Biology subjects

Kourtidis, A.

Publications and source records attributed to Kourtidis, A..

5 recordsLinked to original sources

bioRxiv2026

Differences in T-cell counts and neighborhood patterns in human colorectal adenomas and sessile serrated lesions

BackgroundT-cell responses influence recurrence and survival in colorectal cancer. T-cell subset distributions vary by molecular phenotype and location, shaping cytotoxic or immune-cold tumor immune microenvironments (TiMEs). However, the T-cell contexture and their spatial proximities within preinvasive lesions are not well characterized. MethodsWe analyzed sessile serrated lesions (SSLs), tubulovillous/villous adenomas (TVs), and tubular adenomas (TAs) from three completed studies (N=120). Whole-slide multiplex immunofluorescence was used to quantify eight T-cell subsets (CD4, CD8, Th1, Th17, Treg, Tc1, Tc17, TcTreg). Counts were compared by histology using a generalized linear mixed model with a negative binomial distribution, including an offset for total cell counts and adjusting for age, sex, anatomic location, and lesion size. Nearest-neighbor (NN) analyses assessed proximities of T-cell pairs across lesion types. ResultsTAs and SSLs had higher CD4 and CD8 T-cell counts compared with TVs (q<0.05). SSLs had lower Th17 counts than TAs (q<0.05) and compared with TVs leaned toward fewer Tregs (q=0.07). NN analysis showed that TVs, compared with SSLs and TAs, had increased Treg clustering. In contrast, TA versus SSL comparisons revealed predominant CD4 clustering with Th17, Th1, and CD8 subsets. ConclusionTVs are characterized by lower T-cell infiltration and a greater tendency for regulatory T-cell clustering, consistent with an immune-cold TiME relative to TAs. SSLs and TAs were both more immune-infiltrated than TVs, but SSLs appeared less inflamed and less dominated by regulatory subsets. In contrast, CD4dominant clustering in TAs suggested stronger helper coordination. Preinvasive lesions therefore demonstrate immune and spatial heterogeneity by lesion types.

pathology↗

bioRxiv2025

The TRP-channel painless mediates substrate stiffness sensing in the legs during Drosophila oviposition

The distinct textural properties of fruits in varying stages of ripening present unique ecological opportunities for several species of fruit flies, resulting, over evolutionary times, in specialized egg-laying behaviors. In this study we identified a TrpA channel-dependent mechanosensory pathway in the legs, through the gene painless, that modulates the discernment of softer patches for oviposition in gravid D. melanogaster females. We report that the stiffness-sensing role of tarsi is mediated through external sensory organs housed, namely ventral mechanosensory bristles and subsets of campaniform sensilla present primarily at the joints between tarsomeres. Our findings provide new evidence that campaniform sensilla function as indirect stiffness sensors of oviposition substrates, owing to their placement at joints that experience maximal cuticular distortion. We show that Painless is expressed in mechanosensory neurons innervating peripheral organs where it likely participates in the transduction of stiffness-evoked stimuli. Furthermore, we observed that overexpression of painless in both campaniform sensilla and mechanosensory bristles partially rescues preference for the softer substrates in painless mutants, indicating that painless activity in these organs is necessary to mediate the preference. We propose that different interactions with a soft vs. a hard substrate (compression of the cuticle, distribution of contacts) results in differential mechanotransduction in painless-expressing neurons, determining oviposition preferences.

neuroscience↗

bioRxiv2025

PIWIL2 downregulation in colon cancer promotes transposon activity and pro-tumorigenic phenotypes

Reactivation of transposable elements (TEs) in somatic tissues, particularly of LINE-1, is associated with disease by causing gene mutations and DNA damage. Previous work has shown that the PIWI pathway is crucial for TE suppression in the germline. However, the status and function of this pathway is not well characterized in differentiated somatic cells and there is lack of consensus on the role of the pathway in somatic tumorigenesis. To shed light on this conundrum, we examined the PIWI pathway in colon cancer through combining bioinformatic analyses and cell-based assays. Shifted Weighted Annotation Network (SWAN) analysis revealed that the pathway experiences significant allelic losses in colon cancer and that PIWIL2, the main catalytic component of the pathway responsible for TE silencing, experiences the highest percent deletions. PIWIL2 is downregulated in colon tumors of advanced stage, nodal metastasis, and in certain subtypes, correlating with poor survival, while it is also downregulated in ulcerative colitis, an inflammatory bowel disease that predisposes to colon cancer. PIWIL2 depletion in colon epithelial Caco2 cells leads to increased anchorage-independent growth, loss of transposon-targeting - non-canonical - piRNAs, increased LINE-1 levels and activity, and in DNA damage, altogether highlighting a tumor-suppressing role of PIWIL2 in the colon. SUMMARY STATEMENTThis study investigates the PIWI-piRNA pathway in colon cancer using a nuanced bioinformatic and cell-based approach, linking the downregulation of PIWIL2 to disease progression, transposable element activation and DNA damage.

cancer biology↗

bioRxiv2024

The epithelial adherens junction component PLEKHA7 regulates ECM remodeling and cell behavior through miRNA-mediated regulation of MMP1 and LOX

Epithelial adherens junctions (AJs) are cell-cell adhesion complexes that are influenced by tissue mechanics, such as those emanating from the extracellular matrix (ECM). Here, we introduce a mechanism whereby epithelial AJs can also regulate the ECM. We show that the AJ component PLEKHA7 regulates levels and activity of the key ECM remodeling components MMP1 and LOX in well-differentiated colon epithelial cells, through the miR-24 and miR-30c miRNAs. PLEKHA7 depletion in epithelial cells results in LOX-dependent ECM remodeling in culture and in the colonic mucosal lamina propria in mice. Furthermore, PLEKHA7-depleted cells exhibit increased migration and invasion rates that are MMP1- and LOX-dependent, and form colonies in 3D cultures that are larger in size and acquire aberrant morphologies in stiffer matrices. These results reveal an AJ-mediated mechanism, through which epithelial cells drive ECM remodeling to modulate their behavior, including acquisition of phenotypes that are hallmarks of conditions such as fibrosis and tumorigenesis. TeaserEpithelial cells instruct ECM remodeling to modulate their behavior, as a result of adherens junction and miRNA disruption.

cell biology↗

bioRxiv2022

Actin-dependent recruitment of Ago2 to the zonula adherens

Adherens junctions are cadherin-based structures critical for cellular architecture. E-cadherin junctions in mature epithelial cell monolayers tether to an apical actomyosin ring to form the zonula adherens (ZA). We have previously shown that the adherens junction protein PLEKHA7 associates with and regulates the function of the core RNA interference (RNAi) component AGO2 specifically at the ZA. However, the mechanism mediating Ago2 recruitment to the ZA remained unexplored. Here, we reveal that this ZA-specific recruitment of AGO2 depends on both the structural and tensile integrity of the actomyosin cytoskeleton. We found that depletion of not only PLEKHA7, but also either of three PLEKHA7-interacting, LIM-domain family proteins, namely LMO7, LIMCH1, and PDLIM1, results in disruption of actomyosin organization and tension, as well as disruption of AGO2 junctional localization and of its miRNA-binding ability. We also show that AGO2 binds Myosin IIB and that PLEKHA7, LMO7, LIMCH1, and PDLIM1 all disrupt interaction of AGO2 with Myosin IIB at the ZA. These results demonstrate that recruitment of Ago2 to the ZA is sensitive to actomyosin perturbations, introducing the concept of a mechanosensitive RNAi machinery, with potential implications in tissue remodeling and in disease. SummaryRecruitment and miRNA-binding activity of the key RNA interference (RNAi) component AGO2 to epithelial zonula adherens depends on apical actomyosin integrity and tension, revealing the existence of a mechanosensitive RNAi machinery at the zonula adherens. Significance StatementO_LIPrevious work has shown that PLEKHA7 recruits core RNAi components, including AGO2, to regulate tumor-suppressing miRNAs specifically at the zonula adherens (ZA), through an unknown mechanism. C_LIO_LIHere, the authors show that three LIM domain-containing proteins, LMO7, LIMCH1, and PDLIM1, are also responsible for AGO2s recruitment and miRNA activity at the ZA and that all four PLEKHA7, LMO7, LIMCH1, PDLIM1 mediate AGO2 recruitment to the ZA not due to their protein-protein interactions, but through stabilizing actomyosin structure and tension. C_LIO_LIThese findings introduce a mechanosensitive RNAi machinery responsive to actomyosin perturbations, with potentially broad implications in regulation of cellular plasticity. C_LI

cell biology↗