title: Involvement of the SLIT/ROBO pathway in follicle development in the fetal ovary.
abstract: In humans and domestic mammals, pivotal processes in ovary development, including primordial follicle assembly, occur prenatally. These events are essential for determining fertility in adult life; however, they remain poorly understood at the mechanistic level. In mammals, the SLITs (SLIT1, SLIT2 and SLIT3) and their ROBO (ROBO1, ROBO2, ROBO3/RIG-1 and ROBO4/MAGIC ROBO) receptors regulate neural, leukocyte, vascular smooth muscle cell and endothelial cell migration. In addition, the SLIT/ROBO pathway has functional roles in embryonic development and in the adult ovary by inhibiting cell migration and promoting apoptosis. We therefore characterised follicle formation and investigated the expression and localisation of the ROBO/SLIT pathway in the ovine fetal ovary. Using RT-PCR, we identified SLIT2, SLIT3, ROBO1, ROBO2 and ROBO4 in sheep ovaries harvested across gestation. The real-time quantitative PCR results implied that ROBO2 expression and ROBO4 expression were elevated during the early stages of follicle formation and stayed abundant during primordial follicle maturation (P<0.05). Immunohistochemistry examination demonstrated that ROBO1 was localised to the pre-granulosa cells, while ROBO2, ROBO4 and SLIT2 were expressed in the oocytes of the developing primordial follicle. This indicates that in the fetal ovary, SLIT-ROBO signalling may require an autocrine and paracrine interaction. Furthermore, at the time of increased SLIT-ROBO expression, there was a significant reduction in the number of proliferating oocytes in the developing ovary (P<0.0001). Overall, these results suggest, for the first time, that the SLIT-ROBO pathway is expressed at the time of follicle formation during fetal ovary development.
authors.affiliation: MRC Human Reproductive Sciences Unit Division of Reproductive and Developmental Sciences, The Queen's Medical Research Institute, Centre for Reproductive Biology, The University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, Scotland, UK. r.dickinson@hrsu.mrc.ac.uk
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Dickinson
authors.forename: Lynn
authors.initials: L
authors.lastname: Hryhorskyj
authors.forename: Hannah
authors.initials: H
authors.lastname: Tremewan
authors.forename: Kirsten
authors.initials: K
authors.lastname: Hogg
authors.forename: Axel A
authors.initials: AA
authors.lastname: Thomson
authors.forename: Alan S
authors.initials: AS
authors.lastname: McNeilly
authors.forename: W Colin
authors.initials: WC
authors.lastname: Duncan
mesh_terms: D000818:Animals; D019898:Autocrine Communication; D049109:Cell Proliferation; D005260:Female; D005298:Fertility; D018507:Gene Expression Regulation, Developmental; D005865:Gestational Age; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D006080:Ovarian Follicle / Q000196:embryology / Q000378:metabolism*; D010053:Ovary / Q000196:embryology / Q000378:metabolism*; D019899:Paracrine Communication; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012756:Sheep; D015398:Signal Transduction / Q000235:genetics; D000097905:Roundabout Proteins
chemical_list: D006023:Glycoproteins; D009419:Nerve Tissue Proteins; D011971:Receptors, Immunologic; D000097905:Roundabout Proteins; C120566:slit protein, vertebrate