The salmonid myostatin gene family: a novel model for investigating mechanisms that influence duplicate gene fate

Most fishes possess two paralogs for myostatin, a muscle growth inhibitor, while salmonids are presumed to have four: mstn1a, mstn1b, mstn2a and mstn2b, a pseudogene. The mechanisms responsible for preserving these duplicates as well as the depth of mstn2b nonfunctionalization within the family rema...

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Published in:	BMC evolutionary biology Vol. 12; no. 1; p. 202
Main Authors:	Lawson, Casey B, Niino, Takumu, Hermansen, Russell A, Brok-Volchanskaya, Vera, Jackson, Melissa F, Garikipati, Dilip K, Liberles, David A, Rodgers, Buel D
Format:	Journal Article
Language:	English
Published:	England BioMed Central Ltd 08-10-2012 BioMed Central BMC
Subjects:	Amino Acid Sequence Animals Base Sequence Cloning Cloning, Molecular Codon Colleges & universities DNA sequencing Evolution Fish Proteins - classification Fish Proteins - genetics Fishes Gene duplication Gene expression Genes Genes, Duplicate Genetic aspects Genetic engineering Genetic Variation Investigations Methods Models, Genetic Molecular Sequence Data Multigene Family Myostatin Myostatin - classification Myostatin - genetics Nucleotide sequencing Oncorhynchus mykiss - genetics Phylogenetics Phylogeny Protein Isoforms - classification Protein Isoforms - genetics Proteins Salmon Salmonidae Salmonidae - classification Salmonidae - genetics Sequence Analysis, DNA Sequence Homology, Amino Acid Species Specificity Subfunctionalization Trees Trout Trout - genetics United States
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Summary:	Most fishes possess two paralogs for myostatin, a muscle growth inhibitor, while salmonids are presumed to have four: mstn1a, mstn1b, mstn2a and mstn2b, a pseudogene. The mechanisms responsible for preserving these duplicates as well as the depth of mstn2b nonfunctionalization within the family remain unknown. We therefore characterized several genomic clones in order to better define species and gene phylogenies. Gene organization and sequence conservation was particularly evident among paralog groupings and within salmonid subfamilies. All mstn2b sequences included in-frame stop codons, confirming its nonfunctionalization across taxa, although the indels and polymorphisms responsible often differed. For example, the specific indels within the Onchorhynchus tshawytscha and O. nerka genes were remarkably similar and differed equally from other mstn2b orthologs. A phylogenetic analysis weakly established a mstn2b clade including only these species, which coupled with a shared 51 base pair deletion might suggest a history involving hybridization or a shared phylogenetic history. Furthermore, mstn2 introns all lacked conserved splice site motifs, suggesting that the tissue-specific processing of mstn2a transcripts, but not those of mstn2b, is due to alternative cis regulation and is likely a common feature in salmonids. It also suggests that limited transcript processing may have contributed to mstn2b nonfunctionalization. Previous studies revealed divergence within gene promoters while the current studies provide evidence for relaxed or positive selection in some coding sequence lineages. These results together suggest that the salmonid myostatin gene family is a novel resource for investigating mechanisms that regulate duplicate gene fate as paralog specific differences in gene expression, transcript processing and protein structure are all suggestive of active divergence.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1471-2148 1471-2148
DOI:	10.1186/1471-2148-12-202