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Mitochondrial DNA deletion and duplication in Kearns-Sayre Syndrome (KSS) with initial presentation as Pearson Marrow-Pancreas Syndrome (PMPS): Two case reports in Barranquilla, Colombia.

ABSTRACT: BACKGROUND:Kearns-Sayre Syndrome (KSS) and Pearson Marrow-Pancreas Syndrome (PMPS) are among the classic phenotypes caused by mitochondrial DNA (mtDNA) deletions. KSS is a rare mitochondrial disease defined by a classic triad of progressive external ophthalmoplegia, atypical pigmentary retinopathy, and onset before 20 years. PMPS presents in the first year of life with bone marrow failure and exocrine pancreatic dysfunction, and can evolve into KSS later in life. Even though an mtDNA deletion is the most frequent mutation in KSS and PMPS, cases of duplications and molecular rearrangements have also been described. In Colombia, few case reports of KSS and PMPS have been published in indexed journals or have been registered in scientific events. METHODS:We discuss clinical and genetic aspects of two case reports of pediatric female patients, with initial clinical diagnosis of PMPS who later evolved into KSS, with confirmatory molecular studies of an mtDNA deletion and an mtDNA duplication. RESULTS:A large-scale mtDNA deletion, NC_012920.1:m.8286_14416del, was confirmed by Southern Blot in patient 1. An mtDNA duplication of 7.9 kb was confirmed by MLPA in patient 2. CONCLUSIONS:Our findings are compatible with the phenotypic and genetic presentation of PMPS and KSS. We present the first molecularly confirmed case reports of Colombian patients, diagnosed initially with PMPS, who later evolved to KSS.

SUBMITTER: Sabella-Jimenez V

PROVIDER: S-EPMC7667363 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Mitochondrial DNA deletion and duplication in Kearns-Sayre Syndrome (KSS) with initial presentation as Pearson Marrow-Pancreas Syndrome (PMPS): Two case reports in Barranquilla, Colombia.

Sabella-Jiménez Vanessa V Otero-Herrera Carlos C Silvera-Redondo Carlos C Garavito-Galofre Pilar P

Molecular genetics & genomic medicine 20201008 11

<h4>Background</h4>Kearns-Sayre Syndrome (KSS) and Pearson Marrow-Pancreas Syndrome (PMPS) are among the classic phenotypes caused by mitochondrial DNA (mtDNA) deletions. KSS is a rare mitochondrial disease defined by a classic triad of progressive external ophthalmoplegia, atypical pigmentary retinopathy, and onset before 20 years. PMPS presents in the first year of life with bone marrow failure and exocrine pancreatic dysfunction, and can evolve into KSS later in life. Even though an mtDNA del ...[more]

PMID: 33030289

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Project description:Kearns Sayre syndrome (KSS) is mitochondrial multisystem disorder with no proven effective treatment. The underlying cause for multisystem involvement is the energy deficit resulting from the load of mutant mitochondrial DNA (mtDNA), which manifests as loss of cells and tissue dysfunction. Therefore, functional organ or cellular replacement provides a promising avenue as a therapeutic option. Patient-specific induced pluripotent stem cells (iPSC) have become a handy tool to create personalized cell -based therapies. iPSC are capable of self-renewal, differentiation into all types of body cells including cardiomyocytes (CM) and neural progenitor cells (NPC). In KSS patients, mutations in mtDNA are largely found in the muscle tissue and are predominantly absent in the blood cells. Therefore, we conceptualized that peripheral blood mononuclear cells (PBMNC) from KSS patients can be reprogrammed to generate mutation free, patient specific iPSC lines that can be used as isogenic source of cell replacement therapies to treat affected organs. In the current study we generated iPSC lines from two female patients with clinical diagnosis of classic KSS. Our data demonstrate that iPSC from these KSS patients showed normal differentiation potential toward CM, NPC and fibroblasts without any mtDNA deletions over passages. Next, we also found that functional studies including ATP production, reactive oxygen species generation, lactate accumulation and mitochondrial membrane potential in iPSC, CM, NPC and fibroblasts of these KSS patients were not different from respective cells from healthy controls. PBMNCs from these KSS patients in the current study did not reproduce mtDNA mutations which were present in muscle biopsies. Furthermore, we demonstrate for the first time that this phenomenon provides opportunities to create isogenic mutation free iPSC with absent or very low level of expression of mtDNA deletion which can be banked for future cell replacement therapies in these patients as the disease progresses.

Project description:Mitochondrial DNA (mtDNA) genome integrity is essential for proper mitochondrial respiratory chain function to generate cellular energy. Nuclear genes encode several proteins that function at the mtDNA replication fork, including mitochondrial single-stranded DNA-binding protein (SSBP1), which is a tetrameric protein that binds and protects single-stranded mtDNA (ssDNA). Recently, two studies have reported pathogenic variants in SSBP1 associated with hearing loss, optic atrophy, and retinal degeneration. Here, we report a 14-year-old Chinese boy with severe and progressive mitochondrial disease manifestations across the full Pearson, Kearns-Sayre, and Leigh syndromes spectrum, including infantile anemia and bone marrow failure, growth failure, ptosis, ophthalmoplegia, ataxia, severe retinal dystrophy of the rod-cone type, sensorineural hearing loss, chronic kidney disease, multiple endocrine deficiencies, and metabolic strokes. mtDNA genome sequencing identified a single large-scale 5 kilobase mtDNA deletion (m.8629_14068del5440), present at 68% and 16% heteroplasmy in the proband's fibroblast cell line and blood, respectively, suggestive of a mtDNA maintenance defect. On trio whole exome blood sequencing, the proband was found to harbor a novel de novo heterozygous mutation c.79G>A (p.E27K) in SSBP1. Size exclusion chromatography of p.E27K SSBP1 revealed it remains a stable tetramer. However, differential scanning fluorimetry demonstrated p.E27K SSBP1 relative to wild type had modestly decreased thermostability. Functional assays also revealed p.E27K SSBP1 had altered DNA binding. Molecular modeling of SSBP1 tetramers with varying combinations of mutant subunits predicted general changes in surface accessible charges, strength of inter-subunit interactions, and protein dynamics. Overall, the observed changes in protein dynamics and DNA binding behavior suggest that p.E27K SSBP1 can interfere with DNA replication and precipitate the introduction of large-scale mtDNA deletions. Thus, a single large-scale mtDNA deletion (SLSMD) with manifestations across the clinical spectrum of Pearson, Kearns-Sayre, and Leigh syndromes may result from a nuclear gene disorder disrupting mitochondrial DNA replication.

Dataset Information

Mitochondrial DNA deletion and duplication in Kearns-Sayre Syndrome (KSS) with initial presentation as Pearson Marrow-Pancreas Syndrome (PMPS): Two case reports in Barranquilla, Colombia.

Publications

Mitochondrial DNA deletion and duplication in Kearns-Sayre Syndrome (KSS) with initial presentation as Pearson Marrow-Pancreas Syndrome (PMPS): Two case reports in Barranquilla, Colombia.

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