An unequal cross-over event within the CYP2D gene cluster generates a chimeric CYP2D7/CYP2D6 gene which is associated with the poor metabolizer phenotype.
1. The study of the CYP2D genotype and phenotype of a Caucasian family revealed that a XbaI-9 kb allele was associated with the poor metabolizer phenotype. 2. A Polymerase Chain Reaction (PCR)-based assay showed that the previously described mutations D6A and D6B are not associated with the XbaI-9 kb allele. 3. To explore the molecular basis of the poor metabolizer phenotype associated with the XbaI-9 kb allele, complete sequencing of the nine exons and intron-exon boundaries of the CYP2D6 gene was undertaken after amplification by PCR. 4. All the exons were successfully amplified using CYP2D6 gene-specific primers except exon 1 which required a combination of CYP2D7 gene-specific 5' primer and a CYP2D6 gene-specific 3' primer. 5. Sequence data derived from this amplified product revealed that the XbaI-9 kb allele corresponds to a novel rearrangement of the locus. This involved a deletion of an approximately 20 kilobase (kb) DNA segment generating a hybrid 5' CYP2D7/CYP2D6 3' gene. 6. The chimeric gene is non-functional presumably due to an insertion in exon 1 (characteristic of the exon 1 of the CYP2D7 gene) which causes a shift in the reading frame with premature termination of translation.
Panserat
S
S
INSERM U120, Hôpital Robert Debré, Paris, France.
Mura
C
C
Gérard
N
N
Vincent-Viry
M
M
Galteau
M M
MM
Jacoz-Aigrain
E
E
Krishnamoorthy
R
R
D001483:Base Sequence; D019389:Cytochrome P-450 CYP2D6; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D017931:DNA Primers; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000235:genetics*; D044465:White People / Q000235:genetics
D017931:DNA Primers; D011993:Recombinant Fusion Proteins; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D019389:Cytochrome P-450 CYP2D6