Origin and evolution of duplicated <i>lhcgr</i> in actinopterygians.

<p><i>Fshr</i>-<i>lhcgr</i> tandem was inherited by actinopterygians and sarcopterygians from a commun osteichthyan ancestor. The <i>fshr</i>-<i>lhcgr</i> tandem was conserved in sarcopterygians including tetrapod [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135184#pone.0135184.ref052" target="_blank">52</a>] and actinistian (coelacanth) lineages. In actinopterygians, a gene duplication event occurred before the emergence of teleosts, leading to two <i>lhcgr</i> genes, one maintained in tandem position with <i>fshr</i>, and named <i>lhcgr1</i>, and the other one named <i>lhcgr2</i>. The tandem <i>fshr</i>- <i>lhcgr1</i> and the <i>lhcgr2</i> were conserved on the same chromosome after the emergence of the holostean (spotted gar) lineage. Teleost whole-genome duplication (3R) potentially generated duplicated <i>fshr</i>, <i>lhcgr1</i> and <i>lhcgr2</i>. Early after the 3R, multiple and selective gene losses led to the conservation of only single genes for <i>fshr</i>, <i>lhcgr1</i> and <i>lhcgr2</i>, and to the separation of the <i>fshr</i>-<i>lhcgr(1)</i> tandem. Additional loss events of <i>lhcgr1</i> or <i>lhcgr2</i> have occurred independently throughout teleost radiation, so that some extant teleosts have conserved only a single <i>lhcgr</i>, <i>lhcgr1</i> or <i>lhcgr2</i>, according to species.