Biology subjects

Sears, C.

Publications and source records attributed to Sears, C..

4 recordsLinked to original sources

bioRxiv2026

Spatial atlas highlights contribution of C. difficile in early-stage colorectal cancer

Background and AimsIntratumoral heterogeneity with respect to both host and microbial components has emerged as an important contributor to colorectal cancer (CRC) biology. Although the overall taxonomy and abundance of the CRC tumor microbiome have become well characterized, much less is known about bacterial niches within the tumor microenvironment (TME). Escherichia coli and Fusobacterium nucleatum are highly prevalent and abundant species linked to CRC. Less abundant organisms, like Clostridioides difficile and Enterocloster aldenensis, are emerging as potentially important CRC-associated bacteria. Additionally, many studies are confounded by preoperative oral antibiotics or the inclusion of late-stage cancers, both of which may alter the gut microbiome. To better understand the spatial relationships between bacteria and CRC, we generated a molecular atlas based on surgically resected tissue specimens collected from a unique cohort of early-stage CRC patients in whom oral antibiotics were not administered preoperatively. MethodsFrom 20 CRC specimens, we performed matched histopathological analysis, fluorescence in situ hybridization (FISH), whole exome sequencing (WES), 16S rRNA amplicon bacterial DNA sequencing, codetection by indexing (CODEX) multiplex immunofluorescence, and spatial transcriptomics of 756 regions among the specimens. We used 16S rRNA amplicon sequencing data to design and experimentally validate custom bacterial probes that were applied to the spatial transcriptomics. Human colonic organoids were used to validate the relationship between Clostridioides difficile toxin B (TcdB) and an E-twenty-six family transcription factor, ELF3. ResultsWe identified eight intratumoral bacterial niches consisting of a variety of bacterial species, and each niche was associated with unique tumor features. We further defined tumor gene expression patterns correlating with individual bacterial species and show that C. difficile has a disproportionate impact on the tumor transcriptome given its relatively low abundance. Specifically, TcdB induces nuclear localization of ELF3, increased cytosolic {beta}-catenin protein, and upregulated WNT signaling. ConclusionOur study integrates multi-omics to identify bacterial species with biological and spatial relevance in CRC regardless of abundance. These findings will enable further studies to define diagnostic and therapeutic targets for bacteria-associated CRC.

Cancer Biology↗

bioRxiv2025

Murine gut microbiota dysbiosis via enteric infection modulates the foreign body response to a distal biomaterial implant

The gut microbiota influences systemic immunity and the function of distal tissues, including the brain, liver, skin, lung, and muscle. However, the role of the gut microbiota in the foreign body response (FBR) and fibrosis around medical implants is largely unexplored. To investigate this connection, we perturbed the homeostasis of the murine gut microbiota via enterotoxigenic Bacteroides fragilis (ETBF) infection and implanted the synthetic polymer polycaprolactone (PCL) into a distal muscle injury. ETBF infection in mice led to increased neutrophil and {gamma}{delta} T cell infiltration into the PCL implant site. ETBF infection alone promoted systemic inflammation and increased levels of neutrophils in the blood, spleen, and bone marrow. At the PCL implant site, we found significant changes in the transcriptome of sorted fibroblasts but did not observe gross ETBF- induced differences in the fibrosis levels after 6 weeks. These results demonstrate the ability of the gut microbiota to mediate long-distance effects such as immune and stromal responses to a distal biomaterial implant. Significance StatementThe foreign body response to implants leads to chronic inflammation and fibrosis that can be highly variable in the general patient population. Here, we demonstrate that gut dysbiosis via enteric infection promoted systemic inflammation and increased immune cell recruitment to an anatomically distant implant site. These results implicate the gut microbiota as a potential source of variability in the clinical biomaterial response and illustrate that the local tissue environment can be influenced by host factors that modulate systemic interactions.

bioengineering↗

bioRxiv2021

MKLP2 functions in early mitosis to ensure proper chromosome congression

Mitotic kinesin-like protein 2 (MKLP2) is a motor protein with a well-established function in promoting cytokinesis. However, our results with siRNAs targeting MKLP2 and small molecule inhibitors of MKLP2 (MKLP2i) suggested a function earlier in mitosis, prior to anaphase. In this study we provide direct evidence that MKLP2 facilitates chromosome congression in prometaphase. We employed live imaging to observe HeLa cells with fluorescently tagged histones treated with MKLP2i and discovered a pronounced chromosome congression defect. We show that MKLP2 is essential for pole-based error correction as inhibited cells had a significant increase in unstable kinetochore-microtubule attachments due to impaired error correction of syntelic attachments. We propose that MKLP2 mediates kinetochore microtubule attachment stability by regulating Aurora Kinase activity and a downstream target, pHEC1 (Ser 55). Lastly, we show that MKLP2 inhibition results in aneuploidy, confirming that MKLP2 safeguards cells against chromosomal instability. SummarySchrock et al. demonstrate that the mitotic kinesin, MKLP2, is required for congression of chromosomes located near the spindle poles. They show that MKLP2 inhibition causes elevated active Aurora Kinase A, unstable microtubule kinetochore attachments, and impaired syntelic error correction.

cell biology↗

bioRxiv2020

Intestinal Bacteria Maintain Adult Enteric Nervous System and Nitrinergic Neurons via Toll-like Receptor 2-induced Neurogenesis in Mice

Background & AimsThe enteric nervous system (ENS) exists in close proximity to luminal bacteria. Intestinal microbes regulate ENS development, but little is known about their effects on adult enteric neurons. We investigated whether intestinal bacteria or their products affect the adult ENS via toll like receptors (TLRs) in mice. MethodsWe performed studies with conventional C57/BL6, germ-free C57/BL6, Nestin-creERT2:tdTomato, Nestin-GFP, and ChAT-cre:tdTomato. Mice were given drinking water with ampicillin or without (controls). Germ-free mice were given drinking water with TLR2 agonist or without (controls). Some mice were given a blocking antibody against TLR2 or a TLR4 inhibitor. We performed whole-gut transit, bead latency, and geometric center studies. Feces were collected and analyzed by 16S rRNA gene sequencing. Longitudinal muscle myenteric plexus (LMMP) tissues were collected, analyzed by immunohistochemistry, and levels of nitric oxide were measured. Cells were isolated from colonic LMMP of Nestin-creERT2:tdTomato mice and incubated with agonists of TLR2 (receptor for Gram-positive bacteria), TLR4 (receptor for Gram-negative bacteria), or distilled water (control) andd analyzed by flow cytometry. ResultsStool from mice given ampicillin had altered composition of gut microbiota with reduced abundance of Gram-positive bacteria and increased abundance of Gram-negative bacteria, compared with mice given only water. Mice given ampicillin had reduced colon motility compared with mice given only water, and their colonic LMMP had reduced numbers of nitrergic neurons, reduced nNOS production, and reduced colonic neurogenesis. Numbers of colonic myenteric neurons increased after mice were switched from ampicillin to plain water, with increased markers of neurogenesis. Nestin-positive ENPCs expressed TLR2 and TLR4. In cells isolated from the colonic LMMP, incubation with the TLR2 agonist increased the percentage of neurons originating from ENPCs to approximately 10%, compared to approximately 0.01% in cells incubated with the TLR4 agonist or distilled water. Mice given an antibody against TLR2 had prolonged whole-gut transit times; their colonic LMMP had reduced total neurons and a smaller proportion of nitrergic neurons per ganglion, and reduced markers of neurogenesis compared with mice given saline. Colonic LMMP of mice given the TLR4 inhibitor did not have reduced markers of neurogenesis. Colonic LMMP of germ-free mice given TLR2 agonist had increased neuronal numbers compared with control germ-free mice. ConclusionsIn the adult mouse colon, TLR2 promotes colonic neurogenesis, regulated by intestinal bacteria. Our findings indicate that colonic microbiota help maintain the adult ENS via a specific signaling pathway. Pharmacologic and probiotic approaches directed towards specific TLR2 signaling processes might be developed for treatment of colonic motility disorders related to use of antibiotics or other factors.

neuroscience↗