Myostatin-2 gene structure and polymorphism of the promoter and first intron in the marine fish Sparus aurata: evidence for DNA duplications and/or translocations

Elisabeth Nadjar-Boger,Bruria Funkenstein

doi:10.1186/1471-2156-12-22

Elisabeth Nadjar-Boger, Bruria Funkenstein

Open Access

https://doi.org/10.1186/1471-2156-12-22

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Abstract

BackgroundMyostatin (MSTN) is a member of the transforming growth factor-ß superfamily that functions as a negative regulator of skeletal muscle development and growth in mammals. Fish express at least two genes for MSTN: MSTN-1 and MSTN-2. To date, MSTN-2 promoters have been cloned only from salmonids and zebrafish.ResultsHere we described the cloning and sequence analysis of MSTN-2 gene and its 5' flanking region in the marine fish Sparus aurata (saMSTN-2). We demonstrate the existence of three alleles of the promoter and three alleles of the first intron. Sequence comparison of the promoter region in the three alleles revealed that although the sequences of the first 1050 bp upstream of the translation start site are almost identical in the three alleles, a substantial sequence divergence is seen further upstream. Careful sequence analysis of the region upstream of the first 1050 bp in the three alleles identified several elements that appear to be repeated in some or all sequences, at different positions. This suggests that the promoter region of saMSTN-2 has been subjected to various chromosomal rearrangements during the course of evolution, reflecting either insertion or deletion events. Screening of several genomic DNA collections indicated differences in allele frequency, with allele 'b' being the most abundant, followed by allele 'c', whereas allele 'a' is relatively rare. Sequence analysis of saMSTN-2 gene also revealed polymorphism in the first intron, identifying three alleles. The length difference in alleles '1R' and '2R' of the first intron is due to the presence of one or two copies of a repeated block of approximately 150 bp, located at the 5' end of the first intron. The third allele, '4R', has an additional insertion of 323 bp located 116 bp upstream of the 3' end of the first intron. Analysis of several DNA collections showed that the '2R' allele is the most common, followed by the '4R' allele, whereas the '1R' allele is relatively rare. Progeny analysis of a full-sib family showed a Mendelian mode of inheritance of the two genetic loci. No clear association was found between the two genetic markers and growth rate.ConclusionThese results show for the first time a substantial degree of polymorphism in both the promoter and first intron of MSTN-2 gene in a perciform fish species which points to chromosomal rearrangements that took place during evolution.

Highlights

Myostatin (MSTN) is a member of the transforming growth factor-ß superfamily that functions as a negative regulator of skeletal muscle development and growth in mammals
To gain insight into the regulation of MSTN genes in fish, we recently reported the cloning and characterization of MSTN-1 promoter from a commercially very important marine fish species in the Mediterranean region, S. aurata
We describe the genomic organization of the MSTN-2 gene and promoter in S. aurata and the discovery of polymorphism of both the promoter and the first intron, probably as a result of chromosomal re-arrangements

Summary

Introduction

Myostatin (MSTN) is a member of the transforming growth factor-ß superfamily that functions as a negative regulator of skeletal muscle development and growth in mammals. The key role of MSTN in muscle growth and its potential application in animal husbandry encouraged the cloning of MSTN cDNAs and genes from numerous fish species of value to aquaculture [[18] and references therein; [19] and references therein] These studies have shown that in contrast to mammals and chicken, fish possess at least two distinct MSTN genes with differential expression [reviewed in [20]], probably as a result of gene duplication. Subsequent studies identified ‘true’ MSTN-2 genes in the rainbow trout [22] These studies have shown that, in contrast to mammals, fish express MSTN in red and white muscle, and in other tissues, suggesting that MSTN might function in fish in growth and in other physiological processes. In other fish species (coho salmon (Oncorhynchus kisutch) [25], Atlantic salmon (Salmo salar) [26], zebrafish [27] and rainbow trout (Oncorhynchus mykiss) [22]) MSTN-2 is expressed in brain and in other tissues, including muscle

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