The genetic diversity of the BoLA-DRB3 gene has been reported in different cattle breeds owing to its central role in the immune response. However, it is still unknown in hundreds of cattle breeds, especially native populations. Here, we studied BoLA-DRB3 genetic diversity in Highland Creole cattle (CrAl) from Western Bolivia, raised at altitudes between 3800 and 4200 m. DNAs from 48 CrAl cattle were genotyped for BoLA-DRB3 exon 2 alleles using polymerase chain reaction-sequence-based typing (PCR-SBT). The results were compared with 1341 previously reported data from Tropical Creole cattle and other breeds raised in the region. Twenty-three BoLA-DRB3 alleles were identified in CrAl, including the BoLA-DRB3*029:02 variant previously detected in other Creole cattle. Observed and expected heterozygosity were 0.87 and 0.93, respectively. Nucleotide diversity and the number of pairwise difference values were 0.078 and 19.46, respectively. The average number of nonsynonymous and synonymous substitutions were 0.037 and 0.097 for the entire BoLA-DRB3 exon 2, and 0.129 and 0.388 for the antigen-binding site, respectively. Venn analysis and the review of the IPD-MHC database and the literature showed that 2 of 64 alleles were only detected in CrAl, including BoLA-DRB3*029:01 previously reported in African cattle and *048:01 detected in Philippine cattle. Two additional alleles, BoLA-DRB3*007:02 and *029:02, were only present in CrAl and Lowland Creole cattle. Principal Component Analysis (PCA) showed that Bolivian Creole cattle breeds were closely located but they were distant from the Colombian Hartón del Valle Creole. F ST analysis showed a low degree of genetic differentiation between Highland and Lowland Bolivian Creole cattle (F ST = 0.015). The present results contribute to increasing our knowledge of BoLA-DRB3 genetic diversity in cattle breeds.

El complejo principal de histocompatibilidad o MHC(denominado en la especie bovina “antígenoleucocitario bovino, BoLA”) está compuesto por un gran número de genes involucrados en la respuesta inmune dentro de una misma región cromosómica. Muchos de estos genes presentan niveles extraordinarios de polimorfismo. Además, estos loci hansido asociados a enfermedades infecciosas, autoinmunes y a caracteres productivos en diferentes especies de mamíferos. Es por esta razón, que el estudio de su estructura, polimorfismo yevolución ha sido de gran interés para biólogos, genetistas y veterinarios durante las últimas décadas. El objetivo dela presente revisión consiste en analizar el estado del arte sobre la caracterización de la diversidad genética de losloci del BoLA, con especial énfasis en el gen BoLA­DRB3 en las razas bovinas criollas americanas. En este sentido, se detallan las metodologías utilizadas para el genotipado de este gen (serológicas y moleculares). Además, se describen los principales resultados obtenidos a partir del estudio de la diversidad genética del gen BoLA­DRB3, así como de los estudios de asociación de este locus con enfermedades infecciosas en bovinos criollos americanos. Aunque mucho se ha avanzado en el conocimiento de la diversidad genética del gen BoLA­DRB3, aún existe un largo camino por recorrer.

In Bolivia, beef production is mainly based on two genotypes, Bos taurus (Creole cattle) and B. indicus (zebu), being weight gain the main selection criteria used by farmers. However, meat quality and especially tenderness must be incorporated in the selection process. Meat tenderness is partly determined by the calpain CAPN1)/ calpastatin (CAST) protein system. Thus, the objective of the present work was to determine and (compare the genetic variability of the CAPN1 gene in Creole (CreBo), Brahman (BraBo) and Nellore (NelBo) breeds in Bolivia. DNA was extracted from blood samples from 147 CreBo, 59 BraBo and 93 NelBo, and three polymorphisms were genotyped using ARMS­PCR (CAPN1­316 and CAPN1­4751) and PCR­RFLP (CAPN1­530). Furthermore, CAPN1­316 and CAPN1­4751 SNPs were analyzed with Axiom™ Bos 1 Genotyping Array r3 and the Axiom™ ArBos 1 Genotyping Array. Allele frequencies associated with higher tenderness in CreBo, BraBo and NelBo were 0.22, 0 and 0.09 (CAPN1­316 C; P < 0.001), 0.76, 0.16 and 0.08 (CAPN1­4751 C; P < 0.001), and 0.77, 0.92 and 0.94 (CAPN1­530 G; P < 0.001). Linkage disequilibrium (LD) analysis revealed the presence of two LD blocks. Our results evidence that CreBo has a higher frequency of alleles associated with higher meat tenderness than the cebuine breeds. These markers could be used in breeding programs to improve Bolivian cattle herd meat quality either by selection within Creole breeds or crosses with cebuine cattle