Biology subjects

Rajan, N.

Publications and source records attributed to Rajan, N..

12 recordsLinked to original sources

bioRxiv2026

Accurate detection of metagenomic strain-level associations using average nucleotide identity with StrainSpy

Genetic variation among microbial strains of the same species can profoundly influence their phenotypes, ecological functions, and impacts on human health. Traditionally, the relative abundance of a species has been used to identify associations between the microbiome and disease. However, this approach overlooks intra-species genetic variation and is susceptible to spurious correlations arising from the compositional nature of abundance data and microbial load. Fast, k-mer-based algorithms can now accurately estimate strain-level Average Nucleotide Identity (ANI) in metagenomes. Despite its value as an orthogonal metric for strain-level analysis, methods for conducting ANI-based association studies remain limited. To address this, we developed StrainSpy, a statistical algorithm that identifies associations between containment ANI and variables of interest across a wide range of study designs, including longitudinal and multi-cohort designs. Re-analysis of a study examining gut microbiota recovery in 12 healthy adults following antibiotic exposure revealed novel strain-level associations, including a reduction in strain-level diversity despite species persistence. Applying StrainSpy to a multi-cohort analysis of 3,414 colorectal cancer metagenomes identified novel strain-level associations with colorectal cancer. However, in a separate collection of microbiome-immunotherapy studies, no individual strain was consistently associated across cohorts. Importantly, across both datasets, StrainSpy informed containment ANI-based machine learning models achieved comparable accuracy to traditional abundance-based methods. StrainSpy is publicly available as an R package github.com/gtonkinhill/strainspy.

microbiology↗

bioRxiv2026

A Context-Aware Single-Cell Proteomics Analysis pipeline.

Single-cell proteomics (SCP) by mass spectrometry can now quantify hundreds to thousands of proteins per cell, but the field still lacks standardised analytical pipelines that accommodate the diversity of instruments, sample preparation workflows and biological contexts encountered in practice. Existing workflows, largely adapted from single-cell transcriptomics, do not account for the informative missingness, pervasive ambient protein contamination and limited feature space that distinguish proteomic from transcriptomic data. In addition, cell type annotation remains a manual bottleneck that is subjective, difficult to reproduce and hard to scale. Here we present an end-to-end pipeline that integrates adaptive quality control, entropy-guided iterative batch correction, multi-modal marker discovery that exploits detection patterns unique to proteomics, and context-aware annotation by large language models (LLMs) coupled to structured contradiction reasoning and orthogonal data-driven validation. Benchmarking on published single-cell proteomic datasets from developing human brain and glioblastoma-associated neutrophils revealed systematic LLM failure modes, including context-insensitive marker vocabulary and misinterpretation of phagocytic or lytic cell states. We addressed these errors using a three-round prompt architecture that combines general biological principles with auto-generated dataset-specific constraints. In held-out validation on a skin tumour dataset acquired, the pipeline showed high concordance with FACS-sorted ground truth. In the caerulein-injured pancreas, orthogonal immunohistochemistry further supported annotations of macrophage, stellate and immune populations. The pipeline is fully automated under fixed settings, and available as Context-Aware Single-Cell Proteomics Analysis (CASPA), providing SCP laboratories and facilities with a reproducible workflow that delivers interpretable, confidence-quantified annotations suitable for downstream expert review.

bioinformatics↗

bioRxiv2026

Democratised single cell proteomics uncovers tumor associated macrophage signature in CYLD cutaneous syndrome skin tumors

Single-cell proteomics (SCP) reveals cellular heterogeneity and biological insights inaccessible to bulk analysis. Existing limitations are cost, sample loss during processing, and accessibility to state-of-the-art instrumentation. We describe a label free SCP methodology in human tissue, combining fluorescence activated cell sorting (FACS), oil-immersion cell handling, mass-spectrometry, and neural-network derived spectral libraries which address these issues. We tested this methodology in a skin tumor syndrome, CYLD cutaneous syndrome (CCS), assessing tumor heterogeneity. Using a Bruker timsTOF HT platform we quantified > 4000 proteins, averaging [~]700 per cell, through a cost-effective pipeline without specialised liquid handling infrastructure. By utilising pre-existing bioinformatic tools from the scRNA-seq field we implemented a robust analysis methodology, discriminating between macrophages, dendritic cells and tumor keratinocytes, in an unbiased analysis of 419 CCS tumor cells. We validated the biological accuracy of cell annotations by cross referencing with each cells FACS markers. Furthermore, we identified a novel CCS tumor associated macrophage population which carried a tumor microenvironment remodelling signature. Our findings demonstrate an accessible SCP technology capable of yielding novel biological discoveries in clinical tissue. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=86 SRC="FIGDIR/small/704354v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@6fe6a3org.highwire.dtl.DTLVardef@8f0ff9org.highwire.dtl.DTLVardef@61e037org.highwire.dtl.DTLVardef@1c76a43_HPS_FORMAT_FIGEXP M_FIG C_FIG IMPORTANTO_LIManuscripts submitted to Review Commons are peer reviewed in a journal-agnostic way. C_LIO_LIUpon transfer of the peer reviewed preprint to a journal, the referee reports will be available in full to the handling editor. C_LIO_LIThe identity of the referees will NOT be communicated to the authors unless the reviewers choose to sign their report. C_LIO_LIThe identity of the referee will be confidentially disclosed to any affiliate journals to which the manuscript is transferred. C_LI GUIDELINESO_LIFor reviewers: https://www.reviewcommons.org/reviewers C_LIO_LIFor authors: https://www.reviewcommons.org/authors C_LI CONTACTThe Review Commons office can be contacted directly at: office@reviewcommons.org

biochemistry↗

bioRxiv2025

Comparative ubiquitinomics of human skin reveals insulin receptor ubiquitination as a regulator of collagen secretion.

Ubiquitination is central to skin homeostasis and disease, however the cutaneous ubiquitinome remains poorly characterised. We investigated spatial patterns of ubiquitination in human skin, discovering specific ubiquitin linkages located within the hair follicle and epidermis. To create a comprehensive physiological profile of the ubiquitinated proteins within the skin, we profiled healthy skin and CYLD cutaneous syndrome (CCS) skin tumours through di-glycine remnant immunopurification proteomics, enabling identification of 1605 ubiquitin sites across 731 proteins. The healthy cutaneous ubiquitinome comprised substrate classes including keratins, S100 proteins and histones. Predictive upstream enzyme analysis ranked the most frequent E3 ligase as NEDD4, and the most frequent deubiquitinases included USP7 and CYLD. Analysis of the CCS tumor ubiquitinome, characterized by catalytically inactivated CYLD somatic mutations and prominent extracellular matrix (ECM) secretion, identified 251 differentially ubiquitinated sites compared to healthy skin. The CCS ubiquitinome was enriched for cell division and differentiation proteins, including predicted CYLD substrate insulin receptor (INSR). Secretome analysis of INSR knockdown CCS primary cells revealed reduced secretion of basement membrane proteins, particularly COL7A1. By defining how ubiquitination modulates pathophysiological ECM secretory output, our study highlights the ubiquitin post-translational system as a broader determinant of tissue architecture. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=86 SRC="FIGDIR/small/691868v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@565e59org.highwire.dtl.DTLVardef@4c3084org.highwire.dtl.DTLVardef@52a43org.highwire.dtl.DTLVardef@11999d8_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Targeting non-canonical NF-κB signalling in CYLD cutaneous syndrome by selective inhibition of IκB kinase alpha.

CYLD cutaneous syndrome (CCS) skin tumors develop from puberty onwards, can number in the hundreds and progressively grow over time. CCS patients lack medical therapies and require repeated surgery to control tumor burden. CYLD loss of heterozygosity (LOH) drives tumor growth, and CCS tumors have previously been shown to demonstrate increased canonical NF-{kappa}B and Wnt signalling. Here, we demonstrate evidence of non-canonical NF-{kappa}B signalling in CCS tumor keratinocytes, with increased p100 to p52 processing and RelB protein expression compared to normal skin. Utilizing complementary transcriptomics and proteomics on patient derived CCS tumor cell fractions, we identify I{kappa}B kinase alpha (IKK) as a candidate target in the non-canonical NF-{kappa}B signalling pathway. A novel, highly selective, IKK inhibitor (SU1644) used in patient derived CCS tumor spheroid cultures demonstrated that IKK inhibition reduced tumor spheroid viability. These data provide the pre-clinical rationale for the assessment of topical IKK inhibitors as a novel preventative treatment for CCS. TeaserTopical IKK inhibition emerges as a potential therapy for CYLD cutaneous syndrome by targeting non-canonical NF-{kappa}B signalling Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=125 SRC="FIGDIR/small/635629v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@829218org.highwire.dtl.DTLVardef@459f5dorg.highwire.dtl.DTLVardef@e198f6org.highwire.dtl.DTLVardef@1015685_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

A human-specific, concerted repression of microcephaly genes contributes to radiation-induced growth defects in forebrain organoids

AbstractPrenatal radiation-induced DNA damage poses a significant threat to normal brain development, resulting in microcephaly which primarily affects the cerebral cortex. It is unclear which molecular mechanisms are at the basis of this defect in humans as the few mechanistic studies performed so far were done in animals. Here, we leveraged human embryonic stem cell- derived forebrain organoids as a model for human corticogenesis. Organoids were X-irradiated with a moderate and a high dose at different time points, representing very early and mid corticogenesis. Irradiation caused a dose- and developmental-timing-dependent reduction in organoid size, which was more prominent in developmentally younger organoids. This coincided with a dose-dependent canonical p53-DREAM-dependent DNA damage response (DDR), consisting of cell cycle arrest, DNA repair and apoptosis. The DDR was delayed and less pronounced in the older organoids. Besides the DDR, we observed radiation-induced premature differentiation of neural progenitors and changes in metabolism. Importantly, our transcriptomic analysis furthermore demonstrated a concerted p53-E2F4-dependent repression of primary microcephaly genes. We found that this was a human-specific feature, as it was not observed in mouse embryonic brains or primary mouse neural progenitor cells. Thus, human forebrain organoids are an excellent model to investigate prenatal DNA damage-induced microcephaly and to uncover potentially targetable human-specific pathways.

developmental biology↗

bioRxiv2024

Predictive biomarkers of breast ductal carcinoma in situ may underestimate the risk of recurrence due to de novo ipsilateral breast carcinoma development

Development of ipsilateral breast carcinoma following diagnosis of breast ductal carcinoma in situ (DCIS) has been assumed to represent recurrence of the primary tumour. However, this may not be the case and it is important to know how often recurrences are new tumours. Ipsilateral primary-recurrence pairs (n=78) were sequenced to test their clonal relatedness. Shared genetic events were identified from whole exome sequencing (n=54 pairs) using haplotype-specific copy number and phylogenetic analysis. The remaining pairs were sequenced by a targeted panel or low-coverage whole genome sequencing. We included 32 non-recurrent DCIS to compare recurrent and non-recurrent disease. We found that 7% of DCIS recurrences were non-clonal by whole exome sequencing, indicative of a new breast carcinoma. Lower resolution methods detected a higher non-clonality rate (29%). Comparing primary DCIS with their recurrences found that evolution of DCIS to invasive disease was associated with increased ploidy and copy number events. TP53 mutations were enriched in DCIS with clonal recurrence compared with non-recurrent DCIS. Our results verify that de novo "recurrent tumours" of independent origin occur in patients who may be at high risk.

cancer biology↗

bioRxiv2023

A human prenatal skin cell atlas reveals immune cell regulation of skin morphogenesis

Human prenatal skin is populated by innate immune cells including macrophages, and whether they act solely in immunity or have additional functions in morphogenesis is unclear. We assembled the first comprehensive multi-omic reference atlas of prenatal human skin (7-16 post-conception weeks), combining single cell and spatial transcriptomic data, to characterise the skins microenvironmental cellular organisation. This revealed that crosstalk between non-immune and immune cells underpins formation of hair follicles, has implications for scarless wound healing, and is critical for skin angiogenesis. We benchmarked a skin organoid model, derived from human embryonic stem (ES) and induced pluripotent stem (iPS) cells, against prenatal and adult skin, demonstrating close recapitulation of the epidermal and dermal skin components during hair follicle development. Notably, the skin organoid lacked immune cells and had markedly diminished endothelial cell heterogeneity and quantity. From our in vivo skin cell atlas data, we found that macrophages and macrophage-derived growth factors play a key role in driving endothelial development prenatally. Indeed, vascular network formation was enhanced following transfer of autologous iPS-derived macrophages into both endothelial cell angiogenesis assays and skin organoid cultures. In summary, innate immune cells moonlight as key players in skin morphogenesis beyond their conventional immune roles, a function they achieve via extensive crosstalk with non-immune cells. Finally, we leveraged our human prenatal skin cell atlas to further our understanding of the pathogenesis of genetic hair and skin disorders.

developmental biology↗

bioRxiv2022

Brief report: Reclassifying SCLC-Y as SMARCA4 deficient malignancies - resolving the controversy

IntroductionThe classification of small cell lung cancer (SCLC) into distinct molecular subtypes defined by ASCL1, NEUROD1, POU2F3 or YAP1 expression, paves the way for the development of targeted therapeutics. However, the existence of a distinct YAP1-expressing SCLC subtype remains controversial. Here we have undertaken a detailed molecular and histological characterisation of YAP1 expressing SCLC-Y to understand the biology of this proposed subtype. MethodsThe mutational landscape of human SCLC cell lines was interrogated to identify pathogenic genomic alterations unique to SCLC-Y. Xenograft tumours generated from cell lines representing the molecular subtypes of SCLC (SCLC-A, -N, -P and -Y) were evaluated by a panel of pathologists. Diagnoses were validated by transcriptomic analysis of primary tumour and human cell line datasets. ResultsUnexpectedly, pathogenic mutations in SMARCA4 were identified in six of eight SCLC-Y cell lines and correlated with reduced SMARCA4 mRNA and protein expression. Pathologist evaluations revealed that SMARCA4-deficient SCLC-Y tumours exhibited features consistent with thoracic SMARCA4-deficient undifferentiated tumours (SMARCA4-UT). Similarly, the transcriptional profile SMARCA4-mutant SCLC-Y lines more closely resembled primary SMARCA4-UT, or SMARCA4-deficient non-small cell carcinoma, than SCLC. Combining clinical, pathological, transcriptomic, and genetic data we found little evidence to support a diagnosis of SCLC for any of the YAP1-expressing cell lines originally used to define the SCLC-Y subtype. ConclusionsSCLC-Y cell lines harbour inactivating SMARCA4 mutations and exhibit characteristics consistent with SMARCA4-deficient malignancies rather than SCLC. Our findings suggest that, unlike ASCL1, NEUROD1 and POU2F3, YAP1 is not a subtype defining transcription factor in SCLC.

cancer biology↗

bioRxiv2022

Utility of stromal lymphocytes in diagnosis and predicting upgrade of B3 breast lesions from core biopsies

For more than two decades attempts have been made to identify a subset of women diagnosed with lesions with uncertain malignant potential (B3 lesions) who could safely be observed rather than being treated with surgical excision and/or chemoprevention. Various histopathological, clinical and imaging parameters for risk recommendation have been evaluated, with little impact on clinical practice. The primary reason for surgery is to rule out an upgrade lesion to either ductal carcinoma in situ (DCIS) or invasive breast cancer (IBC). While on average 30% of these patients are upgraded after diagnostic biopsy, a large number are over treated,making this an important harm of screening. Here we evaluated stromal lymphocytes from B3 biopsies (n=264) as a predictive biomarker for upgrade. A higher number of stromal lymphocytes were observed in upgraded B3 lesions than non-upgraded (p< 0.01, zero inflated binomial model) for both ductal and papillary lesions (n=174). This observation was validated in an independent cohort (p<0.001, p<0.05, zero binomial model, ductal and papillary lesions, respectively) (n=90). Our data suggested that the presence of [≥]5% of lymphocytes in the surrounding specialised stroma of B3 lesions are predictive of B3 lesions being upgraded with a specificity of 93% and 87% in our discovery and validation cohorts, respectively. The area under the curve (AUC) for the discovery cohort using lymphocyte count and age as variables was 0.77 and was validated with an AUC of 0.81 in the validation cohort. In conclusion, we can identify a subset of the patients at risk of upgrade with high specificity. Assessing the tumour microenvironment including stromal lymphocytes may contribute to reducing unnecessary surgeries in the clinic.

cancer biology↗

bioRxiv2020

Poised cell circuits in human skin are activated in disease

The human skin confers biophysical and immunological protection through a complex cellular network that is established early in development. We profiled ~500,000 single cells using RNA-sequencing from healthy adult and developing skin, and skin from patients with atopic dermatitis and psoriasis. Our findings reveal a predominance of innate lymphoid cells and macrophages in developing skin in contrast to T cells and migratory dendritic cells in adult skin. We demonstrate dual keratinocyte differentiation trajectories and activated cellular circuits comprising vascular endothelial cells mediating immune cell trafficking, disease-specific clonally expanded IL13/IL22 and IL17A/F-expressing lymphocytes, epidermal IL23-expressing dendritic cells and inflammatory keratinocytes in disease. Our findings provide key insights into the dynamic cellular landscape of human skin in health and disease. One Sentence SummarySingle cell atlas of human skin reveals cell circuits which are quantitatively and qualitatively reconfigured in inflammatory skin disease.

immunology↗

bioRxiv2019

Epigenetic dysregulation underpins tumorigenesis in a cutaneous tumor syndrome.

Patients with CYLD cutaneous syndrome (CCS; syn. Brooke-Spiegler syndrome) carry germline mutations in the tumor suppressor CYLD and develop multiple skin tumors with diverse histophenotypes 1,2. We comprehensively profiled the genomic landscape of 42 benign and malignant tumors across 13 individuals from four multigenerational families. Novel driver mutations were found in epigenetic modifiers DNMT3A and BCOR in 29% of benign tumors. Multi-level and microdissected sampling strikingly reveal that many clones with different DNMT3A mutations exist in these benign tumors, suggesting that intra-tumor heterogeneity is common. Integrated genomic and methylation profiling suggest that mutated DNMT3A drives tumorigenesis mechanistically through Wnt/{beta}-catenin pathway signaling. Phylogenetic and mutational signature analyses confirm the phenomenon of benign pulmonary metastases from primary skin lesions. In malignant tumors, additional epigenetic modifiers MBD4, CREBBP, KDM6A and EP300 were mutated. We thus present epigenetic dysregulation as a driver in CCS tumorigenesis and propose this may account for the diverse histophenotypic patterns despite the paucity of mutations seen. These findings add novel dimensions to existing paradigms of cutaneous tumorigenesis and metastasis.

cancer biology↗