Novel CYP19A1 Mutations Extend the Genotype-Phenotype Correlation and Reveal the Impact on Ovarian Function

The steroidogenic enzyme aromatase (CYP19A1) is required for estrogen biosynthesis from androgen precursors in the ovary and extragonadal tissues. The role of aromatase, and thus estrogens, is best illustrated by genetic variations of the CYP19A1 gene leading to aromatase deficiency or excess.

The objective of this work is to characterize novel CYP19A1 variants.

Variants causing aromatase deficiency were suspected in four 46,XX children of African and Indian origin by careful clinical phenotyping. Sequencing of the CYP19A1 gene identified novel variants. Minigene experiments, aromatase activity assay, and computational, and histological analysis were used to characterize the variants.

CYP19A1 variants were found in all patients: a deletion in intron 9 leading to p.P423_H503del, a delins variant at p.P154, and point variants p.V161D, p.R264C, p.R375C. Except for R264C, all variants showed a loss of function. Protein structure and dynamics studies were in line with functional assays. The 2 female patients with delins variants manifested with ambiguous genitalia at birth. Histologic investigation revealed normal ovarian tissue on one side and a streak gonad on the other. Two female patients presented with abnormal pubertal development and polycystic ovaries.

In girls, aromatase deficiency usually manifests at birth, but diagnosis may also be made because of abnormal pubertal development or ovarian torsion due to (poly)cystic ovaries. The ovary harboring CYP19A1 variants may present as streak gonad or appears normal at birth, but is then at very high risk to produce cysts with aging and is therefore prone to ovarian torsion.