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Detection and characterization of cytogenetic defects in cattle using large genotypic and phenotypic data sets generated for genomic evaluation
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International audience. Over the past two decades, the French National Cattle Database (FNCD) has accumulated information on the life, performance and pedigree of more than one hundred million animals, as well as SNP array genotypes of 2 million individuals from various breeds generated as part of genomic selection. The exploitation of this vast amount of data offers numerous prospects in applied and basic research.In a recent study, we developed a highly sensitive approach to detect interchromosomal rearrangements (IR) by searching for abnormal linkage disequilibrium patterns between markers from non-homologous chromosomes in large paternal half-sib families (Jourdain et al., Genome Res. 2023 Jun; 33(6)). After validation by cytogenetic analyses, we reported one Robertsonian fusion, 10 reciprocal translocations, and the first case of insertional translocation reported in cattle among 5571 normozoospermic bulls (prevalence =2.15/1000). By combining multiple sources of information, we demonstrated that most of these IRs are the result of recent de novo mutations due to abnormal male meiosis and that they have dramatic negative effects on several fitness related traits in the carrier sires and their carrier daughters. Finally, we performed long-read sequencing to better characterize the exact nature of seven of these IRs and to identify candidate genes whose haploinsufficiency may be health threatening.In this talk, we will detail the main results of this study, which is to our knowledge the most comprehensive and thorough screen for interchromosomal rearrangements compatible with normal spermatogenesis in livestock species. In addition, we will also present the possibilities offered by the analysis of signal intensity and genotypes of markers located on chromosomes X and Y to identify other cytogenetic defects, with a special emphasis on heterochromosome aneuploidy and free martinism.
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