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Abstract: Background: Little is known about xeroderma pigmentosum (XP) in Himalayan countries. Objective: To describe clinical characteristics of XP in Nepal and investigate its genetic bases. Methods: This study was carried out on all consecutive patients referred for XP to a Nepalese tertiary referral centre in 2014–2015. Clinical data were collected using a standardized questionnaire. DNA was extracted from salivary samples, and next‐generation sequencing (NGS) was conducted using a panel covering all 8 known XP genes (classical XP (XP‐A to XP‐G) and XP variant) and a skin cancer modifier gene, the melanocortin 1 receptor gene (MC1R). Results: Seventeen patients (median age: 15 years; range: 1–32) were included. Twelve had skin cancers (including a total of 8 squamous cell carcinomas, 60 basal cell carcinomas, ocular carcinomas requiring an orbital exenteration in 3 patients, but no melanoma). Fifteen patients carried the same homozygous non‐sense XPC mutation c.1243C>T, p.R415X. A homozygous non‐sense XPA mutation (p.W235X) was found in the only patient with a history of early severe sunburn reaction and associated neurological symptoms. Associated genetic alterations included heterozygous missense variants in XPD/ERCC2 gene and the presence of MC1R variant R163Q in 5 and 9 patients, respectively. Conclusion: Although not previously reported, XP seems frequent in Nepal. Patients often presented with a very severe phenotype after a long history of excessive sun exposure without knowledge of the disease. Fifteen of 17 had the same p.R415X XPC mutation, which seems very specific of XP in Nepal, suggesting a founder effect. NGS analyses frequently revealed associated genetic alterations which could play a modifier role in the clinical expression of the disease. [ABSTRACT FROM AUTHOR]

A number of factors influence the performance of an ejector, e.g. working fluid, geometry and operating conditions. In the present work, six low-environmental-impact working fluids were evaluated for their use in an ejector cooling system running on low-temperature thermal energy. The numerical analysis was based on a model applying the 1D constant-pressure mixing theory. Ejector performance was assessed for the temperatures of the generator, evaporator and condenser in the range of 80-120°C, 5-15°C and 25-40°C, respectively. The results indicated that owing to its high coefficient of performance and moderate operating pressures throughout the entire ejector cycle, isobutane is a good choice for a refrigerant. The area ratio required for running the ejector in critical mode, under changing operating conditions, varied in a significant range regardless of the selected refrigerant. This clearly indicates the importance of a variable geometry ejector design to strengthen the position of ejector cooling systems among other refrigeration technologies. [ABSTRACT FROM AUTHOR]

Pearson syndrome (PS) is a mitochondrial disease and clinical presentation is rather varied. These patients are often subjected to extensive biochemical and clinical work-up for diagnosis. We report two new cases and review our experience with PS in Hacettepe University. The first case had large deletion of mitochondrial DNA (mtDNA) and presented with severe metabolic acidosis and anemia associated with hemophagocytosis in bone marrow. He also had liver involvement and tubulopathy. The second case, who had the 4997 bp common deletion, presented with anemia at 8 weeks of age followed by an uneventful 4 years. She developed very severe acidosis and renal Fanconi syndrome at the age of 4.5 years. Our cases revealed once more the clinical diversity of the disease and no correlation between the size and site of mtDNA deletion and clinical presentation. We encourage physicians to look for PS in children with early sideroblastic anemia and multiple organ system involvement. [ABSTRACT FROM AUTHOR]

Isolated complex I deficiency is a frequent cause of respiratory chain defects in childhood. In this study, we report our systematic approach with blue native PAGE (BN-PAGE) to study mitochondrial respiratory chain assembly in skin fibroblasts from patients with Leigh syndrome and CI deficiency. We describe five new NDUFS4 patients with a similar and constant abnormal BN-PAGE profile and present a meta-analysis of the literature. All NDUFS4 mutations that have been tested with BN-PAGE result in a constant and similar abnormal assembly profile with a complete loss of the fully assembled complex I usually due to a truncated protein and the loss of its canonical cAMP dependent protein kinase phosphorylation consensus site. We also report the association of abnormal brain MRI images with this characteristic BN-PAGE profile as the hallmarks of NDUFS4 mutations and the first founder NDUFS4 mutations in the North-African population., (© 2012 Elsevier B.V. All rights reserved.)

Mitochondrial diseases (MD) are the most frequent metabolic disorders. They have in common a respiratory chain deficiency. Clinical presentation of MD is very heterogeneous and the major physiological functions may be affected. Diagnosis is complex due to the potential involvement of two genomes (nuclear or mitochondrial DNA), the large number of candidate genes to screen and the small number of patients reported for each type of MD. Clinical presentation, trait of inheritance, cerebral imaging (MRI and CT-Scan) and specialized biochemical investigations are good indicators, but identification of causing mutation(s) is the clue to confirm diagnosis. Task is huge and progress in diagnosis of MD should come from genotype-phenotype correlations studies and from major technical improvements in molecular diagnosis. Exhaustive study of mitochondrial DNA is the first necessary step that is now possible with methods like Surveyor and Affymetrix resequencing chip. Combination of data including clinical informations, cerebral imaging, respiratory chain deficiency and/or assembly profile of respiratory chain complexes (BN-PAGE profile) may contribute for orientation for nuclear DNA studies. Elucidation of the genetic bases of MD is important for patients: identification of causing mutation(s) allows offering genetic counselling and possibility of prenatal diagnosis., (Copyright © 2009 Elsevier Masson SAS. All rights reserved.)

Deoxyguanosine kinase (dGK) deficiency is a frequent cause of mitochondrial DNA depletion associated with a hepatocerebral phenotype. In this study, we describe a new splice site mutation in the DGUOK gene and the clinical, radiologic, and genetic features of these DGUOK patients. This new DGUOK homozygous mutation (c.444-62C>A) was identified in three patients from two North-African consanguineous families with combined respiratory chain deficiencies and mitochondrial DNA depletion in the liver. Brain MRIs are normal in DGUOK patients in the literature. Interestingly, we found subtentorial abnormal myelination and moderate hyperintensity in the bilateral pallidi in our patients. This new mutation creates a cryptic splice site in intron 3 (in position -62) and is predicted to result in a larger protein with an in-frame insertion of 20 amino acids. In silico analysis of the putative impact of the insertion shows serious clashes in protein conformation: this insertion disrupts the alpha5 helix of the dGK kinase domain, rendering the protein unable to bind purine deoxyribonucleosides. In addition, a common haplotype that segregated with the disease in both families was detected by haplotype reconstruction with 10 markers (microsatellites and SNPs), which span 4.6 Mb of DNA covering the DGUOK locus. In conclusion, we report a new DGUOK splice site mutation that provide insight into a critical protein domain (dGK kinase domain) and the first founder mutation in a North-African population.

Cerebellar ataxia is known to occasionally occur in the course of mitochondrial disorders. We report on MR spectroscopy (1H MRS) evidence of elevated brain lactate in the cerebellar area of 11 patients with cerebellar ataxia ascribed to mitochondrial respiratory chain deficiency (RCD). 1H MRS spectroscopy evidence of lactate peak was found in the cerebellum of 9/11 cases, while no lactate was detected in the putamen in 8/11. We suggest using 1H MRS in cerebellar atrophy in the diagnosis of mitochondrial RCD.

Spinocerebellar ataxia 12 (SCA12) is an autosomal dominant cerebellar ataxia (ADCA) described in a single family with a CAG repeat expansion in the PPP2R2B gene. We screened 247 index cases, including 145 families with ADCA, for this expansion. An expanded repeat ranging from 55 to 61 triplets was detected in 6 affected and 3 unaffected individuals at risk in a single family from India. The association of the PPP2R2B CAG repeat expansion with disease in this new family provides additional evidence that the mutation is causative.

Spinocerebellar ataxia 7 (SCA7) is a neurodegenerative disease caused by the expansion of a CAG repeat encoding a polyglutamine tract in the protein ataxin-7. We developed antibodies directed against two different parts of the ataxin-7 protein and studied its distribution in brain and peripheral tissue from healthy subjects. Normal ataxin-7 was widely expressed in brain, retina and peripheral tissues, including striated muscle, testis and thyroid gland. In the brain, expression of ataxin-7 was not limited to areas in which neurones degenerate, and the level of expression was not related to the severity of neuronal loss. Immunoreactivity was low in some vulnerable populations of neurones, such as Purkinje cells. In neurones, ataxin-7 was found in the cell bodies and in processes. Nuclear labelling was also observed in some neurones, but was not related to the distribution of intranuclear inclusions observed in an SCA7 patient. In this patient, the proportion of neurones with nuclear labelling was higher, on average, in regions with neuronal loss. Double immunolabelling coupled with confocal microscopy showed that ataxin-7 colocalized with BiP, a marker of the endoplasmic reticulum, but not with markers of mitochondria or the trans-Golgi network.

CAG and CGG expansion is associated with 10 inherited neurological diseases and is thought to be involved in other human genetic diseases. To identify new candidate genes, we have undertaken a large-scale screening project for CAG/CTG ([CAG]n) and CGG/GCC ([CGG]n) repeats in human brain reference cDNAs. Here, we present the final classification for 597 cDNAs selected by CAG and CGG hybridization from two libraries (100,128 clones) and the updated characterization of [CAG]n- and [CGG]n-positive cDNAs (repeat polymorphism and cDNA localization). We have selected 124 CAG and 83 CGG hybridization-positive clones representing new genes, from which 49 CAG and 7 CGG repeats could be identified. New [CAG]n and [CGG]n with more than seven to nine units were rare (1/2000), and perfect [CAG]n 9 were more likely polymorphic. Overall, highly polymorphic to monomorphic new [CAG]n > 9 and [CGG]n > 7 were characterized. The comparison of our data with other [CAG]n and [CGG]n resources suggests that the screening of reference cDNAs leads to unique sources of new [CAG]n and [CGG]n and will enhance the study of enlarged triplet repeats in human genetic diseases., (Copyright 1998 Academic Press.)

Spinocerebellar ataxia 7 (SCA7) is caused by the expansion of an unstable CAG repeat in the first exon of the SCA7 gene. We have analyzed the SCA7 mutation in 19 families and one isolated case of various geographical origins, presenting with autosomal dominant cerebellar ataxia with progressive macular dystrophy. The SCA7 CAG repeat was expanded in 77 patients and in 11 at-risk individuals, with alleles containing from 37 to 130 repeats, demonstrating that SCA7 is genetically homogeneous. Repeats on normal alleles contained from 7 to 35 CAGs. There was a strong negative correlation (r = -0.84) between the age at onset and the size of the CAG repeat expansion in SCA7 patients. Larger expansions were associated with earlier onset, a more severe and rapid clinical course, and a higher frequency of decreased vision, ophthalmoplegia, extensor plantar response and scoliosis. The frequency of other clinical signs such as dysphagia and sphincter disturbances increased with disease duration. The mutation was highly unstable during transmission, with a mean increase of 10 +/- 16 CAG repeats, which was significantly greater in paternal (15 +/- 20) than in maternal (5 +/- 5) transmissions. This correlated well with the marked anticipation (19 +/- 13 years) observed in the families. Gonadal mosaicism, observed in the sperm of a patient, was particularly important, with expanded alleles ranging from 42 to >155 CAG repeats. The degree of instability during transmission, resulting mostly in expansions, is greater than in the seven other neurodegenerative disorders caused by polyglutamine expansions.