Embryonic and tissue-specific regulation of myostatin-1 and -2 gene expression in zebrafish

Abstract

Myostatin is a member of the TGF-β superfamily and a potent negative regulator of muscle growth and development in mammals. Its expression is limited primarily to skeletal muscle in mammals, but occurs in many different fish tissues, although quantitative measurements of the embryonic and tissue-specific expression profiles are lacking. A recent phylogenetic analysis of all known myostatin genes identified a novel paralogue in zebrafish, zfMSTN-2, and prompted the reclassification of the entire subfamily to include MSTN-1 and -2 sister clades in the bony fishes. The differential expression profiles of both genes were therefore determined using custom RNA panels generated from pooled (100-150/sampling) embryos at different stages of development and from individual adult tissues. High levels of both transcripts were transiently present at the blastula stage, but were undetectable throughout gastrulation (7 hpf). Levels of zfMSTN-2 peaked during early somitogenesis (11 hpf), returned to basal levels during late somitogenesis and did not begin to rise again until hatching (72 hpf). By contrast, zfMSTN-1 mRNA levels peaked during late somitogenesis (15.5-19 hpf), returned to baseline at 21.5 hpf and eventually rose 25-fold by 72 hpf. In adults, both transcripts were present in a wide variety of tissues, including some not previously known to express myostatin. Expression of zfMSTN-1 was highest in brain, muscle, heart and testes and was 1-3 log orders above that in other tissues. It was also greater than zfMSTN-2 expression in most tissues, nevertheless, levels of both transcripts increased almost 600-fold in spleens of fish subjected to stocking stress. Myostatin expression was also detected in mouse spleens, suggesting that myostatin may influence immune cell development in mammals as well as fish. These studies indicate that zfMSTN-1 and -2 gene expression is differentially regulated in developing fish embryos and in adult tissues. The increased expression of both genes in spleens from stressed fish is further supportive of an immunomodulatory role and may explain increased disease susceptibility associated with stocking stress.

The aging myostatin null phenotype: reduced adiposity, cardiac hypertrophy, enhanced cardiac stress response, and sexual dimorphism

“…Mstn K/K mice (Lin et al 2002), which is consistent with increased negative feedback on pituitary GH, the primary regulator of liver size (Ohlsson et al 2009). Myostatin's role in the spleen is unknown, although it is minimally expressed in the spleens of zebrafish and mice and is significantly upregulated when the former are stressed (Helterline et al 2007). No cellular phenotype was detected in any of these tissues, indicating that the differences were likely due to tissue hypoplasia or atrophy.…”

Characterization of GHRs, IGFs and MSTNs, and analysis of their expression relationships in blunt snout bream, Megalobrama amblycephala

“…While, both transcripts of MSTN a and b were detected as early as post-fertilization of eggs, the level of expression was observed to increase during embryonic development and reached a peak near hatching in barramundi (Lates calcarifer) (De Santis et al, 2012). Although several studies had reported detection of MSTN a transcripts during early development, only in zebrafish (D. rerio) the distinct regulation of the two subtypes had been comparatively analyzed during embryogenesis (Helterline et al, 2007). In this study, both the expression levels of MSTN a and MSTN b were significantly higher than their expression levels before hatching.…”

Molecular characterization of the myosatin gene and the effect of fasting on its expression in Chinese perch (Siniperca chuatsi)

“…Similarly, our results showed that there were remarkably low expressions from 20 to 90 dph (except at 30 dph), it then increased significantly and reached its maximum at 150 dph (P < 0.05). This indicated that the 90 dph stage of Chinese perch development could be a rapid growth stage due to its association with an intense myoblast proliferation and hypertrophy, which mainly contributed to skeletal muscle growth, but also controlled the number of muscle fibers by inhibiting myoblast proliferation in cattle embryos (Helterline et al, 2007) and tilapia, gilthead seabream, and post-hatch larvae of Chilean flounder (Delgado et al, 2008). A recent report indicated that the expression levels in 7-day old larvae of Walking catfish were higher than those in 2-month old juveniles, unchanged from 2-month old juveniles to 6-month old juveniles, and then increased significantly in adult fish of 1-3 years of age (Kanjanaworakul et al, 2015).…”

“…In tilapia, MSTN gene expression was observed in the brain and particularly in the optic lobe (Rodgers et al, 2001). In adult zebrafish, the MSTN gene was expressed highly in all tissues except the eye and gall bladder (Helterline et al, 2007). In the barramundi, it was also observed in various tissues including the skeletal muscles, gills, heart, blood, kidneys, and intestines (De Santis et al, 2008).…”