Two follistatin-like 1 homologs are differentially expressed in adult tissues and during embryogenesis in grass carp (Ctenopharyngodon idellus)

Follistatin-like 1 (Fstl1) peptides play important roles in inhibiting myoblast proliferation and differentiation. Here, we characterized and examined the expression patterns of fstl1 a and -b in grass carp (Ctenopharyngodon idellus). These genes encode 314 aa and 310 aa peptides, respectively, sharing a sequence identity of 83%. Except for the existence of the follistatin-N-terminal (FOLN) and Kazal-type 2 serine protease inhibitor (Kazal 2) domains, grass carp Fstl1 a and -b do not share amino acid sequence similarity with Fst1 and -b. Both fstl1 a and -b mRNAs were widely expressed in adult tissues. During embryogenesis, grass carp fstl1 a and -b mRNA was detected in the presomitic mesoderm and somites at 12 h post fertilization (hpf). At 24 hpf, fstl1 a mRNA was expressed in the hindbrain, somites, notochord and tailbud, while fstl1b mRNA was only detected in the tailbud. At 36 hpf, fstl1a mRNA was detected in the hindbrain and notochord, and fstl1b was also expressed in the notochord. Furthermore, fstl1 a and -b were downregulated in brain and liver tissue following injection with 10 or 50 mu g hGH, while fstl1 b was significantly up-regulated in muscle tissue after 10 mu g hGH treatment. Both fstl1 a and -b were significantly up-regulated at 2, 4 or 6 days of nutrient restriction, and fstl1 a was still highly expressed in the liver and muscle after 3 days of refeeding, as was fstl1b in the brain and muscle. The expression of these genes returned to near control levels following 6 days of refeeding. Our findings suggest that the two fstls play important but divergent roles in embryonic development and tissue growth regulation in grass carp. (C) 2015 Elsevier Inc. All rights reserved.