[Leigh syndrome caused by the mitochondrial m.8993T>G mutation with hypocitrullinemia: a report of four cases and literature review]. / m.8993T>Gç›¸å ³Leighç»¼åˆå¾åˆå¹¶ä½Žç“œæ°¨é ¸è¡€ç—‡æ‚£å„¿4ä¾‹å¹¶æ–‡çŒ®å¤ä¹ .

OBJECTIVES: To explore early diagnostic biological markers for Leigh syndrome caused by the m.8993T>G mutation. METHODS: A retrospective analysis was performed on the clinical data of four children diagnosed with m.8993T>G mutation-related mitochondrial disease at the Children's Hospital of Chongqing Medical University from January 2014 to January 2024. Additionally, a literature review was conducted. RESULTS: All four children had plasma amino acid and acylcarnitine analyses that revealed decreased citrulline levels, and one child was initially identified through neonatal genetic metabolic disease screening. According to the literature review, there were 26 children with mitochondrial disease and hypocitrullinemia caused by the m.8993T>G mutation (including the four children in this study). Among these, 12 children exhibited clinical phenotypes of Leigh syndrome or Leigh-like syndrome, while 18 children were identified with hypocitrullinemia and/or elevated levels of 3-hydroxyisovalerylcarnitine (C5-OH) during neonatal genetic metabolic disease screening. CONCLUSIONS: Hypocitrullinemia may serve as a potential biomarker for the early diagnosis of m.8993T>G mutation-associated Leigh syndrome, detectable as early as during neonatal genetic metabolic disease screening.

Cannabidiol ameliorates mitochondrial disease via PPARγ activation in preclinical models.

Mutations in mitochondrial energy-producing genes lead to a heterogeneous group of untreatable disorders known as primary mitochondrial diseases (MD). Leigh syndrome (LS) is the most common pediatric MD and is characterized by progressive neuromuscular affectation and premature death. Here, we show that daily cannabidiol (CBD) administration significantly extends lifespan and ameliorates pathology in two LS mouse models, and improves cellular function in fibroblasts from LS patients. CBD delays motor decline and neurodegenerative signs, improves social deficits and breathing abnormalities, decreases thermally induced seizures, and improves neuropathology in affected brain regions. Mechanistically, we identify peroxisome proliferator-activated receptor gamma (PPARγ) as a key nuclear receptor mediating CBD's beneficial effects, while also providing proof of dysregulated PPARγ expression and activity as a common feature in both mouse neurons and fibroblasts from LS patients. Taken together, our results provide the first evidence for CBD as a potential treatment for LS.

A Method for Producing Induced Pluripotent Stem Cell-Derived Cardiomyocytes from Leigh Syndrome Patients for Its Application in Disease Modeling and Drug Validation.

Leigh syndrome (LS), a complex multisystemic disorder, poses significant challenges in genetic medicine due to its intricate pathogenesis and wide-ranging clinical manifestations. Notably, these arise from mutations in either nuclear genetic DNA or mitochondrial DNA, affecting ATP production and resulting in diverse clinical outcomes. The unpredictable trajectory of this disease, ranging from severe developmental delays to early mortality, underscores the need for improved therapeutic solutions. This research pivots toward the novel use of induced pluripotent stem cells (iPSCs) as a promising platform for understanding disease mechanisms and spearheading patient-specific drug discoveries. Given the past successes of iPSCs in delineating organ-specific disorders and the recent endorsement of human iPSC-derived cardiomyocytes (CMs) by the FDA for drug evaluation, our work seeks to bridge this innovation to Leigh syndrome research. We detail a methodological approach to generate iPSCs from LS patients and differentiate them into iPSCs-CMs. Using multi-electrode array (MEA) analyses, we evaluate the field potential of these cells, spotlighting the potential of hiPSC-CM in drug validation and disease modeling. This pioneering approach offers a glimpse into the future of patient-centric therapeutic interventions for Leigh/Leigh-like syndrome.

Phenotypic assessment of Cox10 variants and their implications for Leigh Syndrome.

OBJECTIVES: Cox10 is an enzyme required for the activity of cytochrome c oxidase. Humans who lack at least one functional copy of Cox10 have a form of Leigh Syndrome, a genetic disease that is usually fatal in infancy. As more human genomes are sequenced, new alleles are being discovered; whether or not these alleles encode functional proteins remains unclear. Thus, we set out to measure the phenotypes of many human Cox10 variants by expressing them in yeast cells. RESULTS: We successfully expressed the reference sequence and 25 variants of human Cox10 in yeast. We quantitated the ability of these variants to support growth on nonfermentable media and directly measured cytochrome c oxidase activity. 11 of these Cox10 variants supported approximately half or more the cytochrome c oxidase activity compared to the reference sequence. All of the strains containing those 11 variants also grew robustly using a nonfermentable carbon source. Cells expressing the other variants showed low cytochrome c oxidase activity and failed to grow on nonfermentable media.

IARS2 mutations lead to Leigh syndrome with a combined oxidative phosphorylation deficiency.

BACKGROUND: Leigh syndrome (LS) is a common mitochondrial disease caused by mutations in both mitochondrial and nuclear genes. Isoleucyl-tRNA synthetase 2 (IARS2) encodes mitochondrial isoleucine-tRNA synthetase, and variants in IARS2 have been reported to cause LS. However, the pathogenic mechanism of IARS2 variants is still unclear. METHODS: Two unrelated patients, a 4-year-old boy and a 5-year-old boy diagnosed with LS, were recruited, and detailed clinical data were collected. The DNA of the patients and their parents was isolated from the peripheral blood for the identification of pathogenic variants using next-generation sequencing and Sanger sequencing. The ClustalW program, allele frequency analysis databases (gnomAD and ExAc), and pathogenicity prediction databases (Clinvar, Mutation Taster and PolyPhen2) were used to predict the conservation and pathogenicity of the variants. The gene expression level, oxygen consumption rate (OCR), respiratory chain complex activity, cellular adenosine triphosphate (ATP) production, mitochondrial membrane potential (MMP) and mitochondrial reactive oxygen species (ROS) levels were measured in patient-derived lymphocytes and IARS2-knockdown HEK293T cells to evaluate the pathogenicity of the variants. RESULTS: We reported 2 unrelated Chinese patients manifested with LS who carried biallelic IARS2 variants (c.1_390del and c.2450G > A from a 4-year-old boy, and c.2090G > A and c.2122G > A from a 5-year-old boy), of which c.1_390del and c.2090G > A were novel. Functional studies revealed that the patient-derived lymphocytes carrying c.1_390del and c.2450G > A variants exhibited impaired mitochondrial function due to severe mitochondrial complexes I and III deficiencies, which was also found in IARS2-knockdown HEK293T cells. The compensatory experiments in vitro cell models confirmed the pathogenicity of IARS2 variants since re-expression of wild-type IARS2 rather than mutant IARS2 could rescue complexes I and III deficiency, oxygen consumption, and cellular ATP content in IARS2 knockdown cells. CONCLUSION: Our results not only expand the gene mutation spectrum of LS, but also reveal for the first time the pathogenic mechanism of IARS2 variants due to a combined deficiency of mitochondrial complexes I and III, which is helpful for the clinical diagnosis of IARS2 mutation-related diseases.

Primary cilia formation requires the Leigh syndrome-associated mitochondrial protein NDUFAF2.

Mitochondria-related neurodegenerative diseases have been implicated in the disruption of primary cilia function. Mutation in an intrinsic mitochondrial complex I component NDUFAF2 has been identified in Leigh syndrome, a severe inherited mitochondriopathy. Mutations in ARMC9, which encodes a basal body protein, cause Joubert syndrome, a ciliopathy with defects in the brain, kidney, and eye. Here, we report a mechanistic link between mitochondria metabolism and primary cilia signaling. We discovered that loss of NDUFAF2 caused both mitochondrial and ciliary defects in vitro and in vivo and identified NDUFAF2 as a binding partner for ARMC9. We also found that NDUFAF2 was both necessary and sufficient for cilia formation and that exogenous expression of NDUFAF2 rescued the ciliary and mitochondrial defects observed in cells from patients with known ARMC9 deficiency. NAD+ supplementation restored mitochondrial and ciliary dysfunction in ARMC9-deficient cells and zebrafish and ameliorated the ocular motility and motor deficits of a patient with ARMC9 deficiency. The present results provide a compelling mechanistic link, supported by evidence from human studies, between primary cilia and mitochondrial signaling. Importantly, our findings have significant implications for the development of therapeutic approaches targeting ciliopathies.

Cranial and spinal nerve enhancement in SURF1-associated Leigh syndrome.

A 23-month-old boy with poor growth, developmental delay, and hypotonia presented with acute onset of ataxia and fatigue. Magnetic resonance imaging (MRI) of the brain and spinal cord was performed as part of diagnostic work-up. MRI showed bilateral symmetrical lesions in basal ganglia, midbrain, and brainstem consistent with Leigh syndrome. Signal abnormalities were also present within the cervical cord, with enhancement of multiple cranial, spinal, and cauda equina nerve roots. Genetic testing confirmed compound heterozygosity for two pathogenic variants in SURF1 implicated in Leigh syndrome. Whilst nerve root enhancement has been described in other mitochondrial disorders, we believe this is the first published case of both cranial and spinal nerve root enhancement in Leigh syndrome.

Distinct Imaging Markers of Leigh's Disease Linked to SURF1 Mutation: A Pediatric Case Study.

BACKGROUND Leigh disease (LD) is a rare progressive mitochondrial neurodegenerative disorder characterized by subacute necrotizing encephalopathy and symmetrical spongiform lesions in the brain. Cytochrome C oxidase deficiencies due to SURF1 Cytochrome C Oxidase Assembly Factor (SURF1) gene mutations are seen only in 15% of LD cases. Consideration of these genetic mutations in young patients is crucial for early diagnosis, intervention, and further genetic counseling. Although only a few cases of the SURF1 mutation have been reported, there are anecdotal case reports describing imaging features. CASE REPORT We report a case of a 2-year-old boy with developmental delay, hypotonia, involuntary movements, shortness of breath, and reduced activity since age 6 months. On blood examination there was mildly elevated lactate levels and increased lactate to pyruvate ratio and cerebrospinal fluid lactate levels. Magnetic resonance imaging findings showed symmetrical lesions in the dentate nucleus, subthalamic nucleus, midbrain (substantia nigra, periaqueductal gray matter), posterolateral pons, and olivary nucleus of the medulla extending into the cervical spinal cord, with mild elevation of the lactate peak on magnetic resonance spectroscopy. CONCLUSIONS These findings prompted further genetic analysis, which indicated a mitochondrial type IV deficiency with the SURF1 gene defect, an intranuclear type 1 mutation (MC4DN1) (OMIM 220110). Treatment is usually supportive with vitamins supplementation and physiotherapy, and genetic counseling of the parents is mandatory.