Action of estradiol on the hermaphroditism induced by testicular graft in the female chick embryo

Perspectives on avian stem cells for poultry breeding

Stem cells have prulipotency to differentiate into many types of cell lineages. Recent progress of avian biotechnology enabled us to analyze the developmental fate of the stem cells: embryonic stem cells / primordial germ cells (PGCs). The stem cells were identified in the central area of the area pellucida of the stage X blastoderms. These cells could be applied for production of germline chimeras and organ regeneration. Generation of medical substrate in transgenic chickens has considerable interests in pharmaceuticals. Sex alteration of the offspring should be enormously beneficial to the poultry industry. Fertilization of the sex-reversed sperm could lead to sexual alteration of the offspring. These strategies using stem cells / PGCs should be one of the most powerful tools for future poultry breeding.

Potential application of sperm bearing female-specific chromosome in chickens

This paper reviews studies on sex reversal experiments in chickens, production of sperm bearing a female-specific chromosome, its application for poultry resources and finally a mechanism of sex differentiation of gonads in the chicken.

Changes in mRNA expression of MMP-2 in the Müllerian duct of chicken embryo

Although asymmetric development of the ovary and the oviduct is a unique characteristic in birds, the mechanism of asymmetric development still remains unclear. Recently, degradation of extracellular matrix has been suggested as an important factor related to the regression of the Müllerian duct in mammals. The present study was conducted to examine a possible role of metalloproteinase-2 (MMP-2) in the regression of the right Müllerian duct in the developing chicken embryo. Morphological changes in the Müllerian ducts were studied on day 15 of incubation and mRNA expresseion of MMP-2 was studied on days 12, 15, and 18 of incubation. Morphological observation demonstrated the disappearance of basement membrane in the right Müllerian duct which undergoes the regression. RT-PCR analysis showed that MMP-2 mRNA expression of the right Müllerian duct increased on days 15 and 18 of incubation coincidently with the time of regression. In the right Müllerian duct, regression was prevented by diethylstilbestrol treatment on day 4 of incubation and a coincident decrease in MMP-2 expression was observed when compared to the control group. These results suggest that MMP-2 may be involved in the regression of the right Müllerian duct in the female embryos of the chicken.

Sex reversal and aromatase in chicken

Aromatase inhibitors administered before sexual differentiation of the gonads can induce sex reversal in female chickens. To analyze the process of sex reversal, we have followed for several months the changes induced by Fadrozole, a nonsteroidal aromatase inhibitor, in gonadal aromatase activity and in morphology and structure of the female genital system. Fadrozole was injected into eggs on day four of incubation, and its effects were examined during the embryonic development and for eight months after hatching. In control females, aromatase activity in the right and the left gonad was high in the middle third of embryonic development, and then decreased up to hatching. After hatching, aromatase activity increased in the left ovary, in particular during folliculogenesis, whereas in the right regressing gonad, it continued to decrease to reach testicular levels at one month. In treated females, masculinization of the genital system was characterized by the maintenance of the right gonad and its differentiation into a testis, and by the differentiation of the left gonad into an ovotestis or a testis; however, in all individuals, the left Müllerian duct and the posterior part of the right Müllerian duct were maintained. In testes and ovotestes, aromatase activity was lower than in gonads of control females (except in the right gonad as of one month after hatching) but remained higher than in testes of control and treated males. Moreover, in ovotestes, aromatase activity was higher in parts displaying follicles than in parts devoid of follicles. The main structural changes in the gonads during sex reversal were partial (in ovotestes) or complete (in testes) degeneration of the cortex in the left gonad, and formation of an albuginea and differentiation of testicular cords/tubes in the two gonads. Testicular cords/tubes transdifferentiated from ovarian medullary cords and lacunae whose epithelium thickened and became Sertolian. Transdifferentiation occurred all along embryonic and postnatal development; thus, new testicular cords/tubes were continuously formed while others degenerated. The sex reversed gonads were also characterized by an abundant fibrous interstitial tissue and abnormal medullary condensations of lymphoid-like cells; in the persisting testicular cords/tubes, spermatogenesis was delayed and impaired. Related to aromatase activity, persistence of too high levels of estrogens can explain the presence of oviducts, gonadal abnormalities and infertility in sex reversed females.

An overview of factors influencing sex determination and gonadal development in birds

The morphological development of the embryonic gonads is very similar in birds and mammals, and recent evidence suggests that the genes involved in this process are conserved between these classes of vertebrates. The genetic mechanism by which sex is determined in birds remains to be elucidated, although recent studies have reinforced the contention that steroids may play an important role in the structural development of the testes and ovaries in birds. So far, few genes have been assigned to the avian sex chromosomes, but it is known that the Z and W chromosomes do not share significant homology with the mammalian X and Y chromosomes. The commercial importance of poultry breeding has motivated considerable investment in developing physical and genetic maps of the chicken genome. These efforts, in combination with modern molecular approaches to analyzing gene expression, should help to elucidate the sex-determining mechanism in birds in the near future.

Characterization of mullerian inhibiting substance binding on cervical carcinoma cells demonstrated by immunocytochemistry

Müllerian inhibiting substance (MIS) is a glycoprotein released from Sertoli cells or follicular cells of gonads, responsible for the regression of Müllerian ducts and/or Müllerian-derived tumor cells. Binding of MIS to target cells is essential for initiating regression. A human cervical carcinoma CaSki cell was examined by quantitative immunocytochemistry detected by anti-avian MIS antibody for MIS binding ability. Various treatments of WGA-peroxidase conjugate, enzyme digestion, sodium periodate or exogenous estrogen before antibody recognition were performed. It was found that the WGA partially blocked MIS binding to CaSki cell surfaces. Protease digestion of CaSki cell surfaces prior to addition of MIS or an anticervical carcinoma monoclonal antibody 1H10 (MAb 1H10), blocked the binding of MIS but not MAb 1H10 to cell surfaces. Sodium periodate and overnight exposure of CaSki cells to estrogen or diethylstilbestrol before or after fixation of the cells, did not influence MIS binding ability in vitro. MIS binding was higher on avian Müllerian duct compared with MIS binding to CaSki cells by quantitative immuno-gold labeling analysis. MAb 1H10 immuno-gold complexes binding to CaSki cells was also obtained and compared with MIS immuno-gold bindings. MIS binding site could be a polypeptide which survived sodium periodate treatment. The 'critical window' period, in which developing Müllerian ducts respond to exogenous estrogen protection from MIS regression, is possibly lost in CaSki cell.

Influence of heterospecific testis graft on the gonadal sex differentiation of female bird embryos

Testes from duck and chick embryos grafted, respectively, to chick and duck genetically female host embryos modifies their gonadal differentiation. It results in masculinization developing, in some cases as far as testis formation. This demonstrates 'in vivo' that the testis inductor(s) secreted by the grafted testis is (are) interspecific. Duck gonads are more sensitive than chick gonads. Such grafts also cause the regression of Müllerian ducts. Comparison of the effects on ducts and gonads reinforces the view that both could depend on the same substance, i.e., anti-Müllerian hormone.

Action of estradiol on müllerian duct regression induced by treatment with norethindrone of female chick embryos

Treatment of genetically female chick embryos with norethindrone (NET), a progesterone-like steroid chemically related to testosterone, caused two types of Müllerian duct (MD) deficiencies. The first consisted in an absence of the caudal part of the ducts owing to their partial agenesia occurring between Days 5 and 7 of embryonic life. This is nonspecific since it was observed after a treatment with almost all steroidal sex hormones. In particular, this was obtained with estradiol which also increases the frequency and extent of agenesia caused by the NET, as reported here. The second type of deficiency appeared between Days 12 and 14 and was due to a regression destroying the more or less large part of the MDs having escaped agenesia, i.e., for most of the cephalic half. This resulted from the influence of the anti-Müllerian hormone originating from the ovary and normally inhibited by the ovarian estrogens. This protective action of endogenous estrogens was inhibited by the NET, but an additional treatment with estradiol removed this inhibition and prevented duct regression. Our results suggest that estrogen protects the duct from the regression induced indirectly by NET, by acting both at gonad and MD levels.

Lectin bindings and diethylstilbestrol effects on the recognition of mullerian inhibiting substance (MIS) on chick mullerian ducts by MIS-antiserum

A high intensity of lectin bindings was demonstrated on the epithelial cells and serosa cells of the regressing right Mullerian ducts (Mds) in the female chick embryos. The strong lectin bindings occurs on, or in the regressing Md cells along with marked surface MIS bindings at the age of day 13. However, at the age of days 5-7 1/2, bindings of lectins were weak. Neither Wheat-germ agglutinin (WGA) or Concanavalin A (Con-A) labelings before MIS-antiserum (MIS-Ab) incubation can block antibody recognitions to the antigens, including MIS and growth hormone at the age of day 13. Our previous studies indicated that after WGA labeling on the surfaces of Md epithelial cells prior to the incubation of MIS-Ab at day 10 did not prevent the recognition of MIS-Ab (Wang 1989). On the contrary, at day 7 1/2, the specific binding of MIS was eliminated after preincubations with lectins and prenatal diethylstilbestrol (DES) treatment at the age of day 5. It is suggested that DES provides a protection to the Mds from MIS-induced regression by preventing the MIS binding to its specific membrane receptors. An increase of extra- and intracellular glycoproteins or carbohydrates of regressing Md epithelial cells were suggested. Internalization of WGA but not MIS molecules was found in Md epithelial cells. The Golgi saccules were negative of lectin bindings.

Development of interstitial cells in experimentally sex-reversed gonads of genetically female chick embryos

A testis graft implanted in young genetically female embryos induced a male gonadal differentiation. The interstitial cell percentage and actual content were strongly lowered in masculinized gonads compared to normal female embryos and became similar to those observed in the normal developing embryonic testis. This effect was enhanced by the association of a graft and an antiestrogenic drug, and was not observed after administration of the drug alone. This inhibiting influence of the graft on interstitial cell formation may be considered as resulting in an inhibition of estrogen production. Its possible causative role in gonadal masculinization is discussed in the light of previous and present results.

Steroid modulation of Mullerian duct regression in the chick embryo

The recent demonstrations that Mullerian inhibiting substance (MIS) is present in embryonic chick ovaries (P. K. Hutson, H. Ikawa, and P. K. Donahoe (1981). J. Pediatr. Surg. 16, 822-827), and that exogenous diethylstilbestrol does not significantly inhibit MIS secretion from feminized testes (Hutson et al. (1982) J. Pediatr. Surg. 17, 953-959), suggest that ovarian estrogens protect the female left Mullerian duct from MIS-induced regression. The possibility exists, however, that ovarian MIS may be inactive. This study was designed to see if interference with estrogen action in ovo would allow MIS to cause regression of the female left Mullerian duct. The "antiestrogens," tamoxifen and LY117018, had little effect on the female Mullerian ducts unless given in high doses or with added testosterone (greater than 0.1 mg). Two compounds known to inhibit estrogen synthesis, aminoglutethimide and 4-hydroxyandrostenedione, had no effect on their own, even in high doses (less than 1.0 mg/egg). However, when administered together (0.5 mg each) there was significant disappearance of the lower ends of both Mullerian ducts. Norethindrone, which has been described recently as an aromatase inhibitor (Y. Osawa, C. Yarborough, and V. Osawa (1982). Science (Washington, D. C.) 215, 1249-1251) caused partial regression of the upper end of the left Mullerian duct as well as complete loss of the lower ends of both ducts in the female. These results suggest that the steroid environment is a critical factor in the response of the Mullerian ducts to MIS, and that estrogen blockage may allow endogenous MIS from the ovary to induce partial regression of the Mullerian ducts in the female chick embryo.