title: Cell-mass structures expressing the aromatase gene Cyp19a1 lead to ovarian cavities in Xenopus laevis.
abstract: The African clawed frog, Xenopus laevis, has a ZZ/ZW-type sex-determination system. We previously reported that a W-linked gene, Dm-W, can determine development as a female. However, the mechanisms of early sex differentiation remain unclear. We used microarrays to screen for genes with sexually dimorphic expression in ZZ and ZW gonads during early sex differentiation in X laevis and found several steroidogenic genes. Importantly, the steroid 17α-hydroxylase gene Cyp17a1 and the aromatase gene Cyp19a1 were highly expressed in ZZ and ZW gonads, respectively, just after sex determination. At this stage, we found that Cyp17a1, Cyp19a1, or both were expressed in the ZZ and ZW gonads in a unique mass-in-line structure, in which several masses of cells, each surrounded by a basement membrane, were aligned along the anteroposterior axis. In fact, during sex differentiation, ovarian cavities formed inside each mass of Cyp17a1- and Cyp19a1-positive cells in the ZW gonads. However, the mass-in-line structure disappeared during testicular development in the ZZ testes. These results suggested that the mass-in-line structure found in both ZZ and ZW gonads just after sex determination might be formed in advance to produce ovarian cavities and then oocytes. Consequently, we propose a view that the default sex may be female in the morphological aspect of gonads in X laevis.
authors: Department of Biosciences (S.M., N.I., K.F., N.T., M.I.), School of Science, Kitasato University, Sagamihara 252-0373, Japan; Research Center for Stem Cell Engineering (Y.I., Y.O.), National Institute of Advanced Industrial Science and Technology, Tsukuba Central 4, Tsukuba 305-8562, Japan; and Department of Biological Function (T.K.), Osaka City University, Sumiyoshi 558-8585, Japan.
authors: Shuuji
authors: S
authors: Mawaribuchi
authors: Nozomi
authors: N
authors: Ikeda
authors: Kazuko
authors: K
authors: Fujitani
authors: Yuzuru
authors: Y
authors: Ito
authors: Yasuko
authors: Y
authors: Onuma
authors: Tohru
authors: T
authors: Komiya
authors: Nobuhiko
authors: N
authors: Takamatsu
authors: Michihiko
authors: M
authors: Ito
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics*; D004625:Embryo, Nonmammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D006066:Gonads / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism; D008297:Male; D046228:Microarray Analysis; D010053:Ovary / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D019849:Sex Determination Processes / Q000235:genetics; D012733:Sex Differentiation / Q000235:genetics*; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics*; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics
chemical_list: D029867:Xenopus Proteins; D001141:Aromatase; C000594130:Cyp19a1 protein, Xenopus; D013254:Steroid 17-alpha-Hydroxylase