Structural characterization and molecular dynamics simulations of the caprine and bovine solute carrier family 11 A1 (SLC11A1)

Natural Resistance-Associated Macrophage Proteins are a family of transmembrane divalent metal ion transporters, with important implications in life of both bacteria and mammals. Among them, the Solute Carrier family 11 member A1 (SLC11A1) has been implicated with susceptibility to infection by Mycobacterium avium subspecies paratuberculosis (MAP), potentially causing Crohn's disease in humans and paratuberculosis (PTB) in ruminants. Our previous research had focused on sequencing the mRNA of the caprine slc11a1 gene and pinpointed polymorphisms that contribute to caprine SLC11A1's susceptibility to infection by MAP in PTB. Despite its importance, little is known on the structural/dynamic features of mammalian SLC11A1 that may influence its function under normal or pathological conditions at the protein level. In this work we studied the structural architecture of SLC11A1 in Capra hircus and Bos taurus through molecular modeling, molecular dynamics simulations in different, functionally relevant configurations, free energy calculations of protein-metal interactions and sequence conservation analysis. The results of this study propose a three dimensional structure for SLC11A1 with conserved sequence and structural features and provide hints for a potential mechanism through which divalent metal ion transport is conducted. Given the importance of SLC11A1 in susceptibility to PTB, this study provides a framework for further studies on the structure and dynamics of SLC11A1 in other organisms, to gain 3D structural insight into the macromolecular arrangements of SLC11A1 but also suggesting a potential mechanism which divalent metal ion transport is conducted.

Gene polymorphisms: the keys for marker assisted selection and unraveling core regulatory pathways for mastitis resistance

One of the most frequent mammary diseases impacting lactating animals is mastitis, an inflammation of the mammary gland most commonly caused by bacterial infection. The severity of mastitis is greatly influenced by the invading organism and the subsequent immune response which must recognize the foreign organism, recruit immune cells, eliminate the invading pathogen, and resolve the inflammatory response. The speed, strength, and duration of this response and subsequent disease susceptibility are critically tied to the genetic background of an animal. However, the genetic contribution has been difficult to identify due to the complex interactions that must occur for effective disease resistance. Recent studies have utilized polymorphisms to better define the genes and chromosomal regions that contribute to mastitis resistance. This review will examine these studies with primary emphasis in bovine systems, as the most work regarding mastitis has been conducted in this species.

The use of rose bengal plate test to asses cattle exposure to Brucella infection in traditional and smallholder dairy production systems of tanga region of Tanzania

A cross-sectional epidemiological study was conducted to determine the seroprevalence and to identify risk factors for bovine brucellosis seropositivity in traditional and smallholder dairy cattle production systems in the Tanga region of North-eastern Tanzania. The study populations comprised 246 indigenous and 409 crossbred cattle, randomly selected from 105 smallholder dairy and 25 traditional managed herds, respectively. Individual animal and herd-level data were collected using a structured questionnaire. Serum samples were screened for Brucella antibodies using the Rose Bengal Plate Test The overall seroprevalence of Brucella antibodies in the smallholder dairy and traditional managed cattle was 4.1% and 7.3% respectively. The corresponding overall herd prevalence was 10.5% and 20% respectively. Using multivariate logistic regression analysis, closeness to stock route, access to surface drinking water and location were identified as the major risk factors for individual herd seroprevalence. Older animals (≥6 years) were associated with increased risk of sero-positivity compared to animals of age category of ≤6 years. The results showed that brucellosis is prevalent and widely distributed locally, underscoring the need for further studies including surveillance and institution of preventive and control measures particularly among female young-stock and the general public who are at high risk of contracting brucellosis.

Effect of polymorphisms in the Slc11a1 coding region on resistance to brucellosis by macrophages in vitro and after challenge in two Bos breeds (Blanco Orejinegro and Zebu)

The resistance/susceptibility of selected cattle breeds to brucellosis was evaluated in an F1 population generated by crossing animals classified as resistant (R) and susceptible (S) (R x R, R x S, S x R, S x S) based on challenges in vitro and in vivo. The association between single nucleotide polymorphisms identified in the coding region of the Slc11a1 gene and resistance/susceptibility was estimated. The trait resistance or susceptibility to brucellosis, evaluated by a challenge in vitro, showed a high heritable component in terms of additive genetic variance (h(2) = 0.54 ± 0.11). In addition, there was a significant association (p < 0.05) between the control of bacterial survival and two polymorphisms (a 3'UTR and SNP4 located in exon 10). The antibody response of animals classified as resistant to infection by Brucella abortus differed significantly (p < 0.05) from that of susceptible animals. However, there was no significant association between single nucleotide polymorphisms located in the Slc11a1 gene and the antibody response stimulated by a challenge in vivo.

Identification of single nucleotide polymorphisms in the bovine solute carrier family 11 member 1 (SLC11A1) gene and their association with infection by Mycobacterium avium subspecies paratuberculosis

Johne's disease is a chronic enteritis caused by Mycobacterium avium ssp. paratuberculosis (MAP) that causes substantial financial losses for the cattle industry. Susceptibility to MAP infection is reported to be determined in part by genetic factors, so marker-assisted selection could help to obtain bovine populations that are increasingly resistant to MAP infection. Solute carrier family 11 member 1 (SLC11A1) was adjudged to be a potential candidate gene because of its role in innate immunity, its involvement in susceptibility to numerous intracellular infections, and its previous association with bovine MAP infection. The objectives of this study were to carry out an exhaustive process of discovery and compilation of polymorphisms in SLC11A1 gene, and to perform a population-based genetic association study to test its implication in susceptibility to MAP infection in cattle. In all, 57 single nucleotide polymorphisms (SNP) were detected, 25 of which are newly described in Bos taurus. Twenty-four SNP and two 3'-untranslated region polymorphisms, previously analyzed, were selected for a subsequent association study in 558 European Holstein-Friesian animals. The SNP c.1067C>G and c.1157-91A>T and a haplotype formed by these 2 SNP yielded significant association with susceptibility to MAP infection. The c.1067C>G is a nonsynonymous SNP that causes an amino acid change in codon 356 from proline to alanine (P356A) that could alter SLC11A1 protein function. This association study supports the involvement of SLC11A1 gene in susceptibility to MAP infection in cattle. Our results suggest that SNP c.1067C>G may be a potential causal variant, although functional studies are needed to assure this point.

SLC11A1 gene polymorphisms are not associated to somatic cell score and milk yield in Chinese Holstein

It has been well established that mutations of the solute carrier family 11 A1 (SLC11A1) gene are responsible for susceptibility to a number of intracellular pathogens. Mastitis is the most common and most costly disease of dairy cattle, commonly caused by bacteria. As SLC11A1 protein is involved in bacterial killing, we assumed SLC11A1 gene as a candidate gene for bovine mastitis resistance. In this study, polymorphisms in the SLC11A1 gene were identified in the Chinese Holstein population. Genotypes were constructed, and their associations with somatic cell score and milk yield were determined. Single-strand conformation polymorphisms and DNA sequencing were used to reveal polymorphisms in SLC11A1 gene. A SNP in coding region and a variation of GT repeats in 3'-untranslated region were detected. The SNP resulted in an amino acid variation of p.P356A in transmembrane 8 of SLC11A1 peptide, which is the most conserved consecutive region. However, no associations were observed between the detected polymorphisms and somatic cell scores and milk yield in the Chinese Holstein population.