Biology subjects

Doan, P.

Publications and source records attributed to Doan, P..

4 recordsLinked to original sources

bioRxiv2025

Simultaneous Sensing and Stimulation in Neuromodulation Systems: Quantifying and Mitigating Charge Accumulation Effects

This paper describes the operation of a low-noise amplifier and neurostimulation circuit when both functions are used simultaneously. The design of this circuitry along with the circuit model used to investigate system interactions is described. Expected circuit operation is explored in conjunction with the impact of charge storage at the electrode tissue interface. The test results for the system during independent use of the amplifier and during simultaneous use of the amplifier and stimulator are presented. As seen in the circuit analysis, test results confirm that the charge storage that occurs in the tissue/electrode interface used for stimulation interferes with the measurement of the neural signals of interest when the two circuits share electrodes. By optimizing the configuration used for the amplifier during high frequency stimulation, biological signals can be measured; however, the effective number of bits (ENOB) will be degraded as a function of the stimulation parameters, limiting the applications in which signal amplification can be meaningfully used when sharing an electrode with stimulation circuitry.

bioengineering↗

bioRxiv2024

Chemical perturbations impacting histone acetylation governcolorectal cancer differentiation

Dysregulated epigenetic programs that restrict differentiation, reactivate fetal genes, and confer phenotypic plasticity are critical to colorectal cancer (CRC) development. By screening a small molecule library targeting epigenetic regulators using our dual reporter system, we found that inhibiting histone deacetylase (HDAC) 1/2 promotes CRC differentiation and anti-tumor activity. Comprehensive biochemical, chemical, and genetic experiments revealed that on-target blockade of the HDAC1/2 catalytic domain mediated the differentiated phenotype. Unbiased profiling of histone posttranslational modifications induced by HDAC1/2 inhibition nominated acetylation of specific histone lysine residues as potential regulators of differentiation. Genome-wide assessment of implicated marks indicated that H3K27ac gains at HDAC1/2-bound regions associated with open chromatin and upregulation of differentiation genes upon HDAC1/2 inhibition. Disrupting H3K27ac by degrading acetyltransferase EP300 rescued HDAC1/2 inhibitor-mediated differentiation of a patient-derived CRC model using single cell RNA-sequencing. Genetic screens revealed that DAPK3 contributes to CRC differentiation induced by HDAC1/2 inhibition. These results highlight the importance of specific chemically targetable histone modifications in governing cancer cell states and epigenetic reprogramming as a therapeutic strategy in CRC. BRIEF SUMMARYHDAC1/2 inhibition promotes colorectal cancer differentiation via gains in H3K27ac, which can be reversed by blocking its acetyltransferase EP300.

cancer biology↗

bioRxiv2023

Utilizing a dual endogenous reporter system to identify functional regulators of aberrant stem cell and differentiation activity in colorectal cancer

Aberrant stem cell-like activity and impaired differentiation are central to the development of colorectal cancer (CRC). To identify functional mediators that regulate these key cellular programs in CRC, we developed an endogenous reporter system by genome-editing human CRC cell lines with knock-in fluorescent reporters at the SOX9 and KRT20 locus to report aberrant stem cell-like activity and differentiation, respectively, and then performed pooled genetic perturbation screens. Constructing a dual reporter system that simultaneously monitored aberrant stem cell-like and differentiation activity in the same CRC cell line improved our signal to noise discrimination. Using a focused-library CRISPR screen targeting 78 epigenetic regulators with 542 sgRNAs, we identified factors that contribute to stem cell-like activity and differentiation in CRC. Perturbation single cell RNA sequencing (Perturb-seq) of validated hits nominated SMARCB1 of the BAF complex (also known as SWI/SNF) as a negative regulator of differentiation across an array of neoplastic colon models. SMARCB1 is a dependency in CRC and required for in vivo growth of human CRC models. These studies highlight the utility of a biologically designed endogenous reporter system to uncover novel therapeutic targets for drug development.

cancer biology↗

bioRxiv2022

Developmental reprogramming mediates aberrant cell state plasticity in colorectal cancer initiation

Cell state (phenotypic) plasticity is a carefully regulated feature of adult epithelial cells that enables adaptive responses to injury, inflammation, and other forms of stress. Aberrant expansion of the normally restricted capability for cell state plasticity to escape terminal differentiation is a critical aspect of neoplasia. The nongenetic factors and specific programs that mediate aberrant cell state plasticity and impaired differentiation require deeper characterization to understand this elusive aspect of cancer pathogenesis. Using genetically engineered and carcinogen-induced murine models of intestinal neoplasia, we demonstrate that impaired differentiation is a conserved event preceding cancer development. Single cell RNA-sequencing (scRNA-seq) of neoplastic intestinal lesions from both mouse models and a patient with familial adenomatous polyposis revealed that cancer initiates by adopting an aberrant transcriptional state characterized by nonoverlapping expression of a regenerative pathway, marked by Ly6a (Sca-1), and a fetal intestinal program, positive for Tacstd2 (Trop2). Genetic inactivation of Sox9 prevented adenoma formation in ApcKO mice, obstructed emergence of aberrant regenerative and fetal intestinal programs, and restored multi-lineage differentiation by scRNA-seq. Expanded chromatin accessibility at regeneration and fetal genes upon Apc inactivation was reduced by concomitant Sox9 suppression. These studies indicate that aberrant cell state plasticity mediated by unabated regenerative activity and developmental reprogramming precedes cancer development.

cancer biology↗