In diverse organisms, neighbouring genes in the genome tend to be positively coexpressed more than expected by chance. When the similarity of transcription regulation is controlled for, adjacent genes have much higher coexpression rates than unlinked genes, supporting a role for chromatin modelling. Consequently, many incidences of low-to-moderate level coexpression of linked genes might well be spurious rather than an indication of functional coordination. These results have implications for gene therapy and for understanding gene order evolution, suggesting that chromosomal proximity alone is adequate to achieve some level of coexpression.
Batada, N. N., Urrutia, A. O., & Hurst, L. D. (2007). Chromatin remodelling is a major source of coexpression of linked genes in yeast. Trends in Genetics, 23(10), 480-484. https://doi.org/10.1016/j.tig.2007.08.003