Biology subjects

Challen, G.

Publications and source records attributed to Challen, G..

2 recordsLinked to original sources

bioRxiv2025

Stathmin 1 regulates mitophagy and cellular function in hematopoietic stem cells

Stathmin 1 is a cytoplasmic phosphoprotein that regulates microtubule dynamics via promotion of microtubule catastrophe and sequestration of free tubulin heterodimers. Stathmin 1 is highly expressed in hematopoietic stem cells (HSCs), and overexpressed in leukemic cells, however its role in HSCs is not known. Herein, we found that loss of Stathmin 1 is associated with altered microtubule architecture in HSCs, and markedly impaired HSC function. Transcriptomic studies suggested alterations in oxidative phosphorylation in Stmn1-/- HSCs, and further mechanistic studies revealed defective mitochondrial structure and function in the absence of Stathmin 1 with increased ROS production. Microtubules associate with mitochondria and lysosomes to facilitate autophagosome formation and mitophagy, and indeed we found that this critical mitochondrial quality control process is impaired in Stathmin 1-deficient HSCs. Finally, stimulation of autophagy improved the colony forming ability of Stmn1-/- hematopoietic stem and progenitor cells. Together, our data identify Stathmin 1 as a novel regulator of mitophagy and mitochondrial health in HSCs. Key PointsO_LIThe microtubule regulating protein Stathmin 1 is highly expressed in HSPCs and promotes normal microtubule architecture. C_LIO_LILoss of Stathmin 1 in HSPCs leads to impaired autophagy with abnormal mitochondrial morphology, decreased respiratory capacity, and impaired cellular function. C_LI

cell biology↗

bioRxiv2021

DUSP6 mediates resistance to JAK2 inhibition and drives leukemic progression

Chronic myeloproliferative neoplasms (MPNs) exhibit a propensity for transformation to secondary acute myeloid leukemia (sAML), for which the underlying mechanisms remain poorly understood, resulting in limited treatment options and dismal clinical outcomes. Here, we performed bulk transcriptome profiling accompanied by single cell RNA-sequencing on CD34+ stem/progenitor cells from serial patient samples obtained at the chronic MPN and sAML phases, and identified aberrantly increased expression of dual-specificity phosphatase 6 (DUSP6) underlying disease transformation. Genetic and pharmacologic targeting of DUSP6 led to inhibition of S6 and JAK/STAT signaling, resulting in potent suppression of cell proliferation, while also reducing inflammatory cytokine production in primary samples. Furthermore, ectopic DUSP6 expression augmented proliferation and mediated JAK2 inhibitor resistance, while DUSP6 inhibition reduced colony-forming potential of JAK2 inhibitor-persistent patient cells. Mechanistically, DUSP6 perturbation dampened S6 signaling via inhibition of RSK1, which we identified as a second indispensable candidate associated with poor clinical outcome. Lastly, DUSP6 inhibition potently suppressed disease development across Jak2 V617F and MPL W515L MPN mouse models, and sAML patient-derived xenografts. These findings underscore DUSP6 in driving disease transformation and therapeutic resistance, and highlight the DUSP6-RSK1 axis as a novel, druggable pathway in myeloid malignancies.

cancer biology↗