Genetics of Recurrent Early-Onset Major Depression (GenRED): Significant Linkage on Chromosome 15q25-q26 After Fine Mapping With Single Nucleotide Polymorphism Markers

Objective: The authors studied a dense map of single nucleotide polymorphism (SNP) DNA markers on chromosome 15q25-q26 to maximize the informativeness of genetic linkage analyses in a region where they previously reported suggestive evidence for linkage of recurrent early-onset major depressive disorder. Method: In 631 European-ancestry families with multiple cases of recurrent early-onset major depressive disorder, 88 SNPs were genotyped, and multipoint allele-sharing linkage analyses were carried out. Marker-marker linkage disequilibrium was minimized, and a simulation study with founder haplotypes from these families suggested that linkage scores were not inflated by linkage disequilibrium. Results: The dense SNP map increased the information content of the analysis from around 0.7 to over 0.9. The maximum evidence for linkage was the Z likelihood ratio score statistic of Kong and Cox (Z LR )=4.69 at 109.8 cM. The exact p value was below the genomewide significance threshold. By contrast, in the genome...