Abstract
BackgroundRA (retinoic acid) signal pathway has been proved to be required for germ cell meiotic initiation in mammals, aves and amphibians. Stra8 (Stimulated by retinoic acid gene 8) is an important factor in RA signal pathway. However, the role of RA and Stra8 in germ cell meiotic initiation in teleosts is poorly characterized.ResultsIn this study, the full length cDNA of Stra8 was cloned from Southern catfish (Silurus meridionalis), and its spatio-temporal expression profiles were analyzed. The Stra8 cDNA (1606 bp) includes 163 bp 5’-UTR (untranslated region), 456 bp 3’-UTR, and an ORF (open reading frame) of 987 bp, encoding a polypeptide of 328 aa. Phylogenetic analysis revealed its existence in some primitive teleosts, such as Siluriformes and Salmoniformes. Tissue distribution analysis by RT-PCR showed that Stra8 is specifically expressed in gonads. By real-time PCR, in situ hybridization and immunohistochemistry, the highest expression level of Stra8/Stra8 was detected in 50 and 130 dah (day after hatching), the premeiotic stage of germ cells in XX and XY gonads, respectively.ConclusionsOur results suggest that Stra8 might be involved in germ cell meiotic initiation in S. meridionalis as it did in tetrapods.
Highlights
RA signal pathway has been proved to be required for germ cell meiotic initiation in mammals, aves and amphibians
The full length cDNA of Stra8 was successfully isolated by Rapid amplification of cDNA ends (RACE)-PCR
The overall similarity between fish and tetrapods Stra8 is very low, averagely less than 30%
Summary
RA (retinoic acid) signal pathway has been proved to be required for germ cell meiotic initiation in mammals, aves and amphibians. Meiosis is a special type of cell division necessary for sexual reproduction in eukaryotes It generates genetic diversity on which natural selection can act, and helps maintain the immortality of the germ line [1]. A model was proposed in which RA signaling and metabolism regulate whether female and male germ cells initiate meiosis during embryogenesis. Stra which was first identified in a screen for genes induced by RA is expressed in mammalian germ cells before their transition from mitosis to meiosis [13,14,15,16]. Stra is the key factor involved in RA signal pathway in the control of germ cell meiosis
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