Studies on sex-organ development. Ontogeny of cytoplasmic oestrogen receptor in chick Müllerian duct.

Oestradiol receptors were observed in the cytoplasm of the chick Müllerian duct at several embryonic stages. The sedimentation coefficients and the dissociation constants of the receptor protein remained unchanged throughout the various stages of development. Specific binding of cytoplasmic receptor to [3H]oestradiol assayed in vitro was shown to be saturable at concentration of 10nM or higher. The number of oeastradiol-binding sites on a per-cell basis increased linearly from day 8 to day 12 of incubation and then levelled off from day 12 to the fourth day after hatching. These results indicate that in the developing embryonic sex organ, the same receptor protein is present throughout prenatal development. The concentration of the oestradiol receptor increases and reaches a constant value, but the capacity for the receptor to interact with the hormone does not change.     

Study on sex-organ development. Oestrogen-receptor translocation in the developing chick Müllerian duct.

After oestradiol administration in vivo, 87-95% of the initial concentration of oestradiol receptor in the cytoplasm of the embryonic-chick Müllerian-duct cell was translocated into the nucleus. The process of translocation depends on the amount of oestardiol administered in vivo. At 6 h after oestradiol administration in vivo, about 30% replenishment of the initial content of the cytosol receptor was observed in the cytoplasm. The Müllerian-duct nuclei, after exposure to non-radioactive oestradiol, exhibit saturable exchange with [3H]oestradiol in vitro. The exchange of oestradiol is temperature- and time-dependent. The optimal temperature and time for exchange are 37-41 degrees C and 2h respectively. The [3H]oestradiol-receptor complex extracted from the exchanged nuclei is present in 5-6S form, and its isoelectric point is 6.8. The number of nuclear oestradiol-binding sites of the developing Müllerian duct are 1.66, 2.22, 2.63, and 2.50 pmol/mg of DNA respectively for embryos of 10, 12, 15 and 18 days. The dissociation constants of the nuclear oestradiol receptor of the four observed developmental stages range from 3.0 to 3.1 nM.     

Studies on sex-organ development. Changes in chemical composition and oestradiol-binding capacity in chromatin during the differentiation of chick Müllerian ducts

Biochemical and immunochemical techniques were used to probe the changes in composition of the chromatin of differentiating Müllerian ducts. The non-histone protein increases gradually in the left duct and reaches a constant amount at day 15 of incubation, then remains at the same value until after birth. In the regressing right duct, the non-histone protein increases and then decreases. Gel electrophoresis indicated an increased heterogeneity in the composition of the non-histone protein corresponding to Müllerian-duct differentiation. Little variation in quantity and quality of the histone was observed; however, immunochemical assay confirmed the structural change of Müllerian-duct chromatin during development. An antibody against the chromatin of the newborn-chick oviduct was produced in the rabbit. The chromatin of Müllerian ducts from the early embryonic stage showed a small affinity with the antibody; the affinity increased during the late embryonic stages. The affinity was greatly decreased in the regressing right duct. Oestrogen-binding sites were present in the chromatin of the left and right Müllerian ducts during differentiation, with more sites in the left duct than in the right one during the late stages of development. After oestrogen treatment in vivo, the oestrogen-binding sites on the chromatin of both the left and the right ducts were increased, with a greater increase in the left duct than in the right. In the developing left duct the binding sites reach a maximum on day 15 of incubation, and remain constant at that value until birth.     

Studies on sex-organ development. Oestrogenic effect on ornithine decarboxylase activity in the differentiating Müllerian ducts and other organs of the chick embryo.

The activity of ornithine decarboxylase in the differentiating left and right Müllerian ducts was assayed and compared with that in other embryonic organs, i.e. the liver and the brain throughout the stages of development. In general the enzyme activity was high in the early stages and decreased extensively in the late stages of development. Specifically, in the left and righ Müllerian ducts, the enzyme activity was high from day 8 to day 9 of incubation. In the right duct the enzyme activity started to decline on day 9 and then continuously decreased to an almost undetectable value on day 18 of incubation. In the left duct the enzyme activity also decreased slightly from day 9 to day 12; however, it increased from day 13 to day 15 and finally decreased to a constant value from day 18 until hatching. The alteration in enzyme activity in the Müllerian duct as assayed in vitro during development is not due to the effect of the size of the endogenous ornithine pool. When the enzyme activity was subjected to oestrogen stimulation, an increase of 5--10-fold for the left duct and of 5--3-fold for the right duct was observed during the course of development. No such stimulation was observed with the treatment of progesterone. Testosterone consistently caused a 25--30% inhibition of the enzyme activity in the Müllerian duct. Oestrogen slightly stimulated the enzyme activity in the developing liver but inhibited that of the brain. The concentration of the three polyamines measured in the Müllerian duct corresponds to the activity of the enzyme determined.     

Identification of differentially expressed genes involved in the regression and development of the chicken Müllerian duct

Müllerian ducts of male chickens undergo regression around day 12 of incubation, but the underlining mechanisms remain unclear. The purpose of this study was to identify factors that contribute to regression of the Müllerian duct in the chicken. We first employed annealing control primer-based RT-PCR to screen candidate genes differentially expressed in the Müllerian ducts between male and female. Four differentially expressed genes (MSX2, GAL10, VCP and PLCH1) were partially sequenced. The expression of mRNA of the latter genes and MSX1 in the male and female Müllerian ducts were compared at 7.5, 8 and 9 days of incubation using semi-quantitative RT-PCR. The results indicated that both MSX1 and MSX2 mRNA was highly expressed in the male Müllerian duct at day 9 of incubation, whereas, PLCH1 mRNA was lower in the male duct at day 9 of incubation compared to that of the female duct. Although VCP mRNA was expressed in both left and right female Müllerian ducts, no expression was detected in the male duct. Whole mount in situ hybridyzation analysis showed that the expression of MSX1 and MSX2 mRNA were localized specifically in the mesenchymal cells of the male Müllerian duct at day 9 of incubation. In contrast, VCP mRNA expression was observed in both mesenchymal and epithelial cells of the female Müllerian duct but not detected in the male duct. These results suggest that both up-regulation of MSX1 and MSX2 mRNA expression is involved in the regression of the Müllerian duct in male chicken embryo, whereas VCP expression is involved in development of the female duct.     

Müllerian inhibiting substance regulates its receptor/SMAD signaling and causes mesenchymal transition of the coelomic epithelial cells early in Müllerian duct regression

Examination of Müllerian inhibiting substance (MIS) signaling in the rat in vivo and in vitro revealed novel developmental stage- and tissue-specific events that contributed to a window of MIS responsiveness in Müllerian duct regression. The MIS type II receptor (MISRII)-expressing cells are initially present in the coelomic epithelium of both male and female urogenital ridges, and then migrate into the mesenchyme surrounding the male Müllerian duct under the influence of MIS. Expression of the genes encoding MIS type I receptors, Alk2 and Alk3, is also spatiotemporally controlled; Alk2 expression appears earlier and increases predominantly in the coelomic epithelium, whereas Alk3 expression appears later and is restricted to the mesenchyme, suggesting sequential roles in Müllerian duct regression. MIS induces expression of Alk2, Alk3 and Smad8, but downregulates Smad5 in the urogenital ridge. Alk2-specific small interfering RNA (siRNA) blocks both the transition of MISRII expression from the coelomic epithelium to the mesenchyme and Müllerian duct regression in organ culture. Müllerian duct regression can also be inhibited or accelerated by siRNA targeting Smad8 and Smad5, respectively. Thus, the early action of MIS is to initiate an epithelial-to-mesenchymal transition of MISRII-expressing cells and to specify the components of the receptor/SMAD signaling pathway by differentially regulating their expression.     

Contacts between Wolffian and Müllerian cells at the tip of the outgrowing Müllerian duct in rat embryos

The developing Müllerian duct was studied at the light microscopic as well as the electron microscopic level in rat embryos, especially in the section of the terminal bud and its tip, where Wolffian and Müllerian duct are enclosed by a common basal membrane. In this zone desmosomes can be found among Wolffian cells and also among Müllerian cells. In addition, we found cell contacts between Müllerian and Wolffian cells, namely short electron-dense segments on adjacent surfaces or disc-shaped thickenings within opposite plasma membranes, as well as fusions of the plasmalemmata over short distances. Until now, these cell contacts have not been described in rat embryos.     

Biosynthesis and secretion of fibronectin in the cultured mesenchymal cells of the developing chick müllerian duct

We have developed a method to separate and isolate the mesenchymal cells from the epithelial cells in the left Müllerian duct of the developing chick. We then cultured the mesenchymal cells in a serum-free medium. Through an enzyme-linked immunosorbent assay, we detected fibronectin synthesis and release into the medium at stages of Müllerian duct development. Our results demonstrate that the amount of fibronectin secreted by cultured cells gradually decreased in accordance with Müllerian duct differentiation. Similar observations found in the developing embryonic intestine indicate that the highest fibronectin synthesis occurs during early stages of development, when morphogenetic movement and mesenchymal-epithelial interaction are prominent features of embryonic organ differentiation and growth.     

Cellular mechanisms of Müllerian duct formation in the mouse

Regardless of their sex chromosome karyotype, amniotes develop two pairs of genital ducts, the Wolffian and Müllerian ducts. As the Müllerian duct forms, its growing tip is intimately associated with the Wolffian duct as it elongates to the urogenital sinus. Previous studies have shown that the presence of the Wolffian duct is required for the development and maintenance of the Müllerian duct. The Müllerian duct is known to form by invagination of the coelomic epithelium, but the mechanism for its elongation to the urogenital sinus remains to be defined. Using genetic fate mapping, we demonstrate that the Wolffian duct does not contribute cells to the Müllerian duct. Experimental embryological manipulations and molecular studies show that precursor cells at the caudal tip of the Müllerian duct proliferate to deposit a cord of cells along the length of the urogenital ridge. Furthermore, immunohistochemical analysis reveals that the cells of the developing Müllerian duct are mesoepithelial when deposited, and subsequently differentiate into an epithelial tube and eventually the female reproductive tract. Our studies define cellular and molecular mechanisms for Müllerian duct formation.     

Isolation and characterization of an antimicrobial peptide from bovine hemoglobin ��-subunit

In this study, a novel 18-residue linear antimicrobial peptide derived from the central part of the bovine hemoglobin ??-subunit was identified. The peptide was purified by a combination of cationic exchange and reversed-phase high-performance liquid chromatography. The sequence was determined to be VNFKLLSHSLLVTLASHL. The theoretical molecular weight of this peptide was calculated to be 1992.38 Da, which is the same as that determined (1992.401 Da) by matrix-assisted laser desorption ionization mass spectrometry. Sequence analysis showed that there is a high degree of homology in this peptide among hemoglobin ??-subunits of bovine, sheep, deer, porcine, and human. In a radial-diffusion plate assay, this purified peptide exhibited antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans.     

Isolation and characterization of an inter-α-trypsin inhibitor-IgG complex from human serum

Inter-α-trypsin inhibitor is a human serum protease inhibitor of M_r 180 000 which may release physiological derivatives. A complex between IgG and an inter-α-trypsin inhibitor derivative of M_r 30000 has been recently detected in human serum and was found to be inactive against trypsin, in contrast with the known inhibitory activity of the free 30-kDa derivative. The present study deals with detailed characterization of an inter-α-trypsin inhibitor-IgG complex following its purification by affinity chromatography techniques (anti-inter-α-trypsin inhibitor immunoadsorbent and Protein A-Sepharose) in mild conditions. The resulting product reacted simultaneously with anti-IgG and anti-inter-α-trypsin inhibitor antibodies. This complex contained M_r 180 000 inhibitor at least to some extent. It migrated in the β-γ zone in agarose; its molecular weight was estimated to be 1500 000 or more; part of it displayed covalent bonding between inter-α-trypsin inhibitor and IgG; it had a trypsin inhibitor activity. Immunoelectrophoresis allowed one to demonstrate the native complex in serum owing to the use of anti-inter-α-trypsin inhibitor and anti-γ radioactively labelled antibodies. The double immunoreactivity thus evidenced proved to be heterogeneous with respect to its level and location in the native as well as in the purified complex.     

Essential roles of mesenchyme-derived beta-catenin in mouse Müllerian duct morphogenesis

Members of the Wnt family of genes such as Wnt4, Wnt5a, and Wnt7a have been implicated in the formation and morphogenesis of the Müllerian duct into various parts of the female reproductive tract. These WNT ligands elicit their action via either the canonical WNT/beta-catenin or the non-canonical WNT/calcium pathway and could possibly function redundantly in Müllerian duct differentiation. By using the Müllerian duct-specific anti-Müllerian hormone receptor 2 cre (Amhr2-cre) mouse line, we established a conditional knockout model that removed beta-catenin specifically in the mesenchyme of the Müllerian duct. At birth, loss of beta-catenin in the Müllerian duct mesenchyme disrupted the normal coiling of the oviduct in the knockout embryo, resembling the phenotype of the Wnt7a knockout. The overall development of the female reproductive tract was stunted at birth with a decrease in proliferation in the mesenchyme and epithelium. We also discovered that Wnt5a and Wnt7a expression remained normal, excluding the possibility that the phenotypes resulted from a loss of these WNT ligands. We examined the expression of Frizzled (Fzd), the receptors for WNT, and found that Fzd1 is one receptor present in the Müllerian duct mesenchyme and could be the putative receptor for beta-catenin activation in the Müllerian duct. In summary, our findings suggest that mesenchymal beta-catenin is a downstream effector of Wnt7a that mediates the patterning of the oviduct and proper differentiation of the uterus.     

Isolation and characterization of an α-satellite repeated sequence from human chromosome 22

We constructed a library in IL47.1 with DNA isolated from flow-sorted human chromosome 22. Over 50% of the recombinants contained the same highly repetitive sequence. When this sequence was used to probe Southern blots of EcoRI-digested genomic DNA, a ladder of bands with increments of about 170 bp was observed. This sequence comigrates with satellite III in Ag⁺/Cs₂SO₄ gradients and may account for at least part of the 170 bp Hae III ladder seen in isolated satellite III DNA. Partial sequence analysis revealed homology to the 171 bp monomeric repeat unit of -R1-DNA and the X specific -satellite consensus sequence. After low stringency in situ hybridization, silver grains were found over the centromeres of a number of chromosomes. Under high stringency conditions, however, the labeling was concentrated over the centromeric region of chromosome 22. This localization was confirmed using DNA from a panel of human/hamster cell lines which showed that the homologous 2.1 and 2.8 kb EcoR1 restriction fragments were chromosome 22 specific. These clones therefore contain chromosome 22 derived -satellite sequences analogous to other chromosome-specific satellite sequences described previously.     

Müllerian inhibiting substance is present in testes of dogs with persistent müllerian duct syndrome

Breeding studies in a strain of miniature schnauzer dogs with Persistent Müllerian Duct Syndrome (PMDS) indicate this syndrome is inherited as an autosomal recessive trait, as it is in man. Testes of neonatal dogs affected with PMDS and normal male littermates were examined for Müllerian Inhibiting Substance (MIS) production by immunohistochemistry and bioassay. MIS immunoactivity was detected in Sertoli cells of normal and affected pups using an avidin-biotin complex-enhanced method. Rat embryonic Müllerian ducts regressed when cocultured with testis fragments of both normal and affected pups in a graded organ culture bioassay, demonstrating that the MIS produced was bioactive. These findings indicate that Müllerian duct persistence in affected dogs is not due to a mutation in the structural gene for MIS, but rather, by inference, to a failure of response to MIS at the receptor level.