Foxp3 and BATF cooperatively direct cis-regulatory programs and gene expression for effector Treg cell differentiation [scMultiome]

Mechanisms by which diverse transcription factors (TFs), particularly the master regulator Foxp3, shape the heterogeneous transcriptional and epigenetic landscape of regulatory T (Treg) cells remain poorly understood. Here, we discovered that Foxp3 cooperates with BATF to direct cis-regulatory programs and gene expression essential for differentiation of immunosuppressive effector Treg (eTreg) cells. Simultaneous single-cell chromatin accessibility and transcriptome profiling, combined with topic modeling, identified cis-regulatory elements and associated programs jointly regulated by these TFs in eTreg cells. Genome-wide mapping of Treg cell-specific BATF and eTreg cell-specific Foxp3 binding sites revealed their co-binding at some of these cis-elements, synergistically enhancing accessibility and transcription. Furthermore, we provide evidence that Foxp3 interacts with specific TFs to orchestrate diverse cis-regulatory programs among Treg cell differentiation states. Thus, Foxp3 serves as a master, but context-dependent regulator, cooperating with other TFs, including BATF, to shape the heterogeneous cis-regulatory and transcriptional landscape critical for functional Treg cell differentiation.