Hensley, J. | Search bioRxiv

bioRxiv2019

Chromatin information content landscapes inform transcription factor and DNA interactions

Interactions between transcription factors (TFs) and chromatin are fundamental to genome organization and regulation and, ultimately, cell state. Here, we use information theory to measure signatures of TF-chromatin interactions encoded in the patterns of the accessible genome, which we call chromatin information enrichment (CIE). We calculate CIE for hundreds of TF motifs across human tissues and identify two classes: low and high CIE. The 10-20% of TF motifs with high CIE associate with higher protein-DNA residence time, including different binding sites subclasses of the same TF, increased nucleosome phasing, specific protein domains, and the genetic control of both gene expression and chromatin accessibility. These results show that variations in the information content of chromatin architecture reflect functional biological variation, with implications for cell state dynamics and memory.

genomics↗

bioRxiv2018

Genome-wide chromatin accessibility and transcriptome profiling show minimal epigenome changes and coordinated transcriptional dysregulation of hedgehog signaling in Danforth’s short tail mice

Danforths short tail (Sd) mice provide an excellent model for investigating the underlying etiology of human caudal birth defects, which affect 1 in 10,000 live births. Sd animals exhibit aberrant axial skeleton, urogenital, and gastrointestinal development similar to human caudal malformation syndromes including urorectal septum malformation, caudal regression, VACTERL association, and persistent cloaca. Previous studies have shown that the Sd mutation results from an endogenous retroviral (ERV) insertion upstream of the Ptf1a gene resulting in its ectopic expression at E9.5. Though the genetic lesion has been determined, the resulting epigenomic and transcriptomic changes driving the phenotype have not been investigated. Here, we performed ATAC-seq experiments on isolated E9.5 tailbud tissue, which revealed minimal changes in chromatin accessibility in Sd/Sd mutant embryos. Interestingly, chromatin changes were localized to a small interval adjacent to the Sd ERV insertion overlapping a known Ptf1a enhancer region, which is conserved in mice and humans. Furthermore, mRNA-seq experiments revealed increased transcription of PTF1A target genes and, importantly, downregulation of hedgehog pathway genes. Reduced sonic hedgehog (SHH) signaling was confirmed by in situ hybridization and immunofluorescence suggesting that the Sd phenotype results, in part, from downregulated SHH signaling. Taken together, these data demonstrate substantial transcriptome changes in the Sd mouse, and indicate that the effect of the ERV insertion on Ptf1a expression may be mediated by increased chromatin accessibility at a conserved Ptf1a enhancer. We propose that human caudal dysgenesis disorders may result from dysregulation of hedgehog signaling pathways.

genetics↗