The Second Case of Non-Mosaic Trisomy of Chromosome 26 with Homologous Fusion 26q;26q in the Horse

Cytogenetic Analysis of a Mare and Her Foal with Suspected Genetic Causes of Disability

Hereditary diseases represent a serious problem in horses, especially in terms of sport use and breeding. Nowadays, we know the genetic basis of several breed-specific inherited diseases. In this study, we focused on the cytogenetic analysis of the clinical case of a healthy mare and her foal with numerous malformations in order to confirm or disprove the suspicion of genetic causes of a disability in this offspring. We used conventional metaphase staining to analyse chromosomal aberrations – breaks and gaps. In general, the number of breaks exceeding the norm (2—3 breaks/100 meta-phases) may indicate the influence of the external environment with a potential teratogenic effect on the offspring during its mother gravidity. Compared to the norm, we found a slightly increased percentage of chromosomal aberrations in both the mother and the foal. As another method, we used karyotyping to assess the number and morphology of chromosomes, where in addition to conventional staining, we also applied differential staining of metaphases (G-banding). Multiplication, loss or rearrangement of chromosome segments are almost always associated with pathology. In the karyotypes we constructed, we observed changes in both individuals, compared to the international standard; in the mare, we probably recorded the mosaic form of her karyotype. In the foal, we found 64, XX with a suspected morphological change which was probably related to autosomal chromosome pair 31. The cytogenetic analysis of suspected individuals is also very beneficial for horse owners and breeders. Thanks to the combination of cytogenetic and modern molecular-genetic methods, we were able to identify individuals unsuitable for breeding.