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Circular DNA intermediate in the duplication of Nile tilapia vasa genes.

ABSTRACT: vasa is a highly conserved RNA helicase involved in animal germ cell development. Among vertebrate species, it is typically present as a single copy per genome. Here we report the isolation and sequencing of BAC clones for Nile tilapia vasa genes. Contrary to a previous report that Nile tilapia have a single copy of the vasa gene, we find evidence for at least three vasa gene loci. The vasa gene locus was duplicated from the original site and integrated into two distant novel sites. For one of these insertions we find evidence that the duplication was mediated by a circular DNA intermediate. This mechanism of gene duplication may explain the origin of isolated gene duplicates during the evolution of fish genomes. These data provide a foundation for studying the role of multiple vasa genes in the development of tilapia gonads, and will contribute to investigations of the molecular mechanisms of sex determination and evolution in cichlid fishes.

SUBMITTER: Fujimura K

PROVIDER: S-EPMC3245284 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Circular DNA intermediate in the duplication of Nile tilapia vasa genes.

Fujimura Koji K Conte Matthew A MA Kocher Thomas D TD

PloS one 20111222 12

vasa is a highly conserved RNA helicase involved in animal germ cell development. Among vertebrate species, it is typically present as a single copy per genome. Here we report the isolation and sequencing of BAC clones for Nile tilapia vasa genes. Contrary to a previous report that Nile tilapia have a single copy of the vasa gene, we find evidence for at least three vasa gene loci. The vasa gene locus was duplicated from the original site and integrated into two distant novel sites. For one of t ...[more]

PMID: 22216289

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Project description:BACKGROUND: The probable influence of genes and the environment on sex determination in Nile tilapia suggests that it should be regarded as a complex trait. Detection of sex determination genes in tilapia has both scientific and commercial importance. The main objective was to detect genes and microRNAs that were differentially expressed by gender in early embryonic development. RESULTS: Artificial fertilization of Oreochromis niloticus XX females with either sex-reversed ?XX males or genetically-modified YY 'supermales' resulted in all-female and all-male embryos, respectively. RNA of pools of all-female and all-male embryos at 2, 5 and 9 dpf were used as template for a custom Agilent eArray hybridization and next generation sequencing. Fifty-nine genes differentially expressed between genders were identified by a false discovery rate of p?<?0.05. The most overexpressed genes were amh and tspan8 in males, and cr/20?-hsd, gpa33, rtn4ipl and zp3 in females (p?<?1?×?10-9). Validation of gene expression using qPCR in embryos and gonads indicated copy number variation in tspan8, gpa33, cr/20?-hsd and amh. Sequencing of amh identified a male-specific duplication of this gene, denoted amhy, differing from the sequence of amh by a 233 bp deletion on exonVII, hence lacking the capability to encode the protein motif that binds to the transforming growth factor beta receptor (TGF-? domain). amh and amhy segregated in the mapping family in full concordance with SD-linked marker on LG23 signifying the QTL for SD. We discovered 831 microRNAs in tilapia embryos of which nine had sexually dimorphic expression patterns by a false discovery rate of p?<?0.05. An up-regulated microRNA in males, pma-mir-4585, was characterized with all six predicted target genes including cr/20?-hsd, down-regulated in males. CONCLUSIONS: This study reports the first discovery of sexually differentially expressed genes and microRNAs at a very early stage of tilapia embryonic development, i.e. from 2 dpf. Genes with sexually differential expression patterns are enriched for copy number variation. A novel male-specific duplication of amh, denoted amhy, lacking the TGF-? domain was identified and mapped to the QTL region on LG23 for SD, thus indicating its potential role in SD.

Dataset Information

Circular DNA intermediate in the duplication of Nile tilapia vasa genes.

Publications

Circular DNA intermediate in the duplication of Nile tilapia vasa genes.

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