To further investigate the possible role of DDC in BPAD, we analyzed a 1- and a 4-bp deletion variant-both of putative functional significance-in two new samples: a case-control sample with 140 cases and 204 controls, and 100 case-parents trios.
The orphan G protein-coupled receptor 78 (GPR78) gene lies within a region of chromosome 4p where we have previously shown linkage to bipolar affective disorder (BPAD) in a large Scottish family.
Quantification of ITGA9 transcripts in the peripheral blood of patients with BPAD and controls showed an upregulation of ITGA9 (Kruskal-Wallis P = 0.0339) in patients with the disease-associated genotype (rs166508*A/A), compared to those with rs166508*G/G and rs166508*G/A genotypes.
In the family-based analysis, an approximately 200 kilobase (kb) deletion in the first intron of the MAGI1 gene was identified that segregated with BPAD in a pedigree (six out of six affected individuals; parametric logarithm of the odds score = 1.14).
We found 33 MLC1 sequence variations, including three novel mutations: Val210Ile, Leu308Gln, and Arg328His in six BPAD cases and Val210Ile in one control individual.
GPR50 is an orphan G protein-coupled receptor (GPCR) located on Xq28, a region previously implicated in multiple genetic studies of bipolar affective disorder (BPAD).
Alternatively, other as yet unknown imprinted gene(s) adjacent to IMPACT could contribute to the BPAD trait, since multiple imprinted genes may occasionally form clusters.