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 directly. Direct sequencing of the amplified
DNA from the patient revealed two single-base changes, at bp 1303 (C-->T) and bp 1310 (G-->A) in exon X, which were newly found missense mutations and resulted in
codon changes of R435C and C437Y, respectively. Subcloning followed by sequencing confirmed that the patient is a compound heterozygote. The results of restriction fragment length polymorphism analysis and direct sequencing of the amplified 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 approximately 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 disease.