SP1 and Hyperglycemia: We recently showed that there are two SP1 binding sites in the promoter region of ROBO4 in human retinal endothelial cells (HRECs) under hyperglycaemia.39 We concluded that the binding site at –1912/–1908 could be induced by hyperglycaemia and played a major role in increasing ROBO4 transcription in HRECs in the simulated DR environment.