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Association studies have indicated profound effects of copy number variations (CNVs) on various phenotypes in different species. In this study, we identified the CNV distributions and expression levels of guanylate-binding protein 6 (GBP6) associated with the growth traits of Chinese cattle. The results showed that the phenotypic values of body size and weight of Xianan (XN) cattle were higher than those of Nanyang (NY) cattle. The medium CNV types were mostly identified in the XN and NY breeds, but their CNV distributions were significantly different (adjusted p < 0.05). The association analysis revealed that the body weight, cannon circumference and chest circumference of XN cattle had significantly different values in different CNV types (p < 0.05), with CNV gain types (Log22−ΔΔCt > 0.5) displaying superior phenotypic values. We also found that transcription levels varied in different tissues (p < 0.001) and the CNV gain types showed the highest relative gene expression levels in the muscle tissue, consistent with the highest phenotypic values of body weight and cannon circumference among the three CNV types. Consequently, our results suggested that CNV gain types of GBP6 could be used as the candidate markers in the cattle-breeding program for growth traits.

The GBP6 gene belongs to the gene family of interferon-gamma inducible GTPases, and is located in a previously characterized QTL region of porcine reproductive and respiratory syndrome virus (PRRSV) resistance in SSC4. In the current study, RT-PCR assay revealed that the GBP6 gene was widely distributed but highly expressed in spleen and lung. Under PRRSV infection, the GBP6 gene was up-regulated and differentially expressed in the pulmonary alveolar macrophages (PAMs) of Large White and Tongcheng pigs. Multiple sequences alignment and phylogenetic analysis revealed that GBP6 is highly conserved across species. We validated and analyzed the polymorphism of a missense mutation (n.932A>G, rs322187731) in the F2 resource population of Duroc × Erhualian, which changed the Valine (V) to Methionine (M) in the 300th residue of porcine GBP6. Through a linear mixed effects model, the polymorphism of the mutation (n.932A>G, rs322187731) was significantly associated with five haematological traits, namely platelet count at 20 days (PLT-20), plateletcrit at 20 days (PCT-20), white blood cell at 33 days (WBC-33), neutrophil count at 33 days (NE-33) and red blood cell count at 80 days (RBC-80). The findings presented here provide basic information for the function and possible involvement of the GBP6 gene in immune regulation and disease resistance. [ABSTRACT FROM AUTHOR]

Association studies have indicated profound effects of copy number variations (CNVs) on various phenotypes in different species. In this study, we identified the CNV distributions and expression levels of guanylate-binding protein 6 ( GBP6 ) associated with the growth traits of Chinese cattle. The results showed that the phenotypic values of body size and weight of Xianan (XN) cattle were higher than those of Nanyang (NY) cattle. The medium CNV types were mostly identified in the XN and NY breeds, but their CNV distributions were significantly different (adjusted p < 0.05). The association analysis revealed that the body weight, cannon circumference and chest circumference of XN cattle had significantly different values in different CNV types ( p < 0.05), with CNV gain types (Log 2 2 -ΔΔCt > 0.5) displaying superior phenotypic values. We also found that transcription levels varied in different tissues ( p < 0.001) and the CNV gain types showed the highest relative gene expression levels in the muscle tissue, consistent with the highest phenotypic values of body weight and cannon circumference among the three CNV types. Consequently, our results suggested that CNV gain types of GBP6 could be used as the candidate markers in the cattle-breeding program for growth traits.