Biology subjects

Shirgaonkar, N.

Publications and source records attributed to Shirgaonkar, N..

4 recordsLinked to original sources

bioRxiv2026

HLiCA: An integrated cell atlas of the healthy human liver

The human liver is composed of a heterogeneous mix of cell types. How these distinct populations contribute individually and collectively to liver function remains poorly understood. Although single-cell technologies have advanced our understanding of liver biology, individual studies have often been limited by small donor cohorts and inconsistent cell type annotations. Integrating multiple datasets can overcome these challenges and better capture biological variability. We present the Human Liver Cell Atlas (HLiCA), an integrated reference of non-disease liver cells assembled from eight datasets across six research centers, encompassing more than 525,000 cells from 110 donors. Developed in collaboration with the Human Cell Atlas Liver Bionetwork, the HLiCA incorporates expert-curated cell annotations refined through community feedback and dedicated cell type annotation meetings. The HLiCA classifies cells into six lineages and expands the cell type resolution to include 47 distinct cell types. Starting from raw sequencing reads, we realigned all data and performed rigorous benchmarking to ensure robust integration across technical and biological variables. Genetic ancestry was inferred for all samples to evaluate the range of ancestral backgrounds represented in the atlas. The expanded cell type annotation enabled identification of previously unrecognized liver cell types, including NRXN1+ stromal cells. Their presence was validated using spatial transcriptomics, which localized NRXN1+ stromal cells to periportal regions. With the number of donors included in the HLiCA we were able to examine cell type specific associations with demographic covariates. In hepatocytes, drug metabolism genes showed differential expression between sexes, and in cholangiocytes, mucus-production genes varied with age. As the largest and most genetically diverse human liver cell atlas to date, the HLiCA provides a comprehensive, well-annotated reference for the field, annotated by expert consensus. This resource will enable deeper interrogation of liver cellular diversity, architecture, and function in the healthy human liver and serve as a reference to understand changes that occur with disease.

genomics↗

bioRxiv2024

Modelling oxaliplatin resistance in colorectal cancer reveals a SERPINE1-based gene signature (RESIST-M) and therapeutic strategies for pro-metastatic CMS4 subtype

Drug resistance and distant metastases are major contributors to mortality in colorectal cancer (CRC). Here we investigate mechanisms underlying acquired resistance to oxaliplatin, a first-line, standard-of-care CRC treatment. We generated oxaliplatin-resistant CRC tumor cells with clinically relevant dosing regimen, which displayed enhanced metastatic potential. Transcriptomic and phenotypic analyses revealed a critical function for cholesterol biogenesis in modulating TGF-{beta} signaling activity, which in turn regulates SERPINE1 expression, a gene we identified as a key player in promoting drug resistance and metastasis. Additionally, we uncovered a SERPINE1-associated nine-gene expression signature, RESIST-M, that can predict overall and relapse-free survival (RFS) in clinical cohorts and is able to stratify patients into CMS4/iCMS3-fibrotic CRC-subtypes, underscoring its clinical utility. Using mouse tumor models, we provide further evidence that targeting SERPINE1 and cholesterol biogenesis can be viable approaches to re-sensitize the resistant pro-metastatic CRC cells to oxaliplatin. This study not only elucidates the molecular underpinnings of drug resistance and metastasis in primary CRC, but also offers prognostic and therapeutic strategies to guide clinical management of the disease. SignificanceThis study reveals critical resources and insights on oxaliplatin resistance and metastasis in CRC via a novel TGF-{beta} cholesterol axis. We generated improved oxaliplatin-resistant models that enabled identification of a prognostic SERPINE1-based gene signature to predict oxaliplatin resistance-induced metastasis in CRC. This gene signature derived from our models showed that the models can mimic CMS-4/iCMS-fibrotic-like metastatic CRC patients. We validated therapeutic candidates targeting CMS-4/iCMS-fibrotic-like metastatic CRC cells which can reverse drug resistance and metastasis.

cancer biology↗

bioRxiv2024

Identification of Cyclin L1 as a host factor regulating Hepatitis B Virus replication

Background & AimsUnderstanding the regulatory interactions between Hepatitis B virus (HBV) and human host factors is key to the development of next-generation host-directed antiviral therapies and achieving a functional HBV cure. In this study, we aimed to investigate HBV-induced alterations in host gene expression in primary human hepatocytes (PHH) to identify host-specific factors that are regulated and exploited by the virus for replication and survival. MethodsWe performed whole transcriptome sequencing (WTS) of HBV-infected PHH to identify host pathways that could potentially influence the HBV life cycle. RNA-interference-based validation of putative targets to evaluate the function of dysregulated candidate genes resulted in the identification of Cyclin L1 (CCNL1) as a key host factor. ResultsRNAi-knockdown of CCNL1 revealed that it is essential for HBV gene expression, including HBV-surface antigen (HBsAg). Mechanistically, we found that CCNL1 can phosphorylate the C-terminal domain (CTD) of RNA Polymerase II (RNAPII) at serine 2 (S2), likely to regulate HBV transcription. Furthermore, the knockdown of CCNL1 inhibited the binding of total and phospho- (Ser2-Ser5) RNAPII, pan-acetylated H3ac, and H3K27ac to HBV cccDNA, implicating its function in the regulation of cccDNA-dependent viral transcription. Finally, enhanced CCNL1 expression in chronic hepatitis B patients, as compared to those with resolved infection, underscores a functional link between this host factor and CHB. ConclusionOur data demonstrates that CCNL1 regulates HBV RNA transcription and replication by modulating RNAPII phosphorylation and activity, making it a potential host susceptibility factor for HBV. LAY SUMMARYHepatitis B requires human host cell factors and biological processes to establish an efficient infection. Identifying host factors that support and/or restrict HBV infection is essential for understanding the molecular basis of chronic HBV infection and for developing host-targeting anti-HBV drugs. Here, we report that CCNL1 can serve as a potential host susceptibility factor for HBV, as reduced CCNL1 function results in reduced viral replication and gene expression. Graphical SummaryGraphical summary, highlighting the approach and validation experiments. From whole transcriptomics analysis, we identified known HBV-host factors such as SRPK1, CDK1, NXF1 among others as well as new factors such as CCNL1. Employing various RNAi approaches and different cell models including primary human hepatocytes, we validated the role of CCNL1 during HBV infection cycle. Pull-down experiments followed by ChIP-PCR further showed a reduction in cccDNA-based transcription upon knockdown of CCNL1. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/619969v2_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1ee9cd9org.highwire.dtl.DTLVardef@7bac2dorg.highwire.dtl.DTLVardef@164c3bborg.highwire.dtl.DTLVardef@6e497a_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

Temporal transcriptional response of Candida glabrata during macrophage infection reveals a multifaceted transcriptional regulator CgXbp1 important for macrophage response and drug resistance

Candida glabrata can thrive inside macrophages and tolerate high levels of azole antifungals. These innate abilities render infections by this human pathogen a clinical challenge. How C. glabrata reacts inside macrophages and what is the molecular basis of its drug tolerance are not well understood. Here, we mapped genome-wide RNA polymerase II (RNAPII) occupancy in C. glabrata to delineate its transcriptional responses during macrophage infection in high temporal resolution. RNAPII profiles revealed dynamic C. glabrata responses to macrophage with genes of specialized pathways activated chronologically at different times of infection. We identified an uncharacterized transcription factor (CgXbp1) important for the chronological macrophage response, survival in macrophages, and virulence. Genome-wide mapping of CgXbp1 direct targets further revealed its multi-faceted functions, regulating not only virulence-related genes but also genes associated with drug resistance. Finally, we showed that CgXbp1 indeed also affects azole resistance. Overall, this work presents a powerful approach for examining host-pathogen interaction and uncovers a novel transcription factor important for C. glabratas survival in macrophages and drug tolerance.

microbiology↗