Effects of source of DNA on genotyping success rates and allele percentages in the Preschoolers with Attention-Deficit/Hyperactivity Disorder Treatment Study (PATS).
OBJECTIVE
In children diagnosed with attention-deficit/hyperactivity disorder (ADHD) and their parents, who were participants of the Preschool ADHD Treatment Study (PATS), we assessed the effect of source of DNA (from buccal or blood cells) on the genotyping success rate and allele percentages for the five polymorphisms in three candidate genes (DAT1, DRD4, and SNAP 25) investigated in the PATS pharmacogenetic study of response to stimulant medication.


METHODS
At baseline assessment, 241 individuals (113 probands and 128 parents) consented to participate; 144 individuals (52 probands and 92 parents) provided blood samples from venipuncture, and 97 individuals (61 probands and 36 parents) provided buccal samples from cheek swab as specimens for isolation of DNA. Three types of polymorphisms-variable number of tandem repeat (VNTR) polymorphism, tandem duplication polymorphism (TDP), and single nucleotide polymorphism (SNP)-were evaluated, including the DRD4 gene 48-bp VNTR in exon III, the DAT1 gene 40-bp VNTR in 3'-untranslated region, the DRD4 gene TDP 120-bp duplication in the promoter region, the SNAP-25 gene TC-1069 SNP, and the SNAP-25 gene TG-1065 SNP. Standard procedures were used to genotype individuals for each of these five polymorphisms.


RESULTS
Using the methods available in 2004, the genotyping success rate was on the average much greater for DNA from blood cells than buccal cells (e.g., 91% vs. 54% in probands). For some polymorphisms (DRD4-VNTR, DRD4-TDP, and SNAP25-TC SNP), allele proportion also varied by blood versus buccal source of DNA (e.g., 26.5% vs. 18.6% for the 7-repeat allele of the DRD4 gene).


CONCLUSIONS
The much lower success rate for genotyping based on DNA from buccal than blood cells is likely due to the quality of DNA derived from these two sources. The observed source differences in allele proportion may be due to self-selection related to choice of how specimens were collected (from cheek swab or venipuncture), or to a selective detection of some alleles based on differences in DNA quality.
Swanson
James M
JM
Child Development Center, University of California-Irvine, 19722 MacArthur Boulevard, Irvine, CA 92612, USA. jmswanso@uci.edu
Moyzis
Robert K
RK
McGough
James J
JJ
McCracken
James T
JT
Riddle
Mark A
MA
Kollins
Scott H
SH
Greenhill
Laurence L
LL
Abikoff
Howard B
HB
Wigal
Tim
T
Wigal
Sharon B
SB
Posner
Kelly
K
Skrobala
Anne M
AM
Davies
Mark
M
Ghuman
Jaswinder K
JK
Cunningham
Charles
C
Vitiello
Benedetto
B
Stehli
Annamarie
A
Smalley
Susan L
SL
Grady
Deborah
D
D000483:Alleles; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000235:genetics*; D002675:Child, Preschool; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D016015:Logistic Models; D008297:Male; D018598:Minisatellite Repeats / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics; D050638:Receptors, Dopamine D4 / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics; D020080:Tandem Repeat Sequences / Q000235:genetics
D050483:Dopamine Plasma Membrane Transport Proteins; C493214:SLC6A3 protein, human; D050825:Synaptosomal-Associated Protein 25; D050638:Receptors, Dopamine D4; D004247:DNA