Sorted By Test Name - Mayo Medical Laboratories

DRD4
89096
Useful For: Influencing choice of antipsychotics prior to treatment, especially to ascertain if atypical
antipsychotics may be used with low risk of tardive dyskinesia Identifying those patients receiving
antipsychotics who are at increased risk of developing tardive dyskinesias. Individuals with the 25G allele
should be monitored closely for signs of tardive dyskinesia if a decision is made to treat with
antipsychotics Testing may also be considered for individuals who will receive antipsychotic medications,
if they are first-degree relatives of patients who have developed tardive dyskinesia. Assessing potential for
effective treatment response with clozapine, olanzapine, and risperidone
Interpretation: An interpretive report will be provided.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Lerer B, Segman RH, Fangerau H, et al: Pharmacogenetics of tardive
dyskinesia: combined analysis of 780 patients supports association with dopamine D3 receptor gene
Ser9Gly polymorphism. Neuropsychopharmacology 2002;27:105-119 2. de Leon J, Susce MT, Pan RM,
et al: Polymorphic variations in GSTM1, GSTT1, PgP, CYP2D6, CYP3A5, and dopamine D2 and D3
receptors and their association with tardive dyskinesia in severe mental illness. J Clin Psychopharmacol
2005;25:448-456 3. Scharfetter J, Chaudry HR, Hornik K, et al: Dopamine D3 receptor gene
polymorphism and response to clozapine in schizophrenic Pakistani patients. Eur Neuropsychopharmacol
1999;10(1):17-20 4. Lane HY, Hsu SK, Liu YC, et al: Dopamine D3 receptor Ser9Gly polymorphism and
risperidone response. J Clin Psychopharmacol 2005;25(1):6-11 5. Reynolds GP, Yao Z, Zhang X, et al:
Pharmacogenetics of treatment in first-episode schizophrenia: D3 and 5-HT2C receptor polymorphisms
separately associate with positive and negative symptom response. Eur Neuropsychopharmacol
2005;15:143-151
Dopamine Receptor D4 Genotype (DRD4), Blood
Clinical Information: The dopamine receptor D4 gene (DRD4) is located near the telomeric region
of chromosome 11q and is a highly variable gene. A 48-base pair (bp) variable number tandem repeat
(VNTR) polymorphism in exon 3 of DRD4, which ranges from 2 to 11 repeats, creates a 32- to
176-amino acid variation in the third intracellular loop on the dopamine receptor. The frequency of these
alleles is shown in the table. The DRD4 7-repeat allele (7R) has functional consequences and is associated
with lower affinity for dopamine receptor agonists and reduced signal transduction (eg, cAMP levels)
compared to the more common DRD4 4-repeat allele (4R). The effect of other copy number repeats is not
as well defined to date. Frequency of alleles with various DRD4 exon 3 48-bp repeats Allele/Number of
repeats (R) Allelic Frequency (%) 2R 8.8 3R 2.4 4R 65.1 5R 1.6 6R 2.2 7R 19.2 8R 0.6 9R