BackgroundA novel sarcomeric myosin heavy chain gene, MYH14, was identified following the completion of the human genome project. MYH14 contains an intronic microRNA, miR-499, which is expressed in a slow/cardiac muscle specific manner along with its host gene; it plays a key role in muscle fiber-type specification in mammals. Interestingly, teleost fish genomes contain multiple MYH14 and miR-499 paralogs. However, the evolutionary history of MYH14 and miR-499 has not been studied in detail. In the present study, we identified MYH14/miR-499 loci on various teleost fish genomes and examined their evolutionary history by sequence and expression analyses.ResultsSynteny and phylogenetic analyses depict the evolutionary history of MYH14/miR-499 loci where teleost specific duplication and several subsequent rounds of species-specific gene loss events took place. Interestingly, miR-499 was not located in the MYH14 introns of certain teleost fish. An MYH14 paralog, lacking miR-499, exhibited an accelerated rate of evolution compared with those containing miR-499, suggesting a putative functional relationship between MYH14 and miR-499. In medaka, Oryzias latipes, miR-499 is present where MYH14 is completely absent in the genome. Furthermore, by using in situ hybridization and small RNA sequencing, miR-499 was expressed in the notochord at the medaka embryonic stage and slow/cardiac muscle at the larval and adult stages. Comparing the flanking sequences of MYH14/miR-499 loci between torafugu Takifugu rubripes, zebrafish Danio rerio, and medaka revealed some highly conserved regions, suggesting that cis-regulatory elements have been functionally conserved in medaka miR-499 despite the loss of its host gene.ConclusionsThis study reveals the evolutionary history of the MYH14/miRNA-499 locus in teleost fish, indicating divergent distribution and expression of MYH14 and miR-499 genes in different teleost fish lineages. We also found that medaka miR-499 was even expressed in the absence of its host gene. To our knowledge, this is the first report that shows the conversion of intronic into non-intronic miRNA during the evolution of a teleost fish lineage.

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BackgroundmicroRNAs (miRNAs) in fish have not been as extensively studied as those in mammals. The fish species Takifugu rubripes is an intensively studied model organism whose genome has been sequenced. The T. rubripes genome is approximately eight times smaller than the human genome, but has a similar repertoire of protein-coding genes. Therefore, it is useful for identifying non-coding genes, including miRNA genes. To identify miRNA expression patterns in different organs of T. rubripes and give fundamental information to aid understanding of miRNA populations in this species, we extracted small RNAs from tissues and performed deep sequencing analysis to profile T. rubripes miRNAs. These data will be of assistance in functional studies of miRNAs in T. rubripes.ResultsAfter analyzing a total of 139 million reads, we found miRNA species in nine tissues (fast and slow muscles, heart, eye, brain, intestine, liver, ovaries, and testes). We identified 1420 known miRNAs, many of which were strongly expressed in certain tissues with expression patterns similar to those described for other animals in previous reports. Most miRNAs were expressed in tissues other than the ovaries or testes. However, some miRNA families were highly abundant in the gonads, but expressed only at low levels in somatic tissue, suggesting specific function in germ cells. The most abundant isomiRs (miRNA variants) of many miRNAs had identical sequences in the 5′ region. However, isomiRs of some miRNAs, including fru-miR-462-5p, varied in the 5′ region in some tissues, suggesting that they may target different mRNA transcripts. Longer small RNAs (26–31 nt), which were abundant in the gonads, may be putative piRNAs because of their length and their origin from repetitive elements. Additionally, our data include possible novel classes of small RNAs.ConclusionsWe elucidated miRNA expression patterns in various organs of T. rubripes. Most miRNA sequences are conserved in vertebrates, indicating that the basic functions of vertebrate miRNAs share a common evolution. Some miRNA species exhibit different distributions of isomiRs between tissues, suggesting that they have a broad range of functions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1622-1) contains supplementary material, which is available to authorized users.

Cervical cancer is one of the leading causes of death in women worldwide, particularly in developing countries. Human papillomavirus has been reported as one of the key etiologic factors in cervical carcinoma. Likewise, epigenetic aberrations have ability to regulate cancer pathogenesis and progression. Recent research suggested that methylation has been detected already at precancerous stages, which methylation markers may have significant value in cervical cancer screening. The retinoic acid receptor beta (RARβ) gene, a potential tumor suppressor gene, is usually expressed in normal epithelial tissue. Methylation of CpG islands in the promoter region of the RARβ gene has been found to be associated with the development of cervical cancer. To investigate whether RARβ methylation is a potential biomarker that predicts the progression of invasive cancer, we reviewed 14 previously published articles related to RARβ methylation. The majority of them demonstrated that the frequency of RARβ promoter methylation was significantly correlated with the severity of cervical epithelium abnormalities. However, methylation of a single gene may not represent the best approach for predicting disease prognosis. Analyzing combinations of aberrant methylation of multiple genes may increase the sensitivity, and thus this approach may serve as a better tool for predicting disease prognosis.