Genetic bases of executive control in preschool children: TRAILS-P performance is related to DRD2 genotype

Several studies link the D2 dopamine receptor (DRD2) with executive control and the ability to adapt behavior to changing contextual contingencies in human adults (Roesch-Ely 2005; Rodriguez-Jimenez 2006) and in animal models (Kruzich 2004). The present study examined relations between DRD2 and executive control in human development. Recently, a version of the Trail-Making Task suitable for preschool children was developed, which does not require knowledge of letters or numbers (TRAILS-P; Espy 2004). The Trail-Making Test is a neuropsychological test sensitive to frontal or executive dysfunction (Reitan 1955) where subjects must connect stimuli on a page in sequence, connecting letters only in the non-executive condition, and alternating between numbers and letters in the condition with executive demands. In TRAILS-P Control condition, children stamp a family of 5 dogs in order from smallest to biggest. The Switch condition adds executive demands by requiring children to switch response set by alternating stamping dogs and bones ordered by size. In the Inhibit condition, dogs and bones are present on the page but children must only stamp dog stimuli, requiring suppression of the response set acquired in the Switch condition. For each condition, the number of errors and completion latency are scored. A sample of 98 typically developing preschool children (mean age 4.3 years, range 2.5 to 6 years) completed the TRAILS-P task, and were genotyped on the Taq1A polymorphism linked to the DRD2 gene. The sample included 43 carriers of the higher-risk A1 allele (A1A1: n = 41; A1A2: n = 2) and 55 non-carriers (A2A2). For DRD2, presence of the A1 allele was associated with poorer performance on the switch condition (p \u3c .01 for time, p .17), statistically controlling for age. A1 carriers also made more errors on the Inhibit condition (p \u3c .005). The finding that DRD2 contributes to variation in executive control in young children provides a developmental continuity in this brain-behavior relationship between dopamine genotype and behavioral phenotype, and may be attributable to the lower availability of dopamine receptors associated with the DRD2 A1 genotype

Genes and behavior in preschool children: The relation between dopamine genotype and latent executive control

Objective: Dopaminergic neurotransmission is implicated in the executive control of cognition and behavior (Braver & Cohen, 2000). Presence or absence of particular dopamine gene alleles relates to executive control performance (Casey, 2002; Roesch-Ely, 2005) and to attention problems and ADHD (Durston, 2005; Schmidt, 2001). The present study examined the relation between dopamine genotype and executive control in normally-developing preschool children. Participants and Methods: The sample included 133 children (66 girls; mean age 4 years, range 2;2-6 years). Children completed a battery of executive control tasks, and were genotyped for 4 dopamine genes: the dopamine receptors DRD2 and DRD4, the dopamine transporter DAT, and the enzyme COMT. Based on a literature review, for each gene, children were classified as carrying the high- or low-risk allele, and a risk score was constructed by summing the number of high-risk alleles (range 0-4). In Mplus, structure equation modeling was used to examine the relation between the genetic risk score and a latent factor representing the executive control battery, controlling for age. Results: The SEM model evidenced good fit to the data (chisquare(43)=43.15, p=.46). Age had a strong positive relationship with executive control, and higher risk scores for dopamine genotype were associated with lower executive control performance (standardized regression coefficients=.76 and -.10, respectively). Conclusions: Dopamine genotype is correlated with executive control performance, perhaps reflecting differences in dopamine availability and efficiency of neurotransmission related to different dopamine alleles. Given that executive control problems are implicated in ADHD (Nigg, 2005), these findings may shed light on how genetic risk contributes to behavioral problems

Deformed Epidermal Autoregulatory Factor-1 (DEAF1) Interacts with the Ku70 Subunit of the DNA-Dependent Protein Kinase Complex

<div><p>Deformed Epidermal Autoregulatory Factor 1 (DEAF1) is a transcription factor linked to suicide, cancer, autoimmune disorders and neural tube defects. To better understand the role of DEAF1 in protein interaction networks, a GST-DEAF1 fusion protein was used to isolate interacting proteins in mammalian cell lysates, and the XRCC6 (Ku70) and the XRCC5 (Ku80) subunits of DNA dependent protein kinase (DNA-PK) complex were identified by mass spectrometry, and the DNA-PK catalytic subunit was identified by immunoblotting. Interaction of DEAF1 with Ku70 and Ku80 was confirmed to occur within cells by co-immunoprecipitation of epitope-tagged proteins, and was mediated through interaction with the Ku70 subunit. Using <em>in vitro</em> GST-pulldowns, interaction between DEAF1 and the Ku70 subunit was mapped to the DEAF1 DNA binding domain and the C-terminal Bax-binding region of Ku70. In transfected cells, DEAF1 and Ku70 colocalized to the nucleus, but Ku70 could not relocalize a mutant cytoplasmic form of DEAF1 to the nucleus. Using an <em>in vitro</em> kinase assay, DEAF1 was phosphorylated by DNA-PK in a DNA-independent manner. Electrophoretic mobility shift assays showed that DEAF1 or Ku70/Ku80 did not interfere with the DNA binding of each other, but DNA containing DEAF1 binding sites inhibited the DEAF1-Ku70 interaction. The data demonstrates that DEAF1 can interact with the DNA-PK complex through interactions of its DNA binding domain with the carboxy-terminal region of Ku70 that contains the Bax binding domain, and that DEAF1 is a potential substrate for DNA-PK.</p> </div

DEAF1 interacts with the DNA-PK complex.

<p>Recombinant GST and GST-DEAF1 fusion proteins were isolated from bacterial extracts, bound to glutathione-Sepharose beads, and incubated overnight in the presence (+) or absence (−, buffer only) of PC-3 cell lysates. Interacting proteins were eluted, separated by SDS-PAGE, and stained with Coomassie blue (<b>A</b>) or analyzed by Western blot with an antibody to DNA-PKcs (<b>B</b>). The 70 kDa and 80 kDa proteins (arrows) were determined by mass spectrometry to be Ku70 and Ku80. (<b>C</b>) CV1 cells were transfected with expression plasmids for DEAF1-FLAG and/or HA-tagged Ku proteins. Cell lysates were immunoprecipitated (IP) with anti-FLAG coupled beads followed by Western blot analysis with anti-HA antibody. (<b>D</b>) Reversing the epitopes described in (C), lysates of cells transfected with DEAF1 and FLAG-tagged or HA-tagged Ku proteins were immunoprecipitated with anti-FLAG coupled beads followed by Western blot analysis with anti-DEAF1 antibody. Levels of the proteins in 1.0% of the cell lysates (inputs) used in the immunoprecipitation reactions in C and D were assessed using the antibodies indicated. The results are representative of two independent experiments.</p

Ku70 is unable to relocalize a cytoplasmic form of DEAF1 to the nucleus.

<p>CV-1 cells were transfected either alone or in combinations with DEAF1-HA, HA-Ku70, GFP-DEAF1, or GFP-DEAF1nls (mutated nuclear localization signal). Cellular localization of HA-tagged proteins were determined by indirect immunofluorescence using anti-HA antibodies and secondary antibodies conjugated to CY3 and GFP-tagged proteins were determined by intrinsic GFP fluorescence.</p

DEAF1 interacts with Ku70.

<p>GST pull-downs assays were performed by incubation of <i>in vitro</i> translated, [³⁵S]methionine-labeled Ku70, Ku80, or DEAF1 with the indicated GST fusion proteins and GST. 10% of the <i>in vitro</i> translated proteins used in the pull-downs are shown on the left of each panel. The results are representative of two independent experiments.</p