Biomedical subjects

D M Vasiliou

Publications and source records attributed to D M Vasiliou.

5 recordsLinked to original sources

PubMed1999

Analysis of exon 1 mutations in the androgen receptor gene.

Eleven mutations in exon 1 of the androgen receptor gene (AR) have been identified in 15 individuals with Androgen Insensitivity syndrome (AIS). Nine of the mutations yield a stop codon directly, or due to a frameshift, in individuals with complete AIS (CAIS). One individual with CAIS had three different mutations in exon 1: one is nominally silent (Glu 211; GAG 995 GAA); two are missense (Pro 390 Arg and Glu 443 Arg). Five unrelated individuals with either CAIS, partial AIS (PAIS) or mild AIS (MAIS) had GAG 995 GAA as their only alteration. This report almost doubles the number of exon 1 mutations stored in the AR Mutation Database, reinforces their highly predominant nonsense character, and identifies Pro 390 and/or Gln 443 as residues that are probably necessary for one or more specific functions of the AR's N-terminal transactivation domain.

Androgen-Insensitivity Syndrome↗

PubMed1997

Codon-usage variants in the polymorphic (GGN)n trinucleotide repeat of the human androgen receptor gene.

The human androgen receptor gene (hAR) has a long, polymorphic trinucleotide (GGN; glycine)n repeat in the 3' portion of its first exon, with n = 10-31. Owing to technical difficulties that have precluded routine sequencing of this region, it is widely unknown that N represents T, G or C, and that the usual sense codon sequence of the GGN tract is (GGT)3GGG(GGT)2(GGC)4-25. Furthermore, on 4 of 61 X chromosomes, we observed that the internal GGT sequence was present three or four times instead of twice. Strikingly, each of the three alleles with an internal (GGT)3, and only these three, also had a (GGC)20 repeat. The size or composition of a (GGN)n repeat was not correlated with the length of the accompanying (CAG)nCAA repeat in the 5' portion of exon one. Hence, codon-usage variants of the GGN tract may be used to seek associations with particular diseases, as diagnostic aids in families with androgen insensitivity whose AR mutations have not yet been identified, or as internal controls for observations on intergenerational contractions or expansions of the (CAG)nCAA tract in a given hAR allele.

Alleles↗

PubMed1996

The androgen receptor gene mutations database.

The current version of the androgen receptor (AR) gene mutations database is described. We have added (if available) data on the androgen binding phenotype of the mutant AR, the clinical phenotype of the affected persons, the family history and whether the pathogenicity of a mutation has been proven. Exonic mutations are now listed in 5'-->3' sequence regardless of type and single base pair changes are presented in codon context. Splice site and intronic mutations are listed separately. The database has allowed us to substantiate and amplify the observation of mutational hot spots within exons encoding the AR androgen binding domain. The database is available from EML (ftp://www.ebi.ac.uk/pub/databases/androgen) or as a Macintosh Filemaker file (MC33@musica.mcgill.ca).

Androgens↗

PubMed1994

Complete androgen insensitivity due to mutations in the probable alpha-helical segments of the DNA-binding domain in the human androgen receptor.

We describe different single-amino acid aberrations in the DNA-binding domain (DBD) of the human androgen receptor (hAR) in three families with complete androgen insensitivity. No additional alteration was found in the translated portion of each mutant gene. In one family, an in-frame 3 nt deletion removes codon 581-(or 582) and, thereby, one of two phenylalanines that invariably occupy adjacent positions in the N-terminal alpha-helical region of the DBD in the steroid/thyroid/vitamin D receptor superfamily. In the second, an in-frame 3 nt loss deletes Arg614, an invariant residue in the C-terminal alpha-helix of the DBD. In the third, a G-->A transition causes Arg614His. Following transient transfection of COS cells with each mutant AR plasmid, there is a normal concentration of specific androgen-binding activity that has a reduced ability to bind two types of androgen response element (ARE), and to transregulate an androgen-responsive human growth hormone reporter gene. In genital skin fibroblasts with delta Phe581 or Arg614His, androgen-binding, AR protein and AR mRNA are markedly reduced; in gonadal fibroblasts with delta Arg614, AR mRNA may be reduced. Our data substantiate the primary contributions of Phe581 and Arg614 to normal hAR-ARE binding, and expose important secondary effects of the mutations affecting each residue.

Amino Acid Sequence↗

PubMedDate not supplied

Altered mRNA expression due to insertion or substitution of thymine at position +3 of two splice-donor sites in the androgen receptor gene.

We have discovered two types of 5' intronic gene mutation that impair androgen receptor (AR) mRNA expression severely, and cause complete androgen insensitivity. Labium majus skin fibroblasts (LMSF) hemizygous for each mutation had negligible specific androgen binding, and did not react to an antibody against an N-terminal peptide of the AR. Both mutations were detected by direct sequencing of exons PCR-amplified with flanking primers. One mutation is an adenine to thymine transversion at position +3 of the intron 6 splice-donor site. Using LMSF mRNA, RT-PCR of a portion of the AR androgen-binding domain yielded a small amount of a 302-bp mutant fragment instead of a 433-bp wild-type product. Sequencing established that exon 5 was followed, out of frame, by exon 7: exon 6 was skipped. The other mutation is a thymine insertion at the +3 position of the intron 1 donor-splice site. RT-PCR and sequencing revealed a small amount of normal-size mRNA with normal exon 1-exon 2 splicing. Quantitative RT-PCR on mutant LMSF showed AR mRNA levels were well below 10% of normal; hence, most of the aberrant AR mRNA resulting from each mutation is probably unstable. The misbehavior caused by these two mutations indicates that in the AR the splice-donor site +3 adenine is critical; indeed, 57% of eukaryotic introns have adenine in the +3 position, while only 2% have thymine.

Adolescent↗