Developmental expression of a candidate müllerian inhibiting substance type II receptor

We have isolated a candidate Müllerian inhibiting substance (MIS) type II receptor complementary DNA from an embryonic rat urogenital ridge library and have studied its binding to MIS, its developmental pattern of expression and tissue distribution. By in situ hybridization with a full-length riboprobe, the receptor is expressed in the mesenchymal cells surrounding the Müllerian duct at embryonic days 14, 15, and 16 and in tubular and follicular structures of the rat fetal gonads. Expression of the messenger RNA was also seen in the granules cells and seminiferous tubules of pubertal gonads. Northern analysis revealed that the MIS type II receptor messenger RNA is highly expressed in embryonic, pubertal, and adult testes and ovaries, as well as in the gravid uterus. The timing of expression in the gonads of both sexes was also analyzed by Northern analyses that showed high levels of expression at the time of Müllerian duct regression, much lower levels neonatally and prepubertally and then increased expression again with sexual maturation. The tissue and developmental specificity of expression of this receptor, which make it likely that this is the functional MIS type II receptor, can be used to advantage in therapeutic targeting strategies and to decipher the function of MIS in the gonads.

An SRY mutation causing human sex reversal resolves a general mechanism of structure-specific DNA recognition: application to the four-way DNA junction

SRY, a genetic "master switch" for male development in mammals, exhibits two biochemical activities: sequence-specific recognition of duplex DNA and sequence-independent binding to the sharp angles of four-way DNA junctions. Here, we distinguish between these activities by analysis of a mutant SRY associated with human sex reversal (46, XY female with pure gonadal dysgenesis). The substitution (168T in human SRY) alters a nonpolar side chain in the minor-groove DNA recognition alpha-helix of the HMG box [Haqq, C.M., King, C.-Y., Ukiyama, E., Haqq, T.N., Falsalfi, S., Donahoe, P.K., & Weiss, M.A. (1994) Science 266, 1494-1500]. The native (but not mutant) side chain inserts between specific base pairs in duplex DNA, interrupting base stacking at a site of induced DNA bending. Isotope-aided 1H-NMR spectroscopy demonstrates that analogous side-chain insertion occurs on binding of SRY to a four-way junction, establishing a shared mechanism of sequence- and structure-specific DNA binding. Although the mutant DNA-binding domain exhibits > 50-fold reduction in sequence-specific DNA recognition, near wild-type affinity for four-way junctions is retained. Our results (i) identify a shared SRY-DNA contact at a site of either induced or intrinsic DNA bending, (ii) demonstrate that this contact is not required to bind an intrinsically bent DNA target, and (iii) rationalize patterns of sequence conservation or diversity among HMG boxes. Clinical association of the I68T mutation with human sex reversal supports the hypothesis that specific DNA recognition by SRY is required for male sex determination.

Prenatal hormonal therapy improves pulmonary compliance in the nitrofen-induced CDH rat model

Neonates with congenital diaphragmatic hernia (CDH) experience a high mortality despite intensive medical and surgical management. The associated pulmonary hypoplasia is accompanied by an underlying biochemical deficiency that bears similarity to respiratory distress syndrome (RDS) in the premature newborn. Using therapies extrapolated from those used to treat RDS, the authors have previously shown correction of the immature pulmonary biochemical indices in the nitrofen rat CDH model. This study investigates the functional and histological outcome of prenatal hormone therapy on CDH rats. Compared with saline-treated CDH controls, dexamethasone-treated CDH animals achieved significant increases in lung distensibility (P = .0006) and functional residual capacity (P = .004); CDH rats treated with combined dexamethasone and thyrotropin-releasing hormone (TRH) showed improved functional residual capacity (P = .043) and alveolar stability (P = .025); CDH animals treated with TRH alone (TRH-CDH) showed no improvement in any parameter tested. Histologically, the lungs from dexamethasone- and dexamethasone-TRH-treated CDH animals showed changes that included narrow septal walls, increased air saccule size, and thinning of the pulmonary interstitium compared with the lungs of saline or TRH-CDH rats, which were developmentally arrested at the canalicular stage. Lung weights and lung weight-body weights ratios were similar in all CDH rats, confirming that treatment did not impair pulmonary growth. These results support the potential clinical use of prenatal pharmacological therapies to treat human fetuses with prenatally diagnosed CDH.

Cleavage of Müllerian inhibiting substance activates antiproliferative effects in vivo

Müllerian inhibiting substance (MIS), an inhibitor of growth and development of the female reproductive ducts in male fetuses, requires precise proteolytic cleavage to yield its biologically active species. Human plasmin is now used to cleave and, thereby, activate immunoaffinity-purified recombinant human MIS at its monobasic arginine-serine site at residues 427-428. To avoid the need for exogenous enzymatic cleavage and to simplify purification, we created an arginine-arginine dibasic cleavage site (MIS RR) using site-directed mutagenesis to change the serine at position 428 (AGC) to an arginine (cGC). The mutant cDNA was then stably transfected into a MIS-responsive ocular melanoma cell line, OM431, followed by cloning for amplified expression to test its biological activity in vitro and in vivo. Media from each clone were assayed for production of MIS RR by a sensitive ELISA for holo-MIS, and high- and low-producing clones were selected for further study. Media from the highest MIS RR producer caused Müllerian duct regression in an organ culture bioassay. Other transfections were done with an empty vector (pcDNAI Neo) or a construct lacking the leader sequence and thus failing to secrete MIS, to serve as controls. The OM431 clones containing the MIS RR mutant were growth inhibited in monolayer culture. The high- and low-producing MIS RR OM431 clones, along with transfected OM431 controls, were injected into the tail veins of immunosuppressed severe combined immunodeficiency mice for in vivo analyses. Four to 6 weeks later, pulmonary metastases were counted in uniformly inflated lungs. OM431 clones containing the more easily cleaved MIS RR displayed a significant dose-dependent reduction in pulmonary metastases when compared to the lungs of animals given injections of OM431 clones containing empty vector, leaderless MIS, or wild-type MIS that requires activation by plasmin cleavage. Since the purification protocol of MIS RR is less complicated than that for wild-type MIS, which requires subsequent enzymatic activation, MIS RR can be used for scale-up production with increased yields for further therapeutic trials against MIS-sensitive tumors.

Update on the analysis of the need for pediatric surgeons in the United States

Accurate estimations of pediatric surgical manpower needs are necessary if this specialty is to avoid the consequences of under- or oversupply, and reasonable decisions must be made relative to the number of training programs needed.

METHODS

Fifteen, 10, and 5 years ago, pediatric surgeons (PSs) in 62 standard metropolitan statistical areas (SMSAs) having a population of at least 200,000 were asked to estimate the number of PSs needed in their localities. A computer program analogous to the SOSSUS program was designed to project the number of PSs that would result from various numbers of trainee graduates per year. The program has been updated for comparison. Known input data included the present number and age of PSs, age range of trainees, current US population projections to the year 2025, and the average retirement age.

RESULTS

These PSs estimated that 88 additional PSs are needed in the next 10 years. Currently, 26 programs in the United States graduate an average of 24 trainees per year, and six programs in Canada graduate six trainees per year. The previous projection indicated that 20 trainees per year would result in 525 PSs in 1993, and the actual number is 559; so the figures indicate that 27 or 28 PSs are entering practice each year. The apparent increase in numbers is related to entry of Canadian trainees primarily, and a few others, into practice. The current computer projection indicates that 20 graduate trainees per year would result in an absolute increase of 0.55% per year, and 25 per year would result in an increase of 1.43% per year, to 2020, while the increases in the US population would be 1.02% per year for all ages and 0.52% for 0 to 15 year olds. If all programs currently being considered for approval are certified, as many as 36 trainees per year--or 7 times the rate of the 0-15-year population increase--will result.

CONCLUSION

Although an average of 20 graduates per year entering practice would keep pace with the pediatric population, 25 to 27 graduates per year--or 3.5 to 4 times the rate of the 0- to 15-year population increase--can be accommodated now into the current system of delivery of pediatric surgical care on the basis of estimated need. Many more graduates than this would create an excess of surgeons before long.

Embryonic cell death patterns associated with nitrofen-induced congenital diaphragmatic hernia

The offspring of pregnant Sprague-Dawley rats exposed to nitrofen on gestational day 9.5 develop left-sided congenital diaphragmatic hernia (CDH). Twenty-four hours after treatment, on day 10.5, supravital staining with Nile blue sulfate and histological examination showed bilateral excessive cell death in cervical somites 2 through 4. After 48 hours, on day 11.5, cell death was absent in the cervical somites but was apparent in the mesoderm adjacent to the somites in the septum transversum and in the developing sympathetic ganglia adjacent to the dorsal aortae. Cell death was not apparent in the foregut or lung primordia on either day 10.5 or 11.5. The incidence of nitrofen-exposed embryos with such patterns of cell death closely paralleled that of left-sided CDH in similarly treated day 21.5 fetuses. Control animals treated with olive oil had normal programmed cell death patterns in the regions of interest and had no evidence of CDH on day 21.5. It is possible that these patterns of excessive cell death early in gestation may play a role in the genesis of diaphragmatic hernia. Mesoderm derived from cervical somites 3 through 5 contributes to the diaphragmatic anlage and forms the major portion of the muscle of the diaphragm. Because nitrofen damages mesodermal cell populations in cervical somites 2 through 4 and in the mesenchyme adjacent to the septum transversum 24 to 48 hours after administration, the authors propose that damage to these populations may reduce progenitor cells needed to populate the diaphragmatic anlage, thereby hindering pleuro-peritoneal canal closure.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambiguous genitalia--etiology, diagnosis, and therapy

Patients with ambiguous genitalia stand a far better chance of receiving a rapid diagnosis, appropriate replacement therapy, and functional surgical reconstruction than was the case even a decade ago. Although the etiologies of true hermaphroditism and mixed gonadal dysgenesis remain elusive, most gene defects in female pseudohermaphroditism or CAH have been pinpointed to the 21-hydroxylase gene. Incomplete masculinization has been found to be due to defects in the androgen receptor, 5 alpha-reductase, or enzymes in the pathway from cholesterol to testosterone. SRY point mutations have been implicated in 46XY pure gonadal dysgenesis. Retained müllerian ducts have been attributed to point mutations in the MIS gene; those with normal MIS levels should be expected to have receptor deficits. In utero diagnoses and treatment and diagnosis at the preimplantation stage may prove to be very important for the care of some of these patients, who may be potential candidates for gene replacement therapy. When necessary, surgical reconstruction can be done. If the child is to be raised as a female, clitoral recession, labioscrotal reductions and advancements, and vaginoplasties for exteriorization can be accomplished in early infancy as an extensive one-stage procedure. If patients are to be raised as males, then various types of hypospadias repair can be done, gonads can be replaced with prostheses, the prepenile scrotum can be reconstructed, and müllerian structures can be removed with the goal of preserving the vas deferens. Replacement therapy with glucocorticoids and mineralocorticoids must be precisely managed to permit proper growth, and testosterone, estrogen, and progesterone replacement must be carefully considered and managed. A most important element in the care of these patients is the psychological support that first the families and then the patient require. This must be delivered with sensitivity. The proper care of these complex patients requires that the physician be a scientist as well as a clinician and a skilled technician.

Molecular basis of mammalian sexual determination: activation of Müllerian inhibiting substance gene expression by SRY

The pathway of male sexual development in mammals is initiated by SRY, a gene on the short arm of the Y chromosome. Its expression in the differentiating gonadal ridge directs testicular morphogenesis, characterized by elaboration of Müllerian inhibiting substance (MIS) and testosterone. SRY and MIS each belong to conserved gene families that function in the control of growth and differentiation. Structural and biochemical studies of the DNA binding domain of SRY (the HMG box) revealed a protein-DNA interaction consisting of partial side chain intercalation into a widened minor groove. Functional studies of SRY in a cell line from embryonic gonadal ridge demonstrated activation of a gene-regulatory pathway leading to expression of MIS. SRY molecules containing mutations associated with human sex reversal have altered structural interactions with DNA and failed to induce transcription of MIS.

Mullerian-inhibiting substance secretion is delayed in XX sex-reversed dog embryos

Sertoli cell secretion of Mullerian-inhibiting substance (MIS) begins shortly after testis differentiation. Mullerian ducts regress following MIS exposure during an embryonic critical period. In dogs with XX sex reversal, Mullerian ducts persist in the presence of testicular tissue. This study was conducted to determine whether MIS is present in ovotestes of XX sex-reversed embryos during the period for Mullerian duct regression in normal males. XX sex-reversed embryos and normal littermates were identified by a combination of karyotype and gonadal histology. The degree of regression in the adjacent Mullerian duct was scored. Immunohistochemical staining was used to detect MIS in the contralateral gonad. Testicular differentiation and MIS secretion were identified in XY embryos at all ages studied (35-46 days). Seminiferous tubules were not observed in gonads of embryos at risk of XX sex reversal between 35-38 days (n = 15), but were observed at 40 and 46 days (n = 3). Although positive staining for MIS was observed in ovotestes, adjacent Mullerian ducts persisted. The degree of seminiferous tubule development was reduced and MIS secretion was delayed in ovotestes, compared to normal testes. Mullerian duct persistence in this model is apparently due to an abnormality in the quantity and timing of MIS secretion during embryonic development.

Modulation by sphingolipids of calcium signals evoked by epidermal growth factor

Receptor-activated breakdown of complex sphingolipids has been proposed as a mechanism for generating sphingoid base-containing putative second messenger molecules whose actions may modulate responses to extracellular signals. In human epidermoid carcinoma A431 cells, sphingosine (1-10 microM) by itself had no effect on intracellular free calcium concentrations ([Ca2+]i), yet within seconds, markedly enhanced the epidermal growth factor (EGF)-evoked Ca2+ influx (by up to 2-fold), but failed to alter Ca2+ release from the intracellular stores. Ca2+ signals evoked by serum were not affected by sphingosine. The response to sphingosine was dose-dependent and saturable, exhibiting an EC50 of 2.3 microM. In contrast, a ceramide, N-acetylsphingosine (10 microM), sphingosine 1-phosphate (10 microM), and sphingosylphosphorylcholine (10 microM) inhibited EGF-evoked elevations in [Ca2+]i. The latter two compounds by themselves transiently increased [Ca2+]i. N-Octanoylsphingosine, N,N-dimethylsphingosine, sphingomyelin, and stearylamine were inactive. The potentiation of calcium signals by sphingosine occurred at all concentrations of EGF tested (0.15-15 nM) and did not alter the EGF receptor protein kinase activity as determined by antiphosphotyrosine immunoblotting. Antiphosphoserine immunoblotting revealed that sphingosine (10 microM for 3 min) increased the phosphoserine content of two proteins with approximate molecular masses of 40 and 70 kDa. Serine hyperphosphorylation of the 40-kDa protein was also observed in cells treated with EGF alone, whereas the intensity of the 70-kDa band was highest in cells treated with both sphingosine and EGF. The modulation of growth factor receptor-regulated signaling, including changes in [Ca2+]i, may constitute a mechanism by which elevations in cellular levels of specific sphingolipids, which occur transiently upon activation of certain receptors and chronically in sphingolipid storage diseases, exert their physiological and pathophysiological effects.

Accurate method to study static volume-pressure relationships in small fetal and neonatal animals

We designed an accurate method to study respiratory static volume-pressure relationships in small fetal and neonatal animals on the basis of Archimedes' principle. Our method eliminates the error caused by the compressibility of air (Boyle's law) and is sensitive to a volume change of as little as 1 microliters. Fetal and neonatal rats during the period of rapid lung development from day 19.5 of gestation (term = day 22) to day 3.5 postnatum were studied. The absolute lung volume at a transrespiratory pressure of 30-40 cmH2O increased 28-fold from 0.036 +/- 0.006 (SE) to 0.994 +/- 0.042 ml, the volume per gram of lung increased 14-fold from 0.39 +/- 0.07 to 5.59 +/- 0.66 ml/g, compliance increased 12-fold from 2.3 +/- 0.4 to 27.3 +/- 2.7 microliters/cmH2O, and specific compliance increased 6-fold from 24.9 +/- 4.5 to 152.3 +/- 22.8 microliters.cmH2O-1.g lung-1. This technique, which allowed us to compare changes during late gestation and the early neonatal period in small rodents, can be used to monitor and evaluate pulmonary functional changes after in utero pharmacological therapies in experimentally induced abnormalities such as pulmonary hypoplasia, surfactant deficiency, and congenital diaphragmatic hernia.

Specific interaction of type I receptors of the TGF-beta family with the immunophilin FKBP-12

Transforming growth factor-beta (TGF-beta) family members bind to receptors that consist of heteromeric serine-threonine kinase subunits (type I and type II). In a yeast genetic screen, the immunophilin FKBP-12, a target of the macrolides FK506 and rapamycin, interacted with the type I receptor for TGF-beta and with other type I receptors. Deletion, point mutation, and co-immunoprecipitation studies further demonstrated the specificity of the interaction. Excess FK506 competed with type I receptors for binding to FKBP-12, which suggests that these receptors share or overlap the macrolide binding site on FKBP-12, and therefore they may represent its natural ligand. The specific interaction between the type I receptors and FKBP-12 suggests that FKBP-12 may play a role in type I receptor-mediated signaling.

Müllerian inhibiting substance gene expression in the cycling rat ovary correlates with recruited or graafian follicle selection

Throughout the estrous cycle, Müllerian inhibiting substance (MIS) mRNA signals, as detected by in situ hybridization, were found to be intense in granulosa cells of growing preantral and small antral follicles, especially in the layer closest to the oocyte. Neither primordial follicles, typical atretic follicles, nor CL expressed detectable signals. MIS mRNA signals seen in the cumulus cells of preovulatory follicles at 1000 and 1600 h of proestrus sharply declined at 2400 h, just before ovulation. MIS mRNA signals were intense and uniform in all newly recruited growing antral and Graafian follicles (> 350 microns) at 1000 h of estrus but became heterogeneous in their expression of MIS on metestrus and diestrus and notably absent in atretic follicles; these findings suggest that MIS expression is correlated with recruited follicle selection and suppression with selection for atresia. The fact that all the MIS-positive growing follicles contain oocytes arrested in meiosis, coupled with previous experimental evidence that MIS inhibits germinal vesicle breakdown, suggests that MIS also might act as a regulator of oocyte maturation.

A single heteromeric receptor complex is sufficient to mediate biological effects of transforming growth factor-beta ligands

Transforming growth factor beta (TGF-beta), a multifunctional cytokine that regulates a variety of biological functions, signals through a heteromeric receptor complex of the type I and type II TGF-beta receptors. The type II receptor, a transmembrane serine-threonine kinase, was cloned based on its ability to directly bind TGF-beta. Recently, a number of candidate type I TGF-beta receptors have been isolated. Although only one of these transmembrane kinases (R4) has been shown to mediate TGF-beta-dependent gene activation, others bind TGF-beta when overexpressed in COS cells. Consequently, it has been postulated that the diversity of TGF-beta responses is generated through the association of distinct type I receptors with the type II TGF-beta receptor, thus creating receptor complexes of differential signaling capacities. In contrast to this model, we demonstrate that stable expression of only the R4 type I TGF-beta receptor in a mutant cell line lacking endogenous type I TGF-beta receptor was able to complex with the endogenous type II TGF-beta receptor and restore the effects of TGF-beta on inhibition of cell proliferation and activation of specific genes, regardless of which of the three mammalian isoforms of TGF-beta was used as the ligand. Therefore, R4 acts as a fully functional type I TGF-beta receptor, and the differential effects of TGF-beta are likely mediated by a single receptor complex consisting of R4 and the type II receptor.

Antenatal glucocorticoid corrects pulmonary immaturity in experimentally induced congenital diaphragmatic hernia in rats

Congenital diaphragmatic hernia, a highly lethal condition, displays at term the pulmonary biochemical and morphologic immaturity characteristic of premature delivery. We hypothesized that antenatal glucocorticoid, now the standard treatment to prevent hyaline membrane disease in premature human beings, might correct the parameters of the pulmonary biochemical and morphologic immaturity in severe congenital diaphragmatic hernia. A total of 112 fetal rats with or without nitrofen-induced congenital diaphragmatic hernias from 34 pregnancies were treated antenatally with either saline or dexamethasone. Antenatal dexamethasone increased the lung disaturated phosphatidylcholine content, reduced the lung glycogen concentration, reduced the saccular septal thickness, and increased the mean saccular size and volume fraction of saccules in the lungs of rats with large congenital diaphragmatic hernia in comparison with similar rats not so treated. All differences were statistically significant. Antenatal glucocorticoid therapy was efficacious in treating rats with nitrofen-induced congenital diaphragmatic hernia. This encouraging finding warrants further investigation in a large animal model with surgically created congenital diaphragmatic hernia.

Developmental changes in mullerian inhibiting substance in the cynomolgus monkey, Macaca fascicularis

Mullerian inhibiting substance (MIS) is a glycoprotein hormone produced in Sertoli cells of the fetal and postnatal testis, and granulosa cells of the pubertal ovary. We examined MIS expression in a nonhuman primate, the cynomolgus macaque monkey (Macaca fascicularis), to define an animal model for studying MIS gene regulation. Changes in testicular MIS mRNA with age were assessed by in situ hybridization of prepubertal to adult testes, Northern analysis of pubertal and adult specimens, and determination of serum MIS concentrations from infancy to adulthood. We found that MIS expression was highest in the youngest animals and decreased progressively with increasing age. Serum MIS concentrations correlated inversely with increasing age (r = -0.74), body weight (r = -0.79), and testicular volume (r = -0.73), but not with testosterone levels (r = -0.35). The mean MIS concentrations +/- SEM for the four developmental age groups were 270.6 +/- 23.8 (infants), 195.5 +/- 18.5 (juveniles), 102.7 +/- 28.4 (peripubertals), and 51.6 +/- 7.1 (adults). This study confirms that nonhuman primate and human MIS are highly homologous and have similar developmental patterns. The normative data for serum MIS concentrations in cynomolgus monkeys at different ages and developmental stages will be invaluable for further work examining MIS regulation.

Combined antenatal thyrotropin-releasing hormone and low-dose glucocorticoid therapy improves the pulmonary biochemical immaturity in congenital diaphragmatic hernia

The lungs of patients born with severe congenital diaphragmatic hernia (CDH) are biochemically and morphologically immature. Because antenatal glucocorticoid therapy can accelerate pulmonary maturation in premature neonates who have respiratory distress syndrome, we hypothesized that it may correct the pulmonary biochemical and morphological immaturity associated with CDH. We showed in previous experimental studies that antenatal low-dose dexamethasone improved the biochemical and morphological parameters of pulmonary immaturity in rats that had severe CDH. Somatic and pulmonary growth were inhibited with high doses of dexamethasone. In the present study, we examined the effects of antenatal low-dose dexamethasone and thyrotropin-releasing hormone (TRH), alone or in combination, on the pulmonary maturation in CDH. Combined antenatal low-dose dexamethasone and TRH significantly reduced mean lung glycogen concentration (P = .001), and increased mean disaturated phosphatidylcholine content (P < .005) to better than that observed with either therapy alone, without changing mean body or lung weight. Combined TRH and low-dose glucocorticoid as an antenatal therapy may reduce the morbidity and mortality of CDH.

Early one-stage surgical reconstruction of the extremely high vagina in patients with congenital adrenal hyperplasia

High vaginal atresia is a very rare anomaly seen in the most severely masculinized females with congenital adrenal hyperplasia. These children have a foreshortened vagina conjoining the urogenital sinus proximal to the external urethral sphincter. In the past, they have undergone early clitoral recession and labioscrotal reduction, followed by vaginal pull-through at 2 to 4 years of age. Cumulative experience with repair of this anomaly has led us to attempt earlier one-stage intervention and to develop techniques that circumvent previously encountered vaginal stenoses. One-stage reconstruction of three older children (ages 2 to 9 years) involved: closure of the urethrovaginal fistula, mobilization of the vagina from the rectum and urethra, use of bilateral buttock flaps to augment the anterior vaginal wall, augmentation of the posterior wall with an inverted perineal U flap, clitoral recession, and advancement of labioscrotal and clitoral shaft flaps inferiorly to create labia majora and minora (respectively). The introiti were quite capacious after employing such flaps, did not require postoperative dilatation, and were free of strictures or urethrovaginal fistulae during long-term follow-up. Three younger patients were seen for initial evaluation at 8 to 12 months of age, when early one-stage reconstruction was undertaken. Paradoxically, these repairs were technically less difficult and did not require buttock flap augmentation because an island of anterior perineal skin could be rotated in to reach the anterior vaginal wall. A nerve stimulator was used to identify the external urethral sphincter, while the vagina was aggressively mobilized and advanced forward beyond the site of fistula closure on the urethra to avert formation of a urethro-vaginal fistula.2 +

Male sex determination: current concepts of male sexual differentiation

In order for an infant to develop as a phenotypically complete male or female, a cascade of complex molecular and morphological events must occur at the appropriate time and in the correct sequence during ontogeny. The male embryo's genetic sex is determined by its chromosomal constituents, the most important of which is the sex-determining gene, or testis-determining factor (TDF), on the Y chromosome. Male gonadal sex, or testis formation, is subsequently thought to be determined by this gene and by other secondary pathways. The male gonad, in turn, normally produces hormones such as testosterone and Mullerian inhibiting substance (MIS) that regulate differentiation of the internal and external genitalia, thus determining phenotypic sex. When an abnormality develops in any of the above three processes, an intersex infant with ambiguous genitalia results from the incongruent genetic, gonadal, and phenotypic sex. Clinically, such 46XY males with intersex abnormalities present challenges for gender assignment, timely surgical intervention, and appropriate hormonal therapy.

A transforming growth factor beta type I receptor that signals to activate gene expression

Transforming growth factor beta (TGF-beta) is a multifunctional factor that regulates many aspects of cellular functions. TGF-beta signals through a heteromeric complex of the type I and type II TGF-beta receptors. However, the molecular mechanism of signal transduction by this receptor complex remains unresolved. The type II receptor belongs to a transmembrane receptor serine-threonine kinase family. A new member of this receptor family (R4) was identified and shown to be a functional TGF-beta type I receptor on the basis of its ability to restore a TGF-beta-induced gene response in mutant cell lines lacking endogenous type I receptor. Both ligand binding and signaling of the R4 protein were dependent on the presence of a functional type II receptor. The type I receptor has an intrinsic serine-threonine kinase activity, which was essential for signal transduction.

Identification of a receptor for human müllerian inhibiting substance

Müllerian inhibiting substance (MIS), a Sertoli cell-derived glycoprotein and member of the transforming growth factor-beta supergene family, plays a key down-stream role in mammalian sex determination. Identification of a receptor for MIS has now been achieved in a MIS-responsive human vulvar carcinoma cell line, A431, using fluorescein isothiocyanate labeling of recombinant human MIS (FITC-rhMIS) and RRAs with iodinated carboxy-terminal rhMIS. Confocal fluorescence microscopy of A431 cells incubated on ice with 30-nM concentrations of covalently bound FITC-rhMIS reveals specific punctate cell surface fluorescent signal. Cytosolic fluorescent signal is seen after incubation at 37 C for 1 h as well as occasional apparent perinuclear accumulation. FITC-rhMIS coincubated with molar excesses of unlabeled rhMIS in A431 cells eliminates cell surface and cytosolic fluorescent uptake. Double label experiments with FITC-rhMIS and tetramethyl rhodamine isothiocyanate epidermal growth factor establish separate binding of each ligand, displaceable, respectively, by large molar excesses of unlabeled rhMIS or epidermal growth factor. RRAs reveal a single, high affinity (Kd, 5.8 nM), saturable, low abundance binding species for carboxy-terminal rhMIS. Solubilized supernatants of A431 whole cells cross-linked with 125I-carboxy-terminal rhMIS identify a band with a mol wt of 88,000 on electrophoresis and autoradiography. This identification of a MIS receptor in A431 cells now permits the design of affinity purification protocols using rhMIS, followed by direct protein microsequencing.

Müllerian inhibiting substance production associated with loss of oocytes and testicular differentiation in the transplanted mouse XX gonadal primordium

The mouse XX gonadal primordium develops seminiferous-like tubules after transplantation into the renal subcapsular site of the adult male or female mouse. We examined the ontogeny of Sertoli cell differentiation in XX gonadal grafts by immunocytochemical staining and organ culture bioassay for Müllerian Inhibiting Substance (MIS). During normal in situ development of the XY gonad, MIS staining was first detected in fetal Sertoli cells at 12 days of gestation (d.g.) and remained intense until 4 days postpartum (d.pp.), after which it gradually diminished with progressive testicular development. In the normal in situ XX gonad, MIS was detected in granulosa cells of growing follicles at 7 d.pp. and thereafter. When the XX gonad at 12 d.g. was grafted beneath the renal capsule, a few testicular cords composed of MIS-positive cells appeared on Day 7 post-transplantation (equivalent to 19 d.g.), much earlier than the normal appearance of MIS production in the intact XX ovary. The ovarian region containing germ cells at the meiotic prophase was unstained for MIS in the same sections. The incidence of XX gonadal grafts containing MIS-positive testicular cords and the number of such cords per gonadal graft steadily increased from Day 7 to Day 14 post-transplantation. Germ cells were absent or scarce inside the MIS-positive testicular cords. The MIS bioactivity in both control gonads and gonadal grafts coincided with the immunocytochemical staining for MIS. These results support the hypothesis that XX cells differentiate into Sertoli cells as a consequence of oocyte loss in the gonadal graft.

Müllerian inhibiting substance: new perspectives and future directions

MIS, as a differentiate and antiproliferative agent, is precisely regulated, for example, at the transcriptional level by such transacting factors as SRY, and posttranslationally by testosterone. Processing of MIS most likely requires an as yet unknown in vivo protease which probably serves to control cleavage of MIS and hence its activation at specific sites wherein a localized program of cell death is initiated via a receptor mediated event. Progress has been made in understanding the molecular domains of MIS; current efforts are focused on characterizing the wild type MIS receptor as well as cloning and expressing the MIS receptor. We need now to understand how to target and efficiently activate MIS at its projected site of action. We must focus, after structural analysis of its receptor, on elucidating the MIS initiated intracellular signals which result in localized cell inhibition. Understanding of these mechanisms will permit design of antitumor agents and therapeutic strategies. Similarly, understanding regulation of MIS expression may lead to therapeutic induction of expression in those states where depressed expression is associated with tumorigenesis, sexual ambiguity, or infertility.

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

Müllerian Inhibiting Substance (MIS) causes regression of the Müllerian ducts during a critical period in embryonic development in male mammals. In Persistent Müllerian Duct Syndrome (PMDS), an autosomal recessive trait in humans and dogs, the Müllerian ducts fail to regress in otherwise normal males. Previously we reported that PMDS-affected dogs produce bioactive testicular MIS postnatally. The purpose of the present study was to determine whether PMDS-affected canine embryos appropriately express MIS mRNA and protein during the critical period for Müllerian duct regression. Homozygous (PMDS-affected) and normal canine embryos were removed from timed pregnancies. Gonadal sex and the degree of Müllerian duct regression were determined from histologic sections. Positive immunohistochemical staining for MIS was found in testis sections of PMDS-affected and normal male embryos. A 1.8-kb MIS mRNA transcript was detected in testes of PMDS-affected males and normal male embryos and neonates. Furthermore, equal amounts of MIS mRNA transcript were detected in testes of PMDS-affected embryos and normal male littermates during the critical period for Müllerian duct regression. These data support a hypothesis of target organ resistance, such as an abnormality in the putative MIS receptor, as the etiology of the defect in this dog model.

Mullerian inhibiting substance: a gonadal hormone with multiple functions

Mullerian inhibiting substance (MIS) is the gonadal hormone that causes regression of the Mullerian ducts, the anlagen of the female internal reproductive structures, during male embryogenesis. MIS is a member of the large transforming growth factor-beta (TGF beta) multigene family of glycoproteins that are involved in the regulation of growth and differentiation. The proteins in this gene family are all produced as dimeric precursors and undergo posttranslational processing for activation, requiring cleavage and dissociation to release bioactive C-terminal fragments. Similarly, the 140 kilodalton (kDa) disulfide-linked homodimer of MIS is proteolytically cleaved to generate its active C-terminal fragments. The sexually dimorphic expression of MIS in Sertoli cells of the testis and granulosa cells of the ovary is critical for normal differentiation of the internal reproductive tract structures. A number of extra-Mullerian functions such as control of germ cell maturation and gonadal morphogenesis, induction of the abdominal phase of testicular descent, suppression of lung maturation, and growth inhibition of transformed cells have also been proposed for this growth-inhibitory hormone and will be discussed. This article will summarize the current understanding of the biology and multiple functions of MIS including its activation, regulation, and mechanism of action and discuss areas of interest in ongoing research.

Gonadotropin-releasing hormone agonist-induced differences in granulosa cell cycle kinetics are associated with alterations in follicular fluid müllerian-inhibiting substance and androgen content

We have previously shown that the proliferative index (PI), as determined by flow cytometry of luteinized granulosa cells obtained at oocyte retrieval, is greater in ovulation induction regimens which include the GnRH analog (GnRH-a) leuprolide acetate than those using human menopausal gonadotropin (hMG) only. Specific growth factors or intrafollicular hormones may contribute to this leuprolide acetate-induced difference in cell cycle kinetics. We examined whether differences in the PI of these granulosa cells are associated with the alterations of follicular fluid content of Mullerian-inhibiting substance (MIS) and other intrafollicular hormones including FSH, estradiol, progesterone, androstenedione, and testosterone. The control group consisted of follicular fluid obtained from 18 follicles from 4 women receiving hMG alone. The GnRH-a treated group consisted of follicular fluids obtained from 55 follicles aspirated from 18 women receiving GnRH-a in addition to hMG. One-way analysis of variance using log-transformed data and expressed as geometric means with 95% confidence intervals, demonstrated that the follicles from the control group had a significant 14-fold higher concentration of 2.46 ng/mL MIS, 95% CI (1.8-4.8) vs. 0.18 ng/mL, 95% CI (0.13-0.24) P < 0.0005, a 3-fold higher concentration of 17.55 nmol/L androstenedione, 95% CI (14.6-20.9) vs. 5.76 nmol/L, 95% CI (3.1-10.5) P < 0.02, and a 1.5-fold higher concentration of 29.43 nmol/L testosterone 95% CI (22.5-38.14) vs. 19.3 nmol/L, 95% of CI (11.1-33.9) P < 0.01 than GnRH-a treated follicles, although the PI value in controls was half that of the GnRH-a group. These data demonstrate that GnRH-a induced differences in granulosa cell cycle kinetics are associated with alterations of MIS and androgen intrafollicular fluid content and suggest that MIS may be a mitotic inhibitor of human granulosa cells.

Müllerian inhibiting substance in the diagnosis and management of intersex and gonadal abnormalities

Müllerian inhibiting substance (MIS), a gonadal hormone important in sexual differentiation, is high (10 to 70 ng/mL) in human male serum postnatally for several years before declining during the peripubertal period, but is undetectable in female serum until the onset of puberty. The sexually dimorphic secretion of MIS suggested possibilities for its use in several clinical settings. Thirty-one patients with intersex and gonadal anomalies from 17 institutions were therefore evaluated between 1989 and 1992 with an MIS enzyme-linked immunosorbent assay (ELISA). Serum MIS levels correlated with the presence of testicular tissue in two patients with suspected anorchia, five patients with male pseudohermaphroditism, and eight other intersex patients with undescended testes, dysgenetic gonads, or ovotestes. In these latter patients, serial MIS values were also helpful to confirm complete removal of gonadal tissue postoperatively. MIS may be a more sensitive marker for the presence of testicular tissue than serum testosterone levels, both before and after the neonatal androgen surge, and, consequently, may obviate the need for human chorionic gonadotropin stimulation in the evaluation of certain intersex disorders. In values were useful in differentiating the underlying etiology of the disorder. Four patients with undetectable levels have presumptive MIS gene mutations, while 7 others with MIS values of 2 to 45 ng/mL may have bioinactive hormone of MIS receptor defects. Finally, two young girls with ovarian granulosa cell tumors had elevated MIS values that fell from 18 to 2 ng/mL and from 6.5 to 1 ng/mL during postoperative follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical immaturity of lungs in congenital diaphragmatic hernia

Neonates with congenital diaphragmatic hernia (CDH) continue to have unacceptably high mortality rates. To better understand the associated pulmonary pathology we measured biochemical parameters of lung maturity in neonatal rats with or without congenital diaphragmatic hernia created by maternal feeding of a single dose of nitrofen on day 9.5 or day 11.5 of gestation. Lungs from neonatal rats with large CDH (n = 9, 5 right-sided, 4 left-sided) had a significantly lower lung weight (P = .0001), lung weight/body weight ratio (P = .0001), disaturated phosphatidylcholine (DSPC) per microgram DNA (P < .005), total DSPC (P = .0001), total DNA (P < .05), protein per microgram DNA (P < .05), and total protein content (P < .005) when compared with lungs from the litter mates without congenital diaphragmatic hernia (n = 10). The lungs of rats with hernia also had significantly higher DNA concentrations (P < .05) and glycogen concentrations (P < .05). These data demonstrate that lungs in neonatal rats with large CDH are biochemically immature. Treatment directed toward correcting the pulmonary biochemical immaturity of affected fetuses before birth may improve the prognosis for these babies.

SRY recognizes conserved DNA sites in sex-specific promoters

Formation of male-specific structures and regression of female primordia are regulated in early male embryogenesis by SRY, a single-copy gene on the Y chromosome. Assignment of SRY as the testis-determining factor in eutherian mammals is supported by molecular analysis of cytogenetic sex reversal (i.e., XX males and XY females) and by complementary studies of transgenic murine models. Here we characterize the putative DNA-binding domain of SRY, which contains a conserved sequence motif shared by high-mobility group nuclear proteins and a newly recognized class of transcription factors. The SRY DNA-binding domain specifically recognizes with nanomolar affinity proximal upstream elements (designated SRYe) in the promoters of the sex-specific genes encoding P450 aromatase and Mullerian inhibiting substance (MIS). P450 aromatase catalyzes the conversion of testosterone to estradiol, and in the male embryo its expression is down-regulated. Conversely, MIS is expressed in the male embryo to induce testicular differentiation and regression of female reproductive ducts. SRYe-binding activity is observed in nuclear extracts obtained from embryonic urogenital ridge immediately preceding morphologic testicular differentiation. Our results support the hypothesis that SRY directly controls male development through sequence-specific regulation of target genes.

Developmental expression of four novel serine/threonine kinase receptors homologous to the activin/transforming growth factor-beta type II receptor family

Serine/threonine kinase transmembrane proteins are a new family of growth factor signal transducers that includes several isoforms of the activin type II receptor and the type II receptor for transforming growth factor-beta. In an effort to clone the receptor for Mullerian inhibiting substance, a member of the transforming growth factor-beta superfamily, oligonucleotide primers designed from conserved regions of these receptors' kinase domains were used for PCR amplification of fetal rat urogenital ridge cDNA. We isolated four novel receptors in this manner (designated R1-R4), each of which has structural features of the previously cloned kinases, including a small extracellular ligand-binding domain, a single hydrophobic transmembrane domain, and an intracellular serine/threonine kinase domain. In addition, each has characteristic kinase subdomains and conserved serine/threonine kinase sequences found in this family. Northern analysis revealed mRNA expression of R1-R4 in several tissues, including fetal urogenital ridge, testis, and ovary, as well as brain and lung. In situ hybridization further localized R1 to mesenchyme of the 14.5 to 15-day fetal rat Mullerian duct and to oocytes of preantral and antral follicles, sites that are consistent with the predicted localization of Mullerian inhibiting substance receptor. In addition, R2 localized specifically to seminiferous tubules of the postnatal testis. These newest members of the activin and transforming growth factor-beta type II receptor family should help define the molecular mechanisms by which this ligand superfamily affects cell growth and differentiation via membrane phosphorylation.

Identification of müllerian inhibiting substance specific binding in human cell lines

The receptor for Müllerian Inhibiting Substance (MIS), a gonadal glycoprotein hormone, has not been previously identified. Plasma membranes from MIS-sensitive human tumor cell lines (HTB-111, endometrial carcinoma; and A-431, vulvar squamous carcinoma) were detergent extracted and incubated with 125I-labeled MIS anti-idiotypic antibody, or radioiodinated human recombinant MIS (125I rhMIS), with and without unlabeled competitors. 125I anti-idiotypic MIS antibody bound to HTB-111 membrane extracts was displaceable by unlabeled anti-idiotypic antibody, but not by anti-isotypic antibody prior to cross-linking. Specific binding of the anti-idiotypic MIS antibody to endometrial carcinoma cells was verified using fluorescence activated cell analysis and fluoresceinated antibody. Furthermore, unlabeled anti-idiotypic MIS antibody competed for 125I rhMIS binding to A-431 vulvar carcinoma membranes. The labeled anti-idiotypic MIS antibody binding complex could be separated from 32P labeled EGF receptor in the A-431 membranes, indicating that EGF, a natural inhibitor of MIS activity, and MIS itself bind to different receptors. These studies demonstrate a specific, displaceable binder for MIS in the plasmalemmae of two human tumor lines. Purification of this cell surface receptor protein will be greatly aided by using the MIS anti-idiotypic antibody.

Effect of human recombinant mullerian inhibiting substance on isolated epithelial and mesenchymal cells during mullerian duct regression in the rat

The effect of human recombinant Mullerian Inhibiting Substance (MIS) on the regression of the Mullerian duct (MD) of female rat fetuses was examined in vitro to determine whether MIS acts on MD epithelium and/or mesenchyme at the critical periods of sexual differentiation. Urogenital ridges (URs) of female rat fetuses at 14.5- to 18.5-days of gestation (plug day = 0) were cultured for 3 days with or without recombinant human MIS in CMRL 1066 medium with 10% female fetal calf serum. In URs from 14.5- and 15.5-day-old fetuses, the cranial portion of the MD regressed almost completely during the 3-day culture period in the presence of MIS, whereas the caudal half to third of the MD remained intact but tapered to a fine point cranially. MDs survived in URs from 16.5-day-old fetuses cultured in the presence of MIS except that the cranial portion of the MDs was deformed. MIS did not elicit regression of MDs in URs obtained from 17.5- and 18.5-day-old fetuses, but instead caused the MD epithelium to form bulges projecting into the mesenchyme. MD epithelium at 15.5-days of gestation was separated from the surrounding UR mesenchyme, and both components (MD epithelium and mesenchyme) were cultured separately for 3 days in the presence or absence of MIS. Both epithelial and mesenchymal cells survived in the presence or absence of MIS. MD epithelium formed typical epithelial colonies, whereas UR mesenchyme spread as fibroblastic cells. Analysis of labeling index after incorporation of [3H] thymidine demonstrated that MD epithelial DNA synthesis was not influenced by MIS. In contrast, mesenchymal labeling index was reduced significantly by MIS. This effect of MIS on UR mesenchyme in conjunction with earlier histological observations of mesenchymal condensation during MD regression and an absence of direct effects of MIS on the epithelium suggests that MIS elicits its effect on the MD epithelium via the surrounding mesenchyme.

The inhibitory effects of müllerian-inhibiting substance on epidermal growth factor induced proliferation and progesterone production of human granulosa-luteal cells

This study was undertaken to determine if Müllerian-inhibiting substance (MIS) could block basal and/or epidermal growth factor (EGF)-induced proliferation and progesterone production by cultured human granulosa-luteal cells. Cells from follicles of individual patients were pooled, counted, and aliquoted into Ham's F-10 medium containing 10% MIS-free female fetal calf serum at 37 C in 95% air and 5% CO2. After assessing viability, cells were counted on days 4, 8, 12, and 16 of culture. EGF was added every other day at 0.2, 2, and 20 ng/mL beginning on culture day 4. The greatest stimulatory effect of EGF on cell proliferation was observed at 20 ng/mL on days 12 and 16. EGF increased progesterone production per cell after 4 days exposure, but this effect was lost after 8 days. Granulosa-luteal cells were cultured with 0.2, 2, and 20 ng/mL immunoaffinity purified recombinant human MIS (rhMIS) or conditioned medium from Chinese hamster ovary cells transfected with the human MIS gene, beginning on culture day 4. rhMIS demonstrated its greatest inhibitory effect on cell proliferation at 20 ng/mL on day 16. The rhMIS decreased progesterone production per cell after 4 days exposure, but only in the higher doses. Maintaining EGF at 20 ng/mL and varying rhMIS yielded significant reduction in EGF-mediated proliferation and progesterone production per cell at 2 and 20 ng/mL rhMIS. These experiments demonstrate rhMIS inhibits basal and EGF-stimulated human granulosa-luteal cell proliferation and progesterone production.

Bilateral rotated buttock flaps for vaginal atresia in severely masculinized females with adrenogenital syndrome

The addition of large bilateral rotated buttock flaps to the flap vaginoplasty enhances the introitus in severely masculinized patients with high vaginal atresia. The flaps are rotated medially to create the distal aspect of the lateral and anterior vaginal wall. The inferior advancement of the labioscrotal folds aids in closing the donor defect, while at the same time creating the appearance of labia majora. Finally, the use of these local tissues will result, in later life, in a vaginal reconstruction free of unwanted hair. This reconstruction technique should obviate dilatation in the older child and prevent further stenosis.

Mullerian inhibiting substance messenger ribonucleic acid expression in granulosa and Sertoli cells coincides with their mitotic activity

In males, Mullerian inhibiting substance (MIS) mRNA was first detected on the medial aspect of the urogenital ridge early on the morning of day 13 of gestation before testicular differentiation was evident, and localized to the more obvious Sertoli cells later on embryonic day 13. MIS transcripts remained at maximal levels between 14.5 and 17.5 days gestation, while the Mullerian duct involutes, and remained high until birth. MIS gene expression decreased progressively after birth and, as germ cell meiosis increased, became barely detectable in the Sertoli cells of the seminiferous tubules. In female rats, MIS mRNA was first detected in the single layer of cuboidal granulosa cells surrounding larger primary follicles 3 days after birth, coincident with the initiation of follicular growth. As follicular growth progressed, MIS mRNA expression was high in preantral and small antral follicles, especially in those granulosa cells closest to the oocyte. MIS mRNA expression decreased gradually in larger antral follicles, remaining prominent only in the cumulus cells and the dividing population of granulosa cells closest to the lumen. MIS gene expression was absent in follicles with features of atresia and in the larger antral follicles. The expression of MIS mRNA in actively dividing Sertoli and granulosa cells correlates with the stages of germ cell division. These findings are suggestive of a role for MIS in the control of germ cell maturation.

Mullerian duct regression and antiproliferative bioactivities of mullerian inhibiting substance reside in its carboxy-terminal domain

A 25-kilodalton dimeric carboxy-terminal fragment of the recombinant human Mullerian inhibiting substance protein (rhMIS) was produced by proteolytic cleavage with plasmin and purified by size-exclusion chromatography. The identity of the isolated dimer as the carboxy-terminal fragment was confirmed by gel electrophoresis and Western analysis. As was true of every sample of the holo molecule, all preparations of the carboxy-terminal domain of rhMIS (n = 10), when added in the 0.5-5.0 micrograms/ml range, exhibited a dose-dependent partial to complete regression of the 14.5-day fetal rat Mullerian duct in an organ culture assay. The carboxy-terminal dimer also inhibited, in a dose-dependent manner, the growth of A431 cells in monolayer cultures. Daily addition of 5, 10, or 20 micrograms carboxy-terminus for 3 days resulted in 0%, 25%, and 100% inhibition of cell proliferation, respectively. Similar and higher doses of holo rhMIS had no or inconsistent antiproliferative activity (0-34% inhibition), even though the preparations caused Mullerian duct regression. All amino-terminal fragments prepared using this separation protocol were found to be inactive in these assays. These findings suggest that the bioactivity of rhMIS as a regressor of fetal Mullerian ducts and an inhibitor of A431 cell growth resides in its carboxy-terminal domain. These results indicate that the urogenital ridge tissue, but not A431 cells in culture, may be capable of cleaving intact MIS to a biologically active conformation.

Human müllerian inhibiting substance: enhanced purification imparts biochemical stability and restores antiproliferative effects

Separation of copurifying protease activity from recombinant human Müllerian inhibiting substance (rhMIS) bound to a monoclonal antibody immunoaffinity column by a high-salt wash results in cleaner preparations of rhMIS resistant to cleavage upon storage. In addition, an inhibitor of rhMIS antiproliferative activity is removed. Proteolytic cleavages produced by either a copurifying protease or exogenous plasmin occur at residues 229 and 427 but do not abolish rhMIS biological activity. This report details the modified immunoaffinity column isolation protocol suitable for proteins such as rhMIS and describes the biochemical and antiproliferative properties of this protein.

Müllerian inhibiting substance in reproduction and cancer

During embryogenesis normal male phenotypic development requires the action of Müllerian Inhibiting Substance (MIS) which is secreted by Sertoli cells of the fetal testis. As testes differentiate in genetic (XY) males, they produce MIS which causes regression of the Müllerian ducts, the anlagen of the female reproductive tract. Soon thereafter, testicular androgens stimulate the Wolffian ducts. In females, on the other hand, MIS is not produced by grandulosa cells until after birth, before which, estrogens induce Müllerian duct development, while the Wolffian ducts passively atrophy in the absence of androgenic stimulation. High serum MIS levels in males are maintained until puberty, whereupon they fall to baseline levels. In females MIS is undetectable in serum until the peripubertal period when values approach the baseline levels of males. This distinct pattern of sexual and ontogenic expression presupposes and requires tight regulation. MIS may play a role in gonadal function and development. Our laboratory has shown that an important role for ovarian MIS is to inhibit oocyte meiosis, perhaps providing maximal oocyte maturation prior to selection for ovulation and subsequent fertilization. Furthermore, Vigier et al. (Development 100:43-55) have recently obtained evidence that MIS may influence testicular differentiation, coincident with inhibition of aromatase activity. Current structure-function studies demonstrate that MIS, like other growth regulators in its protein family, requires proteolytic cleavage to exhibit full biological activity. MIS can be inhibited by epidermal growth factor. This antagonism, which is common to all MIS functions so far investigated, is associated with inhibition of EGF receptor autophosphorylation. We have provided evidence that bovine MIS can inhibit female reproductive tract tumors arising in adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Mullerian inhibiting substance binding and uptake

Mullerian inhibiting substance (MIS) is a 140,000 M(r) Sertoli cell derived glycoprotein with a critical regulatory role in the male fetus initiated presumably by ligand binding with receptor. To localize this binding species we performed time course incubations of cultured fetal rat lungs or control tissues with MIS, applied rabbit anti-MIS IgG, and fluorescein conjugated anti-rabbit IgG, and examined specimens with laser confocal microscopy. Punctate surface fluorescence followed by cytosolic and nuclear localization in lung consistent with specific adsorptive endocytosis was seen. Confocal imaging also detected MIS binding to the Mullerian duct in the urogenital ridge. Crosslinking of 125I-MIS with plasma membranes revealed a high molecular mass binder with signal displaceable by excess unlabeled ligand. These data support the hypothesis that a specific plasma membrane binding protein for MIS exists.

Isolation of the rat gene for Mullerian inhibiting substance

Mullerian inhibiting substance (MIS), a testicular glycoprotein also known as anti-Mullerian hormone, plays a key role in male sexual development by causing regression of the Mullerian duct, the anlagen of the uterus, the Fallopian tubes, and part of the vagina. MIS is also expressed in the postnatal ovary, but its precise function is still not known. We report here the complete nucleotide sequence of the rat MIS gene. Rat MIS is encoded in five exons and is synthesized as a precursor of 553 amino acids, containing a 24-amino-acid leader. Based on homology with human MIS, we predict that the rat protein undergoes proteolytic processing at a site 108 amino acids from the C-terminus. Expression of the rat MIS mRNA is high in the 1-day-postnatal testis and decreases to a low level in the adult testis. In contrast, expression is not detected in the 1-day ovary, but increases to an intermediate level in the adult ovary. The rat gene should provide a good model for studying transcriptional regulation of MIS in the testis and ovary.

Recombinant human mullerian inhibiting substance inhibits human ocular melanoma cell lines in vitro and in vivo

Since Mullerian Inhibiting Substance (MIS) causes regression of the Mullerian duct, the anlagen of the uterus, vagina, and fallopian tube, we expected and have previously observed that purified recombinant human MIS causes regression of gynecological tumors. However, recent experiments indicating that neural crest derivatives might be responsive to MIS prompted study of a group of human ocular melanoma cell lines in 4 in vitro inhibition assays, and a subrenal capsule assay in vivo. Ocular melanoma cell lines that grew well in a respective assay were studied with MIS to determine whether this biological modifier could inhibit growth. Three human ocular melanomas, OM431 (P less than 0.01), OM467 (P less than 0.02), and OM482 (P less than 0.03), were growth-inhibited by highly purified human recombinant MIS in soft agarose. A dose-dependent tumor inhibition was noted when OM431 cells were incubated with MIS in a liquid colony inhibition assay (P less than 0.05). In addition, OM467 was inhibited (P less than 0.05) by MIS in a multicellular tumor spheroid assay. Cell cycle analysis indicated that OM431 cells were inhibited in monolayer by MIS while in G1. At 100-fold lower serum concentrations than required in the media of in vitro assays, MIS delivered via i.p. osmotic pumps inhibited (P less than 0.05) in vivo the growth of OM431 implanted beneath the renal capsule of nude and CD-1 irradiated mice when compared to mice given implants of pumps containing no MIS. The responsiveness of ocular melanoma to MIS broadens the spectrum of tumors that might be treated with MIS and suggests further investigation of other neural crest tumors.

Rejection of murine congenic bile ducts: a model for immune-mediated bile duct disease

Immune-mediated injury of prenatal and postnatal extrahepatic bile duct epithelium has been poorly characterized. In a transplantation model of bile duct allografts, segments of the common bile duct from fetal day 18, postnatal day 7 and day 21, and adult (greater than 6-weeks) mice were grafted under the renal capsule of adult congenic mice. The progression of rejection injury in these bile duct allografts was then followed by histological evaluation at 1-week intervals. After 3 weeks there was a significant difference in the number of fetal congenic bile duct grafts that had maintained their luminal architecture compared with the more mature adult congenic grafts that had fibrosclerosed. The onset and progression of the rejection injury in the adult congenic bile duct grafts was associated with an induction of class I and class II histocompatibility antigen expression in the adult bile duct epithelium; the severity of this injury could be attenuated by treatment of the recipient mice with cyclosporin A. Thus, the fibrosclerosing lesion of extrahepatic ducts observed in this model of rejection injury is similar to the histopathology of neonatal biliary atresia or primary sclerosing cholangitis, and susceptibility to this injury is dependent on the age of the donor tissue. The immune nature of the injury and the ontogeny of expression of histocompatibility antigen in bile duct tissue indicate that the above factors may be important to the pathogenesis of these extrahepatic bile duct diseases. This experimental model may be used to test for novel factors that may modulate immune responses directed against extrahepatic bile duct epithelium.

Ectopic class II major histocompatibility antigens in Hirschsprung's disease and neuronal intestinal dysplasia

Although the etiology of Hirschsprung's disease and neuronal intestinal dysplasia remains obscure, both have histological abnormalities involving ganglion cells and neuronal elements. Searching for a common pathway that may inhibit normal maturation of neurogenic precursors, we examined the possible role of an immune mechanism in the maldevelopment of the enteric neural network. Six patients with Hirschsprung's disease were studied by comparing biopsy specimens from diseased colon with ones taken from proximal ganglionic colon in the same patients. These were similarly compared with colonic biopsy specimens from patients studied with chronic constipation or bowel removed at the time of operation for other disorders. Biopsies were taken from four other patients with neuronal intestinal dysplasia. Each was examined by hematoxylin & eosin staining, acetylcholinesterase histochemistry, and immunohistochemistry of major histocompatibility complex (MHC) class I and class II antigens. All rectal samples from Hirschsprung's disease patients exhibited elevated acetylcholinesterase histochemistry and absent ganglia to confirm the diagnosis. These findings were correlated with marked elevation of class II MHC in the aganglionic area, whereas the proximal normal ganglionic segments showed no elevation. Rectal biopsy specimens from patients with chronic constipation exhibited no such elevation. A similar elevation of class II MHC was detected in the mucosa and submucosa of all four patients with the rare neuronal intestinal dysplasia disorder whose diagnosis was confirmed by giant ganglia in Auerbach's plexuses, aberrant Meissner's ganglia in the lamina propria mucosa, and giant neurofibrils in the mucosa and submucosa. The correlation of elevated class II MHC in these two neuronal dysfunction disorders may indicate an underlying autoimmune mechanism as is seen in thyroiditis and insulin dependent diabetes mellitus.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmentally regulated polyadenylation of two discrete messenger ribonucleic acids for müllerian inhibiting substance

Mullerian inhibiting substance (MIS) is a 140-kilodalton homodimeric glycoprotein that causes regression of the Mullerian ducts in male embryos, and may also have a role in both males and females in the regulation of germ cell maturation. We examined the ontogeny of MIS messenger RNA (mRNA) in rat testes from midgestation through adulthood and found two discrete MIS mRNA species that are developmentally regulated. The larger 2.0-kilobase species is abundant at embryonic day 14, then decreases in late gestation, and is barely detectable after birth. The smaller 1.8-kilobase species is first noted at embryonic day 18 and is the major species detected postnatally. Both species are abundant just prior to birth, at embryonic day 21, then decrease markedly after birth. This variation in MIS mRNA levels correlates with the developmental expression of MIS protein. A series of oligonucleotide-directed ribonuclease H mapping experiments determined that the two mRNA species differ at their 3' ends in the extent of polyadenylation. Thus, differential polyadenylation of MIS mRNA may be an additional mechanism for regulating MIS expression during fetal and postnatal development.

Müllerian inhibiting substance production and cleavage is modulated by gonadotropins and steroids

Analysis of the ontogeny and localization of the amino (N)-terminal and carboxy (C)-terminal cleavage products of Müllerian Inhibiting Substance (MIS) and their modulation by hormones of the hypothalamic-pituitary gonadal axis by immunohistochemistry and Northern analysis led to the discovery of a novel mode of posttranslational regulation of this differentiating agent. Antibody to both holo- and C-terminal MIS identically stained the cytosol of testicular Sertoli cells from 21-day fetal rats, whereas staining of antibody to N-terminal MIS localized to the basement membrane of seminiferous tubules. In addition, when studied longitudinally, basement membrane staining for N-terminal MIS persisted; cytosolic staining for C-terminal MIS was no longer detectable in post-natal testes, but marked basement membrane staining for the N-terminal fragment could still be observed in the testes of untreated 7-day postnatal animals. When 19-day fetuses were injected with FSH, testes collected 2 days later showed less immunohistochemical staining for holo-, N-, and C-terminal MIS, and less MIS messenger RNA. This suggested that FSH downregulates MIS transcription, as had been shown previously in neonatal testes treated with FSH. Testes collected at 21 days from fetuses treated at day 19 in utero with human CG or testosterone, also showed less staining for holo-MIS, but, surprisingly, increased staining for the N- and C-terminal fragments. These changes in MIS protein were accompanied by no or minimal changes in MIS messenger RNA levels, indicating that human CG and testosterone do not affect transcription, but may regulate the cleavage and/or dissociation of MIS. This study describes a form of post-translational regulation of MIS and shows that both transcription and processing of MIS may be differentially modulated by gonadotropins and sex steroids.

Müllerian inhibiting substance blocks epidermal growth factor receptor phosphorylation in fetal rat lung membranes

Neonatal males develop respiratory distress syndrome more frequently than females for unknown reasons. The fetal testis secretes testosterone and müllerian inhibiting substance (MIS); MIS has been shown to inhibit fetal lung maturation in vitro and in vivo and to block phosphorylation of epidermal growth factor (EGF) receptors in A431 cells. We hypothesized that MIS would also inhibit membrane phosphorylation of EGF receptors in fetal lung, and that ultrastructural study of MIS-exposed lung might complement the biochemical data by assessing the effect of MIS on tissue morphology. Lung membranes were prepared from 19.5-day fetal rats and phosphorylation assays performed with 3 to 4 micrograms of membrane protein, with or without EGF (26 nmol/L), 0.025 mCi AT32P (0.136 mumol/L), and either recombinant human MIS (rhMIS, 30 pmol) from media of Chinese hamster ovary (CHO) cells, rhMIS dialysis buffer, or wild-type CHO media. The 170,000 molecular weight EGF receptor, visualized by autoradiography of polyacrylamide gels, was phosphorylated in both female and male membranes. rhMIS, when added to EGF-stimulated membranes, caused significant inhibition of EGF receptor phosphorylation (females: 32.42% +/- 11.5%; males: 32.3% +/- 19.1%, P less than 0.001; rhMIS-treated v EGF-stimulated state, P = NS, male v female, Cerenkov counting). Electron microscopy (EM) of rhMIS-exposed lung showed decreased lamellar bodies (LB) in both male alveolar spaces and female parenchyma, and, unexpectedly, increased numbers in female alveoli. Immunoabsorption experiments using coincubation of rhMIS with anti-rhMIS IgG polyclonal antibodies or equiprotein normal IgG demonstrated MIS antibody-specific reversal of rhMIS activity in membrane phosphorylation.(ABSTRACT TRUNCATED AT 250 WORDS)

The critical period for mullerian duct regression in the dog embryo

The embryonic period during which Mullerian duct regression and Mullerian Inhibiting Substance (MIS) secretion occur was determined in canine embryos removed from timed pregnancies (32, 36, 37, 39, 42, and 46 days gestation). Sex chromosomes of each embryo were identified in metaphase spreads prepared from fibroblast cultures. Testicular differentiation, defined by seminiferous tubule formation and the presence of Sertoli cells and Leydig cells, and the degree of Mullerian duct regression were determined by careful morphologic analysis of histologic sections of canine embryonic gonads (n = 20) and Mullerian ducts (n = 20). MIS was detected immunohistochemically in embryonic testes using avidin-biotin complex enhancement of a specific rabbit polyclonal anti-MIS antibody. Testicular differentiation was observed at 36 days gestation. The earliest evidence of Mullerian duct regression in male embryos was observed at 36 days gestation, and regression was completed by 46 days gestation. Positive staining for MIS was present in testes from 36 to 46 days (n = 9). Staining was absent in the undifferentiated testis (n = 1) at 32 days gestation and in ovaries at all ages tested (n = 10). Thus, MIS is normally present throughout the critical period for Mullerian duct regression in the embryonic male dog.

Laryngotracheoesophageal cleft (type IV): management and repair of lesions beyond the carina

Since the first successful repair of a complete laryngotracheoesophageal cleft (LTEC) to the carina in 1982, three newborn infants were observed with a particularly difficult variant in which the cleft extends beyond the carina into the mainstem bronchi. This type IV LTEC creates a long common tracheoesophagus, whose successful separation requires meticulous preoperative, operative, and postsurgical care. Three infants had complete surgical repair at our institution at 29, 49, and 225 days old and survived a minimum of 8 months. Recurrent tracheoesophageal fistulae at the thoracic inlet occurred in two infants, but was not observed in one patient when sternocleidomastoid muscle was interposed between the trachea and esophagus in the neck. Microgastria is an associated finding in each infant with the tracheoesophageal cleft extending beyond the carina. The small stomach is problematic as it is anatomically inadequate for any antireflux procedure and has not grown well, even with prolonged feeding. Early cleft repair is essential to prevent the development of chronic lung disease secondary to recurrent aspiration. The techniques to make the diagnosis, the preferred treatment to initially protect the airway, a single-stage operation performed simultaneously through the chest and neck to definitively repair the cleft, and finally the intraoperative and postoperative management critical for an optimal outcome are described.