Corinne Belville

Hormonal and cellular regulation of Sertoli cell anti-Müllerian hormone production in the postnatal mouse.

Anti-Müllerian hormone (AMH) is secreted by immature testicular Sertoli cells. Clinical studies have demonstrated a negative correlation between serum AMH and testosterone in puberty but not in the neonatal period. We investigated AMH regulation using mouse models mimicking physiopathological situations observed in humans. In normal mice, intratesticular, not serum, testosterone repressed AMH synthesis, explaining why AMH is downregulated in early puberty when serum testosterone is still low. In neonatal mice, AMH was not inhibited by intratesticular testosterone, due to the lack of expression of the androgen receptor in Sertoli cells. We had shown previously that androgen-insensitive patients exhibit elevated AMH in coincidence with gonadotropin activation. In immature normal and in androgen-insensitive Tfm mice, follicle stimulating hormone (FSH) administration resulted in elevation of AMH levels, indicating that AMH secretion is stimulated by FSH in the absence of the negative effect of androgens. The role of meiosis on AMH expression was investigated in Tfm and in pubertal XXSxrb mice, in which germ cells degenerate before meiosis. We show that meiotic entry acts in synergy with androgens to inhibit AMH. We conclude that AMH represents a useful marker of androgen and FSH action within the testis, as well as of the onset of meiosis.

Persistence of müllerian derivatives in males

The persistent müllerian duct syndrome is a rare, autosomal recessive disorder, characterized by the persistence of müllerian duct derivatives-uterus and fallopian tubes-in genetic males otherwise normally virilized. We have collected DNA from 69 families with this syndrome. In 45%, a mutation of the anti-müllerian hormone (AMH) gene was detected; 52% were homozygous. The level of circulating AMH was extremely low in the great majority of patients, even before puberty, when AMH levels are normally high. Single-strand conformation polymorphism (SSCP)-polymerase chain reaction (PCR) was a very effective screening method. In 39% of families, characterized by an AMH level normal for the age of the patient, a mutation of the type II receptor of AMH was detected by automatic sequencing, because SSCP-PCR was not very effective. Forty-eight percent of the mutations were homozygous. A 27-base-pair deletion in exon 10 was noted in 45% of the families. When this very common mutation is not taken into account, the proportion of recurrent mutations is 42% for the AMH gene and 33% for the AMH receptor type II gene. In 16% of families, no mutation of either the AMH or the AMH receptor gene was detectable; this group may correspond to mutations of unknown genes involved in AMH processing or in downstream AMH transduction.

Role of type I receptors for anti-Mullerian hormone in the SMAT-1 Sertoli cell line

Anti-Müllerian hormone (AMH) is a member of the transforming growth factor-β family responsible for regression of Müllerian ducts during male sexual differentiation and for regulation of gonadal steroidogenesis. AMH is also a gonadal tumor suppressor which mediates its effects through a specific type II receptor and the bone morphogenetic protein (BMP)-specific Smad proteins, suggesting that AMH and BMPs could also share type I receptors, namely activin-like kinases (ALKs)2, 3 or 6. However, attempts to identify a unique AMH type I receptor among them were unsuccessful. Here, using kinase-deficient type I receptors and small interfering RNA technology, we demonstrate that, in an AMH Sertoli target cell line, ALK3 mediates AMH effects on both Smad1 activation and P450 side-chain cleavage enzyme. In addition, transfecting a combination of normal and kinase-deficient receptors, we show that ALK2 can compensate for the absence of ALK3 and probably acts in synergy with ALK3 at high concentrations of AMH to activate Smad1, whereas ALK6 has a competitive inhibitory effect. These results are a first step in understanding how AMH transduces its effects in immature Sertoli cells.

A novel mutation in the anti-müllerian hormone gene as cause of persistent müllerian duct syndrome

Abstract. Persistent müllerian duct syndrome is a relatively rare inherited defect of sexual differentiation characterised by failure of regression of the müllerian ducts in males. In affected individuals, uterus and tubes are present because of defects of synthesis or action of anti-müllerian hormone (AMH), normally produced by the Sertoli cells of the testis. Patients are normally virilised, although mono- or bilateral cryptorchidism may be present. We observed two brothers (chromosomes 46 XY), aged 11 years and 2 months and 8 years and 3 months respectively, with bilateral cryptorchidism. The diagnosis of persistent müllerian duct syndrome was made on the basis of laparoscopic evidence of uterus and tubes, undetectable plasma levels of AMH and a 23 base pair duplicative insertion in exon 5 of the AMH gene, causing the introduction of a premature stop codon, homozygous in the two brothers. The surgical correction of the genital abnormalities was successfully carried out by laparoscopic orchidopexy according to Fowler-Stephens. Conclusion: persistent müllerian duct syndrome should be taken into consideration in all cases of bilateral cryptorchidism. Laparoscopy is the elective procedure for diagnosis of this disease and laparoscopic surgery for orchidopexy of intra-abdominal testes. Mutation analysis of the anti-müllerian hormone gene in these patients helps to understand the structure-function relationship of the anti-müllerian hormone protein, although it is not clear at present whether anti-müllerian hormone is necessary to maintain normal testicular function.

Une forme de cryptorchidie d’origine génétique: le syndrome de persistance des canaux de Müller@@@A genetic form of cryptorchidism: Persistent Müllerian duct syndrome

ResumeLe syndrome de persistance des canaux de Müller (PMDS) est une forme rare de pseudohermaphrodisme masculin caractérisé par la présence de dérivés Müllériens chez un sujet 46, XY normalement virilisé. Les circonstances de découverte sont chirurgicales, à l’occasion d’une intervention pour une cryptorchidie ou pour une cure de hernie inguinale.Une étude génétique réalisée sur 76 familles de sujets porteurs d’un PMDS a montré que des anomalies de l’hormone anti-Müllérienne (AMH) ou de l’un de ses récepteurs (AMHR-II) étaient observées chez 85% des familles étudiées, ce syndrome se transmettant selon un mode autosomique récessif. Pour les 15% des cas restants, l’origine du PMDS reste encore inconnue, aucune anomalie n’ayant été trouvée sur ces deux gènes.L’AMH est synthétisée par les cellules de Sertoli dès le début de la différenciation testiculaire. Cette glycoprotéine, qui fait partie de la famille du Transforming Growth Factor-β (TGF-β), présente une mutation chez 47% des familles de PMDS.Le récepteur de type II de l’AMH (AMHR-II) est exprimé par les cellules mésenchymateuses entourant le canal de Müller. II n’a qu’un seul domaine transmembranaire et possède une activité sérine/thréonine kinase. Chez 38% des familles PMDS étudiées, une anomalie de ce récepteur a été observée.AbstractPersistent Müllerian duct syndrome (PMDS), a rare form of male peudohermaphrodism, is characterized by lack of regression of Müllerian derivatives. These patients are externally phenotypic males in whom the presence of a uterus and Fallopian tubes is discovered during surgical correction of cryptorchidism and/or inguinal hernia. Molecular studies, in a total of 76 PMDS families, were performed by automatic sequencing after amplification by polymerase chain reaction (PCR) of different parts of the gene.AMH, synthesized by Sertoli cells, is a member of the Transforming Growth Factor-β superfamily. The 560 amino-acid glycoprotein is formed by two 70 kDa monomers linked by disulfide bonds. This hormone is cleaved at a proteolytic site 109 amino acids upstream of the C-terminus, yielding the bioactive C-terminal domain and a N-terminus which is not itself bioactive, but which enhances the bioactivity of the C-terminus. The gene, composed of five exons, is located on chromosome 19 (band p13.3). AMH gene mutations are present on the whole length of the gene in 47% of PMDS families. Sixty-one per cent were homozygous due to a high proportion of patients from Arabic or Mediterranean countries, characterized by a high rate of consanguinity. The serum AMH level, assessed by a commercially available enzyme immunoassay technique (ELISA), is extremely low in the great majority of patients, even before puberty when AMH levels are normally high.AMH binds to two distinct membrane-bound receptors, both serine/threonine kinases. The type II AMH receptor (AMHR-II) binds to the ligand, and this complex recruits receptor type I, which acts as a signal transducer by activating specific cytoplasmic substrates, the Smad molecules.AMHR-II, coded by a 8 kbp gene on chromosome 12 (band q13), contains 11 exons. Exons 1–3 encode the extracellular domain, exon 4 encodes the transmembrane part and exons 5–11 encode the intracellular serine/threonine kinase domain. An AMHR-II mutation was detected in 38% of PMDS families, characterized by a normal AMH level for the patient’s age. A particular mutation, a deletion of 27 bp in exon 10, was present in 45% of families of this group.No mutation of either AMH or the AMHR-II gene could be detected in 11 PMDS families.