Distinct DNA-binding modes of Sp8 and Sp6 shape a hierarchical regulatory network in limb ectoderm [ChIP]

Combining genome-wide chromatin occupancy with transcriptomic profiling in vivo, we identify shared and specific targets and reconstruct the Sp8/Sp6 gene regulatory network, establishing Sp8 as its dominant, hierarchical node.

Mechanistically, the two factors diverge: Sp8 binds DNA directly at canonical GC-rich Sp motifs, regulating targets including Fgf8 and Sp6 itself, whereas Sp6 acts as a transcriptional cofactor. Via indirect binding to AT-rich motifs through Dlx, both cooperatively regulate limb-patterning pathways, including Wnt, FGF, TGF-β/BMP, and Notch. Biochemical assays confirm that both form homo- and heterodimers and interact with Dlx5 through their zinc-finger domains.