the two karyotypes.

Corresponding Areas and Unknowns

• Nevertheless, the correspondence between 7-8 pairs of chromosomes/arms remains unknown – a gap that needs to be bridged by future studies.
• These findings mirror the differences seen in the karyotypes of human-gibbon and mouse-rat, which also display significant genetic rearrangements compared to each other.

Future Implications

• Understanding how the differences in donkey and horse karyotypes developed over a short period (5-10 Myr) since they diverged from a common ancestor requires further investigation.
• The answers will become clear only once an ancestral equid karyotype is derived and the direction of change leading to chromosome rearrangements is decrypted.