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Guilgur LG Ortí G Strobl-Mazzulla PH Fernandino JI Miranda LA Somoza GM 《Journal of molecular evolution》2007,64(6):614-627
Most vertebrates express two gonadotropin releasing hormone (GnRH) variants in brain tissue but there is an increasing number
of fish species for which a third GnRH form has been detected. We characterized the precursors (cDNAs) of all three forms
expressed in the brain of the pejerrey (silverside) fish, Odontesthes bonariensis (Atheriniformes): type I (GnRH-I; 440 bp), type II (GnRH-II; 529 bp), and type III (GnRH-III; 515 bp). The expression of
these GnRHs precursors was also observed in peripheral tissues related to reproduction (gonads), visual and chemical senses
(eye and olfactory epithelium), and osmoregulation (gill), suggesting that in teleost fish and possibly other vertebrates
GnRH mediates directly or indirectly many other functions besides reproduction. We also present a comprehensive phylogenetic
analysis including representatives of all chordate GnRH precursors characterized to date that supports the idea of two main
paralogous GnRH lineages with different function. A “forebrain lineage” separates evolutionarily from the “midbrain lineage”
as a result of an ancient duplication (ca. 600 million years ago). A third, fish-only clade of GnRH genes seems to have originated
before the divergence of fish and tetrapods but retained only in fish. Phylogenetic analyses of GnRH precursors (DNA and protein
sequences) under different optimality criteria converge on this result. Although alternative scenarios could not be statistically
rejected in this study due to the relatively short size of the analyzed molecules, this hypothesis also receives support from
chromosomal studies of synteny around the GnRH genes in vertebrates.
[Reviewing Editor: Dr. Axel Meyer] 相似文献