Nearby and non-nested genes in the human genome have more similar genotype tissue expression

Neighboring genes within a shared promoter arrangement (i.e. opposite direction with the neighboring ends as the transcriptional start sites) are expected to have a high similarity in genotype tissue expression due to the potential overlap in the promoter region. This raises the question of whether similarity in expression profiles depends on orientation of the neighboring genes and whether there exist thresholds of locality where the similarity diminishes. Thus, in this work, we compared genotype tissue expression profiles at different genomic orientations and localities. Interestingly, there exist gene pairs in the human genome with very high or low expression similarity. Shorter chromosomes tend to have more similarly expressed genes. Also, a cluster of 3 adjacent genes within the average range of 20 to 60 kilobase pairs can have very similar expression profiles regardless of their orientations. However, when genes are nested and in opposite orientations, a lower than expected similarity was observed. Lastly, in cases where genotype tissue expression data does not exist or have low read counts (e.g. non-coding RNA), our identified influencing range can be a first estimate of the genotype tissue expression.