Deleterious mutation accumulation in asexual Timema stick insects.

Sexual reproduction is extremely widespread in spite of its presumed costs relative to asexual reproduction, indicating that it must provide significant advantages. One postulated benefit of sex and recombination is that they facilitate the purging of mildly deleterious mutations, which would accumulate in asexual lineages and contribute to their short evolutionary life span. To test this prediction, we estimated the accumulation rate of coding (nonsynonymous) mutations, which are expected to be deleterious, in parts of one mitochondrial (COI) and two nuclear (Actin and Hsp70) genes in six independently derived asexual lineages and related sexual species of Timema stick insects. We found signatures of increased coding mutation accumulation in all six asexual Timema and for each of the three analyzed genes, with 3.6- to 13.4-fold higher rates in the asexuals as compared with the sexuals. In addition, because coding mutations in the asexuals often resulted in considerable hydrophobicity changes at the concerned amino acid positions, coding mutations in the asexuals are likely associated with more strongly deleterious effects than in the sexuals. Our results demonstrate that deleterious mutation accumulation can differentially affect sexual and asexual lineages and support the idea that deleterious mutation accumulation plays an important role in limiting the long-term persistence of all-female lineages.

A mutation causing pseudohypoaldosteronism type 1 identifies a conserved glycine that is involved in the gating of the epithelial sodium channel.

Pseudohypoaldosteronism type 1 (PHA-1) is an inherited disease characterized by severe neonatal salt-wasting and caused by mutations in subunits of the amiloride-sensitive epithelial sodium channel (ENaC). A missense mutation (G37S) of the human ENaC beta subunit that causes loss of ENaC function and PHA-1 replaces a glycine that is conserved in the N-terminus of all members of the ENaC gene family. We now report an investigation of the mechanism of channel inactivation by this mutation. Homologous mutations, introduced into alpha, beta or gamma subunits, all significantly reduce macroscopic sodium channel currents recorded in Xenopus laevis oocytes. Quantitative determination of the number of channel molecules present at the cell surface showed no significant differences in surface expression of mutant compared with wild-type channels. Single channel conductances and ion selectivities of the mutant channels were identical to that of wild-type. These results suggest that the decrease in macroscopic Na currents is due to a decrease in channel open probability (P(o)), suggesting that mutations of a conserved glycine in the N-terminus of ENaC subunits change ENaC channel gating, which would explain the disease pathophysiology. Single channel recordings of channels containing the mutant alpha subunit (alphaG95S) directly demonstrate a striking reduction in P(o). We propose that this mutation favors a gating mode characterized by short-open and long-closed times. We suggest that determination of the gating mode of ENaC is a key regulator of channel activity.

Vemurafenib in patients with BRAF(V600) mutation-positive melanoma with symptomatic brain metastases: final results of an open-label pilot study.

BACKGROUND & AIM: Brain metastases are frequent in patients with metastatic melanoma, indicating poor prognosis. We investigated the BRAF kinase inhibitor vemurafenib in patients with advanced melanoma with symptomatic brain metastases. METHODS: This open-label trial assessed vemurafenib (960mg twice a day) in patients with BRAF(V600) mutation-positive metastatic melanoma with non-resectable, previously treated brain metastases. The primary end-point was safety. Secondary end-points included best overall response rate, and progression-free and overall survival. RESULTS: Twenty-four patients received vemurafenib for a median treatment duration of 3.8 (0.1-11.3) months. The majority of discontinuations were due to disease progression (n=22). Twenty-three of 24 patients reported at least one adverse event (AE). Grade 3 AEs were reported in four (17%; 95% confidence interval [CI], 4.7-37.4%) patients and included cutaneous squamous cell carcinoma in four patients. Median progression-free survival was 3.9 (95% CI, 3.0-5.5) months, and median survival was 5.3 (95% CI, 3.9-6.6) months. An overall partial response (PR) at both intracranial and extracranial sites was achieved in 10 of 24 (42%; 95% CI, 22.1-63.4) evaluable patients, with stable disease in nine (38%; 95% CI, 18.8-59.4) patients. Of 19 patients with measurable intracranial disease, seven (37%) achieved >30% intracranial tumour regression, and three (16%; 95% CI, 3.4-39.6%) achieved a confirmed PR. Other signs of improvement included reduced need for corticosteroids and enhanced performance status. CONCLUSIONS: Vemurafenib can be safely used in patients with advanced symptomatic melanoma that has metastasised to the brain and can result in meaningful tumour regression.

Novel mutation in the tyrosine kinase domain of FGFR2 in a patient with Pfeiffer syndrome.

Mutations in the fibroblast growth factor receptor 2 (FGFR2) cause a variety of craniosynostosis syndromes. The mutational spectrum tends to be narrow with the majority of mutations occurring in either exon IIIa or IIIc or in the intronic sequence preceding exon IIIc. Mutations outside of this hotspot are uncommon and the few identified mutations have demonstrated wide clinical variability, making it difficult to establish a clear-cut genotype-phenotype correlation. To better delineate the clinical picture associated with these unusual mutations, we describe a severely affected patient with Pfeiffer syndrome and a missense mutation in the tyrosine kinase (TK) domain of FGFR2.

HIV-1 Subtype Is an Independent Predictor of Reverse Transcriptase Mutation K65R in HIV-1 Patients Treated with Combination Antiretroviral Therapy Including Tenofovir.

Subtype-dependent selection of HIV-1 reverse transcriptase resistance mutation K65R was previously observed in cell culture and small clinical investigations. We compared K65R prevalence across subtypes A, B, C, F, G, and CRF02_AG separately in a cohort of 3,076 patients on combination therapy including tenofovir. K65R selection was significantly higher in HIV-1 subtype C. This could not be explained by clinical and demographic factors in multivariate analysis, suggesting subtype sequence-specific K65R pathways.

Neuropathological, clinical and molecular pathology in female fragile X premutation carriers with and without FXTAS.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder associated with premutation alleles of the fragile X mental retardation 1 (FMR1) gene. Approximately 40% of older male premutation carriers, and a smaller proportion of females, are affected by FXTAS; due to the lower penetrance the characterization of the disorder in females is much less detailed. Core clinical features of FXTAS include intention tremor, cerebellar gait ataxia and frequently parkinsonism, autonomic dysfunction and cognitive deficits progressing to dementia in up to 50% of males. In this study, we report the clinical, molecular and neuropathological findings of eight female premutation carriers. Significantly, four of these women had dementia; of the four, three had FXTAS plus dementia. Post-mortem examination showed the presence of intranuclear inclusions in all eight cases, which included one asymptomatic premutation carrier who died from cancer. Among the four subjects with dementia, three had sufficient number of cortical amyloid plaques and neurofibrillary tangles to make Alzheimer's disease a highly likely cause of dementia and a fourth case had dementia with cortical Lewy bodies. Dementia appears to be more common than originally reported in females with FXTAS. Although further studies are required, our observation suggests that in a portion of FXTAS cases there is Alzheimer pathology and perhaps a synergistic effect on the progression of the disease may occur.

Mutation identification by direct comparison of whole-genome sequencing data from mutant and wild-type individuals using k-mers.

Genes underlying mutant phenotypes can be isolated by combining marker discovery, genetic mapping and resequencing, but a more straightforward strategy for mapping mutations would be the direct comparison of mutant and wild-type genomes. Applying such an approach, however, is hampered by the need for reference sequences and by mutational loads that confound the unambiguous identification of causal mutations. Here we introduce NIKS (needle in the k-stack), a reference-free algorithm based on comparing k-mers in whole-genome sequencing data for precise discovery of homozygous mutations. We applied NIKS to eight mutants induced in nonreference rice cultivars and to two mutants of the nonmodel species Arabis alpina. In both species, comparing pooled F2 individuals selected for mutant phenotypes revealed small sets of mutations including the causal changes. Moreover, comparing M3 seedlings of two allelic mutants unambiguously identified the causal gene. Thus, for any species amenable to mutagenesis, NIKS enables forward genetics without requiring segregating populations, genetic maps and reference sequences.

Retinal Dystrophy In The Oculo-auricular Syndrome Due to HMX1 Mutation.

Purpose: To report on the clinical and electrophysiological findings in a patient with oculo-auricular syndrome due to HMX1 mutation, with a follow-up of 12 years. Background: Oculo-auricular syndrome (MIM: 612109) is a rare developmental recessive condition affecting the eye and external ear that results from a mutation in the HMX1 gene. Previously described ocular abnormalities include bilateral microcornea, posterior synechiae, cataract, chorioretinal colobomas and rod-cone dystrophy. Methods: Retrospective chart review of an affected boy followed over a period of 12 years who had serial complete ophthalmologic examinations, fundus photographs, Goldmann perimetry and full-field electroretinograms (ERG). Results: Initial ERG tracings revealed generalized rod more than cone dysfunction. Thereafter, a rapid deterioration in rod and cone function was detected on follow up ERGs. Conclusion: The retinal degeneration in the recessively inherited oculo-auricular syndrome is a progressive rod-cone dystrophy. Visual prognosis is guarded considering the progressive nature of the retinal dystrophy in early infancy.

Prenatal presentation and postnatal evolution of a patient with Jansen metaphyseal dysplasia with a novel missense mutation in PTH1R.

Wave-shaped ribs were detected at prenatal ultrasound in a 20(+1) week female fetus. At birth, skeletal radiographs showed marked hypomineralization and suggested hypophosphatasia. However, elevated blood calcium and alkaline phosphatase excluded hypophosphatasia and raised the possibility of Jansen metaphyseal dysplasia. Molecular analysis of the PTH/PTHrP receptor gene (PTH1R) showed heterozygosity for a previously undescribed transversion variant (c.1373T>A), which predicts p.Ile458Lys. In vitro evaluation of wild type and mutant PTH/PTHrP receptors supported the pathogenic role of the p.Ile458Lys substitution, and confirmed the diagnosis of Jansen metaphyseal dysplasia. This disorder may present prenatally with wavy ribs and in the newborn with hypomineralization, and may therefore be confused with hypophosphatasia. The mottled metaphyseal lesions typically associated with this disease appear only in childhood.

A missense mutation in myelin oligodendrocyte glycoprotein as a cause of familial narcolepsy with cataplexy.

Narcolepsy is a rare sleep disorder characterized by excessive daytime sleepiness and cataplexy. Familial narcolepsy accounts for less than 10% of all narcolepsy cases. However, documented multiplex families are very rare and causative mutations have not been identified to date. To identify a causative mutation in familial narcolepsy, we performed linkage analysis in the largest ever reported family, which has 12 affected members, and sequenced coding regions of the genome (exome sequencing) of three affected members with narcolepsy and cataplexy. We successfully mapped a candidate locus on chromosomal region 6p22.1 (LOD score ¼ 3.85) by linkage analysis. Exome sequencing identified a missense mutation in the second exon of MOG within the linkage region. A c.398C>G mutation was present in all affected family members but absent in unaffected members and 775 unrelated control subjects. Transient expression of mutant myelin oligodendrocyte glycoprotein (MOG) in mouse oligodendrocytes showed abnormal subcellular localization, suggesting an altered function of the mutant MOG. MOG has recently been linked to various neuropsychiatric disorders and is considered as a key autoantigen in multiple sclerosis and in its animal model, experimental autoimmune encephalitis. Our finding of a pathogenic MOG mutation highlights a major role for myelin and oligodendrocytes in narcolepsy and further emphasizes glial involvement in neurodegeneration and neurobehavioral disorders. [corrected].

A dystroglycan mutation associated with limb-girdle muscular dystrophy.

Dystroglycan, which serves as a major extracellular matrix receptor in muscle and the central nervous system, requires extensive O-glycosylation to function. We identified a dystroglycan missense mutation (Thr192→Met) in a woman with limb-girdle muscular dystrophy and cognitive impairment. A mouse model harboring this mutation recapitulates the immunohistochemical and neuromuscular abnormalities observed in the patient. In vitro and in vivo studies showed that the mutation impairs the receptor function of dystroglycan in skeletal muscle and brain by inhibiting the post-translational modification, mediated by the glycosyltransferase LARGE, of the phosphorylated O-mannosyl glycans on α-dystroglycan that is required for high-affinity binding to laminin.

Zapfen-Stäbchen-Dystrophie durch eine neue reinerbige RPE65-Mutation in Leberscher kongenitaler Amaurose Cone-Rod Dystrophy Caused by a Novel Homozygous RPE65 Mutation in Leber Congenital Amaurosis.

Background: The aim of this study was to describe an unexpected phenotype in a family with Leber congenital amaurosis (LCA) due to a retinal pigment epithelium-specific protein 65 kDa (RPE65) homozygous mutation. History and Signs: We analyzed a family from Yemen in which 3 individuals were affected with LCA. Linkage analysis using markers flanking the known LCA genes was done, followed by direct sequencing of RPE65. Therapy and Outcome: Severe visual impairment and night blindness were observed during infancy. We observed photophobia only in the 8-year-old patient. The youngest affected had bilateral hyperopia of + 3.50 and visual acuity of 1/60. The oldest two had visual acuity limited to hand movements in the right eye (OD) and counting fingers in the left eye (OS) for the oldest and of 5/60 OD, 6/60 OS for the other. They showed disc pallor, attenuated vessels, white flecks in the retina mid-periphery and bull's eye maculopathy. ERGs of the oldest child were completely unresponsive. Genomic sequencing identified a novel homozygous missense mutation, IVS2-3C > G, in the second RPE65 intron. Conclusions: We identified a novel LCA-related homozygous RPE65 mutation associated with a severe clinical presentation including an early and severe cone dysfunction. This is in contrast with the presentation associated with other RPE65 mutations predominantly causing rod-cone dystrophy with residual visual function.

Mitochondrial DNA (mt DNA) A3243G mutation associated with an annular perimacular retinal atrophy

Résumé:Background:La mutation 3243 de 1'ADN mitochondrial est associee avec le syndrome l\/HDD (surdite, diabète transmis par la mère) et le syndrome MELAS (Myopathie, Encéphalopathie, acidose Lactique et attaques cérébrales). Elle est aussi associe à des troubles cardiaques, digestifs, endo- et exocrines. Nous rapportons deux cas de maculopathie associée à cette mutation.Histoire et symptomes: pCas l: il s'agit d'une femme de 60 ans soufrant d'un diabète et d'une surdité sans plainte visuelle lors de la présentation. Son acuité visuelle était de 10/ l0 des deux yeux.Cas 2: il s'agit d'une femme de 54 ans souffrant d'une surdité et d'un diabète qui se plaint d'une baisse de vision principalement de l'oeil gauche. Son acuité visuelle était de 6/10 pour l'oeil droit et de 0.5/l0 pour l'oeil gauche.Les deux patientes présentaient une atrophie choriorétinienne aréolaire centrale. La patiente 1 a été suivie durant plus de 15 ans. Une évolution lente et progressive de la maculopathie a été observée. Lors de la dernière visite, l'acuité visuelle était de 6/ l0 dans les deux yeux. Elle présentait un handicap marqué des suites du scotome annulaire.Thérapie et pronostic:AucunConclusion:Les deux patientes présentaient une atrophie rétinienne annulaire périmaculaire. Les patients atteints d'une mutation 3243 de l'ADN mitochondrial devraient bénéficier d'un examen du fond d'oeil à la recherche d'une maculopahtie, même s'ils sont asymptomatiques.Inversement, la découverte d'une telle maculopathie géographique devrait suggérer la possibilité d'une mutation au locus 3243 de l'ADN mitochondrial, surtout en présence d'un diabète et/ou d'une surdité.