Ethylmalonic Encephalopathy Research Articles

ETHE1 dampens colorectal cancer angiogenesis by promoting TC45 Dephosphorylation of STAT3 to inhibit VEGF-A expression

Angiogenesis is critical for colorectal cancer (CRC) progression, but its mechanisms remain unclear. Here, we reveal that ethylmalonic encephalopathy protein 1 (ETHE1), an essential enzyme in hydrogen sulfide catabolism, inhibits VEGF-A expression and tumor angiogenesis in vitro and in vivo. Moreover, we find that this biological function of ETHE1 depends on the STAT3/VEGF-A pathway. Further investigation demonstrates that ETHE1 promotes the interaction between T cell protein tyrosine phosphatase (TC45) and STAT3, resulting in decreased STAT3 phosphorylation and inhibition of the STAT3 signaling pathway. In clinical samples, we find that ETHE1 is downregulated in CRC and positively correlates with survival outcomes of CRC patients. Meanwhile, the negative correlation of ETHE1 and VEGF-A expression is verified in CRC specimens, and the patients with low ETHE1 and high VEGF-A expression exhibits poorer prognosis. Collectively, our study identifies ETHE1 as a novel regulator of tumor angiogenesis, implying its potential as a prognostic biomarker and promising antiangiogenic target for CRC patients.

Curcumin reduces myocardial ischemia-reperfusion injury, by increasing endogenous H2S levels and further modulating m6A.

Our previous research shows that Curcumin (CUR) attenuates myocardial ischemia-reperfusion injury (MIRI) by reducing intracellular total RNA m6A levels. However, the mechanism remains unknown. For ischemia-reperfusion (IR), H9c2 cells were cultured for 6h in serum-free low-glycemic (1g/L) medium and a gas environment without oxygen, and then cultured for 6h in high-glycemic (4.5g/L) medium supplemented with 10% FBS and a 21% oxygen environment. The effects of different concentrations of CUR (5, 10, and 20 µM) treatments on signaling molecules in conventionally cultured and IR-treated H9c2 cells were examined. CUR treatment significantly up-regulated the H2S levels, and the mRNA and protein expression of cystathionine γ-lyase (CSE), and down-regulated the mRNAs and proteins levels of thiosulfate sulfurtransferase (TST) and ethylmalonic encephalopathy 1 (ETHE1) in H9c2 cells conventionally cultured and subjected to IR. Exogenous H2S supply (NaHS and GYY4137) significantly reduced intracellular total RNA m6A levels, and the expression of RNA m6A "writers" METTL3 and METTL14, and increased the expression of RNA m6A "eraser" FTO in H9c2 cells conventionally cultured and subjected to IR. CSE knockdown counteracted the inhibitory effect of CUR treatment on ROS production, promotion on cell viability, and inhibition on apoptosis of H9c2 cells subjected to IR. CUR attenuates MIRI by regulating the expression of H2S level-regulating enzymes and increasing the endogenous H2S levels. Increased H2S levels could regulate the m6A-related proteins expression and intracellular total RNA m6A levels.

Result of a Pilot External Quality Assessment Scheme for Clinical Diagnosis of Inherited Metabolic Disorders in China.

We aimed to evaluate the diagnostic capabilities of Chinese laboratories for inherited metabolic disorders (IMDs) using gas chromatography-mass spectrometry (GC-MS) on urine samples. Meanwhile, based on the result of the pilot external quality assessment (EQA) scheme, we hope to establish a standardized and reliable procedure for future EQA practice. We recruited laboratories that participated in the EQA of quantitative analysis of urinary organic acids with GC-MS before joining the surveys. In each survey, a set of five real urine samples was distributed to each participant. The participants should analyze the sample by GC-MS and report the "analytical result", "the most likely diagnosis", and "recommendation for further tests" to the NCCL before the deadline. A total of 21 laboratories participated in the scheme. The pass rates were 94.4% in 2020 and 89.5% in 2021. For all eight IMDs tested, the analytical proficiency rates ranged from 84.7% - 100%, and the interpretational performance rate ranged from 88.2% - 97.0%. The performance on hyperphenylalaninemia (HPA), 3-methylcrotonyl-CoA carboxylase deficiency (MCCD), and ethylmalonic encephalopathy (EE) samples were not satisfactory. In general, the participants of this pilot EQA scheme are equipped with the basic capability for qualitative organic acid analysis and interpretation of the results. Limited by the small size of laboratories and samples involved, this activity could not fully reflect the state of clinical practice of Chinese laboratories. NCCL will improve the EQA scheme and implement more EQA activities in the future.

ETHE1 Accelerates Triple-Negative Breast Cancer Metastasis by Activating GCN2/eIF2α/ATF4 Signaling.

Triple-negative breast cancer (TNBC) is the most fatal subtype of breast cancer; however, effective treatment strategies for TNBC are lacking. Therefore, it is important to explore the mechanism of TNBC metastasis and identify its therapeutic targets. Dysregulation of ETHE1 leads to ethylmalonic encephalopathy in humans; however, the role of ETHE1 in TNBC remains elusive. Stable cell lines with ETHE1 overexpression or knockdown were constructed to explore the biological functions of ETHE1 during TNBC progression in vitro and in vivo. Mass spectrometry was used to analyze the molecular mechanism through which ETHE1 functions in TNBC progression. ETHE1 had no impact on TNBC cell proliferation and xenograft tumor growth but promoted TNBC cell migration and invasion in vitro and lung metastasis in vivo. The effect of ETHE1 on TNBC cell migratory potential was independent of its enzymatic activity. Mechanistic investigations revealed that ETHE1 interacted with eIF2α and enhanced its phosphorylation by promoting the interaction between eIF2α and GCN2. Phosphorylated eIF2α in turn upregulated the expression of ATF4, a transcriptional activator of genes involved in cell migration and tumor metastasis. Notably, inhibition of eIF2α phosphorylation through ISRIB or ATF4 knockdown partially abolished the tumor-promoting effect of ETHE1 overexpression. ETHE1 has a functional and mechanistic role in TNBC metastasis and offers a new therapeutic strategy for targeting ETHE1-propelled TNBC using ISRIB.

Disruption of Bioenergetics in the Intestine of Wistar Rats Caused by Hydrogen Sulfide and Thiosulfate: A Potential Mechanism of Chronic Hemorrhagic Diarrhea in Ethylmalonic Encephalopathy.

Ethylmalonic encephalopathy (EE) is a severe inherited metabolic disorder that causes tissue accumulation of hydrogen sulfide (sulfide) and thiosulfate in patients. Although symptoms are predominantly neurological, chronic hemorrhagic diarrhea associated with intestinal mucosa abnormalities is also commonly observed. Considering that the pathophysiology of intestinal alterations in EE is virtually unknown and that sulfide and thiosulfate are highly reactive molecules, the effects of these metabolites were investigated on bioenergetic production and transfer in the intestine of rats. We observed that sulfide reduced NADH- and FADH2-linked mitochondrial respiration in the intestine, which was avoided by reduced glutathione (GSH) but not by melatonin. Thiosulfate did not change respiration. Moreover, both metabolites markedly reduced the activity of total, cytosolic and mitochondrial isoforms of creatine kinase (CK) in rat intestine. Noteworthy, the addition of GSH but not melatonin, apocynin, and Trolox (hydrosoluble vitamin E) prevented the change in the activities of total CK and its isoforms caused by sulfide and thiosulfate, suggesting a direct protein modification on CK structure by these metabolites. Sulfide further increased thiol content in the intestine, suggesting a modulation in the redox state of these groups. Finally, sulfide and thiosulfate decreased the viability of Caco-2 intestinal cells. Our data suggest that bioenergetic impairment caused by sulfide and thiosulfate is a mechanism involved in the gastrointestinal abnormalities found in EE.

Ethylmalonic Encephalopathy: a literature review and two new cases of mild phenotype.

Ethylmalonic encephalopathy (EE) is a rare intoxication-type metabolic disorder with multisystem involvement. It is caused by mutations in ETHE1, which encodes the ETHE1 enzyme in the mitochondrial matrix that plays a key role in hydrogen sulfide (H2S) detoxification acting as a sulphur dioxygenase. This review focuses on the clinical, metabolic, genetic and neuroradiological features of 70 reported cases, including two new cases. The common manifestations of EE are psychomotor regression, hypotonia, developmental delay, petechia, pyramidal signs, chronic diarrhoea, orthostatic acrocyanosis and failure to thrive, respectively. A significant difference was found in EMA and C4 levels (p=0.003, p=0.0236)between classical and mild phenotypes. Urinary EMA, C4 and C5 levels were found to exhibit normal values in milder cases during attack-free periods. The most common ETHE1 gene homozygous state mutations were (p.R163Q) (c.488G>A), exon 4 deletion, (p.R163W)(c.487C>T), (p.Glu44ValfsTer62)(c.131_132delAG) and (p.M1I)(c.3G>T) mutations, respectively. Fifty-two patients underwent cranial MRI. Basal ganglia signal alterations were detected in 42 cases. Of the 70 cases, eight had a mild phenotype and slow neurological progression with low levels of ethylmalonic acid (EMA) and C4 acylcarnitine. The current age of alive patients in the published articles with mild phenotype was significantly higher than the classical phenotype. (p=0.002). Reducing the accumulation and inducing detoxification of sulfide is the main long-term treatment strategy for EE, including metronidazole, N-acetylcysteine (NAC), dietary modification, liver transplantation and continuous renal replacement therapy (CRRT). Measuring EMA and C4 acylcarnitine during metabolic attacks is critical to diagnosing EE, allowing for early treatment initiation to prevent further encephalopathic crises. Experience with liver transplantation, diet and CRRT, is currently limited. An early multidisciplinary approach with combination therapies is vital to prevent irreversible neurological damage.

An atypically mild case of ethylmalonic encephalopathy with pathogenic ETHE1 variant

Ethylmalonic encephalopathy (EE) is a rare, severe, autosomal recessive condition caused by pathogenic variants in ETHE1 leading to progressive encephalopathy, hypotonia evolving to dystonia, petechiae, orthostatic acrocyanosis, diarrhea, and elevated ethylmalonic acid in urine. In this case report, we describe a patient with only mild speech and gross motor delays, subtle biochemical abnormalities, and normal brain imaging found to be homozygous for a pathogenic ETHE1 variant (c.586G>A) via whole exome sequencing. This case highlights the clinical heterogeneity of ETHE1 mutations and the utility of whole-exome sequencing in diagnosing mild cases of EE.

Depleted uranium causes renal mitochondrial dysfunction through the ETHE1/Nrf2 pathway

The kidney is the main organ affected by acute depleted uranium (DU) toxicity. The mechanism of nephrotoxicity induced by DU is complex and needs to be further explored. This study aimed to elucidate the function of mitochondrial dysfunction in nephrotoxicity generated by DU and confirm the latent mechanism. We verified that DU (2.5–10 mg/kg) caused mitochondrial dysfunction in male rat kidneys and decreased ATP content and the mitochondrial membrane potential. In addition, melatonin (20 mg/kg), as an antioxidant, alleviated DU-induced oxidative stress and mitochondrial dysfunction in male rats, further reducing kidney damage caused by DU. These results indicate that mitochondrial dysfunction plays a vital role in DU nephrotoxicity. When ethylmalonic encephalopathy 1 (ETHE1) was knocked down, DU-induced oxidative stress and mitochondrial dysfunction were increased, and renal injury was aggravated. When exogenous ETHE1 protein was applied to renal cells, the opposite changes were observed. We also found that ETHE1 knockdown increased the expression of NF-E2-related factor 2 (Nrf2), a vital oxidative stress regulator, and its downstream molecules heme oxygenase-1 (HO-1) and NADPH quinone oxidoreductase 1 (NQO1). Nrf2 knockout also aggravated DU-induced oxidative stress, mitochondrial dysfunction, and kidney damage. In conclusion, DU causes oxidative stress and antioxidant defense imbalance in renal cells through the ETHE1/Nrf2 pathway, further causing mitochondrial dysfunction and ultimately leading to nephrotoxicity.

P036: Atypically mild ethylmalonic encephalopathy expands phenotypic spectrum

P036: Atypically mild ethylmalonic encephalopathy expands phenotypic spectrum

Hydrogen Sulfide Metabolizing Enzymes in the Intestinal Mucosa in Pediatric and Adult Inflammatory Bowel Disease.

Hydrogen sulfide (H2S) is a toxic gas that has important regulatory functions. In the colon, H2S can be produced and detoxified endogenously. Both too little and too much H2S exposure are associated with inflammatory bowel disease (IBD), a chronic intestinal disease mainly classified as Crohn's disease (CD) and ulcerative colitis (UC). As the pathogenesis of IBD remains elusive, this study's aim was to investigate potential differences in the expression of H2S-metabolizing enzymes in normal aging and IBD. Intestinal mucosal biopsies of 25 adults and 22 children with IBD along with those of 26 healthy controls were stained immunohistochemically for cystathionine-γ-lyase (CSE), 3-mercapto-sulfurtransferase (3-MST), ethylmalonic encephalopathy 1 protein (ETHE1), sulfide:quinone oxidoreductase (SQOR) and thiosulfate sulfurtransferase (TST). Expression levels were calculated by multiplication of the staining intensity and percentage of positively stained cells. Healthy adults showed an overall trend towards lower expression of H2S-metabolizing enzymes than healthy children. Adults with IBD also tended to have lower expression compared to controls. A similar trend was seen in the enzyme expression of children with IBD compared to controls. These results indicate an age-related decrease in the expression of H2S-metabolizing enzymes and a dysfunctional H2S metabolism in IBD, which was less pronounced in children.

Human ultrarare genetic disorders of sulfur metabolism demonstrate redundancies in H2S homeostasis

Regulation of H2S homeostasis in humans is poorly understood. Therefore, we assessed the importance of individual enzymes in synthesis and catabolism of H2S by studying patients with respective genetic defects. We analyzed sulfur compounds (including bioavailable sulfide) in 37 untreated or insufficiently treated patients with seven ultrarare enzyme deficiencies and compared them to 63 controls. Surprisingly, we observed that patients with severe deficiency in cystathionine β-synthase (CBS) or cystathionine γ-lyase (CSE) - the enzymes primarily responsible for H2S synthesis - exhibited increased and normal levels of bioavailable sulfide, respectively. However, an approximately 21-fold increase of urinary homolanthionine in CBS deficiency strongly suggests that lacking CBS activity is compensated for by an increase in CSE-dependent H2S synthesis from accumulating homocysteine, which suggests a control of H2S homeostasis in vivo. In deficiency of sulfide:quinone oxidoreductase - the first enzyme in mitochondrial H2S oxidation - we found normal H2S concentrations in a symptomatic patient and his asymptomatic sibling, and elevated levels in an asymptomatic sibling, challenging the requirement for this enzyme in catabolizing H2S under physiological conditions. Patients with ethylmalonic encephalopathy and sulfite oxidase/molybdenum cofactor deficiencies exhibited massive accumulation of thiosulfate and sulfite with formation of large amounts of S-sulfocysteine and S-sulfohomocysteine, increased renal losses of sulfur compounds and concomitant strong reduction in plasma total cysteine. Our results demonstrate the value of a comprehensive assessment of sulfur compounds in severe disorders of homocysteine/cysteine metabolism and provide evidence for redundancy and compensatory mechanisms in the maintenance of H2S homeostasis.

Sequential Accumulation of ‘Driver’ Pathway Mutations Induces the Upregulation of Hydrogen-Sulfide-Producing Enzymes in Human Colonic Epithelial Cell Organoids

Recently, a CRISPR-Cas9 genome-editing system was developed with introduced sequential ‘driver’ mutations in the WNT, MAPK, TGF-β, TP53 and PI3K pathways into organoids derived from normal human intestinal epithelial cells. Prior studies have demonstrated that isogenic organoids harboring mutations in the tumor suppressor genes APC, SMAD4 and TP53, as well as the oncogene KRAS, assumed more proliferative and invasive properties in vitro and in vivo. A separate body of studies implicates the role of various hydrogen sulfide (H2S)-producing enzymes in the pathogenesis of colon cancer. The current study was designed to determine if the sequential mutations in the above pathway affect the expression of various H2S producing enzymes. Western blotting was used to detect the expression of the H2S-producing enzymes cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST), as well as several key enzymes involved in H2S degradation such as thiosulfate sulfurtransferase/rhodanese (TST), ethylmalonic encephalopathy 1 protein/persulfide dioxygenase (ETHE1) and sulfide-quinone oxidoreductase (SQR). H2S levels were detected by live-cell imaging using a fluorescent H2S probe. Bioenergetic parameters were assessed by Extracellular Flux Analysis; markers of epithelial-mesenchymal transition (EMT) were assessed by Western blotting. The results show that the consecutive mutations produced gradual upregulations in CBS expression—in particular in its truncated (45 kDa) form—as well as in CSE and 3-MST expression. In more advanced organoids, when the upregulation of H2S-producing enzymes coincided with the downregulation of the H2S-degrading enzyme SQR, increased H2S generation was also detected. This effect coincided with the upregulation of cellular bioenergetics (mitochondrial respiration and/or glycolysis) and an upregulation of the Wnt/β-catenin pathway, a key effector of EMT. Thus sequential mutations in colon epithelial cells according to the Vogelstein sequence are associated with a gradual upregulation of multiple H2S generating pathways, which, in turn, translates into functional changes in cellular bioenergetics and dedifferentiation, producing more aggressive and more invasive colon cancer phenotypes.

Ethylmalonic encephalopathy masquerading as meningococcemia.

Ethylmalonic encephalopathy (MIM #602473) is a rare autosomal recessive metabolic condition caused by biallelic variants in ETHE1 (MIM #608451), characterized by global developmental delay, infantile hypotonia, seizures, and microvascular damage. The microvascular changes result in a pattern of relapsing spontaneous diffuse petechiae and purpura, positional acrocyanosis, and pedal edema, hemorrhagic suffusions of mucous membranes, and chronic diarrhea. Here, we describe an instructive case in which ethylmalonic encephalopathy masqueraded as meningococcal septicemia and shock. Ultrarapid whole-genome testing (time to result 60 h) and prompt biochemical analysis facilitated accurate diagnosis and counseling with rapid implementation of precision treatment for the metabolic crisis related to this condition. This case provides a timely reminder to consider rare genetic diagnoses when atypical features of more common conditions are present, with an early referral to ensure prompt biochemical and genomic diagnosis.

Case Series of Ethylmalonic Encephalopathy from Southern India.

Ethylmalonic encephalopathy is a rare neurometabolic disorder with central nervous system involvement and vasculopathy. It is presented in infancy with developmental delay, acrocyanosis, petechiae, chronic diarrhea, and early death. This was a retrospective study of confirmed cases of ethylmalonic aciduria from a tertiary care hospital over a period of 5 years from January 2015 to December 2020. Case details including analysis of clinical history, investigations, and outcomes are presented. Of six cases, male-to-female ratio was 4:2. Mean age of presentation was 35.5 months (range: 14-83 months). Consanguinity, global developmental delay, failure to thrive, skin rashes, microcephaly, hypotonia, and exaggerated deep tendon reflexes were observed in all cases. Chronic diarrhea was presented in five cases. The serum levels of C4 carnitine and urinary levels of ethylmalonic acid were increased in all cases. Magnetic resonance imaging (MRI) of the brain showed heterogenous bilateral symmetrical changes in the basal ganglia in five cases, and in one case, MRI could not be done. Genetic testing in two cases showed a homozygous variant in ETHE1 gene. Four children died, while the other two cases showed a decreased in recurrent encephalopathies and diarrhea after starting metronidazole. All children had global developmental delay, failure to thrive, skin rashes, central hypotonia, increased C4 carnitine levels in the serum, and increased ethylmalonic acid in the urine. Chronic diarrhea, acrocyanosis, and basal ganglia change in the MRI of the brain also give important clues for diagnosis. Metronidazole is useful in preventing recurrent episodes of encephalopathy.

Ethylmalonic Encephalopathy 1 Protein Is Increased in Colorectal Adenocarcinoma.

Ethylmalonic encephalopathy 1 protein (ETHE1) plays an important role in sulfide catabolism and polysulfide formation. As sulfides and polysulfides have recently been identified as playing important roles in cancer, we hypothesized that ETHE1 expression would be increased in colon cancer. We used tissue microarray analysis to compare ETHE1 expression in benign colonic epithelium compared to colonic adenocarcinoma. In total, 26 benign colonic epithelial samples were compared to 122 cases of colonic adenocarcinomas. Compared to benign colonic epithelium, ETHE1 expression was significantly increased (~two-fold) in colonic adenocarcinoma. Additionally, this expression increased with increasing colon cancer tumor grades. ETHE1 expression is increased in colon cancer compared to benign colonic epithelium. These data, combined with previous studies, suggest that ETHE1 may contribute to colon carcinogenesis by promoting tumor cell bioenergetics and polysulfide formation.

Ethylmalonic encephalopathy and liver transplantation: long-term outcome of the first treated patient

BackgroundEthylmalonic encephalopathy (EE) is a severe intoxication-type metabolic disorder with multisystem clinical features and leading to early death. In 2014, based on the promising results obtained by liver-targeted gene therapy in Ethe1−/− mouse model, we successfully attempted liver transplantation in a 9-month-old EE girl. Here we report her long-term follow-up, lasting over 6 years, with a comprehensive evaluation of clinical, instrumental and biochemical assessments.ResultsNeurological signs initially reverted, with a clinical stabilization during the entire follow-up course. Accordingly, gross motor functions improved and then stabilized. Psychomotor evaluations documented an increasing communicative intent, the acquisition of new social skills and the capability to carry out simple orders. Neurophysiological assessments, which included EEG, VEP/ERG and BAEPs, remained unchanged. Brain MRI also stabilized, showing no further lesions and cerebral atrophy improvement. Compared to pre-transplant assessments, urinary ethylmalonic acid strikingly reduced, and plasma thiosulphate fully normalized. The child maintained good clinical conditions and never experienced metabolic crises nor epileptic seizures.ConclusionsThe long-term follow-up of the first EE transplanted patient demonstrates that liver transplantation stabilizes, or even improves, disease course, therefore representing a potentially elective option especially in early-diagnosed patients, such as those detected by newborn screening, before irreversible neurological damage occurs.

Ethylmalonic acid impairs bioenergetics by disturbing succinate and glutamate oxidation and induces mitochondrial permeability transition pore opening in rat cerebellum.

Tissue accumulationand high urinary excretion of ethylmalonic acid (EMA) are found in ethylmalonic encephalopathy (EE), an inherited disorder associated with cerebral and cerebellar atrophy whose pathogenesis is poorly established. The in vitro and in vivo effects of EMA on bioenergetics and redox homeostasis were investigated in rat cerebellum. For the in vitro studies, cerebellum preparations were exposed to EMA, whereas intracerebellar injection of EMA was used for the in vivo evaluation. EMA reduced state 3 and uncoupled respiration in vitro in succinate-, glutamate-, and malate-supported mitochondria, whereas decreased state 4 respiration was observed using glutamate and malate. Furthermore, mitochondria permeabilization and succinate supplementation diminished the decrease in state 3 with succinate. EMA also inhibited the activity of KGDH, an enzyme necessary for glutamate oxidation, in a mixed manner and augmented mitochondrial efflux of α-ketoglutarate. ATP levels were markedly reduced by EMA, reflecting a severe bioenergetic disruption. Docking simulations also indicated interactions between EMA and KGDH and a competition with glutamate and succinate for their mitochondrial transporters. In vitro findings also showed that EMA decreased mitochondrial membrane potential and Ca2+ retention capacity, and induced swelling in the presence of Ca2+ , which were prevented by cyclosporine A and ADP and ruthenium red, indicating mitochondrial permeability transition (MPT). Moreover, EMA, at high concentrations, mildly increased ROS levels and altered antioxidant defenses in vitro and in vivo. Our data indicate that EMA-induced impairment of glutamate and succinate oxidation and MPT may contribute to the pathogenesis of the cerebellum abnormalities in EE.

Acute Strokelike Presentation and Long-term Evolution of Diffusion Restriction Pattern in Ethylmalonic Encephalopathy

Ethylmalonic encephalopathy is a rare autosomal recessive mitochondrial disorder caused by pathogenic biallelic variants in the ETHE1 gene. The phenotype of this disease has been attributed to deficiency in the mitochondrial sulfur dioxygenase leading to many downstream effects. Ethylmalonic encephalopathy classically presents with developmental regression, petechiae, acrocyanosis, and chronic diarrhea. The neurologic phenotype includes hypotonia, spastic diplegia, ataxia, and developmental delay. As more patients with this condition are described, the neurologic phenotype continues to expand. Although strokelike episodes or metabolic strokes have been studied in other mitochondrial disorders, they have not been thoroughly reported in this disorder. Herein, we describe 3 patients with ethylmalonic encephalopathy who presented clinically with strokelike episodes and strokelike abnormalities on brain magnetic resonance imaging in the setting of acute illness, and the long-term sequelae with evolution into cystic changes in one of these subjects.

Ethylmalonic encephalopathy ETHE1 p. D165H mutation alters the mitochondrial function in human skeletal muscle proteome

Ethylmalonic encephalopathy (EE) is a rare autosomal recessive inborn error of metabolism. To study the molecular effects of ETHE1 p. D165H mutation, we employed mass spectrometry-based mitochondrial proteome and phosphoproteome profiling in the human skeletal muscle. Eighty-six differentially altered proteins were identified, of which thirty-seven mitochondrial proteins were differentially expressed, and most of the proteins (37%) were down-regulated in the OXPHOS complex-IV. Also, nine phosphopeptides that correspond to eight mitochondrial proteins were significantly affected in EE patient. These altered proteins recognized are involved in several pathways and molecular functions, predominantly in oxidoreductase activity. This is the first study that has integrated proteome and phosphoproteome of skeletal muscle and identified multiple proteins associated in the pathogenesis of EE.

A founder mutation in the ETHE1 gene and ethylmalonic encephalopathy in the Omani population

Background: Ethylmalonic encephalopathy (EE) is a devastating early-onset inborn error of metabolism, and heterogenous disorders manifest as chronic diarrhea, petechial rash, and neurological manifestations. The mutation in the ETHE1 gene leads to hydrogen sulfide accumulation and eventually results in mucosal cell damage in the large intestines and vascular endothelial cells system. Case presentation: Here, we describe four patients from three different tribes in Oman, and the clinical data revealed that the four patients shared an early-onset phenotype and the neurological manifestations were variable. The biochemical markers, specifically the urine organic acid and hyperlactimic acidosis, supported and tailored the diagnosis. Molecular diagnosis was confirmed by full gene sequencing of the ETHE1 gene in the index case and followed by target variant testing for others. Interestingly, all four patients identified to harbor the same homozygous missense pathogenic variant (c.487c > t) in the ETHE1 gene, and their parents were all heterozygous. These findings indicate that we probably have a founder variant associated with EE in our area. Conclusion: These findings are of great importance for diagnosis and surveillance for Omani families with EE. Given the relatively high number and frequency of genetic diseases in the region and the limited resources, screening for these founder mutations should provide a rapid and cost-effective tool for molecular diagnosis. Additionally, these findings should help in designing appropriate measures for carrier screening measures at the regional level.