2000; Masson et al., 1996). Other genes distal to SLC6A15 are TSPAN19, LRRIQ1 and ALX1 (fig. 1A). Their function is largely unknown and their expression levels are low in the vertebrate brain (Anonymous2009; UniGene, 2009). The nearest gene on the proximal side, transmembrane and tetratricopeptide repeat containing 2 gene (TMTC2, NM_152588) ends 989 kb from the region of association. It is expressed in a variety of tissues including the brain, but its function is also unknown. According to HapMap- and Perlegen (Myers et al., 2005) genotyping data, several hotspots of homologous recombination are predicted between the associated region and the flanking genes (fig. 1A), making it unlikely that the underlying functional variant might directly hit a classical promoter region or the open reading frame of a known gene. However, long-range regulatory effects have been described (van Heyningen et al., 2006). To address this issue, we analysed genome-wide gene expression data sets of human hippocampus and lymphoblastoid cell lines (Stranger et al., 2005).
