Characterization of MUSTN1 gene and its relationship with skeletal muscle development at postnatal stages in Pekin ducks.

Musculoskeletal embryonic nuclear protein 1 (MUSTN1) gene is involved in myogenic fusion and differentiation in rats. We previously showed the differential expression of MUSTN1 in week (W) 2 and W6 breast muscles of Pekin ducks. In this study, we further investigated its molecular characteristics and expression profiles in different tissues at W7 and in breast and leg muscles at W1, W3, W5, W7, and W9. The relationship between muscle development and muscle fiber areas was also investigated. A 358-bp cDNA sequence was obtained. The coding sequence of duck MUSTN1 cDNA encoded a 78-amino acid sequence, which showed high similarity with those of other species (96% similarity with zebra finch and 94% with chicken). In addition, a 6435-bp genomic DNA sequence of MUSTN1 was obtained. In total, 231 transcription factor-binding sites were found in the promoter region, and many of these transcription factors were involved in the regulation of muscle development. MUSTN1 expression in breast muscle increased from W1 to W5 and then decreased at W9. In leg muscle, the expression increased from W1 to W3 and then decreased. The relative growth rates of breast and leg muscle fibers reached their peaks at W3-W5 and W1-W3, respectively. Since the greatest relative growth rates appeared at the highest expression levels of the MUSTN1 gene, it was thought to play roles in duck muscle development. Our findings would be helpful in understanding the molecular characteristics and functions of the MUSTN1 gene in breast muscle development of ducks.