Expression Profiles of IGF-I, IGF-II, bFGF and TGF-b2 Growth Factors during Chicken Embryonic Development


Abstract: Skeletal muscle development in avian embryos depends on the activation, proliferation, differentiation, and fusion of embryonic myoblasts. These processes as well as early embryonic development are mainly regulated by major growth factors such as IGF-I, IGF-II, TGF-b and FGFs. In order to determine their differential expression, total RNA was isolated from whole embryos on each of the embryonal days (E) 0 to 6, from the thoracic/abdominal half of the embryo at E 7 and E 8, and from pectoralis muscle tissues at E 9 to E 20. Growth factor cDNAs were synthesized by reverse-transcription polymerase chain reaction (RT-PCR). All growth factor messages except TGF-b2 were first detected as early as the blastula stage. IGF-I mRNA levels gradually declined on E 1 and remained lower through E 10. Levels then dramatically increased on E 11 (~ 3.5-fold) and remained high through E 13. On the other hand, overall the amount of IGF-II mRNA fluctuated from E 0 to E 20. Levels between E 0 and E 5 remained high and then declined (~ 3-fold) through E 16. TGF-b2 mRNA first appeared on E 3 and then levels remained high with slight fluctuations until E 18. bFGF mRNA levels increased (~ 2.5-fold) on E 3 and remained high with slight fluctuations until E 13. Because of the correlation of gene expression with the timing of major myogenic events, we suggest that IGF-I, bFGF and TGF-b2 are major regulators of embryonic skeletal muscle development in chickens.

Keywords: IGF-I, IGF-II, bFGF, TGF-b2, Chicken Embryos

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