Biology subjects

Murshed, M.

Publications and source records attributed to Murshed, M..

6 recordsLinked to original sources

bioRxiv2026

Arterial Elastin Abundance, Rather Than Orthologue Origin, Modulates Medial Arterial Calcification in Matrix Gla Protein-Deficient Mice

Abstract Calcific deposits in the arterial media have been associated with a number of metabolic and genetic disorders including diabetes, chronic kidney disease and generalized arterial calcification of infancy. While medial calcification and physiologic hard tissue mineralization in the skeleton are both regulated by several common determinants, emerging data suggest that there might be fundamental differences in the mechanisms underlying these two processes. Objective: We previously demonstrated that elastin haploinsufficiency delays medial calcification in MGP-deficient mice. Here, using mice in which a human ELN transgene rescues mouse elastin deficiency, we investigated whether the origin and abundance of arterial elastin differentially affect the initiation and progression of medial calcification. Approach and Results: We pursued a transgenic approach to alter the arterial elastin scaffold in MGP-deficient mice. Our analyses of a humanized MGP-deficient model with 40% reduction of medial elastin content showed a complete absence of the early-stage vascular calcification. Additionally, we showed that mouse and human elastin orthologues affect vascular calcification in a comparable manner. Conclusion: Arterial elastin abundance, rather than orthologue origin, modulates the initiation and progression of medial calcification in MGP-deficient mice. A further reduction in arterial elastin beyond that achieved by elastin haploinsufficiency profoundly delays mineral deposition and maturation, whereas restoration of elastin abundance through transgenic human ELN expression restores arterial calcification.

cell biology↗

bioRxiv2025

Vitamin K-dependent carboxylation in osteoblasts regulates bone resorption through GAS6

Studies in humans suggest that vitamin K is involved in the regulation of bone remodeling, but the precise mechanism at play remains unknown. In cells, vitamin K functions as a co-factor for the {gamma}-glutamyl carboxylase (GGCX), an enzyme responsible for the conversion of glutamic acid residues (Glu) into {gamma}-carboxyglutamic acid (Gla) residues in secreted proteins. We aim here at determining the role of {gamma}-carboxylation in bone remodeling and at identifying the Gla protein(s) involved. We show that male mice lacking {gamma}-carboxylation specifically in osteoblasts (Ggcxflox/flox;OCN-Cre) have increased bone mass at 6 months of age due to a reduced number of multinucleated bone resorbing osteoclasts. In co-culture experiments, Ggcx-deficient osteoblasts were less effective than control osteoblasts at supporting osteoclast formation. Among known Gla proteins, we identify GAS6 as an osteoblast-secreted {gamma}-carboxylated factor which signals to differentiating osteoclasts. The GAS6 receptors MerTK and AXL are expressed in pre-osteoclasts and pharmacological inhibitors of AXL and MerTK block osteoclast generation in co-culture. Conversely, recombinant {gamma}-carboxylated GAS6 dose-dependently increases the size of osteoclasts and the number of nuclei per osteoclast in culture. GAS6 marginally affected the induction of osteoclast-specific genes during osteoclast differentiation but significantly increased pre-osteoclast fusion. Finally, increasing bone marrow GAS6 level in transgenic male mice was sufficient to increase the number and size of osteoclasts and to decrease bone mass. This work identifies GAS6 as a novel osteoblast-derived vitamin K-dependent protein regulating osteoclast maturation.

cell biology↗

bioRxiv2024

Circulating plasma fibronectin affects normal adipose tissue insulin sensitivity and adipocyte differentiation

Plasma fibronectin (pFN), a liver-derived, circulating protein, has been shown to affect adipocyte morphology, adipogenesis, and insulin signalling in preadipocytes in vitro. In this study, we show via injections of fluorescence-labelled pFN to mice in vivo its abundant accrual visceral and subcutaneous adipose tissues (VAT and SAT). Diet-induced obesity model of liver-specific conditional Fn1 knockout (pFN KO), showed no altered weight gain or differences, whole-body fat mass or SAT or VAT volumes after 20- week HFD-feeding, however, mice showed significantly improved glucose clearance and whole-body insulin sensitivity on normal diet. Furthermore, in vivo insulin sensitivity assay revealed significant increase in AKT phosphorylation in pFN KO SAT on normal diet as well as in normal and obese VAT of the pFN KO. Histological assessment of the pFN KO depots showed significant increase in small adipocytes on normal diet, which was particularly prominent in SAT. RNA sequencing of the normal diet-fed pFN versus control SAT revealed alterations in fatty acid metabolism and thermogenesis suggesting presence of beige adipocytes. VAT RNA sequencing after HFD showed alternations in genes reflecting stem cell populations. Our data suggests that the absence of pFN alters cell pools in AT favoring cells with increased insulin sensitivity.

cell biology↗

bioRxiv2022

Modeling Microtubule-Cytoplasm Interaction in Plant Cells

Although microtubules in plant cells have been extensively studied, the mechanisms that regulate the spatial organization of microtubules are poorly understood. We hypothesize that the interaction between microtubules and cytoplasmic flow plays an important role in the assembly and orientation of microtubules. To test this hypothesis, we developed a new computational modeling framework for microtubules based on theory and methods from the fluid-structure interaction. We employed the immersed boundary method to track the movement of microtubules in cytoplasmic flow. We also incorporated details of the encounter dynamics when two microtubules collide with each other. We verified our computational model through several numerical tests before applying it to the simulation of the microtubule-cytoplasm interaction in a growing plant cell. Our computational investigation demonstrated that microtubules are primarily oriented in the direction orthogonal to the axis of cell elongation. We validated the simulation results through a comparison with the measurement from laboratory experiments. We found that our computational model, with further calibration, was capable of generating microtubule orientation patterns that were qualitatively and quantitatively consistent with the experimental results. The computational model proposed in this study can be naturally extended to many other cellular systems that involve the interaction between microstructures and the intracellular fluid.

cell biology↗

bioRxiv2022

Pten regulates endocytic trafficking of cell adhesion and signaling molecules to pattern the retina

The retina is an exquisitely patterned tissue, with neuronal somata positioned at regular intervals to completely sample the visual field. Cholinergic amacrine cells are spectacular exemplars of precision, distributing in two radial layers and tangentially, forming regular mosaics. Here, we investigated how the intracellular phosphatase Pten and the cell adhesion molecule Dscam cooperate to regulate amacrine cell patterning. Using double mutants to test epistasis, we found that Pten and Dscam function in parallel pathways to regulate amacrine cell positioning. Mechanistically, Pten regulates endocytic remodeling of cell adhesion molecules (Dscam, Megf10, Fat3), which are aberrantly redistributed in Pten conditional-knock-out (cKO) amacrine cells. Furthermore, extracellular vesicles derived from multivesicular endosomes have altered proteomes in PtencKO retinas. Consequently, Wnt signaling is elevated in PtencKO retinal amacrine cells, the pharmacological disruption of which phenocopies PtencKO patterning defects. Pten thus controls endocytic trafficking of critical cell adhesion/signaling molecules to control amacrine cell spacing. HIGHLIGHTSO_LIPten and Dscam act in parallel pathways to regulate amacrine cell spacing C_LIO_LIEndocytic remodeling of cell adhesion molecules is perturbed in PtencKO retinas C_LIO_LIExtracellular vesicle content is altered in PtencKO retinas C_LIO_LIPerturbation of Wnt signaling phenocopies defects in amacrine cell positioning C_LI eTOC BLURBPatterns in nature range from stereotyped distributions of colored patches on butterfly wings to precise neuronal spacing in the nervous system. Waddington proposed that built-in constraints canalize developmental patterns. Touahri et al. identified Pten-mediated endocytic trafficking of cell adhesion/signaling molecules as a novel constraint measure controlling retinal amacrine cell patterning.

neuroscience↗

bioRxiv2020

PHOSPHO1, a novel skeletal regulator of insulin resistance and obesity

The skeleton is recognised as a key endocrine regulator of metabolism. Here we show that mice lacking the bone mineralization enzyme PHOSPHO1 (Phospho1-/-) exhibited improved basal glucose homeostasis and resisted high-fat-diet induced weight gain and diabetes. The metabolic protection in Phospho1-/- mice was manifested in the absence of altered levels of osteocalcin. Osteoblasts isolated from Phospho1-/- mice were enriched for genes associated with energy metabolism and diabetes; Phospho1 both directly and indirectly interacted with genes associated with glucose transport and insulin receptor signalling. Canonical thermogenesis via brown adipose tissue did not underlie the metabolic protection observed in adult Phospho1-/- mice. However, the decreased serum choline levels in Phospho1-/- mice were normalized by feeding a 2% choline rich diet resulting in a normalization in insulin sensitivity and fat mass. This study identifies PHOSPHO1 as a potential therapeutic target for the treatment of obesity and diabetes.

physiology↗