Molecualr and Developmental Studies on Genetic Control for Sexual Differentiation in Birds

为了阐明控制鸟类性别分化的遗传因素，我们进行了以下几个方面的研究：1)性染色体上性别分化相关基因的研究，2)性类固醇激素和代谢酶基因的表达，3)雌性性腺交替发育的机制。1)在本研究期间，我们在性染色体上寻找基因的结果并不令人满意，因为用小鼠的Sry基因和鸡的W染色体特异性DNA探针进行氢化分析，在鸡和鸡中没有检测到DNA条带。2)研究了P450芳香化酶(P450 aromatase，P450 arom)基因在鸡性腺中的表达及定位。从孵化第10天到孵化后7天，左侧卵巢中P450arom基因的表达水平始终高于右侧卵巢和睾丸。原位杂交分析表明，孵化第6.5天，雌性性腺中首次检测到P450arom。这些结果表明，P450arom mRNA在第6天左右出现在遗传雌性性腺中，可能通过增加雌激素的产生而促进左侧性腺的细胞增殖，从而与雌性向雌性分化有关。3)在性腺分化的研究中，我们采用了鸡的双输卵管系。这条线在其一生中发育并保留右输卵管，而在正常鸡的孵化前右输卵管退化。对该品系的右输卵管按年龄顺序进行观察，发现该品系内右输卵管发育程度的变化。配对交配实验表明，父本(其表型与双输卵管有关的表型不可检测)的遗传效应足够高。我们打算进行双输卵管基因的遗传分析，并研究右性腺发育/退化的机制。

We investigated the following subjects in order to elucidate genetic factors that control sexual differentiation in birds ; 1) research for genes related to sexual differentiation on sex chromosome, 2) gene expression of sex steroid hormones and metabolic enzymes, 3) mechanism of alternative development of female gonads.1) We did not get satisfactory results about searching genes on sex chromosome in this research period, because no DNA bands were detected in chickens and quails by hydridization analysis with probes of the Sry gene in mice and W chromosome specific DNA in chickens, respectively. 2) The onsent and localization of P450 aromatase (P450arom) mRNA expression were studied in the gonad of chickens. Levels of P450arom mRNA in the left ovary were invariably higher than those of the right ovary and testis throughout the period between day 10 incubation and 7 days of posthatching. In situ hybridization analysis showed the first detection of P450arom at day 6.5 of incubation in the female gonad. These results suggest that expression of P450arom mRNA occurring in the genetic female gonad around day 6 is associated with sexual differentiation toward femaleness by increasing estrogen production which may promote cellular proliferation of the left gonad. 3) In the study on gonadal differentiation we used the double-oviduct line of the chicken. This line develops and retains the right oviduct throughout its life while it is degenerated before hatching in normal chickens. We observed the right oviduct of this line in order of age and found the variation of developmental degree of the right oviduct within the line. The pair-mating experiment suggests that genetic effect of sire (whose phenotype concerned with the double-oviduct is not detectable) is sufficiently high. We intend to proceed with the genetical analysis of the double-oviduct gene and examine the mechanism of development/degeneration of the right gonad.