Biology subjects

Tam, B.

Publications and source records attributed to Tam, B..

7 recordsLinked to original sources

bioRxiv2026

The Multi-scale Copula Index (MCI): a new information-theoretic measure of association and its applications in functional cancer genomics

Cancer genomic analyses increasingly involve large, complex datasets representing diverse omics variables, such as gene expression, mutations, copy number alterations, genetic perturbations (e.g. CRISPR or iRNA), drug sensitivity, and clinical phenotypes, making it crucial to accurately measure associations among these variables. Traditional correlation-based methods, like the Pearson correlation coefficient, often assume linearity, Gaussian distributions, and independence among variables, leading to oversimplified assumptions, less sensitive readouts and less accurate significance estimation. Information-theoretic measures overcome these limitations by being one step removed from the data and assessing dependencies at the level of probability distributions, thus providing a more data-agnostic, robust measure for identifying associations in common analysis tasks such as feature selection, pattern recognition, and predictive modeling. Building on these foundations, we introduce the Multi-scale Copula Index (MCI), a novel information-theoretic measure of association. The MCI offers significant advantages over existing methods by eliminating the need for density estimation and parameter tuning, thereby ensuring consistent estimation with reduced computational complexity. Furthermore, it enhances statistical power at lower sample sizes, exhibits strong robustness to outliers, and successfully captures both directionality and important symmetries under input-data transformations, such as reflection or complementation. Due to these strengths, the MCI is particularly useful for functional cancer genomic applications involving, e.g., transcriptional and perturbational data, with different statistical properties across a wide range of dataset sizes and complexity. Contextual associations often arise in functional genomics datasets: two genomic variables show little or no correlation in most samples, yet display a strong linkage within the subset that reflects the active biological context. These situations are ideal for quantifying associations with the MCI. We illustrate the performance of the MCI in a variety of benchmarks and cancer genomic examples and applications. We also introduce the Cumulative Entropy Diagram (CED), a graphical display that allows the visualization of the MCI between a reference vector, such as a phenotype, pathway activation or drug response, and a complete set of genomic features.

bioinformatics↗

bioRxiv2026

Trigeminal Nerve Stimulation Attenuates Traumatic Brain Injury-Induced Neuronal Damage via CGRP-PINK1 Mitophagy Axis

Secondary damage after traumatic brain injury (TBI) is driven by progressive mitochondrial failure, yet clinically viable strategies to directly safeguard mitochondrial networks remain a major therapeutic gap. Here, we show that non-invasive trigeminal nerve stimulation (TNS), which engages the brain's endogenous oxygen-conserving diving reflex, preserves neuronal survival by directly regulating the mitochondrial PINK1/Parkin quality-control pathway. We demonstrate that TBI induces the pathological aggregation of the outer mitochondrial membrane receptor TOM20, in a CGRP-dependent manner, which affects binding of the damage-sensor PINK1 and renders downstream Parkin-mediated rescue ineffective. TNS-induced neuronal CGRP release prevents this TOM20 aggregation, restoring proper PINK1 function and downstream Parkin activation. This preservation of mitochondrial architecture reinforces the outer membrane's barrier function, limiting pro-apoptotic cytochrome c leakage and supporting NRF2 antioxidant defenses, ultimately reducing progressive infarct expansion and recovering sensorimotor functions. The significance of this work lies in bridging physical neuromodulation directly to the preservation of organelle-level architecture. By demonstrating that stimulation of trigeminal afferents to recruit an oxygen-conserving reflex can stabilize outer membrane signaling architecture and preserve mitochondrial survival machinery, this study outlines a non-pharmacological strategy to protect mitochondrial function and inhibit acute post-traumatic neurodegeneration.

neuroscience↗

bioRxiv2023

Deciphering the Functional Roles of Individual Cancer Alleles Across Comprehensive Cancer Genomic Studies

Cancer genome data has been growing in both size and complexity, primarily driven by advances in next-generation sequencing technologies, such as Pan-cancer data from TCGA, ICGC, and single-cell sequencing. Yet, discerning the functional role of individual genomic lesions remains a substantial challenge due to the complexity and scale of the data. Previously, we introduced REVEALER, which identifies groups of genomic alterations that significantly associate with target functional profiles or phenotypes, such as pathway activation, gene dependency, or drug response. In this paper, we present a new mathematical formulation of the algorithm. This version (REVEALER 2.0) is considerably more powerful than the original, allowing for rapid processing and analysis of much larger datasets and facilitating higher-resolution discoveries at the level of individual alleles. REVEALER 2.0 employs the Conditional Information Coefficient (CIC) to pinpoint features that are either complementary or mutually exclusive but still correlate with the target functional profile. The aggregation of these features provides a better explanation for the target functional profile than any single alteration on its own. This is indicative of scenarios where several activating genomic lesions can initiate or stimulate a key pathway or process. We replaced the initial three-dimensional kernel estimation with multiple precomputed one-dimensional kernel estimations, resulting in an approximate 150x increase in speed and efficiency. This improvement, combined with its efficient execution, makes REVEALER 2.0 suitable for much larger datasets and a more extensive range of genomic challenges.

bioinformatics↗

bioRxiv2021

Altered interaction between RBD and ACE2 receptor contributes towards the increased transmissibility of SARS CoV-2 delta, kappa, beta, and gamma strains with RBD double mutations.

The COVID-19 pandemics by SARS-CoV-2 causes catastrophic damage for global human health. The initial step of SARS-CoV-2 infection is the binding of the receptor-binding domain (RBD) in its spike protein to ACE2 receptor in host cell membrane. The evolving of SARS-CoV-2 constantly generates new mutations across its genome including RBD. Besides the well-known single mutation in RBD, the recent new mutation strains with RBD "double mutation" is causing new outbreaks globally, as represented by the delta strain containing RBD L452R/T478K. Although it is considered that the increased transmissibility of the double mutated strains could be attributed to the alteration of mutated RBD to ACE2 receptor, the molecular details remains to be unclear. Using the methods of molecular dynamics simulation, superimposed structural comparison, free binding energy estimation and antibody escaping, we investigated the relationship between ACE2 receptor and the RBD double mutant L452R/T478K (delta), L452R/E484Q (kappa) and E484K/N501Y (beta, gamma). The results demonstrated that each of the three RBD double mutants altered RBD structure, led to enhanced binding affinity of mutated RBD to ACE2 receptor, leading to increased transmissibility of SARS-CoV-2 to the host cells.

bioinformatics↗

bioRxiv2020

Cell-penetrating peptide conjugates of indole-3-acetic acid-based DNA primase/Gyrase inhibitors as potent antitubercular agents against planktonic and biofilm culture of Mycobacterium smegmatis

Mycobacterium tuberculosis (Mtb) is a pathogenic bacterium that caused 1.5 million fatalities globally in 2018. New strains of Mtb resistant to all known classes of antibiotics pose a global healthcare problem. In this work we have conjugated novel indole-3-acetic acid-based DNA primase/gyrase inhibitor with cell-penetrating peptide via cleavable and non-cleavable bonds. For non-cleavable linkage, inhibitor was conjugated with peptide via an amide bond to the N-terminus, whereas a cleavable linkage was obtained by conjugating the inhibitor through a disulfide bond. We performed the conjugation of the inhibitor either directly on a solid surface, or by using solution-phase chemistry. M. smegmatis (non-pathogenic model of Mtb) was used to determine the minimal inhibitory concentration (MIC) of the synthetic conjugates. Conjugates were found more active as compared to free inhibitor molecules. Strikingly, the conjugate also impair the development of biofilm, showing a therapeutic potential against infections caused by both planktonic and sessile forms of mycobacterium species.

microbiology↗

bioRxiv2019

Novel lead compounds that target the ribosomal peptidyl transferase center

M. tuberculosis (Mtb) is a pathogenic bacterium that causes tuberculosis, which kills more than 1.5 million people worldwide every year. Strains resistant to available antibiotics pose a significant healthcare problem. The enormous complexity of the ribosome poses a barrier for drug discovery. We have overcome this in a tractable way by using an RNA segment that represents the peptidyl transferase center as a target. By using a novel combination of NMR transverse relaxation times (T2) and computational chemistry approaches, we have obtained improved inhibitors of the Mtb ribosomal PTC. Two phenylthiazole derivatives were predicted by machine learning models as effective inhibitors, and this was confirmed by their IC50 values, which were significantly improved over standard antibiotic drugs.

biochemistry↗

bioRxiv2019

Synthetic Dual-Acting Small-Molecule Inhibitors That Target Mycobacterial DNA Replication

Mycobacterium tuberculosis (Mtb) is a pathogenic bacterium and a causative agent of tuberculosis (TB), a disease that kills more than 1.5 million people worldwide annually. One of the main reasons for this high mortality rate is the evolution of new Mtb strains that are resistant to available antibiotics. Therefore, new therapeutics for TB are in constant demand. Here we report the development of such inhibitors that target two DNA replication enzymes of Mtb, namely DnaG primase and DNA gyrase, which share a conserved TOPRIM fold near the inhibitors binding site. The molecules were developed on the basis of previously reported inhibitors for T7 DNA primase that bind near the TOPRIM fold. In order to improve the physicochemical properties of the molecules as well as their inhibitory effect on primase and gyrase, 49 novel compounds were synthesized as potential drug candidates in three stages of optimization. The last stage of chemical optimization yielded two novel inhibitors for the fast-growing nonpathogenic model Mycobacterium smegmatis (Msmg).

biochemistry↗