Three novel mutations of ARG1 identified in Chinese patients with argininemia detected by newborn screening

Two Japanese siblings with arginase-1 deficiency identified using a novel frameshift mutation of ARG1 (p.Lys41Thrfs∗2)

We described two Japanese siblings with arginase-1 (ARG1) deficiency. A 10-year-old girl (the proband and elder sister) was referred to our hospital complaining about her short stature. We diagnosed her with ARG1 deficiency, possibly with elevated levels of blood ammonia and plasma arginine. Her younger sister was found to have spastic paraparesis in her lower extremities and short stature at the age of 4 years. The younger sister also had high levels of plasma arginine, instead of normal levels of blood ammonia. Interestingly, they also prefer to avoid protein-rich foods such as meat, soybeans, cow milk, and dairy products. Genetic testing identified compound heterozygous mutations (c.121_122insCTT [p.Lys41Thrfs^∗2] and c.298G>A [p.Asp100Asn]) in the ARG1 gene. The ARG1 mutation of p.Lys41Thrfs^∗2 is a novel pathogenic mutation according to open databases and literature.

Common Variants in the ARG1 Gene Contribute to the Risk of Dilated Cardiomyopathy in the Han Chinese Population

Background: Arginase I, encoded by the ARG1 gene, is an enzyme that catalyzes the conversion of arginine to ornithine in the urea cycle; mutations in this gene has recently been reported to be associated with dilated cardiomyopathy (DCM) in Pakistan. The present study aimed to investigate the relationship between ARG1 gene mutations and DCM in the Han Chinese population. Methods: A total of 488 DCM cases and 924 matched-healthy controls were recruited. All subjects were genotyped for 12 tag single nucleotide polymorphisms (SNPs) within the ARG1 gene. Genetic association studies, including SNP and haplotype analyses, were performed. Further analyses were conducted to examine the correlations between the associated SNPs and specific clinical characteristics. Results: Only the rs2781666 and rs2781667 loci in the ARG1 gene were found to be significantly associated with DCM compared to the healthy controls. The risk of DCM at both of these loci for T allele carriers was ∼1.42-fold higher than that for carriers of the alternative alleles. There were significant differences in end-diastolic interventricular septal diameter, end-diastolic left ventricular posterior wall diameter, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, and left ventricular ejection fraction among the genotype distributions of both SNPs. Furthermore, we found that the T alleles at the rs2781666 and rs2781667 loci were significantly associated with DCM in gender subgroups and the subgroup of patients <58 years of age. The haplotype T-T (rs2781666-rs2781667) also showed a significant association with DCM. Conclusion: Our results support the hypothesis that alleles and haplotypes of the ARG1 gene are significantly involved in the etiology of DCM in the Han Chinese population, but further research is necessary to elucidate the mechanism governing this association.

Aminoacidopathies: Prevalence, Etiology, Screening, and Treatment Options

Inborn errors of metabolism (IEMs) are a group of inherited metabolic disorders which are caused by mutations in the specific genes that lead to impaired proteins or enzymes production. Different metabolic pathways are perturbed due to the deficiency or lack of enzymes. To date, more than 500 IEMs have been reported with most of them being untreatable. However, fortunately 91 such disorders are potentially treatable, if diagnosed at an earlier stage of life. IEMs have been classified into different categories and one class of IEMs, characterized by the physiological disturbances of amino acids is called as aminoacidopathies. Out of 91 treatable IEM, thirteen disorders are amino acid related. Aminoacidopathies can be detected by chromatography and mass spectrometry based analytical techniques (e.g., HPLC, GC-MS, LC-MS/MS) for amino acid level changes, and through genetic assays (e.g., PCR, TaqMan Genotyping, DNA sequencing) at the mutation level in the corresponding genes. Hence, this review is focused to describe thirteen common aminoacidopathies namely: Phenylketonuria (PKU), Maple Syrup Urine Disease (MSUD), Homocystinuria/Methylene Tetrahydrofolate Reductase (MTHFR) deficiency, Tyrosinemia type II, Citrullinemia type I and type II, Argininosuccinic aciduria, Carbamoyl Phosphate Synthetase I (CPS) deficiency, Argininemia (arginase deficiency), Hyperornithinemia-Hyperammonemia-Homocitrullinuria (HHH) syndrome, N-Acetylglutamate Synthase (NAGS) deficiency, Ornithine Transcarbamylase (OTC) deficiency, and Pyruvate Dehydrogenase (PDH) complex deficiency. Furthermore, the etiology, prevalence and commonly used analytical techniques for screening of aminoacidopathies are briefly described. This information would be helpful to researchers and clinicians especially from developing countries to initiate newborn screening programs for aminoacidopathies.