Kinetic networks identify key regulatory nodes and transcription factor functions in early adipogenesis

Abstract

Sequence-specific transcription factors (TFs) bind DNA, modulate chromatin structure, regulate gene expression, and or- chestrate transcription cascades. Activation and repression of TFs drive tightly controlled regulatory programs that lead to cellular processes such as differentiation. We measured chromatin accessibility and nascent transcription at seven time points over the first four hours of induced adipogenesis of 3T3-L1 mouse preadipocytes to construct dynamic gene regulatory networks. Regulatory networks describe successive waves of TF binding and dissociation followed by direct regulation of proximal genes. We identified 14 families of TFs that coordinate with and antagonize each other to regulate early adipogenesis. We developed a compartment model to quantify individual TF contributions to RNA polymerase initiation and pause release rates. Network analysis showed that the glucocorticoid receptor and AP1 drive immediate gene activation, including induction of Twist2. Twist2 is a highly interconnected node within the network and its expression leads to repression of target genes. Although Twist2’s role in adipogenesis has not been previously appreciated, both Twist2 knockout mice and Setleis syndrome (Twist2-/-) patients lack subcutaneous and brown adipose tissue. We found that kinetic networks integrating chromatin structure and nascent transcription dynamics identify key genes, TF functions, and coordinate interactions within regulatory cascades.