Biology subjects

Markus, H. S.

Publications and source records attributed to Markus, H. S..

3 recordsLinked to original sources

bioRxiv2026

HTRA1 deficiency in COL4A1 mutant hiPSC-derived astrocytes, a convergent mechanism of cerebral small vessel disease

Cerebral small vessel disease (cSVD) is a major contributor to stroke and cognitive decline, ultimately leading to vascular dementia (VaD). Genetic factors play a key role in disease susceptibility and progression, and variants in COL4A1 cause one of the most common forms of genetic cSVD. COL4A1 encodes the 1 chain of collagen type IV which is the major structural component of the basement membrane, a specialised extracellular matrix (ECM) structure, in the vasculature. In addition to this vascular basement membrane (vBM), in the central nervous system (CNS), the neurovascular unit (NVU) also has a unique parenchymal basement membrane (pBM) that is largely produced by astrocytes and forms a critical interface anchoring astrocyte end-feet to vascular cells. Together, these BMs play essential roles in regulating blood-brain barrier (BBB) function. However, the role of the pBM in cSVD has been relatively less investigated compared to the vBM. The lack of relevant human disease models that faithfully recapitulate the pBM, makes it difficult to dissect pBM-related cell-cell and cell-matrix interactions specific to cSVD, hindering the identification of effective therapeutic targets. In this study, we hypothesised that astrocyte-mediated ECM remodelling contributes to BBB dysfunction in COL4A1-associated cSVD. To investigate this, human induced pluripotent stem cells (iPSCs) derived from a patient carrying the COL4A1G755Rvariant and its isogenic control line were differentiated into astrocytes and brain microvascular endothelial cells (BMECs). Comparing to isogenic controls, the COL4A1G755Rastrocytes significantly reduced the expression of ECM-related genes and increased glutamate uptake. ECM preparations from COL4A1G755R astrocytes significantly damaged the tight junction (TJ) structure formed by control iPSC-BMECs and failed to rescue the TJ integrity in COL4A1G755R BMECs. The secretome from COL4A1G755Rastrocytes exacerbated the ECM defects in COL4A1G755R BMECs. Most importantly, COL4A1G755R astrocytes exhibited reduced expression of HTRA1, a serine protease that regulates both ECM turnover and homeostasis, and increased TGF-{beta} signalling. Functional rescue by recombinant human HTRA1 protein rescues TJ defects in COL4A1G755R BMECs, and normalized TGF-{beta} signalling and glutamate uptake in COL4A1G755R astrocytes. Together, these findings define a previously unrecognised astrocyte-driven pBM mechanism in COL4A1-associated cSVD and highlight HTRA1 in ECM remodelling as a therapeutic target for cSVD.

neuroscience↗

bioRxiv2025

Prominent white matter related abnormalities associated with diverse molecular alterations in a mouse model of Col4a1 cerebral small vessel disease.

White matter abnormalities are a hallmark of cerebral small vessel disease (cSVD) and are closely linked to cognitive decline and dementia. However, despite their clinical importance, underlying mechanisms remain poorly understood. Collagen IV, encoded by genes COL4A1/COL4A2, is a major component of the basement membrane, a specialised extracellular matrix (ECM) structure. Mutations in these genes cause a genetic form of cSVD. We tested the hypothesis that ECM defects caused by a Col4a1 mutation lead to white matter pathology using an established mouse model of cSVD (Col4a1+/Svc). Behavioural testing with magnetic resonance diffusion tensor imaging, pathology and ultrastructural investigations of white matter were studied. The studies revealed that Col4a1+/Svc mice have cognitive impairments, reduced myelinating oligodendrocyte pools, axonal myelination defects, and altered white matter structural integrity. Proteomic analysis, of isolated white matter from Col4a1+/Svcmice, identified extensive changes to ECM composition and endoplasmic reticulum (ER) biology including ER stress induction. We also demonstrated that targeting protein folding to promote collagen secretion and reduce ER stress, increased myelinating oligodendrocytes and axon-glial integrity in Col4a1+/Svc mice. These data provide novel insight into the pathomolecular mechanisms of white matter abnormalities in cSVD and identify a modifiable pathway as a putative therapeutic target for cSVD.

neuroscience↗

bioRxiv2023

A novel human iPSC model of COL4A1/A2 small vessel disease unveils a key pathogenic role of matrix metalloproteinases in extracellular matrix abnormalities

Abstract/SummaryCerebral small vessel disease (SVD) affects the small vessels in the brain and is a leading cause of stroke and dementia. Emerging evidence supports a role of the extracellular matrix (ECM), at the interface between blood and brain, in the progression of SVD pathology but this remains poorly characterized. To address ECM role in SVD, we developed a co-culture model of mural and endothelial cells using human induced pluripotent stem cells from patients with COL4A1/A2 SVD-related mutations. This model revealed that these mutations induce apoptosis, migration defects, ECM remodelling and transcriptome changes in mural cells. Importantly, these mural cell defects exert a detrimental effect on endothelial cells tight junctions through paracrine actions. COL4A1/A2 models also express high levels of matrix metalloproteinases (MMP) and inhibiting MMP activity partially rescues the ECM abnormalities and mural cell phenotypic changes. These data provide a basis for targeting MMP as a therapeutic opportunity in SVD. HighlightsO_LIA novel human iPSC-derived model of genetic SVD due to collagen IV (COL4A1/A2) mutations is described C_LIO_LIMural cells expressing COL4A1/A2 mutations have prominent ECM abnormalities as seen in patients and mouse models and contribute to endothelial cells defects C_LIO_LIECM and endothelial cells abnormalities can be rescued by MMP inhibition in the COL4A1/A2 model C_LI

cell biology↗