Biology subjects

Spence, J. R.

Publications and source records attributed to Spence, J. R..

4 recordsLinked to original sources

bioRxiv2018

The Lineage-Specific Transcription Factor CDX2 Navigates Dynamic Chromatin to Control Distinct Stages of Intestine Development

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 Cdx2-loss compromises critical physiological 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, but rather, CDX2 responds to its environment, targeting stage-specific genes to contribute to either intestinal patterning or maturity. This study provides insights into the mechanisms through which lineage-specific regulatory factors achieve divergent functions over developmental time.

developmental biology↗

bioRxiv2018

Non-adhesive alginate hydrogels support growth of pluripotent stem cell-derived intestinal organoids

Human intestinal organoids (HIOs) represent a powerful system to study human development and are promising candidates for clinical translation as drug-screening tools or engineered tissue. Experimental control and clinical use of HIOs is limited by growth in expensive and poorly defined tumor-cell-derived extracellular matrices, prompting investigation of synthetic ECM-mimetics for HIO culture. Since HIOs possess an inner epithelium and outer mesenchyme, we hypothesized that adhesive cues provided by the matrix may be dispensable for HIO culture. Here, we demonstrate that alginate, a minimally supportive hydrogel with no inherent cell adhesion properties, supports HIO growth in vitro and leads to HIO epithelial differentiation that is virtually indistinguishable from Matrigel-grown HIOs. Additionally, alginate-grown HIOs mature to a similar degree as Matrigel-grown HIOs when transplanted in vivo, both resembling human fetal intestine. This work demonstrates that purely mechanical support from a simple-to-use and inexpensive hydrogel is sufficient to promote HIO survival and development.

developmental biology↗

bioRxiv2017

Bacterial Colonization Stimulates A Complex Physiological Response In The Immature Human Intestinal Epithelium

The human gastrointestinal tract is immature at birth, yet must adapt to dramatic changes such as oral nutrition and microbial colonization. The confluence of these factors can lead to severe inflammatory disease in premature infants; however, investigating complex environment-host interactions is diZcult due to limited access to immature human tissue. Here, we demonstrate that the epithelium of human pluripotent stem cell-derived human intestinal organoids is globally similar to the immature human epithelium and we utilize HIOs to investigate complex host-microbe interactions in this naive epithelium. Our findings demonstrate that the immature epithelium is intrinsically capable of establishing a stable host-microbe symbiosis. Microbial colonization leads to complex contact and hypoxia driven responses resulting in increased antimicrobial peptide production, maturation of the mucus layer, and improved barrier function. These studies lay the groundwork for an improved mechanistic understanding of how colonization influences development of the immature human intestine.

developmental biology↗

bioRxiv2017

Identification, Isolation, and Characterization of Human LGR5-positive Colon Adenoma Cells

The intestine is maintained by stem cells located at the base of crypts and distinguished by the expression of LGR5. Genetically engineered mouse models have provided a wealth of information about intestinal stem cells, while less is known about human intestinal stem cells due to difficulty detecting and isolating these cells. We established an organoid repository from patient-derived adenomas, adenocarcinomas, and normal colon, which we analyzed for variants in 71 colorectal cancer (CRC) associated genes. Normal and neoplastic colon tissue organoids were analyzed by immunohistochemistry and fluorescent-activated cell sorting for LGR5. LGR5-positive cells were isolated from 4 adenoma organoid lines and were subjected to RNA-sequencing. We found that LGR5 expression in the epithelium and stroma was associated with tumor stage, and by integrating functional experiments with LGR5-sorted cell RNA-seq data from adenoma and normal organoids, we found correlations between LGR5 and CRC- specific genes, including DKK4 (dickkopf WNT signaling pathway inhibitor 4) and SMOC2 (SPARC related modular calcium binding 2). Collectively, this work provides resources, methods and new markers to isolate and study stem cells in human tissue homeostasis and carcinogenesis.

cancer biology↗