Biology subjects

Sewell, M.

Publications and source records attributed to Sewell, M..

4 recordsLinked to original sources

bioRxiv2026

A rapid, genetically-tractable human iPSC-derived model for studying tissue-resident macrophage biology in Alzheimer's and other diseases

Large-scale genetic and preclinical studies strongly implicate myeloid cells, particularly brain-resident macrophages, in the pathogenesis of Alzheimer's disease (AD). Efferocytic clearance of apoptotic cells and other cholesterol-rich cellular debris is a core macrophage function and represents an active area of AD research. However, human tissue-resident macrophages remain difficult to model in vitro as they acquire their transcriptional and functional identities in response to signals from their host tissue microenvironment. Many existing differentiation protocols mimic human brain macrophage developmental trajectories, but these protocols rely either on multi-step cytokine cocktails and lengthy differentiation or transduction of multiple transcription factors, both of which introduce variability and complicate genetic manipulation. To address these limitations, we developed a simplified protocol that generates high-purity (>90% CD45+CD11b+) human iPSC-derived macrophage-like cells (iMacs) from cryopreservable erythro-myeloid progenitor (EMP)-like intermediates in 19 days, including a final 7-day maturation step driven by macrophage colony-stimulating factor (M-CSF) alone. Transcriptomic profiling reveals that iMacs show enrichment for phagocytic and lysosomal programs, processes integral to efferocytosis. At both the transcriptional and protein level, iMacs have higher expression of scavenger receptors such as CD36, CD163 and MRC1, and of AD risk genes such as TREM2. Functionally, iMacs show enhanced phagocytic uptake of diverse substrates relative to iPSC-derived microglia, including carboxylated latex beads, zymosan, amyloid-{beta} 1-42, and amyloid-{beta} 1-40, and exhibit expanded lysosomal mass. Robust TREM2 expression and signaling make iMacs a sensitive platform for interrogating TREM2 biology, with markedly higher phosphorylation of SYK and PLC{gamma}2 in response to TREM2 engagement compared to iPSC-derived microglia. iMacs also tolerate lipid-mediated siRNA transfection with high survival and knockdown efficiency, enabling rapid genetic perturbation of AD risk genes. Together, these features make iMacs a practical, scalable, and genetically tractable human macrophage model for studying the regulation and cell biology of core macrophage functions that are known to play critical roles in AD, aging, and other disorders.

neuroscience↗

bioRxiv2026

Pericyte Loss Reprogrammes Capillary Endothelium and Drives White Matter Injury in Small Vessel Disease

Pericytes are critical regulators of cerebrovascular homeostasis, yet their contribution to small vessel disease (SVD) and white matter injury remains incompletely understood. Here, we use an inducible Atp13a5-driven genetic strategy to selectively label and ablate brain pericytes, enabling integrated morphological, functional, and transcriptomic analyses across the neurogliovascular unit. Single-cell RNA sequencing and tissue-level mapping identified distinct pericyte subtypes distributed along the vascular tree and revealed subtype-specific vulnerability following depletion. Moderate pericyte loss induced transient cerebrovascular dysfunction characterised by reduced cerebral blood flow and increased blood-brain barrier (BBB) permeability, accompanied by delayed white matter abnormalities, including altered diffusion MRI metrics, oligodendrocyte progenitor cell responses, and myelin loss. At the molecular level, pericyte depletion reprogrammed capillary endothelial cells toward an activated venular-like state characterised by VCAM-1 induction, reduced expression of the BBB-associated transporter MFSD2A, and activation of type I interferon signalling pathways. Cross-species analyses revealed enrichment of human white matter hyperintensity-associated SVD gene signatures across endothelial subtypes following pericyte depletion. Together, these findings identify pericyte dysfunction as a driver of endothelial inflammatory remodelling and white matter injury and establish mechanistic links between microvascular pericyte loss and human SVD.

neuroscience↗

bioRxiv2026

Reduced LACTB expression in myeloid cells is associated with elevated succinylcarnitine levels and reduced Alzheimers disease risk.

BackgroundLactamase {beta} (LACTB) is a serine {beta}-lactamase-like mitochondrial enzyme associated with cancer progression, obesity, and lipid metabolism. LACTB is located in an Alzheimers Disease (AD) risk locus and has been associated with AD in a proteomic study. MethodsWe performed Mendelian Randomization (MR) analysis to estimate the association between LACTB expression, succinylcarnitine levels, and AD risk. We generated LACTB knock-down (KD) THP1 macrophages, LACTB knock-out (KO) iPSC-derived microglia and LACTB enzymatically-dead (ED) mice. The impact of LACTB loss-of-function in myeloid cells was characterized via transcriptomics, metabolomics, lipidomics, and functional assays. Finally, human LACTB KO microglia precursors were xenotransplanted into the brains of mice with amyloid pathology to assess in vivo interactions with amyloid plaques. ResultsMR analyses revealed that lower LACTB expression in myeloid cells may lead to reduced AD risk and higher levels of succinylcarnitine, a metabolite associated with AD risk. We identified LACTB as a primary enzyme responsible for succinylcarnitine hydrolysis. Transcriptional and functional studies showed that loss of LACTB enhances OXPHOS, and reduces protein synthesis and triglycerides. LACTB expression was upregulated following interferon or TNF stimulation, and its loss modified efferocytosis- related functions under inflammatory conditions. In vivo, xenotransplanted human LACTB KO microglia exhibited enhanced association with amyloid plaques. ConclusionsOur findings define a previously unrecognized axis linking LACTB and succinylcarnitine to myeloid cell function and AD susceptibility. Given the druggability of LACTB and the potential for succinylcarnitine to serve as a translational biomarker, this enzyme represents a promising therapeutic target for modulation of neuroinflammation in AD.

neuroscience↗

bioRxiv2019

The Drosophila Afadin and ZO-1 homologs Canoe and Polychaetoid act in parallel to maintain epithelial integrity when challenged by adherens junction remodeling

During morphogenesis cells must change shape and move without disrupting tissue integrity. This requires cell-cell junctions to allow dynamic remodeling while resisting force generated by the actomyosin cytoskeleton. Multiple proteins play roles in junctional-cytoskeletal linkage, but the mechanisms by which they act remain unclear. Drosophila Canoe maintains adherens junction-cytoskeletal linkage during gastrulation. Canoes mammalian homolog Afadin plays similar roles in cultured cells, working in parallel with ZO-1 proteins, particularly at multicellular junctions. We took these insights back into the fly embryo, exploring how cells maintain epithelial integrity when challenged by adherens junction remodeling during germband extension and dorsal closure. We found Canoe helps cells maintain junctional-cytoskeletal linkage when challenged by the junctional remodeling inherent in mitosis, cell intercalation and neuroblast invagination, or by forces generated by the actomyosin cable at the leading edge. However, even in the absence of Canoe many cells retain epithelial integrity. This is explained by a parallel role played by the ZO-1 homolog Polychaetoid. In embryos lacking both Canoe and Polychaetoid, cell junctions fail early, with multicellular junctions especially sensitive, leading to widespread loss of epithelial integrity. Our data suggest Canoe and Polychaetoid stabilize Bazooka/Par3 at cell-cell junctions, helping maintain balanced apical contractility and tissue integrity.

cell biology↗