Persistent Müllerian duct syndrome due to anti-Müllerian hormone receptor 2 microdeletions: a diagnostic challenge.

The persistent Müllerian duct syndrome (PMDS) is defined by the persistence of Müllerian derivatives in an otherwise normally virilized 46,XY male. It is usually caused by mutations in either the anti-Müllerian hormone (AMH) or AMH receptor type 2 (AMHR2) genes. We report the first cases of PMDS resulting from a microdeletion of the chromosomal region 12q13.13, the locus of the gene for AMHR2. One case involved a homozygous microdeletion of five exons of the AMHR2 gene. In the second case, the whole AMHR2 gene was deleted from the maternally inherited chromosome. The patient's paternal allele carried a stop mutation, which was initially thought to be homozygous by Sanger sequencing. Diagnostic methods are discussed, with an emphasis on comparative genomic hybridization and targeted massive parallel sequencing.

Regional variations in the management of testicular or ovotesticular disorders of sex development.

Disorders of sex development arise in parts of the world with different socio-economic and cultural characteristics. We wished to determine the regional variations in the management of these conditions. A questionnaire was e-mailed to the 650 members of the European Society for Paediatric Endocrinology (ESPE), an international society with a mainly European membership but which also includes professionals from other continents. Results were subjected to statistical analysis. A total of 62 answers were received, a satisfactory rate given that not all members are involved in this issue. Results show statistically significant regional differences for available diagnostic resources, age of the patient at gender assignment, parameters considered important for gender assignment, and timing of discussion of various issues with parents and patient. The regional variations exist not only between different continents, as already demonstrated by others, but also between Northern, Latin and Eastern European countries. This suggests that 'one-fits-all' guidelines for management are not appropriate.

Early expression of the androgen receptor in the Sertoli cells of a marsupial coincides with downregulation of anti-Müllerian hormone at the time of urogenital virilization.

Anti-Müllerian hormone (AMH), responsible for the regression of Müllerian ducts, is strongly expressed by eutherian fetal and postnatal Sertoli cells. Both AMH and testosterone levels are high during the period of fetal reproductive tract virilization which occurs largely in utero in eutherian mammals. Taking advantage of the fact that differentiation of the urogenital tract occurs after birth in marsupials, we studied the ontogeny and regulation of AMH in the tammar wallaby testis and related it to the expression of the androgen receptor in Sertoli cells. Testicular AMH expression was high between days 10-30 post partum, then fell to basal levels by day 60 and remained low until day 90, the oldest age examined. AMH expression was repressed by treatment of male pouch young with the potent androgen androstanediol. Thus, in the tammar, AMH expression decreases in response to androgen at the time of initial urogenital masculinization, in contrast to the situation in humans in which AMH is repressed by testosterone only at the time of puberty. The difference might be explained by the timing of androgen receptor expression which appears in tammar Sertoli cells at around day 40 of pouch life but only at a later developmental stage in eutherians.

Professor Alfred Jost: the builder of modern sex differentiation.

Professor Alfred Jost (1916-1991) is famous for his discovery of the Mullerian inhibitor, now called anti-Mullerian hormone (AMH) or Mullerian inhibiting substance (MIS). Alfred Jost resolved the controversy surrounding the mechanism of somatic sex differentiation by proving that male characteristics must be imposed on the fetus by the testicular hormones testosterone and AMH, respectively responsible for the virilization of the Wolffian ducts, urogenital sinus and external genitalia and for the regression of Mullerian ducts. In the absence or inactivity of these hormones, the fetus becomes phenotypically female. Alfred Jost was also a pioneer through his work on testicular differentiation, in collaboration with Solange Magre. He was the first to show that testicular organization is heralded by the development of pre-Sertoli cells, which progressively surround germ cells to form seminiferous tubules. Alfred Jost did not rely only on his brilliant mind. He distrusted theories built on suboptimal experimental data and believed that intelligence was powerless without technical skill. His search for elegant, effective techniques led him to apply surgical methods to fetal endocrinology. He was also a fascinating teacher, particularly for pre-doctoral students. He died aged 75, having retired from the Collège de France, but still active as the Secrétaire Perpétuel of the French Science Academy.

Components of the anti-Müllerian hormone signaling pathway in gonads.

Anti-Müllerian hormone (AMH) is a member of the Transforming Growth Factor-beta (TGF-beta) family implicated in the regression of Müllerian ducts in male fetuses and in the development and function of gonads of both sexes. Members of the TGF-beta family signal through two types of serine/threonine kinase receptors called type I and type II, and two types of Smad proteins, receptor-regulated Smad (R-Smad) and common Smad, Smad4. Components of the AMH signaling pathway have been identified in gonads and gonadal cell lines. The AMH type II receptor is highly specific. In contrast, the identity of the AMH type I receptor is not clear; three type I receptors of Bone Morphogenetic Proteins (BMPs), Alk2, Alk3 and Alk6 may transduce AMH signals, but none of them has all the characteristics of an AMH type I receptor. AMH activates BMP-specific R-Smads and reporter genes.

Persistence of Müllerian derivatives and intestinal lymphangiectasis in two newborn brothers: confirmation of the Urioste syndrome.

We describe two newborn brothers with a pattern of malformation characterized by the persistence of Müllerian duct derivatives, intestinal lymphangiectasia, hypertrophied alveolar ridges, and early death. Postmortem examination showed the presence of a rudimentary uterus, fallopian tubes, the upper third of a vagina, a prostate of normal shape, a dilated colon, and generalized intestinal and pulmonary lymphangiectasia. The syndrome was first delineated by Urioste and co-workers [1993: Am J Med Genet 47:494-503]. These cases confirm the existence of a definite and distinct entity.

Autosomal recessive segregation of a truncating mutation of anti-Müllerian type II receptor in a family affected by the persistent Müllerian duct syndrome contrasts with its dominant negative activity in vitro.

Anti-Müllerian hormone belongs to the TGFbeta family whose members exert their effects by signaling through two related serine/threonine kinase receptors. Mutations of the anti-Müllerian hormone type II receptor occur naturally, causing the persistent Müllerian duct syndrome. In a family with two members with persistent Müllerian duct syndrome and one normal sibling, we detected two novel mutations of the anti-Müllerian hormone type II receptor gene. One, transmitted by the mother to her three sons, is a deletion of a single base leading to a stop codon, causing receptor truncation after the transmembrane domain. The other, a missense mutation in the substrate-binding site of the kinase domain, is transmitted by the father to the two sons affected by persistent Müllerian duct syndrome, indicating a recessive autosomal transmission as in other cases of persistent Müllerian duct syndrome. Truncating mutations in receptors of the TGFbeta family exert dominant negative activity, which was seen only when each of the mutant anti-Müllerian hormone receptors was overexpressed in an anti-Müllerian hormone-responsive cell line. We conclude that assessment of dominant activity in vitro, which usually involves overexpression of mutant genes, does not necessarily produce information applicable to clinical conditions, in which mutant and endogenous genes are expressed on a one to one basis.

Anti-Müllerian hormone and its receptors.

Anti-Müllerian hormone (AMH), a member of the transforming growth factor-beta family, is an important factor of male sex differentiation. It is produced by Sertoli cells from the time of fetal sex differentiation to puberty. AMH is also produced by granulosa cells from the time of birth to the end of ovarian activity. As other members of the transforming growth factor-beta family, AMH signals through two related but distinct receptors, both serine/threonine kinases with a single transmembrane domain, called type II and type I. The type II receptor has been cloned in 1994 and is expressed solely in AMH target organs. Engagement of the type I receptor BMPR-IB and downstream effector Smad1 by AMH has recently been demonstrated, however, its role in AMH biological actions remains to be proven.

Molecular mechanisms of hormone-mediated Müllerian duct regression: involvement of beta-catenin.

Regression of the Müllerian duct in the male embryo is one unequivocal effect of anti-Müllerian hormone, a glycoprotein secreted by the Sertoli cells of the testis. This hormone induces ductal epithelial regression through a paracrine mechanism originating in periductal mesenchyme. To probe the mechanisms of action of anti-Müllerian hormone, we have studied the sequence of cellular and molecular events involved in duct regression. Studies were performed in male rat embryos and in transgenic mice overexpressing or lacking anti-Müllerian hormone, both in vivo and in vitro. Anti-Müllerian hormone causes regression of the cranial part of the Müllerian duct whereas it continues to grow caudally. Our work shows that this pattern of regression is correlated with a cranial to caudal gradient of anti-Müllerian hormone receptor protein, followed by a wave of apoptosis spreading along the Müllerian duct as its progresses caudally. Apoptosis is also induced by AMH in female Müllerian duct in vitro. Furthermore, apoptotic indexes are increased in Müllerian epithelium of transgenic mice of both sexes overexpressing the human anti-Müllerian hormone gene, exhibiting a positive correlation with serum hormone concentration. Inversely, apoptosis is reduced in male anti-Müllerian hormone-deficient mice. We also show that apoptosis is a decisive but not sufficient process, and that epitheliomesenchymal transformation is an important event of Müllerian regression. The most striking result of this study is that anti-Müllerian hormone action in peri-Müllerian mesenchyme leads in vivo and in vitro to an accumulation of cytoplasmic beta-catenin. The co-localization of beta-catenin with lymphoid enhancer factor 1 in the nucleus of peri-Müllerian mesenchymal cells, demonstrated in primary culture, suggests that overexpressed beta-catenin in association with lymphoid enhancer factor 1 may alter transcription of target genes and may lead to changes in mesenchymal gene expression and cell fate during Müllerian duct regression. To our knowledge, this is the first report that beta-catenin, known for its role in Wnt signaling, may mediate anti-Müllerian hormone action.