Twin and family studies have shown that genetic factors play a role in the development of conduct disorder (CD). The purpose of this study was to identify genetic variants associated with CD using a family-based association study. We used 4,720 single nucleotide polymorphisms (SNPs) from the Illumina Panel and 11,120 SNPs from the Affymetrix 10K GeneChips genotyped in 155 Caucasian nuclear families from Genetic Analysis Workshop (GAW) 14, a subset from the Collaborative Study on the Genetics of Alcoholism (COGA). 20 SNPs had suggestive associations with CD (p∈<∈10-3), nine of which were located in known genes, including ADAM10 (rs383902, p=0.00036) and CAMK2A (rs2053053, p=0.00098). Our results were verified using the International Multi-Center ADHD Genetics Project (IMAGE) dataset. In conclusion, we identified several loci associated with CD. Especially, the two genes (ADAM10 and CAMK2A) have been reported to be associated with Alzheimer's disease, bipolar disorder and depression. These findings may serve as a resource for replication in other populations.

The MAPT gene has been shown to be associated with several neurodegenerative disorders, including forms of parkinsonism and Parkinson disease (PD), but the results reveal population differences. We investigated the association of 10 single-nucleotide polymorphisms (SNPs) in the region of MAPT on chromosome 17q21 with PD and age at onset, by using 443 discordant sib pairs in PD from a public dataset (Mayo-Perlegen LEAPS Collaboration). Association with PD was assessed by the FBAT using generalized estimating equations (FBAT-GEE), while the association with age at onset as a quantitative trait was evaluated using the FBAT-logrank statistic. Five SNPs were significantly associated with PD (P < 0.05) in an additive model, and 9 SNPs were associated with PD (P < 0.05) in dominant and recessive models. Interestingly, 8 PD-associated SNPs were also associated with age at onset of PD (P < 0.05) in dominant and recessive models. The SNP most significantly associated with PD and age at onset was rs17649641 (P = 0.015 and 0.021, respectively). Two-SNP haplotypes inferred from rs17563965 and rs17649641 also showed association with PD (P = 0.018) and age at onset (P = 0.026). These results provide further support for the role of MAPT in development of PD.

The neuron navigator 2 (NAV2) gene is highly expressed in brain and involved in the nervous system development and may play a role in Alzheimer's disease (AD). We aimed to investigate the associations of 317 single-nucleotide polymorphisms (SNPs) in the NAV2 gene with the risk and age at onset (AAO) of AD using a family-based sample (1266 AD cases and 1279 healthy relatives). Association with the risk of AD was assessed using family-based association test -generalized estimating equations (FBAT- GEE) statistics while the association with AAO as a quantitative trait was evaluated using the FBAT-Wilcoxon statistic. Single marker analysis showed that 20 SNPs were significantly associated with the risk of AD (top SNP rs7112354 with p = 8.46 × 10− 4) and 11 SNPs were associated with AAO (top SNP rs1354269 with p = 2.87 × 10− 3). Interestingly, two SNPs rs17614100 and rs12364788 were associated with both the risk (p = 1.7 × 10− 2 and 2.71 × 10− 2; respectively) and AAO (p = 1.85 × 10− 3 and 6.06 × 10− 3; respectively). Haplotype analyses further supported the results of single marker analyses. In addition, functional analysis showed that NAV2 mRNA had significant expression across ten human brain regions examined and significantly correlated with APOE expression in four of ten regions. The present study is the first study providing evidence of several genetic variants within the NAV2 gene influencing the risk and AAO of AD.

Conduct disorder (CD) is a psychiatric syndrome in childhood and adolescence that is one of the most common childhood disorders with continuously increasing prevalence but uncertain pathogenesis. We performed a genome-wide, family-based association study of CD using P2BAT/FBAT software. The data is gathered from Collaborative Study on the Genetics of Alcoholism (COGA) and International Multi-Center ADHD Genetics Project (IMAGE). Using COGA data, we identified 20 markers which showed suggestive associations (p<10-3) with CD. Nine of them are located in known genes. Two genes, ADAM10 and CAMK2A, which had been reported associated with Alzheimer's disease (AD), bipolar disorder, and depression, were of more concern. Using IMAGE sample, our results were well replicated. This study identified several CD associated genetic variants, especially two novel candidate genes. These findings may serve as a resource for replication in other populations to elucidate the potential role of these genetic variants in CD.