Transcripts Play Opposite Roles in Chicken Skeletal Muscle Differentiation.

Tumor protein 63 (TP63) comprises multiple isoforms and plays an important role during embryonic development. It has been shown that knockdown inhibits myogenic differentiation, but which isoform is involved in the underlying myogenic regulation remains uncertain. Here, we found that two transcripts of , namely, α and Δα, are expressed in chicken skeletal muscle. These two transcripts have distinct expression patterns and opposite functions in skeletal muscle development. has higher expression in skeletal muscle than in other tissues, and its expression is gradually upregulated during chicken primary myoblast differentiation. Δ can be expressed in multiple tissues and exhibits stable expression during myoblast differentiation. α overexpression inhibits myoblast proliferation, induces cell cycle arrest, and enhances myoblast differentiation. However, although Δα has no significant effect on cell proliferation, the overexpression of Δα inhibits myoblast differentiation. Using isoform-specific overexpression assays following RNA-sequencing, we identified potential downstream genes of α and Δα in myoblast. Bioinformatics analyses and experimental verification results showed that the differentially expressed genes (DEGs) between the α and control groups were enriched in the cell cycle pathway, whereas the DEGs between the Δα and control groups were enriched in muscle system process, muscle contraction, and myopathy. These findings provide new insights into the function and expression of during skeletal muscle development, and indicate that one gene may play two opposite roles during a single cellular process.