Myostatin and TGF-beta2 gene expression patterns in response to in ovo administration of rhIGF-I during chicken embryonic development.

The objective of the study was to evaluate the impact of in ovo administration of recombinant human insulin-like growth factor-I (rhIGF-I) on myostatin and transforming growth factor-beta2 (TGF-beta2) gene expression during chicken embryogenesis with emphasis on skeletal muscle development. Eggs were injected once with 100 ng rh IGF-I in 10 mM acetic acid, 0.1% BSA per embryo on day 3 of embryonic development. Total RNA was isolated from whole embryos on each of embryonic days (E) 0 to 6 (n = 6 per day/per treatment), from thoracic/abdominal halves of the embryo at E 7 to 8 (n = 6 per day/per treatment), and from pectoralis muscle tissues at E 9 to 20 (n = 4 per day/per treatment). Reverse-transcription polymerase chain reaction (RT-PCR) was used to synthesize cDNAs. Myostatin mRNA isolated from pectoralis muscles of the rhIGF-I treated group increased on E 10 (approximately 2.5 fold) and remained high through E 13, whereas myostatin mRNA from control pectoralis muscles increased at E 9 and remained high until E 12. TGF-beta2 gene expression from in ovo rhIGF-I treated pectoralis muscles dramatically increased at E 13 (approximately 2.5 fold), in contrast to E 14 from control pectoralis muscle, and gradually declined through E 16. Our results demonstrate that in ovo administration of rhIGF-I on E 3 may alter developmental expression patterns of myostatin and TGF-beta2 genes.