A genome-wide association study of copy number variations with umbilical hernia in swine.

Umbilical hernia (UH) is one of the most common congenital defects in pigs, leading to considerable economic loss and serious animal welfare problems. To test whether copy number variations (CNVs) contribute to pig UH, we performed a case-control genome-wide CNV association study on 905 pigs from the Duroc, Landrace and Yorkshire breeds using the Porcine SNP60 BeadChip and penncnv algorithm. We first constructed a genomic map comprising 6193 CNVs that pertain to 737 CNV regions. Then, we identified eight CNVs significantly associated with the risk for UH in the three pig breeds. Six of seven significantly associated CNVs were validated using quantitative real-time PCR. Notably, a rare CNV (CNV14:13030843-13059455) encompassing the NUGGC gene was strongly associated with UH (permutation-corrected P = 0.0015) in Duroc pigs. This CNV occurred exclusively in seven Duroc UH-affected individuals. SNPs surrounding the CNV did not show association signals, indicating that rare CNVs may play an important role in complex pig diseases such as UH. The NUGGC gene has been implicated in human omphalocele and inguinal hernia. Our finding supports that CNVs, including the NUGGC CNV, contribute to the pathogenesis of pig UH.

[Identification of susceptibility gene for pig umbilical hernia in different populations using transmission disequilibrium test].

A genome-wide scan for pig umbilical hernia (UH) was performed in a White Duroc × Erhualian resource population reported by our previously study, which detected two susceptibility microsatellite markers (SWR1928 on SSC7 and SW830 on SSC10) significantly affecting pig UH. Herein, fine mapping studies and identification of susceptibility genes for UH were performed in two different populations. A total of 40 SNPs in 12 positional candidate genes located on the two significant segments were genotyped in the F2/F3 resource population. Quality control of the genotype data and transmission disequilibrium test (TDT) were conducted using Plink v1.07 software. The results showed that g.708G>A in IL16 (interleukin 16) gene and g.10664G>A in CDC73 (cell division cycle 73) gene were significantly associated with pig UH. These two prominent SNPs and another two weakly associated SNPs g.10546A>G and g.10811A>G in CDC73 were also undergone the replication TDT test in the outbred commercial populations. All SNPs in the CDC73 gene were confirmed to be significantly associated with pig UH (P<0.05), including g. 10546A>G and g.10811A>G with extreme significant level (P<0.01). Based on these results, CDC73 should be a susceptibility gene for pig UH according to its biological functions and the molecular pathogenesis of UH.