RESUMO
Amniotes, regardless of genetic sex, develop two sets of genital ducts: the Wolffian and Müllerian ducts. For normal sexual development to occur, one duct must differentiate into its corresponding organs, and the other must regress. In mammals, the Wolffian duct differentiates into the male reproductive tract, mainly the vasa deferentia, epididymides, and seminal vesicles, whereas the Müllerian duct develops into the four components of the female reproductive tract, the oviducts, uterus, cervix, and upper third of the vagina. In males, the fetal Leydig cells produce testosterone, which stimulates the differentiation of the Wolffian duct, whereas the Sertoli cells of the fetal testes express anti-Müllerian hormone, which activates the regression of the Müllerian duct. Anti-Müllerian hormone is a member of the transforming growth factor-beta (TGF-beta) family of secreted signaling molecules and has been shown to signal through the BMP pathway. It binds to its type II receptor, anti-Müllerian hormone receptor 2 (AMHR2), in the Müllerian duct mesenchyme and through an unknown mechanism(s); the mesenchyme induces the regression of the Müllerian duct mesoepithelium. Using tissue-specific gene inactivation with an Amhr2-Cre allele, we have determined that two TGF-beta type I receptors (Acvr1 and Bmpr1a) and all three BMP receptor-Smads (Smad1, Smad5, and Smad8) function redundantly in transducing the anti-Müllerian hormone signal required for Müllerian duct regression. Loss of these genes in the Müllerian duct mesenchyme results in male infertility due to retention of Müllerian duct derivatives in an otherwise virilized male.
Assuntos
Receptores de Ativinas Tipo I/metabolismo , Receptores de Proteínas Morfogenéticas Ósseas Tipo I/metabolismo , Ductos Paramesonéfricos/embriologia , Ductos Paramesonéfricos/metabolismo , Proteína Smad1/metabolismo , Proteína Smad5/metabolismo , Proteína Smad8/metabolismo , Receptores de Ativinas Tipo I/deficiência , Receptores de Ativinas Tipo I/genética , Animais , Hormônio Antimülleriano/farmacologia , Receptores de Proteínas Morfogenéticas Ósseas Tipo I/deficiência , Receptores de Proteínas Morfogenéticas Ósseas Tipo I/genética , Feminino , Infertilidade Masculina/embriologia , Infertilidade Masculina/genética , Infertilidade Masculina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Mutantes , Modelos Biológicos , Ductos Paramesonéfricos/efeitos dos fármacos , Gravidez , Transdução de Sinais , Proteína Smad1/genética , Proteína Smad5/genética , Proteína Smad8/genéticaRESUMO
Recent experimental work on the mechanism of action of glycosylasparaginase suggests that the enzyme specifically reacts toward the L-asparagine or L-aspartic acid moiety of its substrates. Based on this, a new sensitive assay for glycosylasparaginase activity has been developed using L-aspartic acid beta-(7-amido-4-methylcoumarin) as substrate. Release of 7-amino-4-methylcoumarin was determined fluorometrically. At pH 7.5, Km = 93 microM, and as little as 1 ng of glycosylasparaginase could be detected with the assay. Hydrolysis of the substrate was inhibited by diazo-oxonorvaline, a specific inhibitor of glycosylasparaginase. In biological samples, the fluorometric assay is 40-100 times more sensitive than other published methods for glycosylasparaginase. This new assay enables a rapid enzymatic diagnosis of aspartylglycosaminuria--a genetic deficiency of glycosylasparaginase activity--with leukocyte and fibroblast samples.
