Biology subjects

Dickman, R.

Publications and source records attributed to Dickman, R..

4 recordsLinked to original sources

bioRxiv2026

PDGFRα-directed fibroblast-homing peptides for targeted delivery of nucleic acid therapeutics

Efficient and cell type-specific delivery remains a major barrier to the clinical translation of nucleic acid therapeutics (NATs), particularly for fibroblast-driven diseases in which target cells are poorly accessible in vivo. By integrating single-cell transcriptomics with cell-surface protein profiling, we identified platelet-derived growth factor receptor alpha (PDGFR) as a fibroblast-enriched surface receptor. A panel of PDGFA-derived short peptides was designed and screened across multiple human and mouse cell types, leading to the identification of two fibroblast-homing peptides, Pep3 and Pep5, which displayed rapid and preferential uptake in fibroblasts. PDGFR; knockdown reduced peptide internalisation as measured by live-cell imaging, confirming receptor-mediated uptake. To evaluate their potential as delivery vehicles for NATs, a fibroblast-based cellular model of collagen VI-related congenital muscular dystrophy (COL6-CMD) was used for further validation. Lead peptides were conjugated to a splice-switching phosphorodiamidate morpholino oligomer (PMO) targeting the recurrent COL6A1 c.930+189C>T variant. Peptide-PMO conjugates retained exon-skipping activity and Pep3-PMO enhanced collagen VI protein deposition in patient-derived fibroblasts following repeated treatment compared to unconjugated PMO. Transcriptomic profiling demonstrated no activation of inflammatory, oncogenic, or PDGFR; receptor-associated signalling pathways following peptide-PMO treatment. Collectively, these findings establish PDGFR-targeting fibroblast-peptides as a promising platform for selective delivery of NATs to fibroblasts.

molecular biology↗

bioRxiv2024

Genetic Manipulation of Caveolin-1 in the Mouse Model of Marfan Syndrome Associated Aortic Root Aneurysm: Effects on Endothelial and Smooth Muscle Function

Marfan Syndrome (MFS) is a systemic connective tissue disorder caused by mutations in the gene encoding for the large glycoprotein Fibrillin-1 (Fbn1), leading to wide-spectrum clinical manifestations, with the most life-threatening being aortic root aneurysm. MFS aortic aneurysm is known to be associated with reduced endothelial nitric oxide synthase (eNOS)-mediated nitric oxide (NO) production. Previous studies have shown that caveolin-1 (Cav1), a coat protein of caveolae structure on the plasma membrane, acts as a negative regulator of eNOS activity. This suggests that Cav1 may play a role in the development of aortic root aneurysm in MFS by modulating eNOS activity. In this study, we investigated the role of Cav1 in regulating aortic smooth muscle and endothelial function, aortic wall elasticity, and wall strength by generating MFS mice (FBN1+/Cys1041Gly) lacking Cav1 gene expression (MFS/Cav1KO). Our data show that ablation of the Cav1 gene results in a significant decrease in aortic smooth muscle contraction in response to the vasoconstricting agent phenylephrine seemingly due to a marked increase in NO production within the aortic wall. We also showed that acetylcholine-induced vasorelaxation was increased in MFS/Cav1KO mice potentially through the endothelial nitric oxide-dependent mechanism, further confirming inhibitory role of Cav1 on endothelial NO production. In addition, aortic wall elastin fiber structure and strength were markedly improved in male MFS/Cav1KO mice. This study demonstrates the regulatory role of Cav1 during the development of aortic root aneurysm in MFS mice through its effects on smooth muscle and endothelial functions in an NO-dependent manner.

physiology↗

bioRxiv2022

Data-driven models of optimal chromatic coding in the outer retina

The functional properties of the outermost retinal circuits involved in color discrimination are not well understood. Recent experimental work on zebrafish has elucidated the in-vivo activity of photoreceptors and horizontal cells as a function of the stimulus spectrum, highlighting the appearance of chromatic-opponent signals at the first synaptic connection between cones and horizontal cells. These findings, together with the observed lack of gap junctions, suggest that the mechanism yielding early color-opponency in zebrafish is dominated by inhibitory feedback. We discuss the observed neuronal activity in the context of efficient codification of chromatic information, hypothesizing that opponent chromatic signals provide optimal codification, minimizing signal redundancy. We examine whether these functional properties are general across species by studying the dynamic properties of dichromatic and trichromatic outer retinal networks. Our findings show that dominant inhibitory feedback mechanisms provide an unambiguous codification of chromatic stimuli, whereas this property is not guaranteed in networks with strong excitatory inter-cone connections, for example via gap junctions. This provides a plausible explanation for the absence of gap junctions observed in the outermost zebrafish retinal layers. In addition, our study suggests that the simplest zebrafish-like network with dominant inhibitory feedback capable of optimally codifying chromatic information requires at least two successive inhibitory feedback layers. Finally, we contrast the chromatic codification performance of zebrafish-inspired retinal networks with networks having different opsin combinations. We find that optimal combinations lead to a chromatic codification improvement of only 13% compared with zebrafish opsins, suggesting that the zebrafish retina performs nearly optimal codification of chromatic information in its habitat. 2 Author summaryRecent experimental work has evidenced that outer neuronal circuits in the zebrafish retina use color-opponent mechanisms to codify and transmit chromatic information at the first synaptic contact between cones and horizontal cells. Inspired by these findings, we propose a data-driven model to study physiological and dynamical properties of outer retinal networks and their implications for color codification across vertebrate retinal circuits. We first study our model in a large parameter space, finding that the primary biological mechanism leading to color-opponent signals is mediated by dominant inhibitory feedback, e.g., via horizontal cell synaptic connections. In contrast, strong coupling among cones leads to ambiguous chromatic codification, undesirable in the outer retina. Then, we parameterize the model using zebrafish experimental data and quantify its chromatic codification performance. Our results suggest that trichromatic retinas with inhibitory feedback are highly efficient and capture most of the chromatic information variance typical from zebrafish environments. More specifically, a comparison among zebrafish-inspired retinal networks suggests that zebrafish retinal circuits are near-optimal chromatic codification of their natural chromatic information.

biophysics↗

bioRxiv2019

Profiling and structural analysis of cardenolides in two species of Digitalis using liquid chromatography coupled with high-resolution mass spectrometry

Plants of the Digitalis genus contain a cocktail of cardenolides commonly prescribed to treat heart failure. Cardenolides in Digitalis extracts have been conventionally quantified by high-performance liquid chromatography yet the lack of structural information compounded with possible co-eluents renders this method insufficient for analyzing cardenolides in plants. The goal of this work is to structurally characterize cardiac glycosides in fresh-leaf extracts using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) that provides exact masses. Fragmentation of cardenolides is featured by sequential loss of sugar units while the steroid aglycon moieties undergo stepwise elimination of hydroxyl groups, which distinguishes different aglycones. The sequence of elution follows diginatigenin[->]digoxigenin[->]gitoxigenin[->]gitaloxigenin[->]digitoxigenin for cardenolides with the same sugar units but different aglycones using a reverse-phase column. A linear range of 0.8-500 ng g-1 has been achieved for digoxigenin, {beta}-acetyldigoxin, and digitoxigenin with limits of detection ranging from 0.09 to 0.45 ng g-1. A total of 17 cardenolides have been detected with lanatoside A, C, and E as major cardenolides in Digitalis lanata while 7 have been found in Digitalis purpurea including purpurea glycoside A, B, and E. Surprisingly, glucodigifucoside in D. lanata and verodoxin and digitoxigenin fucoside in D. purpurea have also been found as major cardenolides. As the first MS/MS-based method developed for analyzing cardenolides in plant extracts, this method serves as a foundation for complete identification and accurate quantification of cardiac glycosides, a necessary step towards understanding the biosynthesis of cardenolide in plants.

biochemistry↗