RESUMO
xol-1 is the earliest-acting gene in the known hierarchy that controls C. elegans sex determination and dosage compensation. We show that the primary sex-determining signal (the X/A ratio) directs the choice of sexual fate by regulating xol-1 transcript levels: high xol-1 expression during gastrulation triggers male development, whereas low expression at that time permits hermaphrodite development. Inappropriately high xol-1 expression causes hermaphrodites to activate the male program of development and die from a disruption in dosage compensation. These results demonstrate that xol-1 functions as an early developmental switch to set the choice of sexual fate and suggest that assessment of the X/A ratio occurs only early in embryogenesis to determine sex. Moreover, sdc-2, a gene that must be repressed by xol-1 to ensure male development, may be a direct target of negative regulation by xol-1.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans/genética , Regulação da Expressão Gênica no Desenvolvimento , Genes de Helmintos , Proteínas de Helminto/genética , Análise para Determinação do Sexo , Processamento Alternativo , Sequência de Aminoácidos , Animais , Caenorhabditis elegans/embriologia , Clonagem Molecular , Transtornos do Desenvolvimento Sexual/genética , Mecanismo Genético de Compensação de Dose , Embrião não Mamífero/metabolismo , Gástrula/metabolismo , Proteínas de Helminto/química , Proteínas de Helminto/fisiologia , Masculino , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , RNA de Helmintos/genética , RNA de Helmintos/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Recombinantes de Fusão/biossínteseRESUMO
The Sertoli cell is the epithelial cell within the seminiferous tubule responsible for supporting germ cells. Most current in vitro studies of Sertoli cell function use primary cultures because of the limited number of available Sertoli cell lines. In addition, few in vivo models of Sertoli cell malignancy have been described. In this study, a tumorigenic Sertoli cell line was developed by infection of isolated murine Sertoli cells by simian virus 40 tsA255; the ts mutation causes the inactivation of the large T antigen at elevated temperatures. A cloned Sertoli cell line, called S14-1, demonstrated temperature-dependent growth in soft agar and formed tumors in nude mice. Electron microscopy of the S14-1-derived tumor revealed extensive basal intercellular junctions and tubulobulbarlike processes supporting its Sertoli cell origin. Cytogenetic analysis showed that S14-1 cells were aneuploid with an average of 70 chromosomes per cell. At the nonpermissive (40 C) temperature, S14-1 cells in vitro demonstrated a reduced growth rate, enhanced secretion of transferrin, and increased expression of sulfated glycoprotein-2 messenger RNA, indicating the cells manifested increased differentiation following large T antigen inactivation. The murine S14-1 Sertoli cell line should be useful for both in vitro studies of Sertoli cell function and in vivo studies of Sertoli cell malignancy.
