Biology subjects

Mahamdeh, M.

Publications and source records attributed to Mahamdeh, M..

4 recordsLinked to original sources

bioRxiv2025

A Novel FNDC1-NAMPT-NAD axis is Implicated in Small and Large-vessel Arterial Disease and Drives Vascular Calcification

Vascular calcification represents a convergent pathological feature of diverse cardiovascular diseases, yet the upstream molecular programs orchestrating this process remain poorly defined. Here, we uncover fibronectin type III domain-containing 1 (FNDC1) as a previously unrecognized regulator of vascular calcification across both microvascular and macrovascular beds. Integrative transcriptomic profiling of human calciphylaxis lesions and atherosclerotic coronaries identified FNDC1 as one of the most significantly upregulated genes. In primary human vascular smooth muscle cells, FNDC1 drove osteogenic phenotype switch and vascular calcification through activation of PI3K/AKT signaling and metabolic reprogramming. Mechanistically, FNDC1 directly binds to nicotinamide phosphoribosyltransferase (NAMPT) resulting in elevated intracellular NAD levels, thus coupling vascular signaling to control of NAD biosynthesis. In murine models, genetic deletion of Fndc1 or pharmacologic inhibition of NAMPT suppressed arterial calcification and prolonged survival. Clinically, circulating FNDC1 levels were elevated in patients with both calciphylaxis and coronary artery disease and independently predicted cardiovascular risk in 42,687 UK Biobank participants. Together, these findings establish FNDC1 as a central mediator of vascular pathology and highlight the FNDC1- NAMPT-NAD+ axis as a promising target for therapeutic intervention.

cell biology↗

bioRxiv2025

Enhanced mRNA delivery using ultrasound-delivered click reactive anchors

Therapeutic nucleic acid delivery has many potential applications, but it remains challenging to target extrahepatic tissues in a flexible and image-guided manner. To address this issue, we report a bioorthogonal pre-targeting strategy that uses focused ultrasound to promote the delivery of mRNA-loaded lipid nanoparticles (mRNA-LNP). We synthesized amphiphilic click reactive anchors (ACRAs) consisting of a phospholipid PEG-conjugate functionalized with transcyclooctene (TCO) or its companion reactive partner methyltetrazine (mTz), yielding ACRA-TCO and ACRA-mTz. ACRA derivatives were screened for cellular activity, yielding functionalized DOPE-PEG (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N- (polyethylene glycol)) derivatives outperforming those containing saturated lipid or branched PEG. Nanobubbles encapsulating ultrasound-responsive gas precursor delivered ACRA-TCO to targeted cells and tissues using focused ultrasound, and this pre-targeting promoted the subsequent delivery of mRNA- LNP functionalized with companion ACRA-mTz. In cell cultures and in mice, ultrasound pre-targeting enhanced the accumulation of mTz-functionalized small molecule and nanoparticle compounds by 75% and 3.6-fold, respectively, and increased gene expression using mRNA-LNP in vivo. Taken together, this report presents a modular, ultrasound-enabled strategy for enhancing nucleic acid delivery in targeted tissues.

bioengineering↗

bioRxiv2021

RBPMS2 is a conserved regulator of alternative splicing that promotes myofibrillar organization and optimal calcium handling in cardiomyocytes

RationaleThe identification of novel cardiomyocyte-intrinsic factors that support heart function will expand the number of candidate genes and therapeutic options for heart failure, a leading cause of death worldwide. ObjectiveTo identify and characterize conserved regulators of cardiomyocyte function. Methods and ResultsWe report that the RNA-binding protein RBPMS2 is required for myofibril organization and the regulation of intracellular calcium dynamics in both zebrafish embryos and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). A differential expression screen in zebrafish uncovered enrichment of rbpms2 paralogs, rbpms2a and rbpms2b, in the myocardium. Double knock-out (rbpms2-null) embryos suffer from compromised ventricular filling during the relaxation phase of the cardiac cycle, which significantly reduces cardiac output. Whole transcriptome sequencing and validation studies revealed differential alternative splicing of several genes linked to cardiomyopathies in humans, including myosin binding protein C3 (mybpc3) and phospholamban (pln), consistent with a role in causing the observed ventricular deficiencies. Further, RBPMS2-null hiPSC-CMs exhibit myofibril and calcium handling defects that are highly analogous to those observed in the rbpms2-null zebrafish ventricle. ConclusionsTaken together, our data identify RBPMS2 as a conserved and essential regulator of alternative splicing that is required for myofibrillar organization and optimal calcium handling from zebrafish to humans.

developmental biology↗

bioRxiv2018

Label-free high-speed wide-field imaging of single microtubules using interference reflection microscopy

When studying microtubules in vitro, label free imaging of single microtubules is necessary when the quantity of purified tubulin is too low for efficient fluorescent labeling or there is concern that labelling will disrupt its function. Commonly used techniques for observing unlabeled microtubules, such as video enhanced differential interference contrast, dark-field and more recently laser-based interferometric scattering microscopy, suffer from a number of drawbacks. The contrast of differential interference contrast images depends on the orientation of the microtubules, dark-field is highly sensitive to impurities and optical misalignments, and interferometric scattering has a limited field of view. In addition, all of these techniques require costly optical components such as Nomarski prisms, dark-field condensers, lasers and laser scanners. Here we show that single microtubules can be imaged at high speed and with high contrast using interference reflection microscopy without the aforementioned drawbacks. Interference reflection microscopy is simple to implement, requiring only the incorporation of a 50/50 mirror instead of a dichroic in a fluorescence microscope, and with appropriate microscope settings has similar signal-to-noise ratio to differential interference contrast and fluorescence. We demonstrated the utility of interference reflection microscopy by high speed imaging and tracking of dynamic microtubules at 100 frames per second. In conclusion, the image quality of interference reflection microscopy is similar to or exceeds that of all other techniques and, with minimal microscope modification, can be used to study the dynamics of unlabeled microtubules.

biophysics↗