Biology subjects

Philpott, D.

Publications and source records attributed to Philpott, D..

4 recordsLinked to original sources

bioRxiv2024

NLRP1B allele 2 does not respond to Val-boro-Pro (VbP) in the intestinal epithelium

The intestinal mucosa must balance tolerance to commensal microbes and luminal antigens with rapid detection of enteric pathogens in order to maintain homeostasis. This balance is facilitated through the regulation of epithelial layer integrity by innate immune receptors. Certain NOD-like receptors (NLRs) expressed in intestinal epithelial cells, including NLRC4 and NLRP9B, form inflammasomes that protect against pathogens by activating caspase-1 to cause extrusion of infected cells. NLRP1B is a murine NLR encoded by five alleles of a highly polymorphic gene homologous to human NLRP1. NLRP1B forms inflammasomes in response to a variety of pathogens that cause intestinal infections, but it has almost exclusively been studied in immune cells and has not been characterized in cells of the intestinal epithelium. Here, we show that Nlrp1b is expressed in ileal and colonic organoids derived for C57BL/6J mice. Nlrp1b was upregulated by interleukin-13 in organoids and by the protozoan Tritrichomonas muris in vivo, suggesting that NLRP1B may be involved in defense against enteric parasites. Surprisingly, while Val-boro-Pro (VbP) activated NLRP1B in bone marrow-derived macrophages, it did not activate NLRP1B in organoids. We furthermore did not detect Nlrp1b in organoids derived from Balb/cJ mice, which express a different allele than the one expressed in C57BL/6J mice. Together, our results suggest that NLRP1B may have an allele-dependent function in murine IECs whose regulation is distinct from that of macrophages.

immunology↗

bioRxiv2022

Intra- and inter-species interactions drive early phases of invasion in mice gut microbiota

The stability and dynamics of ecological communities are dictated by interaction networks typically quantified at the level of species.1-10 But how such networks are influenced by intra-species variation (ISV) is poorly understood.11-14 Here, we use ~500,000 chromosomal barcodes to track high-resolution intra-species clonal lineages of Escherichia coli invading mice gut with the increasing complexity of gut microbiome: germ-free, antibiotic-perturbed, and innate microbiota. By co-clustering the dynamics of intra-species clonal lineages and those of gut bacteria from 16S rRNA profiling, we show the emergence of complex time-dependent interactions between E. coli clones and resident gut bacteria. With a new approach, dynamic covariance mapping (DCM), we differentiate three phases of invasion in susceptible communities: 1) initial loss of community stability as E. coli enters; 2) recolonization of some gut bacteria; and 3) recovery of stability with E. coli coexisting with resident bacteria in a quasi-steady state. Comparison of the dynamics, stability and fitness from experimental replicates and different cohorts suggest that phase 1 is driven by mutations in E. coli before colonization, while phase 3 is by de novo mutations. Our results highlight the transient nature of interaction networks in microbiomes driven by the persistent coupling of ecological and evolutionary dynamics. One-Sentence SummaryHigh-resolution lineage tracking and dynamic covariance mapping (DCM) define three distinct phases during early gut microbiome invasion.

evolutionary biology↗

bioRxiv2021

Genome-wide in vivo screen of circulating tumor cells identifies SLIT2 as a regulator of metastasis

Circulating tumor cells (CTCs) break free from primary tumors and travel through the bloodstream and lymphatic system to seed metastatic tumors, which are the major cause of death from cancer. The identification of the major genetic factors that enhance production and persistence of CTCs in the bloodstream at a whole genome level would enable more comprehensive molecular mechanisms of metastasis to be elucidated and the identification of novel therapeutic targets, but this remains a challenging task due to the heterogeneity and extreme rarity of CTCs. Here, we describe the first in vivo genome-wide CRISPR KO screen using CTCs directly isolated from a mouse xenograft. This screen elucidated SLIT2 - a gene encoding a secreted protein acting as a cellular migration cue - as the most significantly represented gene knockout in the CTC population. SLIT2 knockout cells are highly metastatic with hypermigratory and mesenchymal phenotype. Reduced expression of SLIT2 is observed in human tumors, indicating its role as a negative modulator of tumor progression and metastasis.

cancer biology↗

bioRxiv2019

Scalable, FACS-Free Genome-Wide Phenotypic Screening

Genome-scale functional genetic screens can identify key regulators of a phenotype of interest, such as determinants of protein expression or modification. Here, we present a rapid, high-throughput approach to phenotypic CRISPR-Cas9 screening. To study factors that modulate the display of CD47 on the cell surface, we processed an entire genome-wide screen containing more than 108 cells in under one hour and maintained high levels of cell viability using a highly scalable cell sorting technology. We robustly identified modulators of CD47 function including QPCTL, an enzyme required for formation of the pyroglutamyl modification at the N-terminus of this protein.

genomics↗