Insights into the architecture of human-induced polygenic selection in Duroc pigs

Pig jejunal single-cell RNA landscapes revealing breed-specific immunology differentiation at various domestication stages

Background

Domestication of wild boars into local and intensive pig breeds has driven adaptive genomic changes, resulting in significant phenotypic differences in intestinal immune function. The intestine relies on diverse immune cells, but their evolutionary changes during domestication remain poorly understood at single-cell resolution.

Methods

We performed single-cell RNA sequencing (scRNA-seq) and marker gene analysis on jejunal tissues from wild boars, a Chinese local breed (Jinhua), and an intensive breed (Duroc). Then, we developed an immune cell evaluation system that includes immune scoring, gene identification, and cell communication analysis. Additionally, we mapped domestication-related clustering relationships, highlighting changes in gene expression and immune function.

Results

We generated a single-cell atlas of jejunal tissues, analyzing 26,246 cells and identifying 11 distinct cell lineages, including epithelial and plasma cells, and discovered shared and unique patterns in intestinal nutrition and immunity across breeds. Immune cell evaluation analysis confirmed the conservation and heterogeneity of immune cells, manifested by highly conserved functions of immune cell subgroups, but wild boars possess stronger immune capabilities than domesticated breeds. We also discovered four patterns of domestication-related breed-specific genes related to metabolism, immune surveillance, and cytotoxic functions. Lastly, we identified a unique population of plasma cells with distinctive antibody production in Jinhua pig population.

Conclusions

Our findings provide valuable single-cell insights into the cellular heterogeneity and immune function evolution in the jejunum during pig at various domestication stages. The single-cell atlas also serves as a resource for comparative studies and supports breeding programs aimed at enhancing immune traits in pigs.

Genome-Wide Association Study Meta-Analysis Elucidates Genetic Structure and Identifies Candidate Genes of Teat Number Traits in Pigs

The teat number is a pivotal reproductive trait that significantly influences the survival rate of piglets. A meta-analysis is a robust instrument, enhancing the universality of research findings and improving statistical power by increasing the sample size. This study aimed to identify universal candidate genes associated with teat number traits using a genome-wide association study (GWAS) meta-analysis with three breeds. We identified 21 chromosome threshold significant single-nucleotide polymorphisms (SNPs) associated with five teat number traits in single-breed and cross-breed meta-GWAS analyses. Using a co-localization analysis of expression quantitative trait loci and GWAS loci, we detected four unique genes that were co-localized with cross-breed GWAS loci associated with teat number traits. Through a meta-analysis and integrative analysis, we identified more reliable candidate genes associated with multiple-breed teat number traits. Our research provides new information for exploring the genetic mechanism affecting pig teat number for breeding selection and improvement.

The jigsaw puzzle of pedigree: whole-genome resequencing reveals genetic diversity and ancestral lineage in Sunong black pigs

The Sunong black pig is a new composite breed under development generated from Chinese indigenous pig breeds (i.e., Taihu and Huai) and intensive pig breeds (i.e., Landrace and Berkshire), which is an important genetic material for studying breeding mechanisms. However, there is currently limited knowledge about the genetic structure and germplasm characteristics of Sunong black pigs. To comprehensively understand their genetic composition and ancestry proportions, we performed population structure and local ancestry inference analysis based on whole-genome sequencing information. The results showed that Sunong black pigs could be clustered independently into a group, whose pedigree was intermediate between indigenous and commercial pig breeds, but closer to commercial pigs. Furthermore, local ancestry inference analysis revealed that Sunong black pigs inherited immune and reproductive traits from indigenous pig breeds, including CC and CXC chemokine family, Toll-like receptor family, IFN gene family, ESR1, AREG and EREG gene, while growth and development-related traits were inherited from commercial pig breeds, including IGF1 and GSY2 gene. Overall, Sunong black pigs have formed a relatively stable genome structure with some advantageous traits inherited from their ancestral breeds. This study deepened the understanding of the breeding mechanism of Sunong black pigs and provided a reference for cross-breeding programmes in livestock.

Molecular Design-Based Breeding: A Kinship Index-Based Selection Method for Complex Traits in Small Livestock Populations

Genomic selection (GS) techniques have improved animal breeding by enhancing the prediction accuracy of breeding values, particularly for traits that are difficult to measure and have low heritability, as well as reducing generation intervals. However, the requirement to establish genetic reference populations can limit the application of GS in pig breeds with small populations, especially when small populations make up most of the pig breeds worldwide. We aimed to propose a kinship index based selection (KIS) method, which defines an ideal individual with information on the beneficial genotypes for the target trait. Herein, the metric for assessing selection decisions is a beneficial genotypic similarity between the candidate and the ideal individual; thus, the KIS method can overcome the need for establishing genetic reference groups and continuous phenotype determination. We also performed a robustness test to make the method more aligned with reality. Simulation results revealed that compared to conventional genomic selection methods, the KIS method is feasible, particularly, when the population size is relatively small.