Biology subjects

Falk, L.

Publications and source records attributed to Falk, L..

5 recordsLinked to original sources

bioRxiv2026

Microbial Invasion and Immunosuppression Drives Adenoma Progression in Early Colorectal Cancer Development

Several inherited predispositions to colorectal cancer exist, most notably familial adenomatous polyposis (FAP), which typically involves a germline loss-of-function mutation in one APC allele. A second hit in APC or related loci leads to aberrant Wnt signalling, triggering adenoma formation with near-complete penetrance. Yet, substantial variability in disease onset and severity, even among siblings with identical APC germline mutations, implicates environmental modifiers. Emerging evidence points to the gut microbiome as a critical regulator of adenoma initiation and progression, particularly in early-onset CRC. Here, we show that bacterial invasion is associated with neutrophil immunosuppression, T-cell exclusion and adenoma progression in a porcine model of FAP. Longitudinal mapping of progressing and regressing polyps using single-cell RNA sequencing, spatial transcriptomics and integrated microbiome profiling resolved the cellular and microbial architecture underlying these divergent lesion states. Single-cell RNA-seq identified 35 cell subpopulations and showed that regressing polyps are enriched for central-memory CD4+ T cells, cytotoxic CD8+ T cells and inflammatory neutrophils, whereas progressing polyps contain immunosuppressive/PD-L1-associated neutrophils, regulatory and dysfunctional T cells. Spatial transcriptomics with a custom host panel and targeted bacterial probes linked bacterial-high adenomatous regions to immunosuppressive neutrophil niches and T cell exclusion, while regressing lesions showed predominantly lumen-adjacent bacterial localization and spatially organized immune surveillance. These results provide a spatially resolved map of cellular and microbial organisation in early colorectal polyp progression and regression and reveal a microbiome-driven, neutrophil-mediated mechanism of early tumour progression with implications for CRC interception. Grant support: This study was funded by the German Research Foundation (DFG) through SFB1371 "Microbiome signature" (Project no. 395357507; TF, DS, FE, DH) and by the German Ministry for Research and Education (BMBF) through Mi-EOCRC consortium project (Project no. 01KD2102D; KF and DH).

cancer biology↗

bioRxiv2022

Lipid network and moiety analyses reveal enzymatic dysregulation and altered mechanisms from lipidomics

Lipidomics is of growing importance for clinical and biomedical research due to many associations between lipid metabolism and diseases. The discovery of these associations is facilitated by improved lipid identification and quantification. Sophisticated computational methods are advantageous for interpreting such large-scale data for understanding metabolic processes and their underlying (patho)mechanisms. To generate hypothesis about these mechanisms, the combination of metabolic networks and graph algorithms is a powerful option to pinpoint molecular disease drivers and their interactions. Here we present LINEX2 (Lipid Network Explorer), a lipid network analysis framework that fuels biological interpretation of alterations in lipid compositions. By integrating lipid-metabolic reactions from public databases we generate dataset-specific lipid interaction networks. To aid interpretation of these networks we present an enrichment graph algorithm that infers changes in enzymatic activity in the context of their multispecificity from lipidomics data. Our inference method successfully recovered the MBOAT7 enzyme from knock-out data. Furthermore, we mechanistically interpret lipidomic alterations of adipocytes in obesity by leveraging network enrichment and lipid moieties. We address the general lack of lipidomics data mining options to elucidate potential disease mechanisms and make lipidomics more clinically relevant. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/479101v2_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@10d722dorg.highwire.dtl.DTLVardef@1c3256borg.highwire.dtl.DTLVardef@cd9deforg.highwire.dtl.DTLVardef@13befc4_HPS_FORMAT_FIGEXP M_FIG C_FIG LINEX2 (Lipid Network Explorer) is a framework to visualize and analyze quantitative lipidomics data. The included algorithms offer new perspectives on the lipidome and can propose potential mechanisms of dysregulation. O_LIUsing the Reactome and Rhea databases, a comprehensive set of lipid class reactions is included and utilized to map the lipidome on custom data-specific networks. C_LIO_LIWith a novel network enrichment method, enzymatic dysregulation can be recovered from lipidomics data. C_LIO_LIWe validate its usability on data with a central lipid enzymatic deficiency. C_LIO_LILINEX2 is the first tool capable of such analysis and includes complimentary analysis options for structural lipid analysis. It is freely available as a web service (https://exbio.wzw.tum.de/linex2). C_LI

systems biology↗

bioRxiv2021

The impact of low input DNA on the reliability of DNA methylation as measured by the Illumina Infinium MethylationEPIC BeadChip

BackgroundDNA methylation (DNAm) is commonly assayed using the Illumina Infinium MethylationEPIC BeadChip, but there is currently little published evidence to define the lower limits of the amount of DNA that can be used whilst preserving data quality. Such evidence is valuable for analyses utilising precious or limited DNA sources. Materials and methodsWe use a single pooled sample of DNA in quadruplicate at three dilutions to define replicability and noise, and an independent population dataset of 328 individuals (from a community-based study including US-born non-Hispanic Black and white persons) to assess the impact of total DNA input on the quality of data generated using the Illumina Infinium MethylationEPIC BeadChip. ResultsData are less reliable and more noisy as DNA input decreases to 40ng, with clear reductions in data quality; however samples with a total input as low as 40ng pass standard quality control tests, and we observe little evidence that low input DNA obscures the associations between DNAm and two phenotypes, age and smoking status. ConclusionsDNA input as low as 40ng can be used with the Illumina Infinium MethylationEPIC BeadChip, provided quality checks and sensitivity analyses are undertaken.

bioinformatics↗

bioRxiv2018

Epigenetic regulation of PAR4-related platelet activation: mechanistic links between environmental exposure and cardiovascular disease

Protease-activated receptor 4 (PAR4) is a potent thrombin receptor. Epigenetic control of the F2RL3 locus (which encodes for PAR4) via DNA methylation is associated with both smoking and cardiovascular disease. We examined the association between DNA hypomethylation at F2RL3 and risk of cardiovascular disease, focusing on acute myocardial infarction (AMI) (n=853 cases / 2,352 controls). We used in vitro cell models to dissect the role of DNA methylation in regulating expression of F2RL3. We investigated the interplay between F2RL3 DNA methylation and platelet function in human (n=41). Lastly, we used Mendelian randomization to unify observational and functional work by assessing evidence for causal relationships using data from UK Biobank (n=407,141) and CARDIoGRAMplusC4D (n=184,305). Observationally, one standard deviation (SD) decrease in DNA methylation at F2RL3 was associated with a 25% increase in the odds of AMI. In vitro, short-term exposure of cells to cigarette smoke reduced F2RL3 DNA methylation and increased gene expression. Transcriptional assays flagged a role for a CEBP recognition sequence in modulating the enhancer activity of F2RL3 exon 2. Lower DNA methylation at F2RL3 was associated with increased platelet reactivity in human. The estimated casual odds ratio of ischaemic heart disease was 1.03 (95% CI: 1.00, 1.07) per 1 SD decrease in F2RL3 DNA. In conclusion, we show that DNA methylation-dependent platelet activation is part of a complex system of features contributing to cardiovascular health. Tailoring therapeutic intervention to new knowledge of F2RL3/PAR4 function should be explored to ameliorate the detrimental effects of this risk factor on cardiovascular health.\n\nOne sentence summaryDNA methylation-dependent platelet activation is a likely causal contributor to cardiovascular health.

epidemiology↗

bioRxiv2018

Genome-wide mapping identifies beta-1,4-N-acetyl-galactosaminyl-transferase as a novel determinant of sclerostin levels and bone mineral density

In bone, sclerostin is mainly osteocyte-derived and plays an important local role in adaptive responses to mechanical loading. Whether circulating levels of sclerostin also play a functional role is currently unclear, which we aimed to examine by two sample Mendelian Randomisation (MR). A genetic instrument for circulating sclerostin, derived from a genome wide association study (GWAS) meta-analysis of serum sclerostin in 10,584 European-descent individuals, was examined in relation to femoral neck bone mineral density (BMD; n= 32,744) in GEFOS, and estimated BMD by heel ultrasound (eBMD; n=426,824), and fracture risk (n=426,795), in UK Biobank. Our GWAS identified two novel serum sclerostin loci, B4GALNT3 (standard deviation (SD)) change in sclerostin per A allele ({beta}=0.20, P=4.6x10-49), and GALNT1 ({beta}=0.11 per G allele, P=4.4x10-11). B4GALNT3 is an N-acetyl-galactosaminyltransferase, adding a terminal LacdiNAc disaccharide to target glycocoproteins, found to be predominantly expressed in kidney, whereas GALNT1 is an enzyme causing mucin-type O-linked glycosylation. Using these two SNPs as genetic instruments, MR revealed an inverse causal relationship between serum sclerostin and femoral neck BMD ({beta}= -0.12, 95%CI= -0.20 to -0.05) and eBMD ({beta}= -0.12, 95%CI= -0.14 to -0.10), and a positive relationship with fracture risk ({beta}= 0.11, 95%CI= 0.01 to 0.21). Colocalization analysis demonstrated common genetic signals within the B4GALNT3 locus for higher sclerostin, lower eBMD, and greater B4GALNT3 expression in arterial tissue (Probability>99%). Our findings suggest that higher sclerostin levels are causally related to lower BMD and greater fracture risk. Hence, strategies for reducing circulating sclerostin, for example by targeting glycosylation enzymes as suggested by our GWAS results, may prove valuable in treating osteoporosis.

genetics↗