Genetic Variation and Population Differentiation in the Bovine Lymphocyte Antigen DRB3.2 Locus of South African Nguni Crossbred Cattle.

Lwamkelekile Sitshilelo Mkize,Oliver Tendayi Zishiri

doi:10.3390/ani11061651

Lwamkelekile Sitshilelo Mkize, Oliver Tendayi Zishiri

Open Access

https://doi.org/10.3390/ani11061651

Copy DOI

Abstract

Simple SummaryIndigenous cattle breeds are important to their native environment as they confer significant and often unique adaptability traits. The Nguni is one such breeds that is indigenous to the Southern African region. This breed confers resistance to thermal stress and diseases, amongst other factors. The bovine major histocompatibility complex is an important region, which codes for alleles that have been associated with a plethora of diseases. In the current study, the genetic diversity within this region was assessed in Nguni crossbred cattle. This was done to detect the gene pool of the Nguni breed, and to identify genes that might be important within this breed. The populations displayed a high degree of genetic diversity, and some alleles were common throughout the populations and accounted for a significant portion of the total alleles. This high genetic diversity could account for the great adaptability of the Nguni breed to Southern Africa. The bovine lymphocyte antigen (BoLA-DRB3) gene is an important region that codes for glycoproteins responsible for the initiation of an immune response. BoLA-DRB3 alleles have been demonstrated to be associated with disease resistance/tolerance. Therefore, great genetic diversity is correlated with better adaptation, fitness, and robustness. The current study was conducted to assess the population genetic structure of the BoLA-DRB3 gene in Nguni crossbred cattle using polymerase chain reaction-sequence based typing (PCR-SBT). High genetic diversity was detected, with 30 alleles, 11 of which are novel to the study. Alleles DRB3*0201, DRB3*0701, DRB*0901, and DRB*1601 were present in all populations and accounted for nearly around 50% of all observed alleles. A mean genetic diversity (HE) of 0.93 was detected. The high overall genetic diversity is possibly associated with pathogen-assisted selection and heterozygote advantage. Such high diversity might explain the hardiness of the Nguni crossbred cattle to the Southern African region. Low population genetic structure was identified (FST = 0.01), suggesting possible gene flow between populations and retention of similar alleles. The study was undertaken to bridge the dearth of such studies in South African breeds and it is imperative for effective sustainability of indigenous breeds and the implementation of effective breeding strategies.

Highlights

The major histocompatibility complex (MHC) is one of the most important genetic regions in living organisms as it is responsible for the resistance or susceptibility to diseases [1]
SuWbistthainntPiaolpguelantieotnics variation12i5n.2t1h5is region could ac0c.4o6u0n3t5for the associatio9n9.b0e3t6w85een efficient imTmotualne response an1d28d.5i8s6ease resistance [307.4,3684]9.7 The current study reveals that South African crossbred Nguni cattle exhibits high genetic polymorphism in the BoLADRB3 region
Great genetic diversity was detected with 11 novel alleles identified

Summary

Introduction

The major histocompatibility complex (MHC) is one of the most important genetic regions in living organisms as it is responsible for the resistance or susceptibility to diseases [1]. Defining the genetic variation in the MHC in different organisms indicates the degree to which populations can recognize foreign polypeptides. Delineating the genetic architecture of the MHC is of paramount importance in defining disease resistance and susceptibility In cattle this component is termed the bovine lymphocyte antigen (BoLA) and is located on chromosome 23 [5]. The second exon in the BoLA-DRB3 is characterized with increased genetic variation and an even distribution of alleles [13] This variation has been postulated to be maintained through different selective mechanisms [13,14]. It is ideal for populations to encompass significant variation in the MHC given that the greater the genetic diversity the greater the spectrum of pathogens that can be identified. As a host’s immune system develops defensive mechanisms against a pathogen, the pathogen in turn develops defense systems and it is this arms race that will require the host to accumulate and retain genetic diversity [24]

Objectives

Methods

Results

Discussion

Conclusion