title: Sexual dimorphism of gonadal structure and gene expression in germ cell-deficient loach, a teleost fish.
abstract: Germ cell-deficient fish usually develop as phenotypic males. Thus, the presence of germ cells is generally considered to be essential for female gonadal differentiation or the maintenance of ovarian structure. However, little is known of the role of germ cells in the determination of the sexual fate of gonadal somatic cells. We have established an inducible germ cell deficiency system in the loach (Misgurnus anguillicaudatus, Cypriniformes: Cobitidae), a small freshwater fish, using knockdown of the dead end gene with a morpholino antisense oligonucleotide. Interestingly, loach lacking germ cells could develop as either phenotypic males or females, as characterized morphologically by the presence or absence of bony plates in the pectoral fins, respectively. The phenotypic males and females had testicular and ovarian structures, respectively, but lacked germ cells. Gene expression patterns in these male and female germ cell-deficient gonads were essentially the same as those in gonads of normal fish. Our observations indicate that sexually dimorphic gonads can develop in germ cell-deficient loach. In contrast to the situation in other model fish species, the gonadal somatic cells in phenotypic females autonomously differentiated into ovarian tissues and also played a role in the maintenance of gonadal structure. On the basis of our observations, we propose two possible models to explain the role of germ cells in sex determination in fish.
authors.affiliation: Laboratory of Aquaculture Genetics and Genomics, Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Fujimoto
authors.forename: Toshiya
authors.initials: T
authors.lastname: Nishimura
authors.forename: Rie
authors.initials: R
authors.lastname: Goto-Kazeto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kawakami
authors.forename: Etsuro
authors.initials: E
authors.lastname: Yamaha
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Arai
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000502:physiology; D003531:Cypriniformes / Q000033:anatomy & histology* / Q000235:genetics* / Q000502:physiology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000166:cytology / Q000502:physiology*; D006066:Gonads / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D012727:Sex Characteristics; D012733:Sex Differentiation
chemical_list: D016376:Oligonucleotides, Antisense