Replication of genome-wide association study (GWAS) susceptibility loci in a Latino bipolar disorder cohort

Abstract

Objectives: Recent genome-wide association studies (GWASs) have identified numerous putative genetic polymorphisms associated with bipolar disorder (BD) and/or schizophrenia (SC). We hypothesized that a portion of these polymorphisms would also be associated with BD in the Latino American population. To identify such regions, we tested previously identified genetic variants associated with BD and/or SC and ancestral haploblocks containing these single nucleotide polymorphisms (SNPs) in a sample of Latino subjects with BD.

Methods: A total of 2254 Latino individuals were genotyped for 91 SNPs identified in previous BD and/or SC GWASs, along with selected SNPs in strong linkage disequilibrium with these markers. Family-based single marker and haplotype association testing was performed using the PBAT software package. Empirical P-values were derived from 10 000 permutations.

Results: Associations of eight a priori GWAS SNPs with BD were replicated with nominal (P≤.05) levels of significance. These included SNPs within nuclear factor I A (NFIA), serologically defined colon cancer antigen 8 (SDCCAG8), lysosomal associated membrane protein 3 (LAMP3), nuclear factor kappa B subunit 1 (NFKB1), major histocompatibility complex, class I, B (HLA-B) and 5'-nucleotidase, cytosolic II (NT5C2) and SNPs within intragenic regions microRNA 6828 (MIR6828)-solute carrier family 7 member 14 (SLC7A14) and sonic hedgehog (SHH)-long intergenic non-protein coding RNA 1006 (LINC01006). Of the 76 ancestral haploblocks that were tested for associations with BD, our top associated haploblock was located in LAMP3; however, the association did not meet statistical thresholds of significance following Bonferroni correction.

Conclusions: These results indicate that some of the gene variants found to be associated with BD or SC in other populations are also associated with BD risk in Latinos. Variants in six genes and two intragenic regions were associated with BD in our Latino sample and provide additional evidence for overlap in genetic risk between SC and BD.

Keywords: Central American; Latinos; Mexican; Mexican-American; bipolar disorder; family studies; genetics; lysosomal associated membrane protein 3 (LAMP3); nuclear factor kappa B subunit 1 (NFKB1); serologically defined colon cancer antigen 8 (SDCCAG8).

Figure 1

Power calculations based on pedigree structure were calculated for odds ratios (ORs) representing a low (OR=1.3) or moderate (OR=1.8) effect. Population prevalence (k) represents the risk for the narrow bipolar phenotype (bipolar disorder type I: k=0.01) and the broad bipolar phenotype (bipolar disorder type I/II, schizoaffective bipolar type, or bipolar disorder not otherwise specified: k=0.05)