Abstract
Gonadotropin-releasing hormone (GnRH) and the GnRH receptor (GnRHR) play an important role in vertebrate reproduction. Although many GnRHR genes have been identified in a large variety of vertebrate species, the evolutionary history of GnRHR in vertebrates is unclear. To trace the evolutionary origin of GnRHR we examined the conserved synteny of chromosomes harboring GnRHR genes and matched the genes to linkage groups of reconstructed vertebrate ancestor chromosomes. Consistent with the phylogenetic tree, three pairs of GnRHR subtypes were identified in three paralogous linkage groups, indicating that an ancestral pair emerged through local duplication before two rounds of whole genome duplication (2R). The 2R then led to the generation of six subtypes of GnRHR. Some subtypes were lost during vertebrate evolution after the divergence of teleosts and tetrapods. One subtype includes mammalian GnRHR and a coelacanth GnRHR that showed the greatest response to GnRH1 among the three types of GnRH. This study provides new insight into the evolutionary relationship of vertebrate GnRHRs.
Highlights
Families of neuropeptides and receptors have emerged through evolutionary processes such as gene/chromosome duplications
To explore the evolutionary relationship among the vertebrate GnRH receptor (GnRHR) lineage, we examined the location of each GnRHR lineage on reconstructed linkage groups of vertebrate ancestors proposed by Nakatani et al [6]
Based on phylogenetic analysis and the gene location on GACs, we propose that vertebrate GnRHRs originated from two ancestral GnRHR genes designated types 1 and 2 that emerged through a local duplication on the same chromosome before 2R
Summary
Families of neuropeptides and receptors have emerged through evolutionary processes such as gene/chromosome duplications. Tracing the family of genes on reconstructed pre-2R vertebrate ancestral chromosomes (VAC) is a fast and relatively accurate way to explore relationships among members of a family that contains a large number of paralogous genes [14,16]. Because this method provides a WGD scheme for each ancestral linkage group, gene duplication and/or loss during each step of genome duplication can be traced [16]
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