Delta-like protein 1 (DLK1) has been implicated in the muscle
hypertrophy observed in DLK1 transgenic mice, callipyge sheep, and mouse paternal
uniparental disomy 12 and human
paternal uniparental disomy 14 syndromes. The current study was aimed to determine chicken DLK1 (gDLK1)
mRNA expression during primary muscle cell differentiation and during muscle regeneration after
cold injury and to compare gDLK1
mRNA expression during skeletal muscle development in layers and broilers. In chicken primary muscle cell culture, gDLK1
mRNA expression was significantly increased from 12 to 48 h (P < or = 0.05) when the nascent myotubes were actively formed at d 2 to 3.
Myogenin, a late myogenic marker gene,
mRNA expression peaked at 36 to 48 h. Myogenic differentiation 1 (MyoD) and paired box gene 7 (Pax7), early myogenic marker genes,
mRNA expression gradually decreased during myogenic differentiation. During muscle regeneration, the expression of MyoD and Pax7 peaked at d 2 (P < or = 0.05), and
myogenin mRNA expression peaked at d 4 (P < or = 0.05). The induction of gDLK1 gene appeared between d 7 to 10 postinjury (P < or = 0.05) when myotubes were actively formed as also demonstrated in histological sections. The expression of gDLK1 was slowly downregulated to the control levels at d 14 when the damaged muscle appeared nearly healed. These data suggest that gDLK1 may be involved in the late myogenic stages of primary muscle cell differentiation and muscle regeneration. The gDLK1
mRNA in the muscle tissues was very abundant at embryonic ages but decreased after hatching in both broiler and layer chickens. Compared with layers, broiler muscle at embryonic d 13 had a 3-fold greater expression of DLK1 (P < or = 0.01). In addition, the gDLK1
mRNA expression at d 1, 11, and 33 post-hatch was significantly higher in broilers than layers (P < or = 0.05). Therefore, the relatively greater expression of the gDLK1 gene in muscles of broilers compared with layers suggests that gDLK1 may serve as a new selection marker for high muscle growth in chickens. These findings may provide new insight into chicken muscle development and regeneration.