Binding motifs of 99 transcription factors (TFs) were significantly enriched (FDR < 1%) in MPRA active elements in MIN6 β cells, which notably included motifs for TFs with reported roles in modulating beta cell identity and function (Hnf1, MafA/B, Foxo1)32–36, glucose-stimulated insulin secretion (Bcl11a37, LXRE38, RARa39), ER quality control and insulin folding and processing (Atfs), circadian regulation of β cell functions (Clock), and regulation of T2D SNP-containing cis-REs (Foxa229,40, Rfx511) (Fig. 1c and Supplementary Data 1). Here, FOXO1 is linked to type 2 diabetes mellitus.