Human BOULE gene rescues meiotic defects in infertile flies Eugene Yujun Xu 1 , Douglas F. Lee 1 , Ansgar Klebes 2 , Paul J. Turek 1 , Tom B. Kornberg 2 and Renee A. Reijo Pera 1, * 1 Department of Obstetrics, Gynecology and Reproductive Sciences, Department of Physiology, Department of Urology, Programs in Human Genetics and Cancer Genetics and 2 Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143-0546, USA Received September 26, 2002; Revised and Accepted November 13, 2002 Defects in human germ cell development are common and yet little is known of genes required for germ cell development in men and women. The pathways that develop germ cells appear to be conserved broadly, at least in outline, in organisms as diverse as flies and humans beginning with allocation of cells to the germ cell lineage, migration of these cells to the fetal gonad, mitotic proliferation and meiosis of the germ cells, and maturation into sperm and eggs. In model organisms, a few thousand genes may be required for germ cell development including meiosis. To date, however, no genes that regulate critical steps of reproduction have been shown to be functionally conserved from flies to humans. This may be due in part to strong selective pressures that are thought to drive reproductive genes to high degrees of divergence. Here, we investigated the micro- and macro-evolution of the BOULE gene, a member of the human DAZ (deleted in azoospermia) gene family, within primates, within mammals and within metazoans. We report that sequence divergence of BOULE is unexpectedly low and that rapid evolution is not detectable. We extend the evolutionary analysis of BOULE to the level of phyla and show that a human BOULE transgene can advance meiosis in infertile boule mutant flies. This is the first demonstration that a human reproductive gene can rescue reproductive defects in a fly. These studies lend strong support to the idea that BOULE may encode a key conserved switch that regulates progression of germ cells through meiosis in men. INTRODUCTION Many genes with direct and specific roles in reproduction are remarkable for their poor conservation even between closely related species. Although rapid evolution of reproductive genes may be relevant to speciation (1,2), the pathways that develop germ cells appear, in contrast, to be conserved broadly at least in outline. From flies to humans, reproductive pathways begin in the early embryo with allocation of cells to the germ cell lineage and migration of these cells to the somatic gonad. The pathways continue with programs of mitotic proliferation, entry and progression through meiosis, and finally culminate with maturation of immature germ cells into fully-differentiated and functional sperm and eggs (3). The molecular mechanisms that coordinate these pathways may also be conserved between distant species and yet no genes that comprise or regulate these critical reproductive processes have been shown to be function- ally conserved from flies to humans. Here we show that one gene that is a candidate for functional conservation is the human BOULE gene, a member of the DAZ gene family (4,5). The DAZ gene family was first identified in a search for Y chromosome genes whose deletion causes infertility. Y chromosome deletions occur in 10–15% of men with spermatogenic defects, and among the genes absent from such chromosomes are members of the deleted in azoospermia (DAZ) family (5). The DAZ genes encode germ cell-specific RNA binding proteins and form a cluster of four genes on the Y chromosome (5–7). In addition, humans have a DAZ-Like (DAZL) gene on chromosome 3 (6,7). More recently, we identified another autosomal DAZ homolog, BOULE. It was identified as a DAZ-binding protein in a two-hybrid screen and its interaction with DAZ has been confirmed by co-immuno- precipitation (F. Moore and R. A. Reijo Pera, unpublished data). Homologs of the DAZ gene family have also been identified throughout metazoans, where they are inevitably expressed only in the germ cell lineage (8–12). Comparative sequence analysis indicated that BOULE represents the ancestral sequence for the DAZ family (4) and our recent iden- tification and analysis of Boule genes from chimpanzee and Old World monkeys is consistent with this suggestion (Fig. 1). *To whom correspondence should be addressed at: Department of Obstetrics, Gynecology and Reproductive Sciences, 513 Parnassus Avenue, Box 0546, University of California at San Francisco, San Francisco, CA 94143-0546, USA. Tel: þ1 4154763178; Fax: þ1 4154763121; Email: reijo@itsa.ucsf.edu Human Molecular Genetics, 2003, Vol. 12, No. 2 169–175 DOI: 10.1093/hmg/ddg017 Human Molecular Genetics, Vol. 12, No. 2 # Oxford University Press 2003; all rights reserved by guest on May 30, 2013 http://hmg.oxfordjournals.org/ Downloaded from