Biology subjects

Haigis, K. M.

Publications and source records attributed to Haigis, K. M..

14 recordsLinked to original sources

bioRxiv2026

Deep-learning-based design of an orthogonal self-labeling protein from K-Ras(G12C)

Self-labeling protein (SLP) tags enable versatile labeling of proteins in live cells, yet only two SLPs are commonly used, limiting multiplexing. Here, we repurposed the oncoprotein K-Ras(G12C) and its covalent inhibitors to create a third, orthogonal SLP system. We used a deep-learning-based approach to radically redesign the sequence of K-Ras(G12C) while preserving its covalent-inhibitor binding pocket. Our top design, LUCI-tag, is a 19 kDa, monomeric, thermostable SLP that rapidly and covalently reacts with commercially available K-Ras(G12C) inhibitors bearing diverse payloads. Unlike existing SLPs, LUCI-tag exhibited payload-agnostic labeling kinetics, outperforming HaloTag7 and SNAP-tag for a negatively charged payload. X-ray crystal structures of drug-bound and drug-free LUCI-tag showed the design was structurally accurate and contained a preorganized inhibitor-binding pocket that could explain its rapid labeling kinetics. Proteomics and cell-signaling experiments confirmed LUCI-tag is biologically inert. LUCI-tag enabled rapid, wash-free, live-cell imaging and simultaneous three-color multiplexed experiments with HaloTag7 and SNAP-tag. This work establishes LUCI-tag as an immediately useful orthogonal SLP and demonstrates that covalent drug-target pairs can be repurposed into a broadly applicable platform for protein labeling.

bioengineering↗

bioRxiv2026

Enteric neurons modulate colorectal cancer cell cycle through a PCSK1 - Methionine-Enkephalin Axis

Background and AimsThe tumor microenvironment in colorectal cancer (CRC) is richly innervated, yet the contribution of the enteric nervous system (ENS) to CRC biology remains poorly defined. ENS neurons express proenkephalin (PENK), which can be processed by proprotein convertase 1/3 (PCSK1) to generate Methionine-enkephalin (M-ENK), a bioactive peptide with growth-regulatory potential. We hypothesized that an ENS-derived PCSK1-M-ENK axis restrains CRC proliferation through opioid growth factor receptor (OGFr) signaling and is modulated by stress-associated glucocorticoid receptor (GR) signaling and GLP1 receptor (GLP1R) activity. MethodsPublicly available human CRC single-cell RNA-sequencing datasets were analyzed for OGFr expression. PCSK1 and M-ENK expression in murine ENS and tumor-associated tissue was assessed by immunofluorescence. Functional studies were performed using murine CRC organoids, and primary murine ENS neurons in mono- and co-culture. CRC proliferation was quantified by EdU incorporation following treatment with recombinant M-ENK, recombinant PCSK1, OGFr synthetic ligand naloxone, or PCSK1 inhibitors. Effects of dexamethasone and liraglutide on PCSK1 expression in ENS-containing murine tissue were evaluated. ResultsOGFr was enriched in CRC cells and positively associated with KRAS gene expression. A subset of adult murine colonic myenteric neurons expressed PCSK1 and M-ENK. M-ENK dose-dependently suppressed proliferation of CRC organoid cells. ENS neurons also suppressed CRC proliferation in a PCSK1-dependent manner. Dexamethasone reduced, whereas liraglutide increased, PCSK1 expression. ConclusionsThese findings define a previously unrecognized ENS-derived neuro-oncologic pathway that is associated with reduced CRC cell proliferation and identify the GR/GLP1R-PCSK1-M-ENK axis as a potentially actionable therapeutic node. SummaryThis study identifies a neuronal PCSK1 - M-ENK pathway in the ENS that directly suppresses colorectal cancer growth through local OGFr activation, revealing a previously unrecognized neuropeptidergic mechanism of tumor control within the intestinal microenvironment.

cancer biology↗

bioRxiv2025

miRISC inhibition causes mitotic defects and synergizes with genotoxic agents in cancers

Although individual microRNAs (miRNAs) can have tumorigenic or tumor-suppressive properties, their overall role in cancer remains controversial. Here, we show that cancer tissues and cell lines are characterized by preferential accumulation of the high-molecular-weight miRNA-induced silencing complex (HMWR), the functionally active form of the effector complex responsible for miRNA-mediated gene repression. Experimentally induced disassembly of the HMWR impairs the growth of human tumor xenografts and of autochthonous tumors in mouse models of human cancer in vivo. Furthermore, disassembly of the HMWR increases chromosome mis-segregation, which synergized with genotoxic agents to potentiate cancer cell vulnerability and improve therapeutic response. These findings suggest pharmacologic inhibition of HMWR as a novel anti-cancer strategy.

cancer biology↗

bioRxiv2025

The tissue specificity of cancer genes

Defining genes that are somatically mutated in different cancers is a central goal of cancer genetics. Nevertheless, traditional definitions of "driver" genes based on pooled mutation frequency are biased toward common cancer types and tend to overlook genes that might be specific to rarer subtypes. As such, our understanding of the compendium of cancer genes is incomplete. In this study, we developed a statistical framework that defines genes enriched for functional somatic mutations in primary cancers to quantify incidence and tissue specificity for each gene. By applying this framework to the AACR GENIE v18.0 dataset, which comprised over 1.15 million mutations identified in 146,394 patients spanning 265 histologic subtypes, we identified a total of 95 genes significantly mutated in at least one subtype. We mined this dataset to derive tissue specificity scores for all 95 genes, demonstrating that tissue specificity in cancer is the norm, not the exception, for nearly all genes. We interrogated these new tissue specificity scores to reveal that oncogenes with restricted expression across normal tissues tend to exhibit higher tissue-specific mutation patterns in cancer. In contrast, tumor suppressors were often ubiquitously expressed irrespective of their underlying tissue specificity, which was partially correlated with differentially expressed compensatory genes and pathways in mutationally permissive tissues. Significance StatementWe present a statistically robust, subtype-aware framework to identify tissue-specific cancer driver genes and uncover their underlying biology. Our findings reveal that tissue-selective oncogenicity arises from expression constraints and tissue-restricted compensatory pathways. These findings provide a systematic, well-powered resource on mutational significance, tissue tropism, and biological consequences for the cancer research community.

cancer biology↗

bioRxiv2025

Cooperativity between Ras pathway mutations in colonic tumorigenesis

The Kirsten rat sarcoma (KRAS) gene is the most frequently mutated oncogene in colorectal cancer (CRC). We previously characterized two activating alleles of KRAS, A59T and A59E, that show impaired BRAF dimerization. These alleles of KRAS are enriched in CRC tumors with genetic alterations in genes that regulate MAPK signaling (e.g. EGFR, NF1). Using a new conditional mouse model of K-Ras (LSL-K-Ras A59E) we show that, despite its inability to universally activate RAF kinases, K-Ras A59E disturbs colon epithelium and decreases mouse survival in a tumor model. By combining LSL-K-Ras A59E mice with a conditional knockout of Nf1, we demonstrate cooperation between these alleles at multiple levels. Consistent with cooperation and clinical observations, we show that K-Ras A59E neither promotes EGF independence of organoid growth, nor confers intrinsic resistance to EGFR inhibition. Thus, our data provide a deeper understanding of the role of RAF isoforms in mutant KRAS driven CRC and argue for the use of anti-EGFR therapies against some Ala59 mutant alleles of KRAS. Statement of significanceOur studies on oncogenic K-RAS mutants demonstrate that the biochemical properties of a mutant oncoprotein are reflected in the somatic genetics of cancer, in particular in the cooperating mutations that occur. These mutant-specific genetic interactions influence therapeutic responses. As such, KRAS mutation may not be a univariate predictor of response to EGFR inhibition.

cancer biology↗

bioRxiv2025

Baseline expression of c-Myc defines the tissue specificity of oncogenic K-Ras

KRAS is among the most frequently mutated oncogenes in cancer. Yet, mutations in KRAS are common only in tumors originating from a subset of tissues. It is critical to understand the molecular mechanisms underlying this oncogene tissue specificity. Utilizing genetically engineered mouse models carrying a conditional oncogenic allele of Kras, we expressed activated K-Ras in adult tissues to investigate its specificity. We discovered that the ability of K-RasG12D to influence the fitness of cells in a given tissue is not determined by its canonical signaling through MAPK. Instead, low baseline expression of c-Myc renders tissues non-permissive to oncogenic K-Ras, a context that can be reversed in the liver by ectopically expressing c-Myc. This functions independently of the proliferative index of the tissue or the induction of cell cycle arrest or apoptosis. Our findings reveal the importance of the basal state of the tissue-inherent signaling network for determining oncogene specificity.

cancer biology↗

bioRxiv2024

Comprehensive structure-function analysis reveals gain- and loss-of-function mechanisms impacting oncogenic KRAS activity

To dissect variant-function relationships in the KRAS oncoprotein, we performed deep mutational scanning (DMS) screens for both wild-type and KRASG12D mutant alleles. We defined the spectrum of oncogenic potential for nearly all possible KRAS variants, identifying several novel transforming alleles and elucidating a model to describe the frequency of KRAS mutations in human cancer as a function of transforming potential, mutational probability, and tissue-specific mutational signatures. Biochemical and structural analyses of variants identified in a KRASG12D second-site suppressor DMS screen revealed that attenuation of oncogenic KRAS can be mediated by protein instability and conformational rigidity, resulting in reduced binding affinity to effector proteins, such as RAF and PI3-kinases, or reduced SOS-mediated nucleotide exchange activity. These studies define the landscape of single amino acid alterations that modulate the function of KRAS, providing a resource for the clinical interpretation of KRAS variants and elucidating mechanisms of oncogenic KRAS inactivation for therapeutic exploitation.

cancer biology↗

bioRxiv2024

Rare germline structural variants increase risk for pediatric solid tumors

AO_SCPLOWBSTRACTC_SCPLOWPediatric solid tumors are rare malignancies that represent a leading cause of death by disease among children in developed countries. The early age-of-onset of these tumors suggests that germline genetic factors are involved, yet conventional germline testing for short coding variants in established predisposition genes only identifies pathogenic events in 10-15% of patients. Here, we examined the role of germline structural variants (SVs)--an underexplored form of germline variation--in pediatric extracranial solid tumors using germline genome sequencing of 1,766 affected children, their 943 unaffected relatives, and 6,665 adult controls. We discovered a sex-biased association between very large (>1 megabase) germline chromosomal abnormalities and a four-fold increased risk of solid tumors in male children. The overall impact of germline SVs was greatest in neuroblastoma, where we revealed burdens of ultra-rare SVs that cause loss-of-function of highly expressed, mutationally intolerant, neurodevelopmental genes, as well as noncoding SVs predicted to disrupt three-dimensional chromatin domains in neural crest-derived tissues. Collectively, our results implicate rare germline SVs as a predisposing factor to pediatric solid tumors that may guide future studies and clinical practice.

genomics↗

bioRxiv2023

In vivo Imaging using Surface Enhanced Spatially Offset Raman Spectroscopy (SESORS): Balancing Sampling Frequency to Improve Overall Image Acquisition

Background and RationaleIn the field of optical imaging, the ability to image tumors at depth with high selectivity and specificity remains a challenge. Surface enhanced resonance Raman scattering (SERRS) nanoparticles (NPs) can be employed as image contrast agents to specifically target cells in vivo, however, this technique typically requires time-intensive point-by-point acquisition of Raman spectra, thus hindering the real-time image acquisition desired for clinical applications. Moreover, traditional approaches involving Raman spectroscopy are limited in their inability to probe through tissue depths of more than a few millimeters. Here, we combine the use of "spatially offset Raman spectroscopy" (SORS) with that of SERRS in a technique known as "surface enhanced spatially offset resonance Raman spectroscopy" (SESORRS) to image deep-seated tumors in vivo. Additionally, by accounting for the laser spot size, we report an experimental SESORRS approach for detecting both the bulk tumor, subsequent delineation of tumor margins at high speed, and the identification of a deeper secondary region of interest with fewer measurements than are typically applied. MethodsTo enhance light collection efficiency, four modifications were made to a previously described custom-built SORS system. Specifically, the following parameters were increased: (i) the numerical aperture (NA) of the lens, from 0.2 to 0.34; (ii) the working distance of the probe, from 9 mm to 40 mm; (iii) the NA of the fiber, from 0.2 to 0.34; and (iv) the fiber diameter, from 100 {micro}m to 400 {micro}m. To calculate the sampling frequency, which refers to the number of data point spectra obtained for each image, we considered the laser spot size of the elliptical beam (6 x 4 mm). Using SERRS contrast agents, we performed in vivo SESORRS imaging on a GL261-Luc mouse model of glioblastoma at four distinct sampling frequencies: par-sampling frequency (12 data points collected), and over-frequency sampling by factors of 2 (35 data points collected), 5 (176 data points collected), and 10 (651 data points collected). ResultsIn comparison to the previously reported SORS system, the modified SORS instrument showed a 300% improvement in signal-to-noise ratios (SNR). Glioblastomas were imaged in vivo using SESORRS in mice (n = 3) and tumors were confirmed using MRI and histopathology. The results demonstrate the ability to acquire distinct Raman spectra from deep-seated glioblastomas in mice through the skull using a low power density (6.5 mW/mm2) and 30-times shorter integration times than a previous report (0.5 s versus 15 s). The ability to map the whole head of the mouse and determine a specific region of interest using as few as 12 spectra (6 second total acquisition time) is achieved. Subsequent use of a higher sampling frequency demonstrates it is possible to delineate the tumor margins in the region of interest with greater certainty. In addition, SESORRS images indicate the emergence of a secondary tumor region deeper within the brain in agreement with MRI and H&E staining. ConclusionIn comparison to traditional Raman imaging approaches, this approach enables improvements in the rapid detection of deep-seated tumors in vivo through depths of several millimeters due to improvements in SNR, spectral resolution, and depth acquisition. This approach offers an opportunity to navigate larger areas of tissues in shorter time frames than previously reported, identify regions of interest, and then image such area with greater resolution using a higher sampling frequency. Moreover, using a SESORRS approach, we demonstrate that it is possible to detect secondary, deeper-seated lesions through the intact skull.

bioengineering↗

bioRxiv2022

Allosteric regulation of switch-II controls K-Ras oncogenicity

Ras proteins are GTPases that regulate a wide range of cellular processes. The activity of Ras is dependent on its nucleotide-binding status, which is modulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Previously, we demonstrated that mutation of lysine 104 to glutamine (K104Q) attenuates the transforming capacity of oncogenic K-Ras by interrupting GEF induced nucleotide exchange. To assess the effect of this mutation in vivo, we used CRISPR/Cas9 to generate mouse models carrying the K104Q point mutation in wild-type and conditional K-RasLSL-G12D alleles. Consistent with our previous findings from in vitro studies, the oncogenic activity of K-RasG12D was significantly attenuated by mutation at K104 in vivo. These data demonstrate that lysine at position 104 is critical for the full oncogenic activity of mutant K-Ras and suggest that modification at K104, for example acetylation, may also regulate its activity. In addition, animals homozygous for K104Q were viable, fertile, and arose at Mendelian frequency, indicating that K104Q is not a complete loss of function mutation. Using biochemical and structural analysis, we found that the G12D and K104Q mutations cooperate to suppress GEF-mediated nucleotide exchange, explaining the preferential effect of K104Q on oncogenic K-Ras. Finally, we discovered an allosteric regulatory network consisting of K104 and residues including G75 on switch II (SWII) that is the key for regulating the stability of the helix on SWII. In this allosteric network, K104-G75 interaction might be primary for keeping stabilization of SWII. Given the high frequency of KRAS mutations in human cancers, modulation of this network may provide a unique therapeutic approach.

cancer biology↗

bioRxiv2021

Regulation of GTPase function by autophosphorylation

A unifying feature of the RAS superfamily is a functionally conserved GTPase cycle that proteins use to transition between active and inactive states. Here, we demonstrate that active site autophosphorylation of some small GTPases is an intrinsic regulatory mechanism that reduces nucleotide hydrolysis and enhances nucleotide exchange, thus altering the on/off switch that forms the basis for their signaling functions. Using x-ray crystallography, nuclear magnetic resonance spectroscopy, biolayer interferometry binding assays, and molecular dynamics on autophosphorylated mutants of H-RAS and K-RAS, we show that phosphoryl transfer from GTP requires dynamic movement of the switch II domain and that autophosphorylation promotes nucleotide exchange by opening of the active site and extraction of the stabilizing Mg. Finally, we demonstrate that autophosphorylated K-RAS exhibits altered effector interactions, including a reduced affinity for RAF proteins. Thus, autophosphorylation leads to altered active site dynamics and effector interaction properties, creating a pool of GTPases that are functionally distinct from the non-phosphorylated counterpart.

biochemistry↗

bioRxiv2021

Inducible and reversible inhibition of miRNA-mediated gene repression in vivo

Although virtually all gene networks are predicted to be controlled by miRNAs, the contribution of this important layer of gene regulation to tissue homeostasis in adult animals remains unclear. Gain and loss of function experiments have provided key insights into the specific function of individual miRNAs, but effective genetic tools to study the functional consequences of global inhibition of miRNA activity in vivo are lacking. Here we report the generation and characterization of a genetically engineered mouse strain in which miRNA-mediated gene repression can be reversibly inhibited without affecting miRNA biogenesis or abundance. We demonstrate the usefulness of this strategy by investigating the consequences of acute inhibition of miRNA function in adult animals. We find that different tissues and organs respond differently to global loss of miRNA function. While miRNA-mediated gene repression is essential for the homeostasis of the heart and the skeletal muscle, it is largely dispensable in the majority of other organs. Even in tissues where it is not required for homeostasis, such as the intestine and hematopoietic system, miRNA activity can become essential during regeneration following acute injury. These data support a model where many metazoan tissues primarily rely on miRNA function to respond to potentially pathogenic events.

molecular biology↗

bioRxiv2019

High-resolution in vivo identification of miRNA targets by Halo-Enhanced Ago2 Pulldown

The identification of miRNA targets by Ago2 crosslinking-immunoprecipitation (CLIP) methods has provided major insights into the biology of this important class of non-coding RNAs. However, these methods are technically challenging and not easily translated to an in vivo setting. To overcome these limitations and to facilitate the investigation of miRNA functions in mice, we have developed a method (HEAP: for Halo-Enhanced Ago2 Pulldown) to map miRNA-mRNA binding sites. This method is based on a novel genetically engineered mouse harboring a conditional, Cre-regulated, Halo-Ago2 allele expressed from the endogenous Ago2 locus. By using a resin conjugated to the HaloTag ligand, Ago2-miRNA-mRNA complexes can be efficiently purified from cells and tissues expressing the endogenous Halo-Ago2 allele. We demonstrate the reproducibility and sensitivity of this method in mouse embryonic stem cells, in developing embryos, in adult tissues and in autochthonous mouse models of human brain and lung cancers.\n\nThe tools and the datasets we have generated will serve as a valuable resource to the scientific community and will facilitate the characterization of miRNA functions under physiological and pathological conditions.

molecular biology↗

bioRxiv2018

A framework for translation of genomic responses from mouse models to human inflammatory disease contexts

The high failure rate of therapeutics showing promise in mouse disease models to translate to patients is a pressing challenge in biomedical science. However, mouse models are a useful tool for evaluating mechanisms of disease and prioritizing novel therapeutic agents for clinical trials. Though retrospective studies have examined the fidelity of mouse models of inflammatory disease to their respective human in vivo conditions, approaches for prospective translation of insights from mouse models to patients remain relatively unexplored. Here, we develop a semi-supervised learning approach for prospective inference of disease-associated human in vivo differentially expressed genes and pathways from mouse model experiments. We examined 36 transcriptomic case studies where comparable phenotypes were available for mouse and human inflammatory diseases and assessed multiple computational approaches for inferring human in vivo biology from mouse model datasets. We found that a semi-supervised artificial neural network identified significantly more true human in vivo associations than interpreting mouse experiments directly (95% CI on F-score for mouse experiments [0.090, 0.175], neural network [0.278, 0.375], p = 0.00013). Our study shows that when prospectively evaluating biological associations in mouse studies, semi-supervised learning approaches combining mouse and human data for biological inference provides the most accurate assessment of human in vivo disease and therapeutic mechanisms. The task of translating insights from model systems to human disease contexts may therefore be better accomplished by the use of systems modeling driven approaches.\n\nAuthor SummaryComparison of genomic responses in mouse models and human disease contexts is not sufficient for addressing the challenge of prospective translation from mouse models to human disease contexts. Here, we address this challenge by developing a semi-supervised machine learning approach that combines supervised modeling of mouse experiment datasets with unsupervised modeling of human disease-context datasets to predict human in vivo differentially expressed genes and pathways as if the model system experiment had been run in the human cohort. A semi-supervised version of a feed forward artificial neural network was the most efficacious model for translating experimentally derived mouse molecule-phenotype associations to the human in vivo disease context. We find that computational generalization of signaling insights from mouse to human contexts substantially improves upon direct generalization of mouse experimental insights and argue that such approaches can facilitate more clinically impactful translation of insights from preclinical studies in model systems to patients.

systems biology↗