Mosaicism due to a Somatic Mutation of the Androgen Receptor Gene Determines Phenotype in Androgen Insensitivity Syndrome1

Premature stop codons of the human androgen receptor (AR) gene are usually associated with a complete androgen insensitivity syndrome. We, however, identified an adult patient with a 46,XY karyotype carrying a premature stop codon in exon 1 of the AR gene presenting with signs of partial virilizatio...

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Veröffentlicht in:The journal of clinical endocrinology and metabolism 1997-11, Vol.82 (11), p.3584-3589
Hauptverfasser: Holterhus, Paul-Martin, Brüggenwirth, Hennie T, Hiort, Olaf, Kleinkauf-Houcken, Annette, Kruse, Klaus, Sinnecker, Gernot H. G, Brinkmann, Albert O
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Sprache:eng
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Zusammenfassung:Premature stop codons of the human androgen receptor (AR) gene are usually associated with a complete androgen insensitivity syndrome. We, however, identified an adult patient with a 46,XY karyotype carrying a premature stop codon in exon 1 of the AR gene presenting with signs of partial virilization: pubic hair Tanner stage 4 and clitoral enlargement. No other family members were affected. A point mutation at codon position 172 of the AR gene was detected that replaced the original TTA (Leu) with a premature stop codon TGA (opal). Careful examination of the sequencing gel, however, also identified a wild-type allele, indicating a mosaicism. In addition, elimination of the unique AflII recognition site induced by the mutation was incomplete, thus confirming the coexistence of mutant and wild-type AR alleles in the patient. Normal R1881 binding and a normal 110/112-kDa AR doublet in Western immunoblots consolidated the molecular genetic data by demonstrating the expression of the wild-type AR in the patient’s genital skin fibroblasts. Transfection analysis revealed that only relatively high plasmid concentrations carrying the mutated AR complementary DNA lead to expression of a shortened AR due to downstream reinitiation at methionine 189. Thus, reinitiation does not play a role in the presentation of the phenotype; rather, the partial virilization is caused by the expression of the wild-type AR due to a somatic mosaic. We conclude that somatic mosaicism of the AR gene can represent a substantial factor for the individual phenotype by shifting it to a higher degree of virilization than expected from the genotype of the mutant allele alone.
ISSN:0021-972X
1945-7197
DOI:10.1210/jcem.82.11.4375