Gene, mRNA, and precursor

The human AMH gene, AMH, location 19p13.3, consists of five exons encompassing a 2.75-kbp genome sequence . Human AMH mRNA has 2065 b and contains a 1683-b open reading frame that encodes a signal peptide of 25 aa residues and a mature protein of 535 aa residues. The AMH gene is evolutionarily conserved in vertebrates. AMH mRNA is expressed in testicular Sertoli cells and ovarian granulosa cells. During rat development, Amh mRNA is detected at embryonic day 14 in the testis during gestation and the expression is retained until birth. After birth, the testicular Amh expression decreases and becomes almost undetectable after postnatal day 5. Conversely, the ovary increasingly expresses Amh after birth.5In the ovary, Amh expression is observed at maximum levels in the granulosa cells of preantral and small antral follicles.

Synthesis and release

In humans, AMH is secreted by testicular Sertoli cells from 6weeks of gestation. This secretion is stimulated by follicle-stimulating hormone (FSH), and the AMH levels remain high until birth. The testicular AMH secretion temporarily declines at birth but is kept high until puberty when Sertoli cells stop proliferation. In adults, AMH is secreted at a low level. Androgen, secreted by Leydig cells in response to LH, negatively regulates AMH production. In mice, a 180-bp Amh promoter is sufficient for the appropriate activation of transcription, and SF-1, SOX-9. GATA binds to the promoter and plays an important role in gene activation.

Receptors

AMH binds to a heterodimer consisting of type I and type II AMH receptors. The type II AMH receptor (AMHR2) is specific to AMH. Human AMHR2 consists of 573 aa residues, containing a 21-aa transmembrane domain and a 309-aa serine/threonine kinase domain. Type I AMH receptors (AMHR1) include activin A receptor type 1 (ACVR1), bone morphogenetic protein receptor type 1A (BMPR1A), and BMPR1B, which function in other TGF-β signaling pathways. By binding to AMHR2, AMH forms a heterodimer of type I and type II receptors, and an intracellular serine/ threonine kinase domain of AMHR2 phosphorylates the type I receptor to be activated. Then, the type I receptor binds to SMAD proteins and activates the Smad signaling pathway.

Biological functions

Both Amh knockout mice and Amhr2 knockout mice showed persistent Mullerian ducts in males, resulting € in the retention of female reproductive organs after birth as well as Leydig cell hyperplasia.The same phenotype was observed in double knockout mice of Amh and Amhr2 genes. The mutation of a SOX9-binding site in the mouse Amh promoter resulted in pseudohermaphrodites. Although Amh knockout female mice were fertile, the number of primordial follicles reduced at the age of 13months. In the medaka, hotei mutants, which contained a mutation in the amhr2 gene, showed excessive germ cell proliferation and male-to-female sex reversal. The zebrafish, which has a short deletion of Amh by the CRISPR/Cas9 system, displayed a female-biased sex ratio and excessive germ cell proliferation in both the male and female. When AMH was chronically expressed, female mice lost the uterus and oviducts.

Clinical implications

Persistent Mullerian duct syndrome (PMDS) is a disease characterized by the persistence of the uterus and Fallopian tubes in males. In most cases, PMDS is due to the mutation of AMH or AMHR2 genes that cause the lack of AMH secretion or receptor insensitivity. Many kinds of mutations such as nonsense and missense mutation, insertion, and deletion were reported throughout the coding sequences of both genes.

Description

Anti-Müllerian hormone is a glycoprotein hormone secreted by testicular Sertoli cells and ovarian granulosa cells. AMH is responsible for the regression of Mullerian ducts during male differentiation. The presence of an anti-Mullerian substance was predicted in the 1940s. AMH was first purified from bovine fetal testes in 1984, and cDNAs for bovine and human AMH were cloned in 1986.

Clinical Use

AMH is thought to be a good marker of ovarian reserve because its serum level is correlated with the number of small antral follicles. However, high levels of serum AMH are often associated with polycystic ovary syndrome (PCOS). For in vitro fertilization (IVF), the AMH levels may predict the response to ovarian stimulation.

Structure and conformation

Mature human AMH is a glycoprotein consisting of 535 aa residues and it forms a homodimer by disulfide bonds. Proteolytic cleavage produces a 426-aa N-terminal domain (AMH-N) and a 109-aa C-terminal domain (AMH-C). AMH-N and AMH-C remain associated in a noncovalent complex. Only AMH-C is biologically active and AMH-N is required for AMH to be fully active. An approximately 100-aa C-terminal sequence shows a similarity with transforming growth factor (TGF)-β family proteins, forming a cysteine knot motif via seven canonical cysteine residues. Therefore, AMH belongs to the TGF-β family. By the cleavage of a 140-kDa homodimer, 110-kDa AMH-N and 25-kDa AMH-C are produced. pI approximately 7.0. AMH solution in 4mM hydrochloric acid with 0.1% bovine serum albumin is stable for 3months at -20°C or lower.

Raw materials

Preparation Products