Meeting Abstract

94.5  Friday, Jan. 7  Convergent evolution of endometrial prolactin expression in the human and elephant lineage through the independent recruitment of transposable elements EMERA, D.*; CASOLA, C.; LYNCH, V.J.; WILDMAN, D.; AGNEW, D.; WAGNER, G.P; Yale University, New Haven, CT; Indiana University, Bloomington; Yale University, New Haven, CT; Wayne State University, Detriot, Michigan; Michigan State University, East Lansing; Yale University, New Haven, CT deena.emera@yale.edu

Prolactin is one of the strongest induced genes upon decidualization of the human endometrium and is essential for pregnancy in rodents. The promoter for human decidual prolactin (dPRL) is about 5.8kb upstream of the pituitary prolactin promoter and is derived from an LTR retroelement called MER39. We previously found that prolactin is also expressed in pregnant elephant endometrium, but not in pregnant opossum endometrial tissue or in the oviduct of chickens. Since the promoter of human dPRL is derived from MER39, which is only shared among a subset of placental mammals, we sought to understand what the ancestral mechanism of dPRL expression was. In this study we test decidual prolactin expression in a range of placental mammals and investigate the location of transcriptional initiation. We present 5’RACE, transcriptomic, and genomic evidence that dPRL expression is not a shared derived character of all placental mammals, but evolved at least twice within this group. In both primates and elephants, dPRL mRNA is transcribed from alternative promoters, different from the pituitary promoter and different from each other. In each case the alternative promoter is derived from a lineage specific family of transposable elements. We show that in the elephant the alternative promoter is derived from a member of the LINE L1-2_LA retroelement family. To our knowledge this is the first reported case of convergent evolution of a derived expression domain through the independent recruitment of different transposable elements.