The Aromatase Excess Syndrome Is Associated with Feminization of Both Sexes and Autosomal Dominant Transmission of Aberrant P450 Aromatase Gene Transcription

Increased extraglandular aromatization has been reported as the cause of familial gynecomastia. We studied a kindred with aromatase excess inherited in an autosomal dominant manner, in which affected males had heterosexual precocity and/or gynecomastia, and affected females had isosexual precocity and/or macromastia. The propositus was a 9-yr-old boy with gynecomastia. His 7.5-yr-old sister had precocious puberty, and their father and paternal grandmother had peripubertal gynecomastia and macromastia, respectively. Serum concentrations of gonadal and adrenal steroid hormones were determined before and after the administration of corticotropin and/or hCG. Aromatase activity was determined by[ 3H]Δ4-androstenedione to[ 3H]estrone conversion by cultured skin fibroblasts and/or Epstein-Barr virus-transformed lymphocytes and was detected by immunohistochemistry and/or Western analysis. Linkage was examined with a polymorphism of the aromatase (P450arom) gene. The P450arom messenger ribonucleic acid was analyzed by rapid amplification of complementary DNA (cDNA) ends, ribonuclease protection assay, and RT-PCR. hCG testing demonstrated a high rate of conversion ofΔ 4-androstenedione to estrone and of testosterone to estradiol in the propositus and his father. Treatment of the propositus and his sister was initiated with an aromatase inhibitor (testolactone) and a GnRH analog, which successfully delayed skeletal and pubertal development in both children. Markedly increased aromatase activity was found in the patients' fibroblasts and Epstein-Barr virus-transformed lymphocytes. The P450arom polymorphism segregated with the disease in the family. A new 5′-splice variant was present in the patients' P450arom messenger ribonucleic acid, thus identifying yet another first exon of this gene, which appears to be aberrantly expressed in this family. In conclusion, a family with the aromatase excess syndrome is described, in which the condition was inherited in an autosomal dominant manner, led to feminizing manifestations in both sexes, and was associated with the aberrant utilization of a novel transcript of the P450arom gene. SOME BREAST development occurs in 30–65% of boys during puberty, but is extremely uncommon in the prepubertal years (1, 2, 3). Prepubertal gynecomastia is most frequently caused by exogenously administered estrogens or hormone-secreting tumors (4). Rarely, this condition is inherited as a familial trait (Mendelian inheritance in man 107910), which has been associated with a high rate of conversion of serum C19 to C18 steroids (5, 6). Increased extraglandular aromatization was first reported in a boy with prepubertal gynecomastia in 1977 (7), then in five members of an African-American kindred in 1985 (8). Interestingly, idiopathic pubertal gynecomastia has been associated with an elevated ratio of serum estrogen to androgen levels during early puberty (9), and excessive aromatase activity in cultured pubic skin fibroblasts from these patients with gynecomastia (10). Aromatase, also known as estrogen synthetase, is the key enzyme in estrogen biosynthesis. It is an enzymatic complex composed by the aromatase cytochrome P450 (P450arom) and the flavoprotein NADPH-P450 reductase, which catalyzes the conversion of androgens to estrogens (11). Cytochrome P450arom, like the other heme-binding P450 isoforms, is a highly conserved, ancient gene, that is widely expressed in a variety of species in a complex, tissue-specific manner. The human P450arom gene contains 10 exons and is located on chromosome 15q21, an area syntenic to mouse chromosome 9, which harbors a cluster of P450 genes (12, 13, 14). It is expressed in the placenta, ovary, testis, brain, skin fibroblasts, adipocytes, normal breast and breast cancer epithelial and stromal cells, and a number of fetal tissues, including liver, brain, and intestine (11). Tissue-specific regulation of the P450arom messenger ribonucleic acid (mRNA) is ensured by alternative splicing of exon 1 and part of exon 2, driven by at least five major promoter regions located in the 5′-untranslated end of the gene (15, 16, 17, 18). A number of additional minor cDNA species have been identified in various tissues, although their functional significance remains uncertain (11, 15). Both sequences with enhancing and silencing function as well as known responsive elements to a variety of transcription factors have been identified in the regulatory region upstream of the P450arom gene (19, 20, 21, 22). Because of its complex regulation of function, the 5′-end of the P450arom gene has long been considered a candidate for disorders in which inappropriate aromatase activity is encountered. Indeed, the 5′-end splicing products of the P450arom gene in mammary neoplastic and human myeloid leukemia cells differ from those in the normal breast or represent new variants, respectively (16, 23, 24). Similarly, the study of uterine, ovarian, and testicular tumors of varying types and grades of malignancy suggested that alternative promoter use was associated with the mechanisms underlying neoplastic transformation (16, 25, 26). Increased aromatization is the mechanism behind the henny feathering trait in an animal model, the Sebright bantam chicken (27, 28). In the present study, we investigated a kindred with several members expressing clinical and biochemical evidence of aromatase excess. We found increased aromatase activity in cell lines established from the patients and identified a novel exon 1 of the P450arom gene that was uniquely transcribed in the cells from affected individuals