Anatomical distributional defects in mutant genes associated with dominant intermediate Charcot-Marie-Tooth disease type C in an adenovirus-mediated mouse model

Dominant aminoacyl-tRNA synthetase disorders: lessons learned from in vivo disease models

Aminoacyl-tRNA synthetases (ARSs) play an essential role in protein synthesis, being responsible for ligating tRNA molecules to their corresponding amino acids in a reaction known as 'tRNA aminoacylation'. Separate ARSs carry out the aminoacylation reaction in the cytosol and in mitochondria, and mutations in almost all ARS genes cause pathophysiology most evident in the nervous system. Dominant mutations in multiple cytosolic ARSs have been linked to forms of peripheral neuropathy including Charcot-Marie-Tooth disease, distal hereditary motor neuropathy, and spinal muscular atrophy. This review provides an overview of approaches that have been employed to model each of these diseases in vivo, followed by a discussion of the existing animal models of dominant ARS disorders and key mechanistic insights that they have provided. In summary, ARS disease models have demonstrated that loss of canonical ARS function alone cannot fully account for the observed disease phenotypes, and that pathogenic ARS variants cause developmental defects within the peripheral nervous system, despite a typically later onset of disease in humans. In addition, aberrant interactions between mutant ARSs and other proteins have been shown to contribute to the disease phenotypes. These findings provide a strong foundation for future research into this group of diseases, providing methodological guidance for studies on ARS disorders that currently lack in vivo models, as well as identifying candidate therapeutic targets.

Precision mouse models of Yars/dominant intermediate Charcot-Marie-Tooth disease type C and Sptlc1/hereditary sensory and autonomic neuropathy type 1

Animal models of neurodegenerative diseases such as inherited peripheral neuropathies sometimes accurately recreate the pathophysiology of the human disease, and sometimes accurately recreate the genetic perturbations found in patients. Ideally, models achieve both, but this is not always possible; nonetheless, such models are informative. Here we describe two animal models of inherited peripheral neuropathy: mice with a mutation in tyrosyl tRNA-synthetase, YarsE196K , modeling dominant intermediate Charcot-Marie-Tooth disease type C (diCMTC), and mice with a mutation in serine palmitoyltransferase long chain 1, Sptlc1C133W , modeling hereditary sensory and autonomic neuropathy type 1 (HSAN1). YarsE196K mice develop disease-relevant phenotypes including reduced motor performance and reduced nerve conduction velocities by 4 months of age. Peripheral motor axons are reduced in size, but there is no reduction in axon number and plasma neurofilament light chain levels are not increased. Unlike the dominant human mutations, the YarsE196K mice only show these phenotypes as homozygotes, or as compound heterozygotes with a null allele, and no phenotype is observed in E196K or null heterozygotes. The Sptlc1C133W mice carry a knockin allele and show the anticipated increase in 1-deoxysphingolipids in circulation and in a variety of tissues. They also have mild behavioral defects consistent with HSAN1, but do not show neurophysiological defects or axon loss in peripheral nerves or in the epidermis of the hind paw or tail. Thus, despite the biochemical phenotype, the Sptlc1C133W mice do not show a strong neuropathy phenotype. Surprisingly, these mice were lethal as homozygotes, but the heterozygous genotype studied corresponds to the dominant genetics seen in humans. Thus, YarsE196K homozygous mice have a relevant phenotype, but imprecisely reproduce the human genetics, whereas the Sptlc1C133W mice precisely reproduce the human genetics, but do not recreate the disease phenotype. Despite these shortcomings, both models are informative and will be useful for future research.

Animal Models as a Tool to Design Therapeutical Strategies for CMT-like Hereditary Neuropathies

Since ancient times, animal models have provided fundamental information in medical knowledge. This also applies for discoveries in the field of inherited peripheral neuropathies (IPNs), where they have been instrumental for our understanding of nerve development, pathogenesis of neuropathy, molecules and pathways involved and to design potential therapies. In this review, we briefly describe how animal models have been used in ancient medicine until the use of rodents as the prevalent model in present times. We then travel along different examples of how rodents have been used to improve our understanding of IPNs. We do not intend to describe all discoveries and animal models developed for IPNs, but just to touch on a few arbitrary and paradigmatic examples, taken from our direct experience or from literature. The idea is to show how strategies have been developed to finally arrive to possible treatments for IPNs.

Functional mechanism of AMPK activation in mitochondrial regeneration of rat peritoneal macrophages mediated by uremic serum

OBJECTIVE

To investigate the effects of AMPK activation on mitochondrial inhibition by uremic serum through the AMPK-activated rat peritoneal macrophages stimulated by uremic serum, thereby providing a reference for the clinical treatment of chronic kidney disease.

METHODS

Twenty-two male Sprague-Dawley (SD) rats were included as experimental subjects. Fifteen rats were constructed into chronic kidney disease models (the model group). The remaining seven rats only received renal capsule stripping instead of nephrectomy (the sham-operated group). Ten weeks after model construction, the bodyweight, blood biochemical indicators, and metabolic parameters of rats in groups were measured. Meanwhile, the expression of the M1 phenotype marker protein in peritoneal macrophages was determined.

RESULTS

Ten weeks after model construction, the bodyweight of rats in the model group was significantly lower than that in the sham-operated group. The values of urea nitrogen and serum creatinine were significantly higher than those in the sham-operated group (P<0.01). The levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and the monocyte chemoattractant protein 1 (MCP-1) of rats in the model group were significantly higher than those in the sham-operated group (P <0.01). After the lipopolysaccharide (LPS) stimulation, the expressions of M1 phenotype marker mRNA in the model group was significantly increased. The expression of mitochondrial structural protein mRNA in the peritoneal macrophages of rats in the model group was significantly lower than that in the sham-operated group. The expression of M1 phenotype marker mRNA was significantly decreased in the uremic serum group after AMPK agonist (P<0.01).

CONCLUSION

In rats with chronic renal insufficiency, mitochondrial regeneration was dysfunctional in macrophages. By activating AMPK, the inhibitory effect of uremia serum on mitochondrial regeneration of macrophages was improved. Therefore, AMPK was a critical factor that could regulate mitochondrial regeneration of macrophages.