Biology subjects

Narkar, A.

Publications and source records attributed to Narkar, A..

4 recordsLinked to original sources

bioRxiv2026

Shaping hydrogel bioinks into 3D, multiscale, perfusable models using multimodal printing

Despite technological advances, the fabrication of multiscale, multi-material, and topologically complex 3D structures using soft hydrogel bioinks remains a challenge due to the inherent trade-offs between print size/resolution, bioink properties, and design complexity. In this work, we combine additive (macroscale) digital light projection (DLP) mode with subtractive (microscale) two-photon ablation (TPA) mode with multi-material exchange capability. We identify ideal hydrogel bioink formulations that are compatible with both DLP and TPA modes of processing. Technical challenges related to multimodal fabrication such as alignment of multiscale topologies to facilitate seamless media perfusion, soft-hard multi-material printing to facilitate handling of mechanically weak hydrogel constructs, and hydrogel swelling during printing, were resolved. To highlight the novelty of this hybrid platform, we fabricated centimeter-scale bioink constructs with embedded microscale perfusable topologies that cannot be achieved by isolated use of either DLP or TPA modes. This includes simpler microfluidic chips with independently perfusable microchannels to more complex 3D constructs with embedded, multiscale, perfusable dual-fluidic circuits that mimic the alveoli-capillary interface, or microfluidic chips with endothelialized microchannels. The unique ability of this multimodal platform to mimic in vivo-like multiscale complexities can be potentially used to develop next-generation organ-on-chips.

bioengineering↗

bioRxiv2025

The scaffold protein PRR14L links the PP2A-TACC3 axis to mitotic fidelity and sensitivity to MPS1 inhibition

Aneuploidy is a hallmark of cancer and is a potential vulnerability that can be selectively targeted. To systematically identify genes that affect the incidence and fitness of aneuploid cells, we conducted a genome-wide CRISPR/Cas9 screen using NMS-P715, an inhibitor of the spindle assembly checkpoint (SAC) kinase MPS1/TTK. In this study, we identified a number of genes known to regulate aneuploidy and mitosis, and subsequently focused on PRR14L, a ubiquitously expressed gene previously implicated in chronic myelomonocytic leukemia (CMML). Proximity labeling of PRR14L using TurboID revealed several cell division proteins, including the PP2A-B56 phosphatase complex and the spindle assembly factor TACC3, as PRR14L-interacting proteins. Loss of PRR14L prolongs SAC-dependent mitotic arrest in response to microtubule depolymerization but, paradoxically, leads to catastrophic mitotic errors upon SAC abrogation by MPS1 inhibitors. A model derived from our findings provides a rationale for exploiting MPS1 inhibition as a potential vulnerability in cancers containing either PRR14L loss of function mutations or FGFR-TACC3 fusions. Significance StatementO_LIAneuploidy is a hallmark of cancer. Whether aneuploidy can be selectively targeted is not known. C_LIO_LIUtilizing a CRISPR/Cas9 screen, the authors found that loss of the gene PRR14L sensitizes cells to aneuploidy induction. Taking advantage of live cell imaging and proximity labeling, they linked PRR14L to TACC3 and mitosis. C_LIO_LIThese findings suggest that spindle checkpoint inhibitors may have therapeutic potential in cancers with either loss-of-function PRR14L and/or gain of function TACC3 mutations. C_LI

cell biology↗

bioRxiv2023

Differential effects of aneuploidy on growth and differentiation in human intestinal stem cells

Aneuploidy, a near ubiquitous genetic feature of tumors, is a context-dependent driver of cancer evolution; however, the mechanistic basis of this role remains unclear. Here, by inducing heterogeneous aneuploidy in non-transformed human colon organoids (colonoids), we investigate how the effects of aneuploidy on cell growth and differentiation may promote malignant transformation. Single-cell RNA sequencing reveals that the gene expression signature across over 100 unique aneuploid karyotypes is enriched with p53 responsive genes. The primary driver of p53 activation is karyotype complexity. Complex aneuploid cells with multiple unbalanced chromosomes activate p53 and undergo G1 cell-cycle arrest, independent of DNA damage and without evidence of senescence. By contrast, simple aneuploid cells with 1-3 chromosomes gained or lost continue to proliferate, demonstrated by single cell tracking in colonoids. Notably, simple aneuploid cells exhibit impaired differentiation when niche factors are withdrawn. These findings suggest that while complex aneuploid cells are eliminated from the normal epithelium due to p53 activation, simple aneuploid cells can escape this checkpoint and may contribute to niche factor-independent growth of cancer-initiating cells.

cell biology↗

bioRxiv2021

Colonic epithelial adaptation to EGFR-independent growth induces induces chromosomal instability and is accelerated by prior injury

Although much is known about the gene mutations required to drive colorectal cancer (CRC) initiation, the tissue-specific selective microenvironments in which neoplasia arises remains less characterized. Here, we determined whether modulation of intestinal stem cell niche morphogens alone can exert a neoplasia-relevant selective pressure on normal colonic epithelium. Using adult stem cell-derived murine colonic epithelial organoids (colonoids), we employed a strategy of sustained withdrawal of EGF and EGFR inhibition to select for and expand survivors. EGFR-signaling-independent (iEGFR) colonoids emerged over rounds of selection and expansion. Colonoids derived from a mouse model of chronic mucosal injury showed an enhanced ability to adapt to EGFR inhibition. Whole-exome and transcriptomic analyses of iEGFR colonoids demonstrated acquisition of deleterious mutations and altered expression of genes implicated in EGF signaling, pyroptosis, and CRC. iEGFR colonoids acquired dysplasia-associated cytomorphologic changes, an increased proliferative rate, and the ability to survive independently of other required niche factors. These changes were accompanied by emergence of aneuploidy and chromosomal instability; further, the observed mitotic segregation errors were significantly associated with loss of interkinetic nuclear migration, a fundamental and dynamic process underlying intestinal epithelial homeostasis. This study provides key evidence that chromosomal instability and other phenotypes associated with neoplasia can be induced ex vivo via adaptation to EGF withdrawal in normal and stably euploid colonic epithelium, without introducing cancer-associated driver mutations. In addition, prior mucosal injury accelerates this evolutionary process. Key definitionsColonoids: adult stem cell-derived colonic epithelial organoids iEGFR: in vitro selective conditions devoid of EGF (epidermal growth factor) and including an EGFR (EGF receptor) inhibitor 1 iEGFR colonoids: colonoids tolerant to iEGFR culture conditions with growth and survival similar to unselected passage-matched controls INM: Interkinetic nuclear migration

cancer biology↗