Cell type- and stage-specific changes in HOXA7 protein expression in human ovarian folliculogenesis: possible role of GDF-9.
Homeobox (HOX) genes are important transcriptional regulators in development and in adult tissues. A major obstacle to the understanding of their roles in humans has been the lack of well-defined anti-human HOX antibodies. We generated a thoroughly characterized polyclonal rabbit antibody against human HOXA7 and used it to study the distribution, role, and regulation of HOXA7 in human ovarian folliculogenesis and in granulosa cell tumors. Immunohistochemically, follicles were strongly HOXA7-positive compared with stroma. Oocytes expressed little HOXA7. Granulosa cells were predominantly negative in primordial follicles, had uniformly HOXA7-positive nuclei in primary follicles, and, as follicles matured, the subcellular localization of HOXA7 changed from nuclear to predominantly cytoplasmic. HOXA7 was mainly cytoplasmic in theca interna, but completely absent in theca externa. Granulosa cell tumors were mainly HOXA7 positive and, like in preovulatory follicles and theca interna, staining was predominantly cytoplasmic. The change in HOXA7 expression from negative primordial to positive primary follicles suggested a relationship with granulosa cell proliferation. To test this hypothesis, SV40 Tag-immortalized human granulosa cells (SVOG) were double stained with anti-HOXA7 antibody and with Ki-67 as proliferation marker. HOXA7 expression was highest in mitotic cells. In addition, growth differentiation factor-9 (GDF-9), known to be secreted by oocytes in primary human follicles, up-regulated HOXA7 protein, and stimulated proliferation of SVOG, while TGF-beta1 inhibited HOXA7 expression and proliferation. This is the first report on the expression of any HOX gene in human ovarian follicles and granulosa cell tumors. It shows that HOXA7 undergoes cell type- and stage-specific changes during ovarian folliculogenesis, likely regulates granulosa cell proliferation, and in subcellular location differs between proliferating and secretory cells. The increase in HOXA7 protein in response to GDF-9 represents the first demonstration of a possible regulatory role of oocytes in ovarian follicular HOX gene expression.
Ota
Takayo
T
Department of Obstetrics and Gynecology, University of British Columbia (UBC), 2H30-4490 Oak St., B.C. Women's Hospital, Vancouver, BC, Canada V6H 3V5.
Choi
Kyung-Bok
KB
Gilks
C Blake
CB
Leung
Peter C K
PC
Auersperg
Nelly
N
D000818:Animals; D015153:Blotting, Western; D055430:Bone Morphogenetic Protein 15; D002454:Cell Differentiation; D049109:Cell Proliferation; D005260:Female; D005498:Follicular Phase / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D005982:Glutathione Transferase / Q000378:metabolism; D006106:Granulosa Cell Tumor / Q000378:metabolism* / Q000473:pathology; D006107:Granulosa Cells / Q000378:metabolism; D055429:Growth Differentiation Factor 9; D018398:Homeodomain Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D006080:Ovarian Follicle / Q000378:metabolism*; D010053:Ovary / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology; D012333:RNA, Messenger; D011817:Rabbits; D011993:Recombinant Fusion Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000378:metabolism / Q000473:pathology; D013347:Subcellular Fractions; D013799:Theca Cells / Q000378:metabolism
C525901:BMP15 protein, human; C525902:Bmp15 protein, mouse; D055430:Bone Morphogenetic Protein 15; C525897:GDF9 protein, human; C525898:Gdf9 protein, mouse; D055429:Growth Differentiation Factor 9; C115962:HOXA7 protein, human; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase