In addition to replication in independent samples, the functional relevance of the associated locus is supported by results of gene expression analyses in pre-mortem human hippocampus and EBV-transformed lymphoblastoid cell lines of the HapMap individuals (Stranger et al., 2005) and peripheral blood monocytes (Heinzen et al., 2008). While there is a strong indication of the regulatory relevance of the region associated with MD for SLC6A15 expression, we cannot exclude that these variants might also influence the expression of six unspliced brain ESTs and four spliced ESTs of other than brain tissue which have been mapped to the region of association, since they were not probed by the used Illumina chip (fig. 1A and supplementary text, tab. S1). Additional non-annotated transcripts, as described in the ENCODE pilot project in regions of the genome previously thought to be transcriptionally silent (Birney et al., 2007) might also be functionally relevant for this association.
