Expression profiles of IGF-I, IGF-II, bFGF and TGF- $beta$2 growth factors during chicken embryonic development

Kanatlı embriyolarındaki çizgili kas gelişimi embriyona! myoblastların aktivasyonu, çoğalması, farklılaşması, ve füzyonuna bağlıdır. IGF-I, IGF-II, TGF-ß ve FGF gibi büyüme faktörleri bu proseslerle birlikte daha erken olan embriyo gelişimini düzenler. Bu büyüme faktörlerinin ayrı ayrı expresyonunu belirlemek için, ilk 6 günde (E O ile E 6 arası) embriyonun tamamından, 7. ve 8. günde (E 7 ve E 8) göğüs ve karın kısmından, 9-20. günlerde ise (E 9 ile E 20 arası) sadece göğüs kaslarından RNA'lar elde edildi. Daha sonra, büyüme faktörlerine ait cDNA'lar, Reverse-Transcription Polymerase Chain Reaction (RT-PCR) tekniği kullanılarak sentez edildi. TGF-ß2 haricindeki bütün büyüme faktörlerinin gen expresyonu en erken blastula aşamasında saptandı. IGF-I mRNA miktarı embriyonun birinci gününden itibaren azaldı ve 10'uncu güne kadar düşük seviyede kaldı. Diğer taraftan, genel IGF-II mRNA miktarı embriyonun 20'nci gününe kadar inişli çıkışli seyretti. Şöyleki, 16'ncı embriyonik güne kadar 1-5'nci günler arasındaki seviyenin yaklaşık olarak 1/3'üne geriledi. TGF-ß2 mRNA ilk olarak embriyonun 3'üncü gününde gözlendi ve miktarı küçük iniş çıkışlarla beraber embriyonun 18'inci gününe kadar yüksek kaldı. bFGF mRNA miktarı ise 3'üncü gününde arttı ve embriyonun 13'üncü gününe kadar küçük iniş çıkışlarla birlikte yüksek seyretti. Bu araştırmada gen expresyonu ile kas gelişimini düzenleyen mekanizmaların zamanlaması arasındaki uyuma paralel olarak, IGF-I, bFGF, TGF-ß2'nin tavukların embriyonik çizgili kas gelişiminde önemli bir düzenleyici olabileceği sonucuna varıldı.

Tavuk embriyolarının gelişim sürecinde, IGF-I, IGF-II, bFGF, ve TGF- $beta$ 2 büyüme faktörlerinin expresyon profili

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-ß 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-ß2 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-ß2 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-ß2 are major regulators of embryonic skeletal muscle development in chickens.

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