title: Widespread presence of human BOULE homologs among animals and conservation of their ancient reproductive function.
abstract: Sex-specific traits that lead to the production of dimorphic gametes, sperm in males and eggs in females, are fundamental for sexual reproduction and accordingly widespread among animals. Yet the sex-biased genes that underlie these sex-specific traits are under strong selective pressure, and as a result of adaptive evolution they often become divergent. Indeed out of hundreds of male or female fertility genes identified in diverse organisms, only a very small number of them are implicated specifically in reproduction in more than one lineage. Few genes have exhibited a sex-biased, reproductive-specific requirement beyond a given phylum, raising the question of whether any sex-specific gametogenesis factors could be conserved and whether gametogenesis might have evolved multiple times. Here we describe a metazoan origin of a conserved human reproductive protein, BOULE, and its prevalence from primitive basal metazoans to chordates. We found that BOULE homologs are present in the genomes of representative species of each of the major lineages of metazoans and exhibit reproductive-specific expression in all species examined, with a preponderance of male-biased expression. Examination of Boule evolution within insect and mammalian lineages revealed little evidence for accelerated evolution, unlike most reproductive genes. Instead, purifying selection was the major force behind Boule evolution. Furthermore, loss of function of mammalian Boule resulted in male-specific infertility and a global arrest of sperm development remarkably similar to the phenotype in an insect boule mutation. This work demonstrates the conservation of a reproductive protein throughout eumetazoa, its predominant testis-biased expression in diverse bilaterian species, and conservation of a male gametogenic requirement in mice. This shows an ancient gametogenesis requirement for Boule among Bilateria and supports a model of a common origin of spermatogenesis.
authors.affiliation: Division of Reproductive Biology Research, Department of Obstetrics and Gynecology, and Center for Genetic Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America.
authors.forename: Chirag
authors.initials: C
authors.lastname: Shah
authors.forename: Michael J W
authors.initials: MJ
authors.lastname: Vangompel
authors.forename: Villian
authors.initials: V
authors.lastname: Naeem
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Chen
authors.forename: Terrance
authors.initials: T
authors.lastname: Lee
authors.forename: Nicholas
authors.initials: N
authors.lastname: Angeloni
authors.forename: Yin
authors.initials: Y
authors.lastname: Wang
authors.forename: Eugene Yujun
authors.initials: EY
authors.lastname: Xu
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D005298:Fertility / Q000235:genetics; D006801:Humans; D007248:Infertility, Male / Q000235:genetics; D008297:Male; D010802:Phylogeny; D016601:RNA-Binding Proteins / Q000235:genetics*; D012098:Reproduction / Q000235:genetics*; D013091:Spermatogenesis / Q000235:genetics
chemical_list: C481351:BOLL protein, human; D016601:RNA-Binding Proteins