Molecular and gene expression analyses of chicken oncomodulin and their association with breast myopathies in broilers.

Oncomodulins (OCMs), also known as non-α-parvalbumins, are small molecules known for their high-affinity binding of Ca ions. They play crucial roles as Ca buffers and participate in signaling pathways within muscle and neuron cells. In chickens, 3 oncomodulin molecules have been identified at the protein level and are named chicken oncomodulin 1 (OCM1), -3 (OCM3), and alpha-parvalbumin (PVALB). OCM4 was newly assigned by genome annotation. A gene cluster containing OCM1, OCM3, and OCM4 is located in chromosome 14, while a single gene of PVALB is on chromosome 1. The Ca signaling pathway may be a potential contributor to the onset of chicken breast myopathies. However, chicken OCMs have not been extensively studied in muscle tissues. In this study, the genetic specifications, tissue-specific and differential expression of OCM1, OCM3, OCM4, and PVALB in the context of chicken breast myopathies were investigated. OCM1 exhibited moderate expression in the liver, intestine, and kidney. OCM3 was highly expressed in thymus and breast muscle. A long noncoding RNA (lncRNA) transcribed from the antisense strand of the OCM3 gene was found to be expressed in liver, lung, heart, intestine, and kidney tissues. OCM4 was barely expressed in thymus, thigh-, and breast muscle. PVALB exhibited high expression across all tissues examined. Results of quantitative PCR (qPCR) indicated that the expression of OCM3 was significantly increased (4.4 ± 0.7 fold; P-value = 0.03) in woody breast (WB) muscle and even greater (8.5 ± 0.6 fold; P-value = 0.004) in WB/white striping (WS) muscles. The expression of PVALB showed no difference in WB muscle, but it was notably higher (4.6 ± 0.7 fold; P-value = 0.054) in WB/WS muscle, although statistical significance was not reached. These findings suggest that increased expression of OCM3 and PVALB may be linked to chicken breast myopathies with regard to disruption of Ca buffering.