Biology subjects

Murillo, A.

Publications and source records attributed to Murillo, A..

4 recordsLinked to original sources

bioRxiv2026

Single-AAV Delivery of the SpCas9 Nickase Improves CAG/CTG Repeat contraction in a mouse model of Huntington's disease

The best studied Cas9 enzyme, from Streptococcus pyogenes, is thought to be too large to be efficiently packaged into a single adeno-associated virus (AAV) together with a single-guide (sg) RNA cassette, requiring a dual-vector system. Here we have circumvented this limitation and packaged the full CRISPR system into a single AAV by using a single promoter driving the expression of both the Cas9 enzyme and a sgRNA. We compared the ability of the dual and single vector systems to induce contraction of CAG/CTG repeats in the striatum of a Huntington's disease model. We show that the all-in-one system led to larger contractions of the CAG/CTG repeats. This approach provides a more efficient and less costly approach for in vivo gene editing and improves the translational potential of AAV-mediated delivery of Cas9.

neuroscience↗

bioRxiv2026

SCIA: A fast and widely applicable pipeline for measuring expanded repeat instability

The expansion of short tandem repeats is a feature of over 60 different human diseases. Ongoing somatic instability throughout a patients lifetime can influence disease progression and has emerged as a therapeutic target. Understanding its mechanism is essential for the identification of both drug targets and therapeutic interventions. A major obstacle towards this translational goal has been to measure changes in repeat size distribution given that these are complex datasets. To address this, here we provide a new analysis method, and accompanying software, that generates delta plots, extracts the instability frequency from targeted long-read sequencing data, the bias towards expansion or contraction, and the average size of the changes. It further provides statistical analysis for comparison between treatments. We show its applicability to non-dividing cells, and in vivo datasets. Moreover, we have developed a streamlined experimental design for dividing cells, Single Clone-based Instability Assay (SCIA), that saves weeks in assessing the effect of a gene knockout on repeat instability and is ideal for an initial screen. We have validated the approach using FAN1, PMS1, and MLH1 knockouts. Using SCIA, we find that although FAN1 knockout clones showed increased frequency of expansions, the size of the expansions were smaller. This highlights the wealth of information that can be extracted and the potential for novel insights into the mechanism of repeat instability.

neuroscience↗

bioRxiv2024

Cas9 nickase-mediated contraction of CAG/CTG repeatsat multiple disease loci

Expanded CAG/CTG repeats cause over 15 different diseases that all remain without a disease-modifying treatment. Because repeat length accounts for most of the variation in disease severity, contracting them presents an attractive therapeutic avenue. Here, we show that the CRISPR-Cas9 nickase targeted to CAG/CTG repeats leads to efficient contractions in Huntingtons disease patient-derived neurons and astrocytes, and in myotonic dystrophy type 1 patient-derived neurons. The approach is allele-selective and free of detectable off-target mutations. Striatal injection of the Cas9 nickase in a mouse model for Huntingtons disease using adeno-associated viral vectors led to contractions in over half the infected cells. Upon injection, we observed a reduction in the number of inclusion bodies, improved transcriptome, and ameliorated locomotion. The effects were greater than expected from the contractions induced and suggest that non-cell autonomous mechanisms may be involved. Our results provide the proof-of-concept that correction of CAG/CTG repeats can improve Huntingtons disease phenotypes in vivo. One sentence summaryThe Cas9 nickase contracts CAG/CTG repeats at multiple disease loci in patient-derived cells and improves molecular and behavioral phenotypes in HD.

neuroscience↗

bioRxiv2023

Chronic activation of the aryl hydrocarbon receptor in muscle exacerbates ischemic pathology in chronic kidney disease

Chronic kidney disease (CKD) accelerates the development of atherosclerosis, decreases muscle function, and increases the risk of amputation or death in patients with peripheral artery disease (PAD). However, the cellular and physiological mechanisms underlying this pathobiology are ill-defined. Recent work has indicated that tryptophan-derived uremic toxins, many of which are ligands for the aryl hydrocarbon receptor (AHR), are associated with adverse limb outcomes in PAD. We hypothesized that chronic AHR activation, driven by the accumulation of tryptophan-derived uremic metabolites, may mediate the myopathic condition in the presence of CKD and PAD. Both PAD patients with CKD and mice with CKD subjected to femoral artery ligation (FAL) displayed significantly higher mRNA expression of classical AHR-dependent genes (Cyp1a1, Cyp1b1, and Aldh3a1) when compared to either muscle from the PAD condition with normal renal function (P<0.05 for all three genes) or non-ischemic controls. Skeletal-muscle-specific AHR deletion in mice (AHRmKO) significantly improved limb muscle perfusion recovery and arteriogenesis, preserved vasculogenic paracrine signaling from myofibers, increased muscle mass and contractile function, as well as enhanced mitochondrial oxidative phosphorylation and respiratory capacity in an experimental model of PAD/CKD. Moreover, viral-mediated skeletal muscle-specific expression of a constitutively active AHR in mice with normal kidney function exacerbated the ischemic myopathy evidenced by smaller muscle masses, reduced contractile function, histopathology, altered vasculogenic signaling, and lower mitochondrial respiratory function. These findings establish chronic AHR activation in muscle as a pivotal regulator of the ischemic limb pathology in PAD. Further, the totality of the results provide support for testing of clinical interventions that diminish AHR signaling in these conditions.

physiology↗