Variants of aminoacyl-tRNA synthetase genes in Charcot-Marie-Tooth disease: A Korean cohort study

Transcriptomic analysis of different intramuscular fat contents on the flavor of the longissimus dorsi tissues from Guangling donkey

BACKGROUND

In this study, researchers aimed to explore the impact of intramuscular fat (IMF) concentration on the flavor of donkey meat, specifically in the longissimus dorsi muscle of Guangling donkeys. The internal volatile organic compounds that cause the flavor differences between donkey muscles are not clear at present. Transcriptomic technologies were utilized to analyze gene expression and its relationship to donkey meat flavor.

METHOD

Thirty Guangling donkeys had their IMF content evaluated in the longissimus dorsi muscle. Based on IMF content, 16 donkeys of similar ages were divided into two groups: low-fat (L) and high-fat (H). Headspace solid-phase microextraction Gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace solid phase microextraction mass spectrometry were used to identify potential flavor components that differed between the two groups.

RESULTS

Five key volatile substances were identified, and WGCNA and KEGG analysis was conducted to analyze the genes associated with these substances. The results showed that pathways like PPAR signaling, nucleotide excision repair, glucagon signaling, arachidonic acid metabolism, and glycolysis/glycogenesis were involved in lipid deposition. Additionally, a gene-gene interaction network map was constructed, highlighting the importance of hub genes such as EEF2, DDX49, GAP43, SNAP25, NDUFS8, MRPS11, RNASEH2A, POLR2E, POLR2C and ALB in regulating key flavor substances.

CONCLUSION

This study provided valuable insights into the regulation of genes and protein expression related to flavor substances in donkey meat. It also deepened understanding of the influence of IMF on flavor and laid a foundation for future molecular breeding improvements in Guangling donkeys.

Hereditary spastic paraplegia: Novel insights into the pathogenesis and management

Hereditary spastic paraplegia is a genetically heterogeneous neurodegenerative disorder characterised primarily by muscle stiffness in the lower limbs. Neurodegenerative disorders are conditions that result from cellular and metabolic abnormalities, many of which have strong genetic ties. While ageing is a known contributor to these changes, certain neurodegenerative disorders can manifest early in life, progressively affecting a person's quality of life. Hereditary spastic paraplegia is one such condition that can appear in individuals of any age. In hereditary spastic paraplegia, a distinctive feature is the degeneration of long nerve fibres in the corticospinal tract of the lower limbs. This degeneration is linked to various cellular and metabolic processes, including mitochondrial dysfunction, remodelling of the endoplasmic reticulum membrane, autophagy, abnormal myelination processes and alterations in lipid metabolism. Additionally, hereditary spastic paraplegia affects processes like endosome membrane trafficking, oxidative stress and mitochondrial DNA polymorphisms. Disease-causing genetic loci and associated genes influence the progression and severity of hereditary spastic paraplegia, potentially affecting various cellular and metabolic functions. Although hereditary spastic paraplegia does not reduce a person's lifespan, it significantly impairs their quality of life as they age, particularly with more severe symptoms. Regrettably, there are currently no treatments available to halt or reverse the pathological progression of hereditary spastic paraplegia. This review aims to explore the metabolic mechanisms underlying the pathophysiology of hereditary spastic paraplegia, emphasising the interactions of various genes identified in recent network studies. By comprehending these associations, targeted molecular therapies that address these biochemical processes can be developed to enhance treatment strategies for hereditary spastic paraplegia and guide clinical practice effectively.

Case Report: A new case of YARS1-associated autosomal recessive disorder with compound heterozygous and concurrent 47, XXY

Aminoacyl-tRNA synthetases play a pivotal role in catalyzing the precise coupling of amino acids with their corresponding tRNAs. Among them, Tyrosyl tRNA synthetase, encoded by the YARS1 gene, facilitates the aminoacylation of tyrosine to its designated tRNA. Heterozygous variants in the YARS1 gene have been linked to autosomal dominant Charcot-Marie-Tooth type C, while recent findings have unveiled biallelic YARS1 variants leading to an autosomal recessive multisystemic disorder in several cases. In this report, we present a novel case characterized by dysmorphic facies, and multisystemic symptoms, prominently encompassing neurological issues and a microarray conducted shortly after birth revealed 47, XXY. Utilizing whole exome sequencing, we uncovered a paternally inherited likely pathogenic variant (c.1099C > T, p.Arg367Trp), previously reported, coinciding with the father's history of hearing loss and neurological symptoms. Additionally, a maternally inherited variant of uncertain significance (c.782T > G, p.Leu261Arg), previously unreported, was identified within the YARS1 gene. The observed phenotypes and the presence of compound heterozygous results align with the diagnosis of an autosomal recessive disorder associated with YARS1. Through our cases, the boundaries of this emerging clinical entity are broadened. This instance underscores the significance of comprehensive genetic testing in patients exhibiting intricate phenotypes.

A missense, loss-of-function YARS1 variant in a patient with proximal-predominant motor neuropathy

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes with a critical role in protein synthesis: charging tRNA molecules with cognate amino acids. Heterozygosity for variants in five genes (AARS1, GARS1, HARS1, WARS1, and YARS1) encoding cytoplasmic, dimeric ARSs have been associated with autosomal dominant neurological phenotypes, including axonal Charcot-Marie-Tooth disease (CMT). Missense variants in the catalytic domain of YARS1 were previously linked to dominant intermediate CMT type C (DI-CMTC). Here, we report a patient with a missense variant of unknown significance predicted to modify residue 308 in the anticodon binding domain of YARS1 (p.Asp308Tyr). Interestingly, p.Asp308Tyr is associated with proximal-predominant motor neuropathy, which has not been reported in patients with pathogenic YARS1 variants. We demonstrate that this allele causes a loss-of-function effect in yeast complementation assays when modeled in YARS1 and the yeast ortholog TYS1; structural modeling of this variant further supports a loss-of-function effect. Taken together, this study raises the possibility that certain YARS1 variants cause proximal-prominent motor neuropathy and indicates that patients with this phenotype should be screened for genetic lesions in YARS1.

Biallelic variants in WARS1 cause a highly variable neurodevelopmental syndrome and implicate a critical exon for normal auditory function

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes for faithful assignment of amino acids to their cognate tRNA. Variants in ARS genes are frequently associated with clinically heterogeneous phenotypes in humans and follow both autosomal dominant or recessive inheritance patterns in many instances. Variants in tryptophanyl-tRNA synthetase 1 (WARS1) cause autosomal dominantly inherited distal hereditary motor neuropathy and Charcot-Marie-Tooth disease. Presently, only one family with biallelic WARS1 variants has been described. We present three affected individuals from two families with biallelic variants (p.Met1? and p.(Asp419Asn)) in WARS1, showing varying severities of developmental delay and intellectual disability. Hearing impairment and microcephaly, as well as abnormalities of the brain, skeletal system, movement/gait, and behavior were variable features. Phenotyping of knocked down wars-1 in a C. elegans model showed depletion is associated with defects in germ cell development. A wars1 knockout vertebrate model recapitulates the human clinical phenotypes, confirms variant pathogenicity and uncovers evidence implicating the p.Met1? variant as potentially impacting an exon critical for normal hearing. Together, our findings provide consolidating evidence for biallelic disruption of WARS1 as causal for an autosomal recessive neurodevelopmental syndrome and present a vertebrate model that recapitulates key phenotypes observed in patients. This article is protected by copyright. All rights reserved.

Peripheral Myelin Protein 22 Gene Mutations in Charcot-Marie-Tooth Disease Type 1E Patients

Duplication and deletion of the peripheral myelin protein 22 (PMP22) gene cause Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP), respectively, while point mutations or small insertions and deletions (indels) usually cause CMT type 1E (CMT1E) or HNPP. This study was performed to identify PMP22 mutations and to analyze the genotype−phenotype correlation in Korean CMT families. By the application of whole-exome sequencing (WES) and targeted gene panel sequencing (TS), we identified 14 pathogenic or likely pathogenic PMP22 mutations in 21 families out of 850 CMT families who were negative for 17p12 (PMP22) duplication. Most mutations were located in the well-conserved transmembrane domains. Of these, eight mutations were not reported in other populations. High frequencies of de novo mutations were observed, and the mutation sites of c.68C>G and c.215C>T were suggested as the mutational hotspots. Affected individuals showed an early onset-severe phenotype and late onset-mild phenotype, and more than 40% of the CMT1E patients showed hearing loss. Physical and electrophysiological symptoms of the CMT1E patients were more severely damaged than those of CMT1A while similar to CMT1B caused by MPZ mutations. Our results will be useful for the reference data of Korean CMT1E and the molecular diagnosis of CMT1 with or without hearing loss.

The Antiepileptic Valproic Acid Ameliorates Charcot-Marie-Tooth 2W (CMT2W) Disease-Associated HARS1 Mutation-Induced Inhibition of Neuronal Cell Morphological Differentiation Through c-Jun N-terminal Kinase

Hereditary peripheral neuropathies called Charcot-Marie-Tooth (CMT) disease affect the sensory nerves as well as motor neurons. CMT diseases are composed of a heterogeneous group of diseases. They are characterized by symptoms such as muscle weakness and wasting. Type 2 CMT (CMT2) disease is a neuropathy with blunted or disrupted neuronal morphological differentiation phenotypes including process formation of peripheral neuronal axons. In the early stages of CMT2, demyelination that occurs in Schwann cells (glial cells) is rarely observed. CMT2W is an autosomal-dominant disease and is responsible for the gene encoding histidyl-tRNA synthetase 1 (HARS1), which is a family molecule of cytoplasmic aminoacyl-tRNA synthetases and functions by ligating histidine to its cognate tRNA. Despite increasing knowledge of the relationship of mutations on responsible genes with diseases, it still remains unclear how each mutation affects neuronal differentiation. Here we show that in neuronal N1E-115 cells, a severe Asp364-to-Tyr (D364Y) mutation of HARS1 leads to formation of small aggregates of HARS1 proteins; in contrast, wild type proteins are distributed throughout cell bodies. Expression of D364Y mutant proteins inhibited process formation whereas expression of wild type proteins possessed the normal differentiation ability to grow processes. Pretreatment with the antiepileptic valproic acid recovered inhibition of process formation by D364Y mutant proteins through the c-Jun N-terminal kinase signaling pathway. Taken together, these results indicate that the D364Y mutation of HARS1 causes HARS1 proteins to form small aggregates, inhibiting process growth, and that these effects are recovered by valproic acid. This could be a potential therapeutic drug for CMT2W at the cellular levels.