SLDB

Speech/Language Disorders Database

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Gene / phenotype associations for DRD2

  • Click column headers to sort. Click to expand any row to see more details about the particular assertion of an association between variants of DRD2 and a particular phenotypic variable.
  • Click the Pubmed IDs in the last column to link out to the primary research article. Click the links in the last column to download the full Genotype-Phenotype record as JSON or XML formatted text.
Entrez Id Symbol Location Disorder Brief Phenotype Reference Year Download
1813 DRD2 11q23 Stuttering Susceptibility to stuttering Lan et al 2009 JSON | XML

Conflicting Studies:

  • Kang et al (2011) - Failed to replicate association to rs6277 in DRD2 in European (N=214 cases /451 controls) and Brazilian (N=50 / 50) samples. Also found no association to rs6275.
  • Additional Phenotype Details: Stuttering may be diagnosed using the Stuttering Severity Instrument (SSI). In some studies, subjects are asked to read a standardized text aloud and to engage in free speech for a certain amount of time, and the percentage of dysfluencies (out of all words, and/or out of all syllables) determines the diagnosis.

    Reference
    Riley, G. 2009. SSI-4: Stuttering severity instrument--Fourth edition; examiner's manual. Pro-Ed, Austin, TX (2009).

    Basic Study Type: Association study

    Study Cohort: 

    "This study included 112 stutterers (the patients) and 112 non-stutterers (the controls). The stutterers were recruited from two Rectification Centres of Stuttering (Beijing Stuttering Correction Centre and Dingguagua Stutter Club in Xi’an) and one hospital (Beijing Charity Hospital). Participants suffering from neurological or other physical diseases were excluded from the study. There were 13 females and 99 males in the patient group and their mean age was 23.53 years (s.d.: 4.99). . .

    "The non-stutterers were recruited from college students who volunteered to participate. Participants with a past history or family history of fluency disorders, severe neurological or other physical diseases were excluded. Among the enrolled control participants, 112 participants were selected to match the sex ratio with the patient group (13 females and 99 males). Their mean age was 25.23 years (s.d.: 3.34).
    "All participants are native Han Chinese. Informed consents were obtained beforehand, and ethical approval was obtained from the Ethical Committee, Graduate University of the Chinese Academy of Sciences."

    Genotyping Methods: 

    The following SNPs were genotyped (significant results were found only for rs6277 in DRD2):
    DRD2: rs6275, rs6277
    SLC6A3: rs2617604, rs28364997, rs28364998

    "A combined approach of PCR and pyrosequencing methods was used for genotyping. The fragments that contained the SNPs in DRD2 were amplified with biotinylated forward primers and non-biotinylated reverse primers, whereas the fragments that contained the SNPs in SLC6A3 gene were amplified with biotinylated reverse primers and non-biotinylated forward primers, respectively (Table 1). PCR amplification was carried out in a 50 µl volume containing 1 µl (10 ng) genomic DNA, 5 µl 10xPCR buffer, 200 µM dNTP, 200 nM primer of each and 0.5 µl (2.5U) Taq DNA polymerase. After 5min of pre-denaturation at 95°C, 50 thermal cycles were repeated, 15 s at 95°C, 30 s at annealing temperature, and 15 s at 72°C, the PCR tubes were then incubated for 5min at 72°C for final extension. The genotypes of the PCR products were determined by pyrosequencing using a standard protocol. Briefly, following strand separation, the biotinylated PCR product was immobilized on streptavidin-coated beads (Streptavidin Sepharose High Performance; Amersham Biosciences, Uppsala, Sweden). The beads were transferred to a filter plate, and the liquid was removed by vacuum filtration (Multiscreen Resist Vacuum Manifold; Millipore, Billerica, MA, USA). The DNA strands were separated in a denaturation solution (0.2mol 1^-1 NaOH) for 5 s. The immobilized template was washed in 10 nmol 1^-1 Tris acetate (pH 7.6), transferred to a PSQ 96 plate, and resuspended in annealing buffer (20mmol 1^-1 Tris acetate (pH 7.6)) that contained sequencing primers (Table 1). The resulting mixture was analyzed on a PSQ 96MA Pyrosequencer (Pyrosequencing AB; Biotage, Uppsala, Sweden) using the multiplex programing function."

    Analysis Methods: 

    The chi-squared test was used to analyse differences in allele frequencies, and to evaluate polymorphisms for Hardy-Weinberg equilibrium.

    Other Details: 

    Diagnostic criteria:

    "Chinese Fluency Interview, an instrument specifically modified from the Fluency Interview to be applicable to Chinese [19], was used for the assessment of stuttering. The total number of times of stuttering and the number of stuttering episodes per minute were calculated. More than 3 times per minute was diagnosed as stuttering."

    Associated Markers:
    rs6277  (P = 0.001; 0.0019)  - P-values for C allele and CC genotype, respectively


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    Negative evidence for association with DRD2

    Conflicting Ref Year Original Report Failed Association Comment
    Kang et al 2011 Lan et al (2009) Susceptibility to stuttering (Stuttering) Failed to replicate association to rs6277 in DRD2 in European (N=214 cases /451 controls) and Brazilian (N=50 / 50) samples. Also found no association to rs6275.