We have identified two different single nucleotide alterations in codon 686 (GAC; aspartic acid) in exon 4 of the human androgen receptor gene in three unrelated families with the complete form of androgen insensitivity. One mutation (G----C) results in an aspartic acid----histidine substitution (with 15-20% of wild-type androgen-binding capacity), whereas the other mutation (G----A) leads to an aspartic acid----asparagine substitution (with normal androgen-binding capacity, but a rapidly dissociating ligand-receptor complex). The mutations eliminate a Hinfl restriction site. Screening for the loss of the Hinfl site in both families with the Asp----Asn mutation resulted in the recognition of heterozygous carriers in successive generations of each. Both mutant androgen receptors were generated in vitro and transiently expressed in COS and HeLa cells. The receptor proteins produced had the same altered binding characteristics as those measured in fibroblasts from the affected subjects. R1881-activated transcription of a GRE-tk-CAT reporter gene construct was strongly diminished by both mutant receptors and was only partially restored using a 100-fold higher concentration of ligand compared with wild-type receptor. Thus, aspartic acid-686 appears essential for normal androgen receptor function. Substitution of this amino acid residue, by either histidine or asparagine, results in androgen insensitivity and lack of androgen-dependent male sexual differentiation.

There is no obvious relation between the degree of androgen resistance and the binding parameters of the AR and/or the nature of mutation in the AR gene. Androgen insensitivity syndrome can occur despite normal androgen binding and presumably non-mutated AR genes. Even if there is abnormal binding of androgen and/or a mutation in the AR gene there is no clear-cut relationship between these parameters and the degree of virilization defects. Thus, in a proportion of patients, neither the determination of binding parameters of the AR nor the detection of mutations in the AR gene are sufficient to understand the mechanisms underlying the androgen insensitivity syndrome.

Estrone sulfate (E1S) is the most abundant estrogen in the circulation of adults. The present study was undertaken to assess estrone (E1) and estradiol formation from E1S in freshly resected bone [bone fragments (BFs)] and osteoblast-like cells (hOB) cultured from BFs. Furthermore, we compared estrogen formation from E1S in rat and human osteosarcoma (OS) cell lines and that of estrogen formation from E1S with that of aromatization of androstenedione and testosterone in BFs and those from E1S and androstenedione in hOB cells. The bone used was from the head of the femur from a total of 15 women and 12 men. Steroid sulfatase activity (STA) was found, and the formation of estrone and estradiol from E1S was demonstrated. STA was similar in cells derived from BFs of men and women. STA was significantly lower in OS cell lines, compared with hOB cells. Estrogen formation from E1S in BFs was at least 20 times higher than that from androstenedione and about 50 times higher than that from testosterone. Similarly, estrogen formation from E1S in hOB cells exceeded the values derived from aromatization of androstenedione by two orders of magnitude. Based on these results, we conclude that hOB cells express the same pattern of E1S metabolism as resected bone and thus may accurately mirror the in vivo situation in man. In comparison with hOB cells, STA is fundamentally lower in widely used OS cell lines that express an osteoblastic phenotype. This shortcoming precludes their use as model cell lines to unravel STA metabolic pathways and its regulation in nontumorous bone. E1S is a major source of local bioactive estrogen formation in human bone. Because bone is highly susceptible to estrogen action, local estrogen formation from E1S may play an important role in bone maturation and homeostasis, particularly in elderly adults.

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