Evaluation of MAFbx expression as a marker for congenital splay leg in piglets.

Splay leg is a hereditary syndrome observed in highly varying frequency in newborn piglets. Although the phenotype indicates a muscular weakness, the etiology is still poorly understood. Only recently, the gene expression of muscle atrophy F-box (MAFbx; FBXO32) was proposed as being of diagnostic value for splay leg in piglet. In this study, total RNA from three healthy and three affected male piglets was isolated. Samples were collected from M. gracilis, Mm. adductores, and M. sartorius. Further samples were taken for histological and biochemical analyses. Expression of MAFbx was analysed by real-time RT-PCR and with the GeneChip Porcine Genome Array (Affymetrix). No significant differences (p>0.05) were observed in relative MAFbx expression, either between the three muscles or between splay leg and healthy piglets for each muscle. The expression of further atrophy-related genes was unchanged, indicating that splay leg is not characterized by general muscular atrophy in the affected hind limbs. This is supported by histological and biochemical data that does not demonstrate signs of atrophy in splay leg muscles. We conclude that the diagnostic value of MAFbx expression for congenital splay leg in piglets is doubtful and that the disease is characterized by heterogeneous alterations in skeletal muscle.