Biology subjects

Tiret, L.

Publications and source records attributed to Tiret, L..

7 recordsLinked to original sources

bioRxiv2025

A missense variant in PAOX in American Staffordshire Terriers with juvenile-onset polyneuropathy

Hereditary polyneuropathies in dogs mirror many features of human Charcot-Marie-Tooth (CMT) disease and offer valuable spontaneous models for discovery of genes variants involved in this disorder. A juvenile-onset polyneuropathy (JOP) in American Staffordshire Terriers (ASTs) resembles CMT, with motor and sensory deficits, often accompanied by laryngeal paralysis. To identify the underlying genetic cause, we conducted a genome-wide association study (GWAS) with 24 affected and 53 control ASTs that identified a significant locus at the distal end of chromosome 28. Homozygosity mapping analysis further defined a critical interval spanning 11 protein-coding genes and whole-genome sequencing revealed a missense variant in the PAOX gene encoding polyamine oxidase (NC_049249.1:g.41474541G>A), leading to a glycine-to-arginine substitution at a highly conserved residue, XP_038435135.1:p.(Gly382Arg). Genotypes at this variant were homozygous alternate in 96% of the affected dogs (n=53) and either homozygous reference or heterozygous in 336 unaffected ASTs; the mutant allele was not detected in any of 2519 genomes of other dog breeds. In silico predictions consistently supported its pathogenicity, and structural modeling suggested altered substrate binding. Although PAOX expression was preserved, proteomic profiling in affected nerve tissue revealed reduced levels of myelin-associated proteins, as well as dysregulation of mitochondrial and proteasomal pathways. Our findings establish this PAOX missense variant as the likely cause of JOP in ASTs and highlight the breed as a valuable large-animal model for studying inherited peripheral neuropathies. These results expand the spectrum of genes implicated in polyneuropathies and provide a basis for genetic testing and informed breeding strategies in ASTs. Author summaryWe studied a hereditary peripheral nerve disorder in American Staffordshire Terriers characterized by exercise intolerance, coordination problems, general weakness and difficulty breathing due to laryngeal paralysis. These signs closely resemble a group of inherited diseases in people known as Charcot-Marie-Tooth disease. To understand the genetic basis of this condition in dogs, we analyzed the genomes of affected and healthy individuals. Our research led us to a single gene, PAOX, which carries a missense variant likely affecting the function of polyamine oxidase and ultimately disrupting how the nerve cells function and survive. Most affected dogs had two copies of the mutant allele, while it was absent or in only one copy in healthy dogs. Additional analyses suggested that the variant may interfere with the nerves ability to maintain their structure and function properly. The mutant allele does not appear to reduce the overall level of PAOX protein, but it may affect how the protein works. Our findings provide a new genetic test that can help breeders avoid producing affected puppies. They also highlight this condition in dogs as a valuable model for understanding similar diseases in humans.

genetics↗

bioRxiv2025

CRISPR/Cas13-mediated Dynamin 2 reduction therapy in a canine model of DNM2-related centronuclear myopathy

We determined the potential of CRISPR/Cas13 technology as a therapeutic approach for centronuclear myopathies (CNMs) by reducing the expression of a single protein, DNM2. CNMs are severe congenital rare muscle disorders that result in muscle hypotrophy and weakness, with no cure. CNMs frequently result from mutations in either BIN1, MTM1, or DNM2 genes, with DNM2 being a key GTPase that plays a pivotal role in muscle membrane interactions with MTM1 and BIN1. Previous studies indicate that reducing DNM2 transcript expression by half could correct CNM phenotypes regardless the genetic forms, paving the way for a broad-spectrum CNM-therapy. We evaluated CRISPR/Cas13X.1-mediated DNM2 transcript knockdown, as a therapeutic application in a unique naturally-occurring canine CNM model harboring the DNM2R465W/+ mutation, the most frequent pathogenic variant in patients. We show that in vivo intramuscular AAV-mediated CRISPR/Cas13X.1 injections, led to a reduction in DNM2 transcript and protein levels at one and two months post-treatment. Our results demonstrate the feasibility of CRISPR/Cas13-based therapy for CNM in a large animal model, paving the way for advancing this approach towards clinical trials.

molecular biology↗

bioRxiv2022

Body condition score and triglyceride concentrations and their associations with other markers of energy homeostasis in healthy, non-obese dogs

Serum triglyceride concentrations increase in dogs in overweight condition, which is typically assessed by body condition score (BCS). However, their associations with other markers of energy homeostasis are poorly characterized. The present study aimed to evaluate the associations between both BCS and triglyceride levels and other markers of lipid and glucose metabolism in healthy dogs in overweight condition. 534 overweight, but otherwise healthy, client-owned dogs were included. Serum concentrations of cholesterol, free fatty acids, triglycerides, insulin, glucose and fructosamine were measured. Dogs were assigned to lean (BCS: 3-5) or overweight (BCS: 6-7) categories, and linear models were used to assess the differences between BCS categories and the associations between triglycerides and the other variables, correcting for the effect of breed. Globally, "overweight" dogs had greater serum cholesterol (95% CI: 5.3-6.2 mmol/L or 205-237 mg/dL versus 5.1-5.4 mmol/L or 198-210 mg/dl, P = .003), insulin (95% CI: 17.5-22.1 U/ml versus 16.7-18.0 U/ml, P = .036) and were older (95% CI: 4.0-5.3 versus 3.4-3.7 years, P = .002) than lean dogs. Triglyceride concentrations were positively associated with fructosamine (r2 = 0.31, P = .001), cholesterol (r2 = 0.25, P < .001), insulin (r2 = 0.14, P = .003) and glucose (r2 = 0.10, P = .002), and negatively associated with free fatty acids (r2 = 0.11, P < .001). There was no association between triglyceride levels and age. In conclusion, both BCS and triglyceride concentrations were associated with other markers of glucose and lipid metabolism in overweight, but otherwise healthy dogs. Triglyceride concentrations were associated with an increase in insulin and fructosamine that might reflect an early-phase impairment in glucose tolerance which, surprisingly, was concurrent with lower basal free fatty acids.

physiology↗

bioRxiv2022

Receptor interacting protein kinase-3 promotes both myopathy and cardiomyopathy in dystrophin-deficient mice

BackgroundDuchenne muscular dystrophy (DMD) is a progressive muscle degenerative disorder, culminating in a complete loss of ambulation, hypertrophic cardiomyopathy and a fatal cardiorespiratory failure. Necroptosis is the form of necrosis that is dependent upon the receptor-interacting protein kinase (RIPK) 3; it is involved in several inflammatory and neurodegenerative conditions. We previously identified RIPK3 as a key player in the acute myonecrosis affecting the hindlimb muscles of the dystrophic mouse model, mdx. Whether necroptosis also mediates respiratory and heart disorders in DMD is currently unknown. MethodsEvidence of activation of the necroptotic axis was examined in dystrophic tissues from Golden retriever muscular dystrophy (GRMD) dogs and R-DMDdel52 rats. A functional assessment of the involvement of necroptosis in dystrophic animals was performed on mdx mice that were genetically depleted for RIPK3. Dystrophic mice aged from 12 to 18 months were analyzed by histology and molecular biology to compare the phenotype of muscles from mdxRipk3+/+ and mdxRipk3-/- mice. Heart function was also examined by echocardiography in 40-week-old mice. ResultsQuantification of RIPK3 transcripts in sartorius and biceps femoris muscles from GRMD dogs positively correlated to myonecrosis levels (r=0.81; p=0.0076). RIPK3 was also found elevated in the diaphragm (p=0<0.05). In the slow progressing heart phenotype of GRMD dogs, the phosphorylated form of RIPK1 at the Serine 161 site was dramatically increased in cardiomyocytes. A similar p-RIPK1 upregulation characterized the cardiomyocytes of R-DMDdel52 rats, associated with a marked overexpression of Ripk1 (p=0.007) and Ripk3 (p=0.008), indicating primed activation of the necroptotic pathway in the dystrophic heart. MdxRipk3-/- mice displayed decreased compensatory hypertrophy of the heart (p=0.014), and echocardiography showed a 19% increase in the relative wall thickness (p<0.05) and 29% reduction in the left ventricle mass (p=0.0144). Besides, mdxRipk3-/- mice presented no evidence of a regenerative default or sarcopenia in skeletal muscles, moreover around 50% less affected by fibrosis (p<0.05). ConclusionsOur data provide evidence of the activation of the necroptotic pathway in degenerative tissues from dystrophic animal models, including the diaphragm and the heart. The genetic inhibition of necroptosis in dystrophic mice improves both cardiac function and histological features of muscles, suggesting that prevention of necroptosis is susceptible to providing multiorgan beneficial effects for DMD.

cell biology↗

bioRxiv2020

Absence of SARS-CoV-2 infection in cats and dogs in close contact with a cluster of COVID-19 patients in a veterinary campus

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which originated in Wuhan, China, in 2019, is responsible for the COVID-19 pandemic. It is now accepted that the wild fauna, probably bats, constitute the initial reservoir of the virus, but little is known about the role pets can play in the spread of the disease in human communities, knowing the ability of SARS-CoV-2 to infect some domestic animals. We tested 21 domestic pets (9 cats and 12 dogs) living in close contact with their owners (belonging to a veterinary community of 20 students) in which two students tested positive for COVID-19 and several others (n = 11/18) consecutively showed clinical signs (fever, cough, anosmia, etc.) compatible with COVID-19 infection. Although a few pets presented many clinical signs indicative for a coronavirus infection, no animal tested positive for SARS-CoV-2 by RT-PCR and no antibodies against SARS-CoV-2 were detectable in their blood using an immunoprecipitation assay. These original data can serve a better evaluation of the host range of SARS-CoV-2 in natural environment exposure conditions.

microbiology↗

bioRxiv2019

Alteration of cardiolipin-dependent mitochondrial coupling in muscle protects against obesity

The tubular shape of mitochondrial cristae depends upon a specific composition of the inner mitochondrial membrane, including cardiolipin that allows strong curvature and promotes optimal organization of ATP synthase. Here we identify Hacd1, which encodes an enzyme involved in very long chain fatty acid biosynthesis, as a key regulator of composition, structure and functional properties of mitochondrial membranes in muscle. In Hacd1-deficient mice, the reduced cardiolipin content was associated with dilation of cristae and caused defective phosphorylating respiration, characterized by absence of proton leak and oxidative stress.\n\nThe skeletal muscle-specific mitochondrial coupling defect produced a global elevation in basal energy expenditure with increased carbohydrate and lipid catabolism, despite decreased muscle mass and locomotor capacities. Mice were protected against diet-induced obesity despite reduced muscle activity, providing an in vivo proof of concept that reducing mitochondrial coupling efficiency in skeletal muscle might be an actionable mechanism in metabolic disease conditions.

cell biology↗

bioRxiv2018

Differential physiological role of BIN1 isoforms in skeletal muscle development, function and regeneration

Skeletal muscle development and regeneration are tightly regulated processes. How the intracellular organization of muscle fibers is achieved during these steps is unclear. Here we focus on the cellular and physiological roles of amphiphysin 2 (BIN1), a membrane remodeling protein mutated in both congenital and adult centronuclear myopathies, that is ubiquitously expressed and has skeletal muscle-specific isoforms. We created and characterized constitutive, muscle-specific and inducible Bin1 homozygous and heterozygous knockout mice targeting either ubiquitous or muscle-specific isoforms. Constitutive Bin1-deficient mice died at birth from lack of feeding due to a skeletal muscle defect. T-tubules and other organelles were misplaced and altered, supporting a general early role of BIN1 on intracellular organization in addition to membrane remodeling. Whereas restricted deletion of Bin1 in unchallenged adult muscles had no impact, the forced switch from the muscle-specific isoforms to the ubiquitous isoforms through deletion of the in-frame muscle-specific exon delayed muscle regeneration. Thus, BIN1 ubiquitous function is necessary for muscle development and function while its muscle-specific isoforms fine-tune muscle regeneration in adulthood, supporting that BIN1 centronuclear myopathy with congenital onset are due to developmental defects while later onset may be due to regeneration defects.

pathology↗