Mitochondrial DNA Copy Number in Rett Syndrome Caused by Methyl-CpG-Binding Protein-2 Variants.

OBJECTIVE: To determine changes in mitochondrial DNA (mtDNA) copy number in peripheral blood in Rett syndrome caused by methyl-CpG-binding protein-2 (MECP2) variants and explore the mechanism of mitochondrial dysfunction in Rett syndrome. STUDY DESIGN: Female patients who were diagnosed with Rett syndrome and had an MECP2 variant (n = 142) were recruited in this study, along with the same number of age- and sex-matched healthy controls. MtDNA copy number was quantified by real-time quantitative polymerase chain reaction with TaqMan probes. The differences in mtDNA copy number between the Rett syndrome group and the control group were analyzed using the independent-samples t test. Linear regression, biserial correlation analysis, and one-way ANOVA were applied for the correlations between mtDNA copy number and age, clinical severity, variant types, functional domains, and hot-spot variants. RESULTS: MtDNA copy number was found to be significantly increased in the patients with Rett syndrome with MECP2 gene variants compared with the control subjects. Age, clinical severity, variant types, functional domains, and hot-spot variants were not related to mtDNA copy number in patients with Rett syndrome. CONCLUSIONS: MtDNA copy number is increased significantly in patients with Rett syndrome, suggesting that changes in mitochondrial function in Rett syndrome trigger a compensatory increase in mtDNA copy number and providing new possibilities for treating Rett syndrome, such as mitochondria-targeted therapies.

Rab27a deletion impairs the therapeutic potential of endothelial progenitor cells for myocardial infarction.

Endothelial progenitor cell (EPC) transplantation has shown advantages in the treatment of myocardial infarction (MI) in animal models and clinical trials through mechanisms of direct intercellular contacts, autocrine, and paracrine. However, the effects of EPC transplantation for MI treatment remain controversial and the underlying mechanisms have not been fully elucidated. Here, we explored the role of Rab27a in the therapeutic potential of EPC transplantation in MI. We found that Rab27a knockout impaired the viability, and reduced the proliferation and tube formation function of ECPs. The recovery of cardiac function and improvement of ventricular remodeling from EPCs transplantation were significantly damaged by Rab27a deletion in vivo. Rab27a deletion inhibited the protein expression of phosphoinositide 3-kinase (PI3K) and cyclin D1 and the phosphorylation levels of Akt and FoxO3a. Therefore, Rab27a knockout suppressed the PI3K-Akt-FoxO3a/cyclin D1 signaling pathway. Furthermore, Rab27a ablation dramatically reduced exosome release in EPCs. These results demonstrated that Rab27a plays an essential role in EPC functions. The elucidation of this mechanism provides novel insights into EPC transplantation as a promising treatment for post-MI injuries.

[G14453A mutation in mitochondrial myopathy encephalomyopathy with lactic acidosis and stroke-like episodes].

OBJECTIVE: To analyz mitochondrial DNA mutation in one case of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS). METHODS: The patient, a 10-years-old boy,clinically diagnosed as MELAS. The clinical information was collected, and the normal mitochondrial mutations (such as A3243G, A8344G, T8993G/C, G13513A etc) were excluded. PCR-sequencing was used to analyz the whole-mitochondrial genome (16.6 kb), and PCR-RFLP was used to confirm the mutations. RESULTS: m.G14453A mutation was detected from the patient's peripheral blood and urine, but it was not found in his parents and 100 normal controls. The m.G14453A mutation was confirmed by PCR-RFLP, and mutation ratio of in blood was 56.8% and urine was 72.5%. The activity of complex I was decreased (67.6 nmol·min⁻¹·mg⁻¹). This was the first report that m.G14453A mutation could lead to MELAS in China according www.mitomap.org web and NCBI. CONCLUSION: m.G14453A mutation is one of the causative mutations in MELAS, but the mechanism of the mutation should be studied in future.

[Analysis of the relationship between mitochondrial DNA deletion and clinical complexity of mitochondrial disease].

OBJECTIVE: To analyze the relationship between proportion of mitochondrial DNA 4 977 bp deletion (ΔmtDNA(4977)) or copy number in blood and the clinical complexity to find the pathogenesis of mitochondrial disease. METHODS: A total of 160 patients with mitochondrial disease and 101 healthy controls of Peking University First Hospital from December 2003 to December 2013 were collected in this study. Their peripheral blood showed no hot-point mutation which detected by polymerase chain reaction-restriction fragment length polymorphism. All the patients were divided into younger group (age<10y) and elder group (10y≤age<20y). The incidence of ΔmtDNA(4977) was detected by real-time quantitative PCR. Internal gene was used to calculate the number of mitochondrial DNA in each cell. Statistical analysis were carried out by the independent t-test, one-way ANOVA and Spearman's bivariate correlation analysis. RESULTS: ΔmtDNA (4977) proportion in the younger group was (2.66 ± 0.63)% and in the elder group was (3.09 ± 0.74)%, both of them were higher than that of healthy control group with the same age (the younger group: t=8.57, P<0.01; the elder group: t=4.38, P<0.01); ΔmtDNA(4977) copy number per cell in the younger group was (2.79 ± 0.50) copy and in the elder group was (2.97 ± 0.48) copy, both of them were higher than that of healthy control group with the same age (the younger group: t=4.50, P<0.01; the elder group: t=-3.67, P<0.01). The ΔmtDNA (4977) proportion was positively correlated with the complexity of the mitochondrial disease(the younger group: r=0.519, P<0.01; the elder group: r=0.772, P<0.01). The ΔmtDNA (4977) copy number per cell was positively correlated with the complexity of the mitochondrial disease(the younger group: r=0.389, P<0.01; the elder group: r=0.607, P<0.05). However, the total mtDNA copy number per cell was negatively correlated with the complexity of the mitochondrial disease (the younger group: r=-0.260, P<0.01; the elder group: r=-0.430, P<0.05). CONCLUSIONS: The proportion or copy number of ΔmtDNA (4977) or total mtDNA copy number in blood are correlated with the complexity of mitochondrial diseases, especially the proportion of ΔmtDNA (4977).

[Multiplex ligation-dependent probe amplification for detecting submicroscopic chromosomal abnormalities in Chinese children with global developmental delay or intellectual disability].

OBJECTIVE: To evaluate the feasibility of screening large cohorts of patients with developmental delay or intellectual disability (DD/ID) with multiplex ligation-dependent probe amplification (MLPA). METHODS: The peripheral blood samples were collected and DNA extracted from 276 patients with DD/ID from June 2012 to December 2013. MLPA was employed, including two distinct kits SALSA P036 and P070 for sub-telomere screening and SALSA P245 for 22 common microdeletion and microduplication syndromes. RESULTS: MLPA analysis revealed 58 (21%) cases of chromosome aberrations. Among 32 cases of subtelomeric rearrangements on one chromosome, there were deletion (n = 25) and duplication (n = 7); subtelomeric deletions on p and q arms of one chromosome (n = 2); subtelomeric rearrangements on 2 chromosomes, one deletion and other duplication (n = 9); subtelomeric rearrangements on 3 chromosomes, 2 duplications and other deletion (n = 1). There were 1 case of subtelomeric rearrangements on chromosome X. A total of 11 syndromes were detected among 22 common microdeletion and microduplication syndromes and 6 located at subtelomeric regions. CONCLUSION: MLPA is an effective cytogenetic diagnostic tool for detecting chromosomal abnormalities, such as DD/ID.

Genetic analysis and prenatal diagnosis of 76 Chinese families with X-linked adrenoleukodystrophy.

BACKGROUND: Variants in the ATP binding cassette protein subfamily D member 1 (ABCD1) gene are known to cause X-linked adrenoleukodystrophy (X-ALD). This study focused on the characteristics of ABCD1 variants in Chinese X-ALD families and elucidated the value of genetic approaches for X-ALD. METHODS: 68 male probands diagnosed as X-ALD were screened for ABCD1 variants by the Sanger sequencing of polymerase chain reaction (PCR) products and multiplex ligation-dependent probe amplification (MLPA) combined with long-range PCR. Prenatal diagnosis was performed in 20 foetuses of 17 probands' mothers. Descriptive statistics were used to summarise the gene variants and prenatal diagnosis characteristics and outcomes. RESULTS: This study allowed the identification of 61 variants occurring in 68 families, including 58 single nucleotide variants or small deletion/insertion variants and 3 large deletions. Three probands with no variants detected by next-generation sequencing were found to have variants by PCR-sequencing. Prenatal diagnosis found that 10 of the 20 foetuses had no variants in ABCD1. CONCLUSION: PCR primers that do not amplify the pseudogenes must be used for PCR-sequencing. MLPA combined with long-range PCR can detect large deletions and insertions, which are usually undetectable by PCR-sequencing. Prenatal diagnosis could help to prevent the birth of infants with X-ALD.

Dual crosslinking of folic acid-modified pectin nanoparticles for enhanced oral insulin delivery.

Pectin-based drug delivery systems hold great potential for oral insulin delivery, since they possess excellent gelling property, good mucoadhesion and high stability in the gastrointestinal (GI) tract. However, lack of enterocyte targeting ability and premature drug release in the upper GI tract of the susceptible ionic-crosslinked pectin matrices are two major problems to be solved. To address these issues, we developed folic acid (FA)-modified pectin nanoparticles (INS/DFAN) as insulin delivery vehicles by a dual-crosslinking method using calcium ions and adipic dihydrazide (ADH) as crosslinkers. In vitro studies indicated insulin release behaviors of INS/DFAN depended on COOH/ADH molar ratio in the dual-crosslinking process. INS/DFAN effectively prevented premature insulin release in simulated GI fluids compared to ionic-crosslinked nanoparticles (INS/FAN). At an optimized COOH/ADH molar ratio, INS/DFAN with FA graft ratio of 18.2% exhibited a relatively small particle size, high encapsulation efficiency and excellent stability. Cellular uptake of INS/DFAN was FA graft ratio dependent when it was at/below 18.2%. Uptake mechanism and intestinal distribution studies demonstrated the enhanced insulin transepithelial transport by INS/DFAN via FA carrier-mediated transport pathway. In vivo studies revealed that orally-administered INS/DFAN produced a significant reduction in blood glucose levels and further improved insulin bioavailability in type I diabetic rats compared to INS/FAN. Taken together, the combination of dual crosslinking and FA modification is an effective strategy to develop pectin nano-vehicles for enhanced oral insulin delivery.

[Screening of mitochondrial deoxyribonucleic acid 3271T > C, 8356T > C, 9176T > C/G and 13513G > A mutations in mitochondrial encephalomyopathies].

OBJECTIVE: To investigate the spectrum of mitochondrial DNA (deoxyribonucleic acid) 3271T > C, 8356T > C, 9176T > C/G and 13513G > A mutations in Chinese patients with mitochondrial encephalomyopathies. METHODS: Peripheral blood samples were collected from 500 mitochondrial encephalomyopathies patients clinically diagnosed as mitochondrial encephalomyopathy lactic acidosis & stroke-like episodes (MELAS), myoclonus epilepsy & ragged-red fibers (MERRF) or Leigh's syndrome from October 2005 to October 2009. The methods of PCR- polymerase chain reaction-restriction fragment length polymorphism (RFLP) and PCR-sequencing were performed to identify the mutations. RESULTS: No patients with the 3271T > C, 8356T > C, 9176T > C/G or 13513G > A mutations were identified. CONCLUSION: The mutations of 3271T > C, 8356T > C, 9176T > C/G and 13513G > A are rare causes of mitochondrial encephalomyopathies in Chinese patients.

[Analysis of clinical phenotype in 42 nuclear pedigrees carrying mitochondrial DNA A3243G mutation].

OBJECTIVE: A3243G mutation in mitochondrial DNA is the most common pathogenic point mutation causing a variety of phenotypes. The clinical phenotype and the relationship between the clinical phenotype and the ratio of A3243G mutation were studied in the members from nuclear families carrying A3243G mutation. METHODS: A total of 42 families carrying A3243G mutation were recruited and their clinical symptoms, laboratory results and the ratio of A3243G analyzed. RESULT: (1) In probands, myopathy, seizure, hirsutism, headache, cognitive impairment, weight loss and short stature were the most common clinical features. They tended to occur simultaneously. Lactic acid, pyruvate and MRI were abnormal in most probands; (2) most carriers had a normal phenotype. Myopathy, weight loss and short stature were their most common clinical features; (3) the ratio of A3243G mutation in urine was higher than that in blood in probands (t = -15.06, P < 0.001). And the ratio of A3243G mutation in urine was higher than that in blood in their mothers (z = -6.241, P < 0.001); (4) the ratio of A3243G mutation in probands was 2-fold higher than that in their mothers in both blood and urine. CONCLUSION: The phenotype of patients carrying A3243G mutation is varied. The clinical symptoms and laboratory results of probands are worse than those of mothers. It is probably due to a higher mutation ratio of m.3243A>G in their tissues.

Deletion of a 4977-bp Fragment in the Mitochondrial Genome Is Associated with Mitochondrial Disease Severity.

Large deletions in mitochondrial DNA (mtDNA) may be involved in the pathogenesis of mitochondrial disease. In this study, we investigated the relationship between a 4,977-bp deletion in the mitochondrial genome (ΔmtDNA(4977)) and the severity of clinical symptoms in patients with mitochondrial disease lacking known point mutations. A total of 160 patients with mitochondrial disease and 101 healthy controls were recruited for this study. The copy numbers of ΔmtDNA(4977) and wild-type mtDNA were determined by real-time quantitative PCR and analyzed using Spearman's bivariate correlation analysis, t-tests, or one-way ANOVA. The overall ΔmtDNA(4977) copy number per cell and the proportion of mtDNA(4977) relative to the total wild-type mtDNA, increased with patient age and symptom severity. Surprisingly, the total mtDNA copy number decreased with increasing symptom severity. Our analyses revealed that increases in the proportion and total copy number of ΔmtDNA(4977) in the blood may be associated with disease severity in patients with mitochondrial dysfunction.

Wild-Type Mitochondrial DNA Copy Number in Urinary Cells as a Useful Marker for Diagnosing Severity of the Mitochondrial Diseases.

The genotype-phenotype relationship in diseases with mtDNA point mutations is still elusive. The maintenance of wild-type mtDNA copy number is essential to the normal mitochondrial oxidative function. This study examined the relationship between mtDNA copy number in blood and urine and disease severity of the patients harboring A3243G mutation. We recruited 115 A3243G patients, in which 28 were asymptomatic, 42 were oligo-symptomatic, and 45 were poly-symptomatic. Increase of total mtDNA copy number without correlation to the proportion of mutant mtDNA was found in the A3243G patients. Correlation analyses revealed that wild-type mtDNA copy number in urine was the most important factor correlated to disease severity, followed by proportion of mutant mtDNA in urine and proportion of mutant mtDNA in blood. Wild-type copy number in urine negatively correlated to the frequencies of several major symptoms including seizures, myopathy, learning disability, headache and stroke, but positively correlated to the frequencies of hearing loss and diabetes. Besides proportion of mutant mtDNA in urine, wild-type copy number in urine is also an important marker for disease severity of A3243G patients.