Molecular basis of aromatase deficiency in an adult female with sexual infantilism and polycystic ovaries.

Abstract

We identified two mutations in the CYP19 gene responsible for aromatase deficiency in an 18-year-old 46,XX female with ambiguous external genitalia at birth, primary amenorrhea and sexual infantilism, and polycystic ovaries. The coding exons, namely exons II-X, of the CYP19 gene were amplified by PCR from genomic DNA and sequenced directy. Direct sequencing of the ampled DNA from the patient revealed two single-base changes, at bp 1303 (C-+ T) and bp 1310 (G -p A) in exon X, which were newly found missense mutations and reulted in codon changes of R435C and C437Y, respectively. Subconlng followed by sequencing confirmed that the patient is a compound heterozygote. The results ofrestriction frgment length polymorphism analysis and direct sequencing of the ampliied exon X DNA from the patient's mother indicate maternal inheritance of the R435C mutation. Transient expression experiments showed that the R435C mutant protein had =1.1% of the activity of the wild type, whereas C437Y was totally inactive. Cysteine-437 is the conserved cysteine in the heme-binding region believed to serve as the fifth coordinating ligand of the heme iron. To our knowledge, this patient is the first adult to have described the cardinal features of a syndrome of aromatase deficiency. Recognition that such defects exist will lead to a better understanding of the role of this enzyme in human development and disea.The biosynthesis ofestrogens from Clg steroids is catalyzed by an enzyme complex known as aromatase, whose activity results in aromatization ofthe A ring of androgens to form the phenolic A ring characteristic of estrogens, with concomitant loss of the Clg angular methyl group (1, 2). This enzyme complex is located in the endoplasmic reticulum of estrogenproducing cells and consists oftwo components. The first is a form of cytochrome P450 named aromatase cytochrome P450 (P450arom), the product of the CYP19 gene (3). The second component, NADPH-cytochrome P450 reductase, a ubiquitous flavoprotein of the endoplasmic reticulum of most cell types, transfers reducing equivalents to the P450arom, which binds the C19 substrate and catalyzes the insertion of oxygen into the molecule, resulting in the formation of C18 estrogens

The genetic basis of polycystic ovary syndrome

“…Some cases of hyperandrogenism have been reported in patients with aromatase deficiency (51,52). Immunohistochemical studies of polycystic ovaries could not detect aromatase in antral follicles of various sizes (53).…”

Oestrogen deficiency in men: where are we today?

“…The significance of oestrogen biosynthesis in the human placenta and adipose tissue remains poorly understood. Recently, sporadic cases of female pseudohermaphroditism at birth coupled with maternal progressive virilization during the third trimester of gestation as a result of aromatase deficiency have shed new light on this issue (6,7,9,10). Seven well-documented cases of aromatase deficiency have been described so far (6)(7)(8)(9)(10)(14)(15)(16)(17).…”

“…Indeed, until recently no condition of oestrogen insensitivity had been reported, unlike well-documented inactivating mutations of other members of the steroid/ thyroid/retinoid receptor gene superfamily, such as androgen (2), thyroid hormone (3,4) and glucocorticoid hormone receptors (5). Thus, the general acceptance that oestrogens are essential for life worked until the beginning of this decade, when sporadic cases of congenital oestrogen deficiency in humans were reported (6)(7)(8)(9)(10)(11) and a viable line of mutant mice lacking functional ERs was created (12,13). Since then, the idea of a pivotal role of oestrogen for survival has begun to look thin in the light of these new findings, which undoubtedly raise many questions in turn.…”

“…Until now, two different conditions have been identified as possible underlying causes of congenital oestrogen deficiency in humans: (a) oestrogen resistance caused by disruptive mutations of the ER gene (11); and (b) aromatase deficiency due to mutations of the gene encoding aromatase cytochrome P450 (P450arom) (6)(7)(8)(9)(10)(14)(15)(16)(17), the enzyme responsible for aromatization of the A ring of androgens to form the A ring characteristic of oestrogens. Whatever the mechanism, all the tissue-and organ-specific physiological responses triggered by oestrogens are lacking.…”

The masculinization of the fetus during pregnancy due to inhalation of diesel exhaust.

“…In addition to these direct transfers of toxic substances from mothers, endogenous sex steroids accumulated to excess in mothers due to enzymatic deficiency can also disrupt differentiation of reproductive organs in offspring. Aromatase deficiency caused by mutations in the CYP19 gene leads to excess circulation of androgens and results in virilization and ambisexual development (12)(13)(14)(15). Prenatal exposure to nicotine (16)(17)(18) and several other drugs (19) reduces or suppresses aromatase activities as well.…”