# Exploring the Effects of Robertsonian Translocation 1/29 (Rob (1;29)) on Genetic Diversity in Minor Breeds of Spanish Berrenda Cattle via Genome-Wide Analysis

## TL;DR

This study examines how a chromosomal translocation affects genetic diversity in two endangered Spanish cattle breeds using genome-wide analysis.

## Contribution

The study provides a genome-wide analysis of the impact of the rob (1;29) translocation on genetic diversity in Berrenda cattle breeds.

## Key findings

- Subpopulations with rob (1;29) showed significantly lower genetic diversity in terms of expected heterozygosity.
- The presence of rob (1;29) did not cause sub-structuring within the Berrenda breeds.
- A region of homozygosity on chromosome 6, containing the KIT gene, was identified.

## Abstract

The Spanish cattle breeds “Berrenda en Colorado” and “Berrenda en Negro” are considered endangered breeds. For years, breeders’ associations have been implementing breeding strategies in herds to address the presence of the Robertsonian translocation (rob (1;29)), which is a disease that causes a decline in reproductive performance. Single-nucleotide polymorphism (SNP) genotyping detection techniques are presented as an appropriate means to evaluate genetic diversity. However, previous research on genetic variability in both breeds has been carried out using DNA microsatellites. Therefore, we studied the genetic diversity, population structure, and potential genetic differences among individuals of both Berrenda breeds and groups based on the presence of the Robertsonian chromosomal translocation, rob (1;29). The genetic diversity in terms of expected heterozygosity was significantly lower in those subpopulations containing rob (1;29) within the breed, but in general, the four subpopulations considered showed minor genetic differences. The presence of this Robertsonian translocation did not result in sub-structuring associated with this chromosomal disorder within either of the breeds. The improvement of the reproductive performance of the Berrenda breeds requires the implementation of breeding strategies based on the contributions to the populations of the breeding stock carrying rob (1;29).

Most of the previous studies on the genetic variability in Spanish “Berrenda” breeds have been carried out using DNA microsatellites. The present work aimed to estimate the genetic diversity, population structure, and potential genetic differences among individuals of both Berrenda breeds and groups based on the presence of the Robertsonian chromosomal translocation, rob (1;29). A total of 373 samples from animals belonging to the two breeds, including 169 cases diagnosed as rob (1;29)-positive, were genotyped using an SNP50K chip. The genetic diversity at the breed level did not show significant differences, but it was significantly lower in those subpopulations containing the rob (1;29). Runs of homozygosity identified a region of homozygosity on chromosome 6, where the KIT (KIT proto-oncogene, receptor tyrosine kinase) gene, which determines the typical spotted coat pattern in both breeds, is located. The four subpopulations considered showed minor genetic differences. The regions of the genome that most determined the differences between the breeds were observed on chromosomes 4, 6, 18, and 22. The presence of this Robertsonian translocation did not result in sub-structuring within each of the breeds considered. To improve the reproductive performance of Berrenda breeds, it would be necessary to implement strategies considering the involvement of potential breeding stock carrying rob (1;29).