The ontogeny of myostatin, follistatin and activin-B mRNA expression during chicken embryonic development

The developmental pattern of myostatin, follistatin and activin-B genes in chick embryonic development was investigated. Total RNA was isolated from w hole embryos on each of embryonic days (E) 0 to 6, from cranial halves of t he embryo at E 7 to 8, and from pectoralis muscle tissues at E 9 to 20. Myo statin, follistatin and activin-B cDNAs were synthesized by reverse-transcr iption polymerase chain reaction (RT-PCR). Myostatin expression was first d etected in embryos as early as the blastoderm stage (unincubated embryo, st age 1, E 0). Myostatin mRNA concentration declined approximately 5 fold by E 2 and remained lower through E 6. Levels then increased 3 fold on E 7 and plateaued through E 16. Follistatin mRNA was first detected in the blastod erm stage of chick embryos. Overall follistatin mRNA increased 6 fold from E 1 to E 20 of development. Follistatin levels declined an E 1 (similar to 2 fold) and remained low through E 9. Follistatin mRNA reached the highest level prior to hatching. Activin-B mRNA from the whole embryo preparations (E 0 - E 6) varied as the embryo matured. Overall activin-B gene expression from E 11 to E 20 appeared to decline (similar to 3.5 fold). This pattern is opposite of follistatin during the same period which is consistent with the opposing functions of these two proteins. We suggest that follistatin, activin-B and myostatin play an important role in embryogenesis and skeleta l muscle development of the chick embryo. This study represents the first c omprehensive report of myostatin mRNA patterns in chicken embryos.