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The brush border is comprised of microvilli surface protrusions on the apical surface of epithelia. This specialized structure greatly increases absorptive surface area and plays crucial roles in human health. However, transcriptional regulatory networks controlling brush border genes are not fully understood. Here, we identify that hepatocyte nuclear factor 4 (HNF4) transcription factor is a conserved and important regulator of brush border gene program in multiple organs, such as intestine, kidney and yolk sac. Compromised brush border gene signatures and impaired transport were observed in these tissues upon HNF4 loss. By ChIP-seq, we find HNF4 binds and activates brush border genes in the intestine and kidney. H3K4me3 HiChIP-seq identifies that HNF4 loss results in impaired chromatin looping between enhancers and promoters at gene loci of brush border genes, and instead enhanced chromatin looping at gene loci of stress fiber genes in the intestine. This study provides comprehensive transcriptional regulatory mechanisms and a functional demonstration of a critical role for HNF4 in brush border gene regulation across multiple murine epithelial tissues., Brush border gene regulation in various different tissues is incompletely understood. Here, the authors show HNF4 regulates the brush border gene program in multiple organs, such as intestine, kidney and yolk sac, and also intestinal chromatin looping in these tissues between promoters and enhancers.

During development, the embryo transitions from a metabolism favoring glycolysis to a metabolism favoring mitochondrial respiration. How metabolic shifts regulate developmental processes, or how developmental processes regulate metabolic shifts, remains unclear. To test the requirement of mitochondrial function in developing endoderm-derived tissues, we genetically inactivated the mitochondrial transcription factor, Tfam, using the Shh-Cre driver. Tfam mutants did not survive postnatally, exhibiting defects in lung development. In the developing intestine, TFAM-loss was tolerated until late fetal development, during which the process of villus elongation was compromised. While progenitor cell populations appeared unperturbed, markers of enterocyte maturation were diminished and villi were blunted. Loss of TFAM was also tested in the adult intestinal epithelium, where enterocyte maturation was similarly dependent upon the mitochondrial transcription factor. While progenitor cells in the transit amplifying zone of the adult intestine remained proliferative, intestinal stem cell renewal was dependent upon TFAM, as indicated by molecular profiling and intestinal organoid formation assays. Taken together, these studies point to critical roles for the mitochondrial regulator TFAM for multiple aspects of intestinal development and maturation, and highlight the importance of mitochondrial regulators in tissue development and homeostasis.

Intestinal stem cell (ISC) function is regulated by diet and cellular metabolism; however, regulatory mechanisms controlling ISC metabolism are not fully understood. HNF4 transcription factors are important regulators of metabolism, but their functions in ISCs are not elucidated. Here, we demonstrate that fatty acid oxidation (FAO) supports ISC renewal, and HNF4 transcription factors bind to and activate the FAO gene program. Loss of HNF4 paralogs reduces fatty acid oxidation and instead increases fatty acid synthesis. Compound mutant mice reveal that HNF4 transcription factors function redundantly to promote ISC renewal. HNF4 loss leads to reduced levels of FAO gene transcripts, FAO activity and TCA metabolites. Metabolic intervention partially restores TCA metabolites and ISC function in the absence of HNF4. These findings link core cellular transcription factor networks with metabolic state to broaden our understanding of metabolic regulation in stem cell homeostasis.

Lineage-restricted transcription factors, such as the intestine-specifying factor CDX2, often have dual requirements across developmental time. Embryonic-loss of CDX2 triggers homeotic transformation of intestinal fate, while adult-onset loss compromises critical physiologic functions but preserves intestinal identity. It is unclear how such diverse requirements are executed across the developmental continuum. Using primary and engineered human tissues, mouse genetics, and a multi-omics approach, we demonstrate that divergent CDX2 loss-of-function phenotypes in embryonic versus adult intestines correspond to divergent CDX2 chromatin-binding profiles in embryonic versus adult stages. CDX2 binds and activates distinct target genes in developing versus adult mouse and human intestinal cells. We find that temporal shifts in chromatin accessibility correspond to these context-specific CDX2 activities. Thus, CDX2 is not sufficient to activate a mature intestinal program; rather, CDX2 responds to its environment, targeting stage-specific genes to contribute to either intestinal patterning or mature intestinal function. This study provides insights into the mechanisms through which lineage-specific regulatory factors achieve divergent functions over developmental time.

After acquiring competence for selected cell fates, embryonic primordia may remain plastic for variable periods before tissue identity is irrevocably determined (commitment). We investigated the chromatin basis for these developmental milestones in mouse endoderm, a tissue with recognizable rostro–caudal patterning and transcription factor (TF)-dependent interim plasticity. Foregut-specific enhancers are as accessible and active in early midgut as in foregut endoderm, and intestinal enhancers and identity are established only after ectopic cis-regulatory elements are decommissioned. Depletion of the intestinal TF CDX2 before this cis element transition stabilizes foregut enhancers, reinforces ectopic transcriptional programs, and hence imposes foregut identities on the midgut. Later in development, as the window of chromatin plasticity elapses, CDX2 depletion weakens intestinal, without strengthening foregut, enhancers. Thus, midgut endoderm is primed for heterologous cell fates, and TFs act on a background of shifting chromatin access to determine intestinal at the expense of foregut identity. Similar principles likely govern other fate commitments.