Pathogenic variants of IBA57 (OMIM ID: 615330) are usually associated with multiple mitochondrial dysfunction syndrome (MMDS) and hereditary spastic paraplegia type 74 (SPG74). Here, we present a novel compound heterozygous IBA57 mutation in a boy with severe global developmental delay, optic atrophy, spastic paraplegia, and focal epileptic seizures. The clinical data of a child diagnosed with MMDS were retrospectively collected. Video electroencephalogram (VEEG), cranial magnetic resonance imaging (MRI), and family whole-exome sequencing (WES) were performed. Suspected mutation sites were further confirmed using Sanger sequencing. The activities of mitochondrial respiratory chain complexes I-IV were determined in peripheral blood mononuclear cells. The phylogenetic conservation of the affected residues was assessed by multiple sequence alignment of IBA57 gene orthologs. Furthermore, we conducted a review of the relevant literature. Whole-exome sequencing identified compound heterozygous variants in the IBA57 gene: c.395_400dup (p.V132_Q133dup) and c.832delC (p.R278Afs*23), inherited from his phenotypically normal father and mother, respectively. Biochemical assays demonstrated selective reduction of complexes I and II activities, with normal complexes III and IV, consistent with impaired 4Fe-4S cluster maturation. Phylogenetic alignment revealed strict conservation of residues V132-Q133 and R278 across vertebrates. These variants had not been previously reported in domestic or international databases. According to the American College of Medical Genetics and Genomics (ACMG) guidelines, the former was classified as a variant of uncertain significance (PM4 + PM2), while the latter was classified as likely pathogenic (PVS1 + PM2). Diseases associated with IBA57 gene variants are autosomal recessive disorders with a broad clinical phenotypic spectrum. Early genetic testing and family screening are beneficial for the diagnosis, treatment, and prognosis of the disease.

Skeletal muscle is crucial for glucose metabolism, but diabetes impairs this function, leading to muscle atrophy. Although the mutation of BOLA Family Member 3 (BOLA3) resulted in disease Multiple Mitochondrial Dysfunctions Syndrome, the role of which in diabetic muscle atrophy is unclear. Firstly, datasets were downloaded and assessed from skeletal muscle tissue with diabetic individuals in GEO database and key genes were screened using weighted gene co-expression network analysis (WGCNA) and machine learning algorithms. Subsequently, external validation datasets were applied to screen and verify specific genes. We also used qRT-PCR, Western Blot, H&E staining and MitoSOX in vitro and vivo experiments. Finally, molecular docking was employed to predict potential therapeutic drugs. BOLA3 and LPIN1, were screened by WGCNA, machine learning and external datasets verification. Among these, only BOLA3 emerged positively correlated with ferroptosis marker. Notably, muscle atrophy and ferroptosis phenotypes were observed in diabetic mice with reduced BOLA3 levels. Moreover, BOLA3 knockdown in C2C12 cells confirmed its association with both ferroptosis and muscle atrophy, with a surge in mitochondrial ROS emerging as a critical factor. At last, based on the protein structure of BOLA3, handelin showed the highest binding affinity to BOLA3. BOLA3 is a potential biomarker and therapeutic target for diabetic skeletal muscle atrophy. Handelin may represent a promising therapeutic candidate for modulating BOLA3 function in diabetes.

BOLA3 is one of the proteins involved in the assembly and transport of [4Fe-4S] clusters, which are incorporated into mitochondrial respiratory chain complexes I and II, aconitase, and lipoic acid synthetase. Pathogenic variants in the BOLA3 gene cause a rare condition known as multiple mitochondrial dysfunctions syndrome 2 with hyperglycinemia, characterized by life-threatening lactic acidosis, nonketotic hyperglycinemia, and hypertrophic cardiomyopathy. The aim of this study was to elucidate the biochemical characteristics of patients with BOLA3 variants and to clarify the role of BOLA3 protein in humans. The characteristics, clinical course, and biochemical data of eight Japanese patients with BOLA3 pathogenic variants were collected. In addition, metabolomic analyses were performed using capillary electrophoresis time-of-flight mass spectrometry, blue native polyacrylamide gel electrophoresis (BN-PAGE)/Western blot analysis of mitochondrial respiratory chain complexes, and in-gel enzyme staining of mitochondrial respiratory chain complexes of fibroblasts from all eight patients. Metabolomic data were compared between the eight patients with BOLA3 variants and three control samples using Welch's t-test. In the metabolomic analysis, levels of lactic acid, pyruvic acid, alanine, tricarboxylic acid (TCA) cycle intermediates (such as α-ketoglutaric acid and succinic acid), branched-chain amino acids, and metabolites of lysine and tryptophan were significantly elevated in the BOLA3 group. Data collected during the patients' lives showed increased lactic acid and glycine levels. In BN-PAGE/Western blot analysis and in-gel enzyme staining, bands for complexes I and II were barely detectable in all eight cases. These results indicate that BOLA3 variants decrease the activity of lipoic acid-dependent proteins (pyruvate dehydrogenase complex, α-ketoglutarate dehydrogenase, 2-oxoadipate dehydrogenase, branched-chain ketoacid dehydrogenase, and the glycine cleavage system), as well as mitochondrial respiratory chain complexes I and II, but do not affect aconitase. Thus, it is believed that BOLA3 is involved in transporting [4Fe-4S] clusters to respiratory chain complexes I and II and lipoic acid synthetase, but does not interfere with aconitase. These findings suggest that while lipoic acid supplementation or vitamin cocktails may provide benefits, the impaired [4Fe-4S] cluster pathway itself should be targeted for treatment to improve the extensive metabolic abnormalities caused by BOLA3 deficiency.

To investigate the clinical features and genetic variants associated with Multiple mitochondrial dysfunction syndrome (MMDS) type 3 in two children. Two children diagnosed with MMDS type 3 at Zhuhai Maternal and Child Health Care Hospital in January 2021 were selected for this study. A retrospective analysis of their clinical data was carried out. Whole exome sequencing was conducted on the two children and their parents, followed by Sanger sequencing for candidate variants and bioinformatic analysis. Both children received comprehensive rehabilitative therapy and were followed up for 3 years. This study was approved by the Ethics Committee of Zhuhai Maternal and Child Health Hospital (Ethics No. 202380). The two MMDS type 3 children were monozygotic twin girls, aged 9 months, presenting with developmental regression, pyramidal signs, and other clinical manifestations. Cranial MRI revealed widespread abnormal signals and vacuolar changes in the white matter. Whole exome sequencing revealed that both children had harbored compound heterozygous variants of the IBA57 gene, namely c.286T>C (p.Tyr96His) and c.307C>T (p.Gln103Ter). Sanger sequencing confirmed that these variants were inherited from their father and mother, respectively. According to the American College of Medical Genetics and Genomics (ACMG) guidelines, both variants were classified as pathogenic (PM2_Supporting+PM3_Very Strong+PP3_Moderate; PVS1+PM2_Supporting+PM3). After treatment with vitamins, levocarnitine, ATP, coenzyme Q10, and other drugs, both children showed partial recovery of neurodevelopmental regression, with improvement in feeding and sleep. Over the 3-year follow-up, there was slow but progressive improvement in motor, language, and cognitive development. The compound heterozygous variants c.286T>C (p.Tyr96His) and c.307C>T (p.Gln103Ter) of the IBA57 gene probably underlay the MMDS type 3 in the twin pair. Clinicians should be vigilant about the possibility of MMDS type 3 in children with neurodevelopmental regression and early cranial MRI findings indicating widespread white matter abnormalities with vacuolar changes, as these may be indicative of IBA57 gene variants.