Biology subjects

Gissot, L.

Publications and source records attributed to Gissot, L..

5 recordsLinked to original sources

bioRxiv2026

Programmable Repair of Disease-Causing UGA Stop Codons in Mammalian Brain

Protein truncating variants caused by UGA stop codons are the most prevalent class of rare variant mutations in neurodevelopmental diseases. Suppressor transfer RNA (sup-tRNA) have therapeutic potential for premature termination codon (PTC) repair, but have thus far underperformed by traditional AAV delivery platforms and progress has been hampered by the lack of methods to non-invasively assess in vivo activity in mammalian brain. To fill this material gap, we utilize transcranial in vivo bioluminescence imaging data from a luciferase-UGA mouse model to enable payload optimization. These data demonstrate that U6 promotor and AAV2/9 capsids have the lowest in vivo activity, whereas self-complementary AAV2/9 with the tRNA in a minimal 100bp genomic context provide broad and efficacious PTC rescue. Further, payload tRNA multiplexing and use of tRNA introns enable efficacy of low viral titers and sustained rescue. tRNA sequencing of scAAV delivered ArgUGA sup-tRNA in brain demonstrate no effects on endogenous tRNA levels, their acylation or processing, and these features are also maintained in scAAV delivered ArgUGA sup-tRNA. Collectively, this work defines a scalable strategy for precision UGA stop codon suppression, supporting development of durable genetic rescue therapies for neurodevelopmental disorders in the mammalian brain. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/724978v3_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@d0fefeorg.highwire.dtl.DTLVardef@1150446org.highwire.dtl.DTLVardef@cbb839org.highwire.dtl.DTLVardef@abddfc_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Position-dependent effects of SCN2A premature stop codons on neuronal excitability and behavior

SCN2A encodes the voltage-gated sodium channel NaV1.2, a key determinant of spike initiation and propagation in glutamatergic neurons. Premature termination codons are often assumed to produce uniform haploinsufficiency via nonsense-mediated decay, yet whether distinct SCN2A premature stop codons yield equivalent molecular, cellular, and behavioral outcomes remains unknown. We generated two mouse lines carrying patient mutations--Scn2aY84X/+ (p.Tyr84UAA; early coding sequence) and Scn2aR1627X/+(p.Arg1627UGA; terminal coding exon)--on a C57BL/6J background. Allele-specific expression was quantified by targeted next-generation sequencing of whole-brain reverse transcribed cDNA. NaV1.2 protein was measured in half-brain lysates by automated western blot and ex vivo whole-cell recordings were obtained from layer 5b pyramidal-tract neurons in medial prefrontal cortex. A panel of behavioral assays assessed locomotion/exploration, motor learning, anxiety-like behavior, sociability, sensorimotor gating, and seizure susceptibility. Allele-specific RNA handling diverged by position: mRNA carrying Y84X engaged partial nonsense-mediated decay, whereas R1627X transcripts were at allelic balance. Despite this difference in RNA fate, NaV1.2 protein was comparably reduced in both lines. Electrophysiologically, both premature termination codon mutations slowed the action-potential upstroke, with a larger decrement in Scn2aY84X/+than in Scn2aR1627X/+. Spike threshold was depolarized only in Scn2aY84X/+, whereas Scn2aR1627X/+ remained similar to wild type. Frequency-current relations showed reduced firing at near-rheobase inputs in both mutants, with responses approaching wild type at stronger currents. Behaviorally, locomotion, sociability, and sensorimotor gating were preserved. Both lines exhibited increased grooming--consistent with restrictive, repetitive behavior; Scn2aY84X/+alone showed greater exploration in the elevated-risk context and a male-predominant deficit in rotarod learning. In maximal electroshock testing, mortality was lower in both lines without differences in seizure threshold or severity. Our results show that distinct SCN2A premature termination codons are not equivalent to one another, nor to a uniform haploinsufficient state. An early, nonsense-mediated decay-competent premature stop codon (Y84X) and a terminal-exon one (R1627X) produce partially overlapping yet allele-specific effects on neuronal excitability and behavior. These findings establish premature termination codon position as a determinant of phenotype, supporting allele-tailored mechanistic studies and therapeutic strategies.

neuroscience↗

bioRxiv2025

Non-canonical Sodium Channel Isoforms Underlie Chamber Specific Cardiac Excitability

Voltage-gated sodium (NaV) channels drive cardiac excitability. While NaV1.5 is the primary cardiac isoform, the composition and functional contributions of non-NaV1.5 isoforms in the heart remain unclear. Here, we developed a chemical-genetic mouse model (NaV1.5-GX) in which NaV1.5 can be selectively and reversibly inhibited by acyl- and aryl-sulfonamide compounds (GX drugs). NaV1.5-GX mice exhibited normal cardiac function at baseline, but acute GX drug administration caused profound conduction defects and arrhythmias. Whole-heart optical mapping revealed dose-dependent chamber-specific sensitivity to NaV1.5 inhibition, with the right ventricle (RV) being the most sensitive, followed by the left ventricle (LV), left atrium (LA), and right atrium (RA). Patch-clamp recordings of isolated cardiomyocytes with application of NaV isoform-selective inhibitors showed that NaV1.5 contributed 93% of sodium current in the LV, 81% in the RV and 78% in the LA. Non-NaV1.5 isoforms were differentially enriched across chambers: NaV1.8 in the LV, NaV1.1/1.3 in the RV, and NaV1.2/1.6/1.7 in the atria. These results reveal a surprising chamber-specific isoform landscape of cardiac sodium currents which may underlie the right ventricular predominant phenotype of Brugada syndrome and highlight non-NaV1.5 isoforms as potential mediators of chamber-specific cardiac pathologies and as pharmacological targets.

physiology↗

bioRxiv2025

Prevenying vision loss in a mouse model of Leber Congenital Amaurosis by engineered tRNA

Premature termination codons (PTCs) are associated with rare genetic disorders. Inducing targeted read-through of these nonsense mutations presents a potential therapeutic strategy for modifying disease outcomes. We previously reported that one such PTC, W53X, in the KCNJ13 gene causes blindness and Leber congenital amaurosis type-16 (LCA-16) due to loss of function of the inwardly rectifying potassium channel 7.1 (Kir7.1). Here, we present the proof of concept of a therapeutic approach based on anticodon-engineered transfer RNA (ACE-tRNA). The ACE-tRNA encodes the amino acid tryptophan (Trp) and suppresses the W53X PTC, restoring full-length protein expression. We used helper-dependent adenovirus (HDAd) to deliver the ACE-tRNATrp.UAG (tRNATrp.UAG) and rescue Kir7.1 function and physiology in patient-specific human induced pluripotent stem cell-derived retinal pigment epithelium (hiPSC-RPE) cells. Furthermore, in a W53X mouse model of LCA16, HDAd delivery of tRNATrp.UAG resulted in durable restoration of vision as measured by retinography. This study provides the first example of the therapeutic application of ACE-tRNA for treating an inherited form of blindness.

physiology↗

bioRxiv2018

Synchrotron FTIR and Raman spectroscopy provide unique spectral fingerprints for Arabidopsis floral stem vascular tissues

Cell walls are highly complex structures that are modified during plant growth and development. For example, the development of phloem and xylem vascular cells, which participate in the transport of sugars and water as well as support, can be influenced by cell-specific cell wall composition. Here, we used synchrotron radiation-based infrared (SR-FTIR) and Raman spectroscopy to analyze the cell wall composition of wild-type and double mutant sweet11-1sweet12-1, which impairs sugar transport, Arabidopsis floral stem vascular tissue. The SR-FTIR spectra showed that in addition to modified xylem cell wall composition, phloem cell walls in the double mutant line were characterized by modified hemicellulose composition. Moreover, combining Raman spectroscopy with a Classification and Regression Tree (CART) method identified combinations of Raman shifts that could distinguish xylem vessels and fibers. Additionally, the disruption of SWEET11 and SWEET12 genes impacts xylem cell wall composition in a cell-specific manner, with changes in hemicelluloses and cellulose observed at the xylem vessel interface. These results suggest that the facilitated transport of sugars by transporters that exist between vascular parenchyma cells and conducting cells is important to ensuring correct phloem and xylem cell wall composition.\n\nHighlightCombining vibrational spectroscopy techniques and multivariate analysis shows that the disruption of SWEET genes impacts phloem cell wall composition and that the effect on xylem cell wall composition is cell-specific.

plant biology↗