MOLECULAR ANALYSIS OF THE ANDROGEN-RECEPTOR GENE IN A FAMILY WITH RECEPTOR-POSITIVE PARTIAL ANDROGEN INSENSITIVITY - AN UNUSUAL TYPE OF INTRONIC MUTATION

In the coding part and the intron-exon boundaries of the androgen-rece ptor gene of a patient with partial androgen insensitivity, no mutatio n was found. The androgen receptor of this patient displayed normal li gand-binding parameters and migrated as a 110-112-kD doublet on SDS-PA GE in the absence of hormone. However, after culturing of the patient' s genital skin fibroblasts in the presence of hormone, the slower-migr ating 114-kD protein, which reflects hormone-dependent phosphorylation , was hardly detectable. Furthermore, receptor protein was undetectabl e in the nuclear fraction of the fibroblasts, after treatment with hor mone, which is indicative of defective DNA binding. By sequencing part of intron 2, a T --> A mutation was found 11 bp upstream of exon 3. I n our screening of 102 chromosomes from unrelated individuals, this ba sepair substitution was not found, indicating that it was not a polymo rphism. mRNA analysis revealed that splicing involved a cryptic splice site, located 71/70 bp upstream of exon 3, resulting in generation of mRNA with an insert of 69 nucleotides. In addition, a small amount of a transcript with a deleted exon 3 and a very low level of wild-type transcript were detected. Translation of the extended transcript resul ted in an androgen-receptor protein with 23 amino acid residues insert ed between the two zinc clusters, displaying defective DNA binding and defective transcription activation.