Biology subjects

Walcheck, M. T.

Publications and source records attributed to Walcheck, M. T..

3 recordsLinked to original sources

bioRxiv2024

Bnip3lb-driven mitophagy sustains expansion of the embryonic hematopoietic stem cell pool

Embryonic hematopoietic stem and progenitor cells (HSPCs) have the unique ability to undergo rapid proliferation while maintaining multipotency, a clinically-valuable quality which currently cannot be replicated in vitro. Here, we show that embryonic HSPCs achieve this state by precise spatio-temporal regulation of reactive oxygen species (ROS) via Bnip3lb-associated developmentally-programmed mitophagy, a distinct autophagic regulatory mechanism from that of adult HSPCs. While ROS drives HSPC specification in the dorsal aorta, scRNAseq and live-imaging of Tg(ubi:mitoQC) zebrafish indicate that mitophagy initiates as HSPCs undergo endothelial-to-hematopoietic transition and colonize the caudal hematopoietic tissue (CHT). Knockdown of bnip3lb reduced mitophagy and HSPC numbers in the CHT by promoting myeloid-biased differentiation and apoptosis, which was rescued by anti-oxidant exposure. Conversely, induction of mitophagy enhanced both embryonic HSPC and lymphoid progenitor numbers. Significantly, mitophagy activation improved ex vivo functional capacity of hematopoietic progenitors derived from human-induced pluripotent stem cells (hiPSCs), enhancing serial-replating hematopoietic colony forming potential. HIGHLIGHTSO_LIROS promotes HSPC formation in the dorsal aorta but negatively affects maintenance thereafter. C_LIO_LIHSPCs colonizing secondary niches control ROS levels via Bnip3lb-directed mitophagy. C_LIO_LIMitophagy protects nascent HSPCs from ROS-associated apoptosis and maintains multipotency. C_LIO_LIInduction of mitophagy enhances long-term hematopoietic potential of iPSC-derived HSPCs. C_LI

cell biology↗

bioRxiv2022

Chronic Jetlag Accelerates Pancreatic Neoplasia in Conditional Kras-Mutant Mice

Misalignment of the circadian clock compared to environmental cues causes circadian desynchrony, which is pervasive in humans. Clock misalignment can lead to various pathologies including obesity and diabetes, both of which are associated with pancreatic ductal adenocarcinoma - a devastating cancer with an 80% five-year mortality rate. Although circadian desynchrony is associated with an increased risk of several solid-organ cancers, the correlation between clock misalignment and pancreas cancer is unclear. Using a chronic jetlag model, we investigated the impact of clock misalignment on pancreas cancer initiation in mice harboring a pancreas-specific activated Kras mutation. We found that chronic jetlag accelerated the development of pancreatic cancer precursor lesions, with a concomitant increase in precursor lesion grade. Cell-autonomous knock-out of the clock in pancreatic epithelial cells of Kras-mutant mice demonstrated no acceleration of precursor lesion formation, indicating non-cell-autonomous clock dysfunction was responsible for the expedited tumor development. Therefore, we applied single-cell RNA sequencing over time and identified fibroblasts as the cell population manifesting the greatest clock-dependent changes, with enrichment of specific cancer-associated fibroblast pathways due to circadian misalignment. Collectively, these results suggest fibroblasts as the putative target of chronic jetlag-induced accelerated pancreas cancer initiation.

cancer biology↗

bioRxiv2022

Pdx1 expression in hematopoietic cells activates Kras-mutation to drive leukemia in KC (Pdx1-Cre ; LSL-KrasG12D/+) mice

BackgroundPdx1 expression in pancreatic lineage cells underlies the utility of the KC mouse model (Pdx1-Cre; LSL-KrasG12D/+) for understanding how KrasG12D-mutation drives formation of pancreas cancer precursor lesions and carcinoma. The highly utilized KC model has a reported mortality rate of about 30%, which has been attributed to pancreas cancer, despite lack of substantive evidence. This study describes a novel cause of the early deaths, in which KC mice develop Kras-driven T-cell acute lymphoblastic leukemia (T-ALL). MethodsKC mice and control mice underwent histopathologic examination including thymus, liver, spleen, bone marrow and pancreas, and immunohistochemistry (IHC) was used to confirm leukemia development. A reporter strain (Ai14) was used to identify location of Pdx1-Cre expression and concomitant mutant-Kras activation, which was confirmed using flow cytometry, IHC, immunofluorescence, mRNA analysis, and bone marrow transplant studies. ResultsPdx1 expression in the hematopoietic compartment of KC mice resulted in Cre-recombinase mediated excision of lox-stop and activation of mutant-Kras gene (KrasG12D/+) in the multipotent progenitor cells (MPP), and subsequent development of Kras-mutant T-ALL creating thymic tumors in a subset of mice. Overall, 20% (5/25) of KC mice developed a large thymic tumor due to T-ALL by 9 months of age. Moreover, through isolation and transplantation of pooled bone marrow from KC mice into CD45 congenic mice, 100% of recipient mice were found to develop T-ALL. These results further confirm mutant-Kras expression in the hematologic compartment is driving the development of T-ALL in the KC mouse model. ConclusionsThese results are an essential consideration for investigators while utilizing this model in pancreas cancer studies, particularly when evaluating factors that may coincidentally enhance the formation of KrasG12D-driven T-ALL (e.g. transcription factors impacting hematopoietic cells). Finally, the lower penetrance of T-ALL development in KC mice (compared to existing leukemia models) suggest that the KC mouse could be considered as an alternative research model to evaluate onset and factors that exacerbate development of T-ALL.

cancer biology↗