[QARS1 gene related glutaminyl-tRNA synthetase deficiency syndrome: report of three cases and a review of literature].

Objective: To investigate the clinical characteristics, treatment and prognosis of QARS1 gene related glutaminyl-tRNA synthetase deficiency. Methods: To summarize and analyze the clinical manifestations, imaging, laboratory examination, genetic variant characteristics and treatment of three patients from the Fujian Medical University Affiliated Union Hospital, the 900th Hospital of People's Liberation Army, the First Medical Center of People's Liberation Army General Hsopital carrying compound heterozygous variations in QARS1 gene with a long-term follow-up in China. A literature search was conducted using Wanfang, Weipu, China National Knowledge Infrastructure (CNKI) and Pubmed databases with the keywords "QARS", "QARS1" and "glutaminyl-tRNA Synthetase"(up to December 2019). Results: Case 1, a female 53 days of age, was admitted to the Fujian Medical University Affiliated Union Hospital for treatment because of the complaint of repetitive seizures for one month after birth and fever for one day. The seizure occurred within the first 2 hours of life with multiple forms and often had a status as persisted from hours to days. The seizures were resistant to many anti-epilepsy drugs (AED) and ketogenic diet but later controlled by clonazepam. However, she died at the age of seven years. Case 2 (younger brother of case 1), a one-hour-old boy, was hospitalized because of seizures after birth for 1 hour. Intrauterine growth retardation was discovered during late-pregnancy. The boy presented seizures and microcephaly immediately after birth, and his epilepsy was pharmacoresisitant. Case 3, an 8-month-old girl, was admitted due to recurrent convulsions for nearly two months. The girl had mild developmental retardation and hypotonia after birth. The infantile spasm was observed at her age of 6 months and disappeared under treatment with Vitamin B6, vigabatrin combined with adreno-cortico-tropic-hormone and magnesium sulfate. However, the seizure pattern turned to tonic seizures later. She was seizures free now with clobazam and zonisamide treatment. All of them manifested as a syndrome composed of severe global developmental retardation, progressive microcephaly, hypotonia from the very beginning, mild hypoproteinemia and diffuse brain atrophy. Genetic studies revealed compound heterozygous variations of QARS1 gene which were not reported previously. A review of the literature reported a total of 22 patients from 18 unrelated families all over the world. Except for 5 cases without epilepsy,all the patients shared very similar clinical manifestations as classic pentalogy. The recommended effective treatment for epilepsy has not been reported yet. Conclusions: Glutaminyl-tRNA synthetase deficiency caused by QARS1 gene variations manifested as a clinical syndrome's pentalogy, characterized by microcephaly, cerebral atrophy, intractable early-onset epileptic encephalopathy, global developmental retardation and severe muscle hypotonia.

Aminoacyl-tRNA synthetase deficiencies in search of common themes.

PURPOSE: Pathogenic variations in genes encoding aminoacyl-tRNA synthetases (ARSs) are increasingly associated with human disease. Clinical features of autosomal recessive ARS deficiencies appear very diverse and without apparent logic. We searched for common clinical patterns to improve disease recognition, insight into pathophysiology, and clinical care. METHODS: Symptoms were analyzed in all patients with recessive ARS deficiencies reported in literature, supplemented with unreported patients evaluated in our hospital. RESULTS: In literature, we identified 107 patients with AARS, DARS, GARS, HARS, IARS, KARS, LARS, MARS, RARS, SARS, VARS, YARS, and QARS deficiencies. Common symptoms (defined as present in ≥4/13 ARS deficiencies) included abnormalities of the central nervous system and/or senses (13/13), failure to thrive, gastrointestinal symptoms, dysmaturity, liver disease, and facial dysmorphisms. Deep phenotyping of 5 additional patients with unreported compound heterozygous pathogenic variations in IARS, LARS, KARS, and QARS extended the common phenotype with lung disease, hypoalbuminemia, anemia, and renal tubulopathy. CONCLUSION: We propose a common clinical phenotype for recessive ARS deficiencies, resulting from insufficient aminoacylation activity to meet translational demand in specific organs or periods of life. Assuming residual ARS activity, adequate protein/amino acid supply seems essential instead of the traditional replacement of protein by glucose in patients with metabolic diseases.

Loss of Leucyl-tRNA synthetase b leads to ILFS1-like symptoms in zebrafish.

Leucyl-tRNA synthetase (LARS) is a kind of aminoacyl-tRNA synthetases (aaRSs), which is important for protein synthesis. Following the discovery of three clinical cases which carry LARS mutations, it has been designated as the infantile liver failure syndrome type 1 (ILFS1) gene. ILFS1 is a kind of infantile hepatopathy, which is difficult to diagnose and manage. As the mechanism underlying this disease is poorly understood and LARS is conserved among vertebrates, we obtained zebrafish larsbcq68 mutant via CRISPR/Cas9 technology to investigate the role of larsb in vivo. In mutant, the proliferation ability of liver was drastically decreased at later stages accompanied with severe DNA damage. Further studies demonstrated that the mTORC1 signaling was hyperactivated in larsbcq68 mutant. Inhibition of mTORC1 signaling pathway by Rapamycin or mTORC1 morpholino can partially rescue the liver failure of the mutants. These data revealed that larsb mutation caused ILFS1-like phenotype in zebrafish, and indicated this mutant may serve as a potential model for ILFS1. Furthermore, we demonstrated that rapamycin treatment can partially rescue the liver defect in mutants, thus providing a practicable therapeutic plan for ILFS1.

FARS2 deficiency; new cases, review of clinical, biochemical, and molecular spectra, and variants interpretation based on structural, functional, and evolutionary significance.

An increasing number of mitochondrial diseases are found to be caused by pathogenic variants in nuclear encoded mitochondrial aminoacyl-tRNA synthetases. FARS2 encodes mitochondrial phenylalanyl-tRNA synthetase (mtPheRS) which transfers phenylalanine to its cognate tRNA in mitochondria. Since the first case was reported in 2012, a total of 21 subjects with FARS2 deficiency have been reported to date with a spectrum of disease severity that falls between two phenotypes; early onset epileptic encephalopathy and a less severe phenotype characterized by spastic paraplegia. In this report, we present an additional 15 individuals from 12 families who are mostly Arabs homozygous for the pathogenic variant Y144C, which is associated with the more severe early onset phenotype. The total number of unique pathogenic FARS2 variants known to date is 21 including three different partial gene deletions reported in four individuals. Except for the large deletions, all variants but two (one in-frame deletion of one amino acid and one splice-site variant) are missense. All large deletions and the single splice-site variant are in trans with a missense variant. This suggests that complete loss of function may be incompatible with life. In this report, we also review structural, functional, and evolutionary significance of select FARS2 pathogenic variants reported here.

Compound heterozygosity for loss-of-function FARSB variants in a patient with classic features of recessive aminoacyl-tRNA synthetase-related disease.

Aminoacyl-tRNA synthetases (ARSs) are ubiquitously expressed enzymes that ligate amino acids onto tRNA molecules. Genes encoding ARSs have been implicated in phenotypically diverse dominant and recessive human diseases. The charging of tRNAPHE with phenylalanine is performed by a tetrameric enzyme that contains two alpha (FARSA) and two beta (FARSB) subunits. To date, mutations in the genes encoding these subunits (FARSA and FARSB) have not been implicated in any human disease. Here, we describe a patient with a severe, lethal, multisystem, developmental phenotype who was compound heterozygous for FARSB variants: p.Thr256Met and p.His496Lysfs*14. Expression studies using fibroblasts isolated from the proband revealed a severe depletion of both FARSB and FARSA protein levels. These data indicate that the FARSB variants destabilize total phenylalanyl-tRNA synthetase levels, thus causing a loss-of-function effect. Importantly, our patient shows strong phenotypic overlap with patients that have recessive diseases associated with other ARS loci; these observations strongly support the pathogenicity of the identified FARSB variants and are consistent with the essential function of phenylalanyl-tRNA synthetase in human cells. In sum, our clinical, genetic, and functional analyses revealed the first FARSB variants associated with a human disease phenotype and expand the locus heterogeneity of ARS-related human disease.

Case Report.

Glutaminyl-tRNA synthetase (QARS) deficiency has been described to be a cause of a neurodegenerative disorder associated with severe developmental delay, microcephaly, delayed myelination, and intractable epilepsy. The epilepsy is thought to be more severe than other tRNA synthetase disorders. Only a few cases have been reported in the literature and there is little information about response to different treatment options. The ketogenic diet is a high-fat, low-carbohydrate diet that is used in treatment resistant epilepsy of various etiologies. There are reports that the diet can also improve neuro-cognitive parameters. The authors report a case of a patient with glutaminyl-tRNA synthetase deficiency and treatment resistant seizures where there was a marked and early favorable response in terms of seizures, alertness and behavior to the ketogenic diet.

Identification of target genes and transcription factors implicated in translation-dependent retrograde signaling in Arabidopsis.

Changes in organellar gene expression (OGE) trigger retrograde signaling. The molecular dissection of OGE-dependent retrograde signaling based on analyses of mutants with altered OGE is complicated by compensatory responses that mask the primary signaling defect and by secondary effects that influence other retrograde signaling pathways. Therefore, to identify the earliest effects of altered OGE on nuclear transcript accumulation, we have induced OGE defects in adult plants by ethanol-dependent repression of PRORS1, which encodes a prolyl-tRNA synthetase located in chloroplasts and mitochondria. After 32h of PRORS1 repression, the translational capacity of chloroplasts was reduced, and this effect subsequently intensified, while basic photosynthetic parameters were still unchanged at 51h. Analysis of changes in whole-genome transcriptomes during exposure to ethanol revealed that induced PRORS1 silencing affects the expression of 1020 genes in all. Some of these encode photosynthesis-related proteins, including several down-regulated light-harvesting chlorophyll a/b binding (LHC) proteins. Interestingly, genes for presumptive endoplasmic reticulum proteins are transiently up-regulated. Furthermore, several NAC-domain-containing proteins are among the transcription factors regulated. Candidate cis-acting elements which may coordinate the transcriptional co-regulation of genes sets include both G-box variants and sequence motifs with no similarity to known plant cis-elements.