A Novel Syndrome Affecting Multiple Mitochondrial Functions, Located by Microcell-Mediated Transfer to Chromosome 2p14-2p13

Abstract

We have studied cultured skin fibroblasts from three siblings and one unrelated individual, all of whom had fatal mitochondrial disease manifesting soon after birth. After incubation with 1 mM glucose, these four cell strains exhibited lactate/pyruvate ratios that were six times greater than those of controls. On further analysis, enzymatic activities of the pyruvate dehydrogenase complex, the 2-oxoglutarate dehydrogenase complex, NADH cytochrome c reductase, succinate dehydrogenase, and succinate cytochrome c reductase were severely deficient. In two of the siblings the enzymatic activity of cytochrome oxidase was mildly decreased (by approximately 50%). Metabolite analysis performed on urine samples taken from these patients revealed high levels of glycine, leucine, valine, and isoleucine, indicating abnormalities of both the glycine-cleavage system and branched-chain alpha-ketoacid dehydrogenase. In contrast, the activities of fibroblast pyruvate carboxylase, mitochondrial aconitase, and citrate synthase were normal. Immunoblot analysis of selected complex III subunits (core 1, cyt c(1), and iron-sulfur protein) and of the pyruvate dehydrogenase complex subunits revealed no visible changes in the levels of all examined proteins, decreasing the possibility that an import and/or assembly factor is involved. To elucidate the underlying molecular defect, analysis of microcell-mediated chromosome-fusion was performed between the present study's fibroblasts (recipients) and a panel of A9 mouse:human hybrids (donors) developed by Cuthbert et al. (1995). Complementation was observed between the recipient cells from both families and the mouse:human hybrid clone carrying human chromosome 2. These results indicate that the underlying defect in our patients is under the control of a nuclear gene, the locus of which is on chromosome 2. A 5-cM interval has been identified as potentially containing the critical region for the unknown gene. This interval maps to region 2p14-2p13.

The spectrum of pyruvate oxidation defects in the diagnosis of mitochondrial disorders

“…It is remarkable that iron-sulphur cluster and lipoic acid defects, especially NFU1, have been associated with pulmonary symptoms like respiratory insufficiency or pulmonary hypertension (Seyda et al 2001;Navarro-Sastre et al 2011;Soreze et al 2013;Mayr et al 2014;Tort et al 2014). All BOLA3 patients published so far suffered from hypertrophic cardiomyopathy (Seyda et al 2001;Haack et al 2013;Baker et al 2014).…”

“…All BOLA3 patients published so far suffered from hypertrophic cardiomyopathy (Seyda et al 2001;Haack et al 2013;Baker et al 2014). Mutations in the DLAT gene encoding the E2 subunit have been described in children with episodic dystonia and normal or mildly elevated lactate levels (McWilliam et al 2010;El-Gharbawy et al 2011).…”

“…Seyda et al 2001;Cameron et al 2011;Haack et al 2013; Baker et al 2014): Patients with BOLA3 mutations are described with severe early onset lactic acidosis, progressive encephalopathy with seizures, intractable cardiomyopathy and early death in infancy. Glycine elevation was found in all patients, enzyme investigations in skeletal muscle tissue revealed a combination of PDHC and combined respiratory chain deficiency.…”

Mitochondrial ribosomal proteins: Candidate genes for mitochondrial disease

“…We see in Tables 1 and 2 that MRP genes are candidates for dwarfism, growth retardation, and limb deformity disorders such as Russell-Silver Syndrome, 49,50 Stuve-Wiedemann Syndrome, 51 and Moebius Syndrome I. 52 Metabolic disorders for which MRP genes associate by map position are Multiple Mitochondrial Dysfunctions, 53 Stuve-Wiedemann Syndrome, 51 Leigh Syndrome, 54 and diabetes. Candidate eye and ear disorders include Corneal Dystrophy and Perceptive Deafness, 55 Spinocerebellar Ataxia with blindness and deafness, Moebius Syndrome I, 52 Usher Syndrome, Type 1E, 56 DiGeorge Syndrome, 57 and nonsyndromic hearing losses (15 dominant and 7 autosomal recessive).…”

Combinations of chromosome transfer and genome editing for the development of cell/animal models of human disease and humanized animal models

“…This technique has been used for the identification of genes related to tumor suppression [13,14], genomic imprinting [15,16], DNA repair [17][18][19], metastasis and genomic instability [20], telomerase regulation [21][22][23], mitochondrial disorders [24], and lysosomal storage diseases [25]. MMCT has also been applied to investigate chromosomal functions such as kinetochore assembly, telomere function, and high-order chromosome architecture [8,26,27].…”