Sixteen additional enhancers associated with the chicken Sox2 locus outside the central 50-kb region.

The transcription factor Sox2 plays a central role in the regulation of neuro-sensory development, and many other developmental processes. To gain an in depth understanding of the Sox2 gene regulation, we previously investigated the Sox2-proximal 50-kb region of the chicken genome to determine enhancers based on functional assays using chicken embryo electroporation. We identified 11 enhancers with specificity for neuro-sensory tissues. In this study, we extended the analysis of Sox2 locus-associated enhancers to a 200-kb region and identified 16 additional enhancers with functions in neuro-sensory development. These enhancers roughly correspond to a fraction of the sequence blocks that are highly conserved between chicken and mammalian genomes. The neural enhancers were activated in sequence, thereby creating a complex pattern of functional overlaps in the developing central nervous system (CNS). The variations in the specificities of the sensory enhancers also reflected the intermediate steps of sensory tissue development. This study provides an example where a single transcription factor gene has numerous regulatory elements that allow it to fulfill many functional roles in different biological contexts.