Biology subjects

Issa, N.

Publications and source records attributed to Issa, N..

6 recordsLinked to original sources

bioRxiv2025

JARID2 Inhibition Reprograms Human Hematopoietic Progenitor Cells To Enhance Bone Marrow Transplantation

Hematopoietic stem cell transplantation is a common treatment for many blood disorders and can be a life-saving therapy for patients with leukemias, lymphomas and multiple myeloma. Umbilical cord blood (UCB) serves as a valuable source of hematopoietic stem and progenitor cells (HSPCs) for transplantation, particularly for patients lacking a matched donor. However, the limited number of repopulating cells in UCB units restricts its clinical utility. Our prior studies showed that genetic deletion of the polycomb repressive complex 2 (PRC2) co-factor Jarid2 in mouse multipotent progenitors (MPPs) conveyed ectopic self-renewal capacity. Here, we hypothesized that the function of human HSPCs could be enhanced through JARID2 inhibition. In this study, we demonstrate that both constitutive and transient knockdown of JARID2 increases the number and enhances the functionality of human HSPCs both in vitro and in vivo. This phenotype was distinct from inhibition of EZH2 in UCB cells, suggesting the mechanism was independent of PRC2 co-factor activity of JARID2. Mechanistically, JARID2 knockdown promotes a quiescent, long-term self-renewal gene expression program governed by upregulating STAT1 and characterized by an MHC class II immunophenotype. Analogous to mice, these mechanisms conferred HSC-like potential to human MPPs in vivo. Taken together, these findings highlight JARID2 inhibition as a novel and reversible approach to expand functional UCB-derived HSPCs ex vivo, potentially improving access to stem cell transplantation for a wider patient population. One Sentence SummaryGenetic inhibition of JARID2 enhances repopulating activity of human hematopoietic stem and progenitor cells in vivo via STAT1 upregulation.

developmental biology↗

bioRxiv2025

Functional Comparison to Ezh2 Reveals PRC2-Independent Functions of Jarid2 in Hematopoietic Stem Cell Lineage Commitment

Previous studies showed the Polycomb Repressive Complex 2 (PRC2) co-factor Jarid2 represses self-renewal transcriptional networks in mouse multipotent progenitor cells (MPPs). But only a fraction of de-repressed HSC-specific genes were associated with loss of H3K27me3, implying Jarid2 may have non-canonical (PRC2-indpendent) in hematopoiesis. Here we sought to delineate any PRC2-independnent functions by comparing stem and progenitor cells genetically deficient for either Jarid2 or Ezh2 (enzymatic component of PRC2). Loss of Ezh2 increased myeloid differentiation in transplantation assays. In contrast, loss of Jarid2 enhanced T-cell output. Single cell transcriptomics showed while loss of Jarid2 had minimal impact across progenitor populations, loss of Ezh2 led to accumulation of lymphoid-biased MPP4 cells and B-cell progenitors in the bone marrow. Functional assays confirmed a differentiation block at the pre-pro B-cell stage. The maturational arrest of Ezh2-deficient B-cell progenitors contrasts with increased T-cell output from loss of Jarid2, suggesting Jarid2 has non-canonical functions in hematopoiesis.

genetics↗

bioRxiv2025

Engineered yeast biofilms deliver plastic degrading enzymes to PET substrates

Enzymes that degrade PET and other plastics are being discovered with increasing pace, and engineering approaches further increase their activity. Most proposed applications for such enzymes require their purification, enabling the regeneration of monomeric subunits suitable for the production of new plastic. However, large amounts of plastics exist as environmental contaminants, and are unlikely to be suitable for standard recycling. Such waste may still be suitable for bioremediation using enzymatic activities, albeit without the economic incentives of a full recycling process. Here we develop a delivery system for PET hydrolases, based on engineered yeast biofilms that grow and secrete enzymes directly on the substrate to be degraded. The system does not require any enzyme purification steps, and the biofilms at least partially assimilate the degradation products into biomass. Our work provides proof-of-principle that demonstrates the potential of biofilm-based approaches.

bioengineering↗

bioRxiv2022

Electrophysiological Markers of Memory Consolidation in the Human Brain when Memories are Reactivated during Sleep

Human accomplishments depend on learning, and effective learning depends on consolidation. Consolidation is the process whereby new memories are gradually stored in an enduring way in the brain so that they can be available when needed. For factual or event knowledge, consolidation is thought to progress during sleep as well as during waking states, and to be mediated by interactions between hippocampal and neocortical networks. However, consolidation is difficult to observe directly, but rather is inferred through behavioral observations. Here, we investigated overnight memory change by measuring electrical activity in and near the hippocampus. Electroencephalographic (EEG) recordings were made in five patients from electrodes implanted to determine whether a surgical treatment could relieve their seizure disorders. One night, while each patient slept in a hospital monitoring room, we recorded electrophysiological responses to 10-20 specific sounds that were presented very quietly, to avoid arousal. Half of the sounds had been associated with objects and their precise spatial locations that patients learned before sleep. After sleep, we found systematic improvements in spatial recall, replicating prior results. We assume that when the sounds were presented during sleep, they reactivated and strengthened corresponding spatial memories. Notably, the sounds also elicited oscillatory intracranial EEG activity, including increases in theta, sigma, and gamma EEG bands. Gamma responses, in particular, were consistently associated with the degree of improvement in spatial memory exhibited after sleep. We thus conclude that this electrophysiological activity in the hippocampus and adjacent medial temporal cortex reflects sleep-based enhancement of memory storage. Significance StatementSleep contributes to memory consolidation, we presume, because memories are replayed during sleep. Understanding this aspect of consolidation can help with optimizing normal learning in many contexts, and with treating memory disorders and other diseases. Here, we systematically manipulated sleep-based processing using targeted memory reactivation; brief sounds coupled with pre-sleep learning were quietly presented again during sleep, producing (a) recall improvements for specific spatial memories associated with those sounds, and (b) physiological responses in the sleep EEG. Neural activity in the hippocampus and adjacent medial temporal cortex was thus found in association with memory consolidation during sleep. These findings advance understanding of consolidation by linking beneficial memory changes during sleep to both memory reactivation and specific patterns of brain activity.

neuroscience↗

bioRxiv2020

A Humanized Animal Model Predicts Clonal Evolution and Therapeutic Vulnerabilities in Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are chronic blood diseases with significant morbidity and mortality. While sequencing studies have elucidated the genetic mutations that drive these diseases, MPNs remain largely incurable with a significant proportion of patients progressing to rapidly fatal secondary acute myeloid leukemia (sAML). Therapeutic discovery has been hampered by the inability of genetically-engineered mouse models to generate key human pathologies such as bone marrow fibrosis. To circumvent these limitations, here we present a humanized animal model of myelofibrosis (MF) patient-derived xenografts (PDXs). These PDXs robustly engrafted patient cells which recapitulated the patients genetic hierarchy and pathologies such as reticulin fibrosis and propagation of MPN-initiating stem cells. The model can select for engraftment of rare leukemic subclones to identify MF patients at-risk for sAML transformation, and can be used as a platform for genetic target validation and therapeutic discovery. We present a novel but generalizable model to study human MPN biology. STATEMENT OF SIGNIFICANCEAlthough the genetic events driving myeloproliferative neoplasms (MPNs) are well-defined, therapeutic discovery has been hampered by the inability of murine models to replicate key patient pathologies. Here, we present a patient-derived xenograft (PDX) system to model human myelofibrosis that reproduces human pathologies and is amenable to genetic and pharmacological manipulation.

cancer biology↗

bioRxiv2018

Baseline human gut microbiota profile in healthy people and standard reporting template

A comprehensive knowledge of the types and ratios of microbes that inhabit the healthy human gut is necessary before any kind of pre-clinical or clinical study can be performed that attempts to alter the microbiome to treat a condition or improve therapy outcome. To address this need we present an innovative scalable comprehensive analysis workflow, a healthy human reference microbiome list and abundance profile (GutFeelingKB), and a novel Fecal Biome Population Report (FecalBiome) with clinical applicability. GutFeelingKB provides a list of 157 organisms (8 phyla, 18 classes, 23 orders, 38 families, 59 genera and 109 species) that forms the baseline biome and therefore can be used as healthy controls for studies related to dysbiosis. The incorporation of microbiome science into routine clinical practice necessitates a standard report for comparison of an individuals microbiome to the growing knowledgebase of \"normal\" microbiome data. The FecalBiome and the underlying technology of GutFeelingKB address this need. The knowledgebase can be useful to regulatory agencies for the assessment of fecal transplant and other microbiome products, as it contains a list of organisms from healthy individuals. In addition to the list of organisms and abundances the study also generated a list of contigs of metagenomics dark matter. In this study, metagenomic dark matter represents sequences that cannot be mapped to any known sequence but can be assembled into contigs of 10,000 nucleotides or higher. These sequences can be used to create primers to study potential novel organisms. All data is freely available from https://hive.biochemistry.gwu.edu/gfkb and NCBIs Short Read Archive.

microbiology↗