Characterization of rainbow trout myostatin-2 genes (rtMSTN-2a and -2b): genomic organization, differential expression, and pseudogenization.
Myostatin is an extremely potent negative regulator of vertebrate skeletal muscle development. A phylogenetic analysis suggests that salmonids should possess four distinct genes, although only MSTN-1 orthologs have been characterized. Described herein are the rainbow trout (rt) MSTN-2a and -2b genes and subsequence analysis of their promoters and their quantitative expression profiles. Both genes are similarly organized, contain several putative myogenic response elements, and are legitimate MSTN-2 orthologs based on Bayesian analyses. However, rtMSTN-2b contains two in-frame stop codons within the first exon and unspliced variants of both transcripts were expressed in a tissue-specific manner. Complete splicing of rtMSTN-2a occurred only in brain, where expression is highest, whereas rtMSTN-2b transcripts were mostly present in unspliced forms. The presence of stop codons in the rtMSTN-2b open reading frame and the expression of mostly unspliced transcripts indicate that this particular homolog is a pseudogene. These results confirm our previous phylogenetic analysis and suggest that all salmonids likely possess four distinct myostatin genes. The tissue-specific expression and differential processing of both rtMSTN-2 transcripts as well the pseudogenization of rtMSTN-2b may reflect compensatory and adaptive responses to tetraploidization and may help limit rtMSTN-2a's influences primarily to neural tissue.
Garikipati
Dilip K
DK
Washington State University, Pullman, Washington 99164-6351, USA.
Gahr
Scott A
SA
Roalson
Eric H
EH
Rodgers
Buel D
BD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D001921:Brain / Q000196:embryology / Q000502:physiology; D005091:Exons / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D023281:Genomics; D008297:Male; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000196:embryology / Q000502:physiology; D055435:Myostatin; D017686:Oncorhynchus mykiss / Q000235:genetics*; D010063:Ovum / Q000502:physiology; D010802:Phylogeny; D011401:Promoter Regions, Genetic / Q000235:genetics; D011544:Pseudogenes / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000235:genetics*
D055435:Myostatin; D016212:Transforming Growth Factor beta