# Association Analysis of SLC11A1 Polymorphisms with Somatic Cell Score in Chinese Holstein Cows

## TL;DR

This study found genetic variations in the SLC11A1 gene that are linked to lower somatic cell scores in Chinese Holstein cows, which could help improve mastitis resistance and milk quality.

## Contribution

The study identifies specific SNPs in the SLC11A1 gene associated with somatic cell scores, suggesting their potential use as molecular markers for improving mastitis resistance in dairy cows.

## Key findings

- The SNP c.723C>T in SLC11A1 was significantly associated with lower somatic cell scores in Chinese Holstein cows.
- The A allele of c.723C>T is a potential marker for improving mastitis resistance in dairy cows.
- Bioinformatic analysis suggests the SNPs may affect SLC11A1 mRNA structure and function.

## Abstract

Milk production traits, including milk yield, fat content, and protein content, are critical economic indicators in the dairy industry. Somatic cell score (SCS) is another important metric, as it reflects the health status of dairy cows and impacts milk quality. The SLC11A1 gene, which is involved in the transport of divalent metals such as iron and manganese, has been implicated in influencing immune responses and potentially milk production traits. Single nucleotide polymorphisms (SNPs) are variations at a single nucleotide position in the DNA sequence and play a vital role in genetic studies of milk production traits. In this research, we identified two SNPs within the SLC11A1 gene and analyzed their associations with SCS. The results indicated that specific SNPs in the SLC11A1 gene were significantly associated with SCS, suggesting that these genetic variations could influence the health status and milk quality of Chinese Holstein cows.

Mastitis is an important disease limiting milk production in dairy cows. Somatic cell score is commonly used as one of the main ways to gauge the level of mastitis in dairy cows, with higher somatic cell scores usually indicating possible mastitis. However, the main molecular markers affecting somatic cell scores remain unknown. The aim of this study was to investigate the association between single nucleotide polymorphisms in the SLC11A1 gene and somatic cell score in Chinese Holstein cows. In this study, 210 Chinese Holstein cows were genotyped and potential SNPs were detected by DNA sequencing, PCR-SSCP and PCR-RFLP analysis. Our results revealed two SNPs were identified in the CDS region of SLC11A1: c.723C>T and c.1144C>G. For the c.723C>T polymorphic site, two genotypes (AA, AB) were found and the genotype frequencies were 0.790 and 0.210, respectively. The results of the association analysis showed that the mean somatic cell score of the AA genotypes were significantly lower than those of the AB genotypes, suggesting that the A allele is a potential marker for improving mastitis resistance in Chinese Holstein cows. For the c.1144C>G polymorphic site, three genotypes (CC, CD, and DD) were found and the genotype frequencies were 0.629, 0.352 and 0.019, respectively. The association analysis revealed that the mean somatic cell score of CC genotypes was lower than that of CD and DD genotypes, however, no significant differences were observed among the various genotype groups when subjected to pair-wise comparisons. The bioinformatic analysis showed that these mutations affected the secondary and tertiary structure of SLC11A1 mRNA, suggesting that they may affect gene expression or protein translation and function. Finally, we predicted the SLC11A1 protein interaction network and found that SPI1, NOD2, TLR2 and S100A12 interacted with SLC11A1 and were reported as candidate genes associated with mastitis resistance. The results indicated that the SNP (c.723C>T) could be potential molecular marker for improving mastitis resistance traits in Chinese Holstein cows. We recommend further validation of this SNP in larger populations and its potential integration into breeding programs to enhance mastitis resistance in dairy cows.