Neurophysiological findings of the late-onset, dominant, proximal spinal muscular atrophies with dysautonomia because of the VAPB PR056SER mutation

The vesicle-associated membrane protein/synaptobrevin-associated membrane protein B (VAPB) Pro56Ser Mutation has been identified in Brazilian families showing various motor neuron syndromes. However, the neurophysiological characteristics of these patients have not been detailed, and some questions Still need to be solved, such as the possible presence of myotonia and the origin of the abdominal protrusion seen in most patients. The eventual finding of suggestive electrophysiological characteristics would be helpful not only for clinical diagnosis but also to selection of the appropriate DNA test. To clarify these questions we carried out sensory and motor conduction Studies, including symphatetic skin response, and needle examination in six genetically proven affected members. The electromyographic findings were those of a slowly progressive motor neuron disorder. Topographically, the abdominal muscles were severely affected, but the facial and laryngeal muscles were preserved or very mildly involved. Sensory conduction studies and sympathetic Skin responses were normal. No myotonic discharge was recorded. These findings are indistinguishable from those of other motor neuron disorders, although the predominant involvement of the proximal limbs and of the abdominal muscles may be of some help in the appropriate clinical setting.

Characterizing the phenotypic manifestations of MFN2 R104W mutation in Charcot-Marie-Tooth type 2

Mutations of the mitofusin 2 (MFN2) gene have been reported to be the most common cause of the axonal form of Charcot Marie Tooth disease (CMT). The aim of this study was to describe a de novo MFN2 p.R104W mutation and characterize the associated phenotype. We screened the entire coding region of MFN2 gene and characterized its clinical phenotype, nerve conduction studies and sural nerve biopsy. Neuropsychological tests and brain MRI were also performed. A de nova mutation was found in exon 4 (c.310C > T; p.R104W). In addition to a severe and early onset axonal neuropathy, the patient presented learning problems, obesity, glucose intolerance, leukoencephalopathy, brain atrophy and evidence of myelin involvement and mitochondrial structural changes on sural nerve biopsy. These results suggest that MFN2 p.R104W mutation is as a hot-spot for MFN2 gene associated to a large and complex range of phenotypes. (C) 2011 Elsevier B.V. All rights reserved.

Holt-Oram syndrome: novel TBX5 mutation and associated anomalous right coronary artery

The Holt-Oram syndrome was confirmed in an asymptomatic 36-year-old man by a novel TBX5-gene mutation (exon 8 acceptor splicing site, c.663-1G greater than A). Computed tomography showed an atrial septal defect and an anomalous right coronary artery crossing between the aorta and pulmonary arteries. Surgery corrected the septal defect and the initial segment of the anomalous vessel was unroofed and enlarged. Anomalous coronary arteries were not previously described in the Holt-Oram syndrome patients and should be added to the list of possible associated cardiac defects.

Saethre-Chotzen Syndrome, Pro136His TWIST Mutation, Hearing Loss, and External and Middle Ear Structural Anomalies: Report on a Brazilian Family

Objective: To describe the clinical, speech, hearing, and imaging findings in three members of a Brazilian family with Saethre-Chotzen syndrome (SCS) who presented some unusual characteristics within the spectrum of the syndrome. Design: Clinical evaluation was performed by a multidisciplinary team. Direct sequencing of the polymerase chain reaction amplified coding region of the TWIST1 gene, routine and electrophysiological hearing evaluation, speech evaluation, and imaging studies through computed tomography (CT) scan and magnetic resonance imaging (MRI) were performed. Results: TWIST1 gene analysis revealed a Pro136His mutation in all patients. Hearing evaluation showed peripherial and mixed hearing loss in two of the patients, one of them with severe unilateral microtia. Computed tomography scan showed structural middle ear anomalies, and MRI showed distortion of the skull contour as well as some of the brain structures. Conclusions: We report a previously undescribed TWIST1 gene mutation in patients with SCS. There is evidence that indicates hearing loss (conductive and mixed) can be related both with middle ear (microtia, high jugular bulb, and enlarged vestibules) as well as with brain stem anomalies. Here we discuss the relationship between the gene mutation and the clinical, imaging, speech, and hearing findings.

Novel mutation in the adiponectin (ADIPOQ) gene is associated with hypoadiponectinaemia in Japanese-Brazilians

P>Objective Adiponectin is an important mediator of insulin sensitivity, encoded by the ADIPOQ gene. Here we describe two Japanese-Brazilian families with hypoadiponectinaemia due to a novel mutation in ADIPOQ. Design and patients In this study, we examined the entire translated regions of adiponectin in Japanese-Brazilians, a population with one of the highest prevalence rates of diabetes worldwide. We screened 200 patients with type 2 diabetes (DM) and 240 age-matched subjects with normal glucose tolerance. Results A novel heterozygous T deletion at position 186 in exon 2 of ADIPOQ, causing a frameshift at codon 62 and leading to a premature termination at codon 168 (p.Gly63ValfsX106), was found in two individuals with diabetes. This mutation was not found in 240 nondiabetic control subjects. In addition, we screened the mutation in an expanded set of 100 nondiabetic subjects from the general Brazilian population, but we found no mutations. In addition, six family members of the probands were identified as mutation-carriers. Individuals who were mutation-carriers had markedly low plasma adiponectin concentrations compared with those without the mutation [DM: 0 center dot 65 (0 center dot 59-1 center dot 34) mu g/ml vs. 5 center dot 30 (3 center dot 10-8 center dot 55) mu g/ml, P < 0 center dot 0001; normal glucose tolerance: 0 center dot 95 (0 center dot 76-1 center dot 48) mu g/ml vs. 8 center dot 50 (5 center dot 52-14 center dot 55) mu g/ml, P = 0 center dot 003]. All individuals carrying the p.Gly63ValfsX106 mutation and older than 30 years were found to be diabetic. Conclusions We describe for the first time a frameshift mutation in exon 2 of the ADIPOQ gene, which modulates adiponectin levels and may contribute to the genetic risk of late-onset diabetes in Japanese-Brazilians.

Functional analysis of a novel missense NBC1 mutation and of other mutations causing proximal renal tubular acidosis

Mutations in the Na+-HCO3- cotransporter NBC1 cause severe proximal tubular acidosis (pRTA) associated with ocular abnormalities. Recent studies have suggested that at least some NBC1 mutants show abnormal trafficking in the polarized cells. This study identified a new homozygous NBC1 mutation (G486R) in a patient with severe pRTA. Functional analysis in Xenopus oocytes failed to detect the G486R activity due to poor surface expression. In ECV304 cells, however, G486R showed the efficient membrane expression, and its transport activity corresponded to approximately 50% of wild-type (WT) activity. In Madin-Darby canine kidney (MDCK) cells, G486R was predominantly expressed in the basolateral membrane domain as observed for WT. Among the previously identified NBC1 mutants that showed poor surface expression in oocytes, T485S showed the predominant basolateral expression in MDCK cells. On the other hand, L522P was exclusively retained in the cytoplasm in ECV304 and MDCK cells, and functional analysis in ECV304 cells failed to detect its transport activity. These results indicate that G486R, like T485S, is a partial loss of function mutation without major trafficking abnormalities, while L522P causes the clinical phenotypes mainly through its inability to reach the plasma membranes. Multiple experimental approaches would be required to elucidate potential disease mechanism by NBC1 mutations.

Variable phenotypic manifestations of a K44N mutation in the TGIF gene

The etiologies and clinical spectra of HPE are extremely heterogeneous. Here, we report a Brazilian boy with lobar holoprosencephaly who was ascertained in a sample of 60 patients with HPE and HPE-like phenotypes and screened for molecular analysis of the major HPE causative genes: SHH, PTCH, SIX3, GLI2, and TGIF This boy presented a p.K44N (c.132G > T) mutation in exon 2 of the TGIF gene which was inherited from his phenotypically normal mother. This mutation leads to lysine to arginine amino acid change and is predicted to be a damaging mutation. Clinical aspects involving variable phenotypical manifestations in different mutations of TGIF are discussed. (c) 2007 Elsevier B.V. All rights reserved.

Carpenter Syndrome: Extended RAB23 Mutation Spectrum and Analysis of Nonsense-mediated mRNA Decay

Carpenter syndrome, a rare autosomal recessive disorder characterized by a combination of craniosynostosis, polysyndactyly, obesity, and other congenital malformations, is caused by mutations in RAB23, encoding a member of the Rab-family of small GTPases. In 15 out of 16 families previously reported, the disease was caused by homozygosity for truncating mutations, and currently only a single missense mutation has been identified in a compound heterozygote. Here, we describe a further 8 independent families comprising 10 affected individuals with Carpenter syndrome, who were positive for mutations in RAB23. We report the first homozygous missense mutation and in-frame deletion, highlighting key residues for RAB23 function, as well as the first splice-site mutation. Multi-suture craniosynostosis and polysyndactyly have been present in all patients described to date, and abnormal external genitalia have been universal in boys. High birth weight was not evident in the current group of patients, but further evidence for laterality defects is reported. No genotype-phenotype correlations are apparent. We provide experimental evidence that transcripts encoding truncating mutations are subject to nonsense-mediated decay, and that this plays an important role in the pathogenesis of many RAB23 mutations. These observations refine the phenotypic spectrum of Carpenter syndrome and offer new insights into molecular pathogenesis. (C) 2011 Wiley-Liss, Inc.

Iodide Transport Defect: Functional Characterization of a Novel Mutation in the Na(+)/I(-) Symporter 5 `-Untranslated Region in a Patient with Congenital Hypothyroidism

Context: Iodide transport defect (ITD) is an autosomal recessive disorder caused by impaired Na(+)/I(-) symporter (NIS)-mediated active iodide accumulation into thyroid follicular cells. Clinical manifestations comprise a variable degree of congenital hypothyroidism and goiter, and low to absent radioiodide uptake, as determined by thyroid scintigraphy. Hereditary molecular defects in NIS have been shown to cause ITD. Objective: Our objective was to perform molecular studies on NIS in a patient with congenital hypothyroidism presenting a clinical ITD phenotype. Design: The genomic DNA encoding NIS was sequenced, and an in vitro functional study of a newly identified NIS mutation was performed. Results: The analysis revealed the presence of an undescribed homozygous C to T transition at nucleotide -54 (-54C>T) located in the 5`-untranslated region in the NIS sequence. Functional studies in vitro demonstrated that the mutation was associated with a substantial decrease in iodide uptake when transfected into Cos-7 cells. The mutation severely impaired NIS protein expression, although NIS mRNA levels remained similar to those in cells transfected with wild-type NIS, suggesting a translational deficiency elicited by the mutation. Polysome profile analysis demonstrated reduced levels of polyribosomes-associated mutant NIS mRNA, consistent with reduced translation efficiency. Conclusions: We described a novel mutation in the 5`-untranslated region of the NIS gene in a newborn with congenital hypothyroidism bearing a clinical ITD phenotype. Functional evaluation of the molecular mechanism responsible for impaired NIS-mediated iodide concentration in thyroid cells indicated that the identified mutation reduces NIS translation efficiency with a subsequent decrease in protein expression and function. (J Clin Endocrinol Metab 96: E1100-E1107, 2011)

A Single Mutation at the Sheet Switch Region Results in Conformational Changes Favoring lambda 6 Light-Chain Fibrillogenesis

Systemic amyloid light-chain (LC) amyloidosis is a disease process characterized by the pathological deposition of monoclonal LCs in tissue. All LC subtypes are capable of fibril formation although lambda chains, particularly those belonging to the lambda 6 type, are overrepresented. Here, we report the thermodynamic and in vitro fibrillogenic properties of several mutants of the lambda 6 protein 6aJL2 in which Pro7 and/or His8 was substituted by Ser or Pro. The H8P and H8S mutants were almost as stable as the wildtype protein and were poorly fibrillogenic. In contrast, the P7S mutation decreased the thermodynamic stability of 6aJL2 and greatly enhanced its capacity to form amyloid-like fibrils in vitro. The crystal structure of the P7S mutant showed that the substitution induced both local and long-distance effects, such as the rearrangement of the V(L) (variable region of the light chain)-V(L) interface. This mutant crystallized in two orthorhombic polymorphs, P2(1)2(1)2(1) and C222(1). In the latter, a monomer that was not arranged in the typical Bence-Jones dimer was observed for the first time. Crystal-packing analysis of the C222(1) lattice showed the establishment of intermolecular beta-beta interactions that involved the N-terminus and beta-strand B and that these could be relevant in the mechanism of LC fibril formation. Our results strongly suggest that Pro7 is a key residue in the conformation of the N-terminal sheet switch motif and, through long-distance interactions, is also critically involved in the contacts that stabilized the V(L) interface in lambda 6 LCs. (C) 2009 Elsevier Ltd. All rights reserved.

Estudo de família brasileira portadora de deficiência auditiva sensorioneural não-sindrômica com herança mitocondrial

O presente estudo teve como objetivo descrever os achados audiológicos e genéticos de nove membros de uma família brasileira que apresenta a mutação no DNA mitocondrial. Todos os nove membros realizaram estudo genético, avaliação foniátrica e audiológica (audiometria tonal e logoaudiometria). O estudo genético revelou a presença de mutação mitocondrial A1555G no gene 12S rRNA (MT-RNR-1) do DNA mitocondrial em todos os sujeitos. Oito sujeitos apresentaram deficiência auditiva e somente um apresentou limiares auditivos normais até o término da realização do estudo. Os resultados audiológicos apontaram para perdas auditivas bilaterais, com prevalência das simétricas, de configurações e graus variados (de moderado a profundo) e pós-linguais. Progressão da perda auditiva foi observada em dois irmãos afetados. Não foi possível afirmar a época do início da perda auditiva por falta de informação dos sujeitos, no entanto, observou-se manifestação da perda em crianças e adultos. As mutações no DNA mitocondrial representam uma causa importante de perda auditiva, sendo imprescindível a realização do diagnóstico etiopatológico, a fim de retardar o início ou evitar a progressão da surdez.

Genotype-phenotype correlation in Brazillian Rett syndrome patients

BACKGROUND: Rett syndrome (RS) is a severe neurodevelopmental X-linked dominant disorder caused by mutations in the MECP2 gene. PURPOSE: To search for point mutations on the MECP2 gene and to establish a correlation between the main point mutations found and the phenotype. METHOD: Clinical evaluation of 105 patients, following a standard protocol. Detection of point mutations on the MECP2 gene was performed on peripheral blood DNA by sequencing the coding region of the gene. RESULTS: Classical RS was seen in 68% of the patients. Pathogenic point mutations were found in 64.1% of all patients and in 70.42% of those with the classical phenotype. Four new sequence variations were found, and their nature suggests patogenicity. Genotype-phenotype correlations were performed. CONCLUSION: Detailed clinical descriptions and identification of the underlying genetic alterations of this Brazilian RS population add to our knowledge of genotype/phenotype correlations, guiding the implementation of mutation searching programs.

Change and Aging Senescence as an Adaptation

Understanding why we age is a long-lived open problem in evolutionary biology. Aging is prejudicial to the individual, and evolutionary forces should prevent it, but many species show signs of senescence as individuals age. Here, I will propose a model for aging based on assumptions that are compatible with evolutionary theory: i) competition is between individuals; ii) there is some degree of locality, so quite often competition will be between parents and their progeny; iii) optimal conditions are not stationary, and mutation helps each species to keep competitive. When conditions change, a senescent species can drive immortal competitors to extinction. This counter-intuitive result arises from the pruning caused by the death of elder individuals. When there is change and mutation, each generation is slightly better adapted to the new conditions, but some older individuals survive by chance. Senescence can eliminate those from the genetic pool. Even though individual selection forces can sometimes win over group selection ones, it is not exactly the individual that is selected but its lineage. While senescence damages the individuals and has an evolutionary cost, it has a benefit of its own. It allows each lineage to adapt faster to changing conditions. We age because the world changes.

No evidence for an association between the-36A > C phospholamban gene polymorphism and a worse prognosis in heart failure

Background: In Brazil, heart failure leads to approximately 25,000 deaths per year. Abnormal calcium handling is a hallmark of heart failure and changes in genes encoding for proteins involved in the re-uptake of calcium might harbor mutations leading to inherited cardiomyopathies. Phospholamban (PLN) plays a prime role in cardiac contractility and relaxation and mutations in the gene encoding PLN have been associated with dilated cardiomyopathy. In this study, our objective was to determine the presence of the -36A>C alteration in PLN gene in a Brazilian population of individuals with HF and to test whether this alteration is associated with heart failure or with a worse prognosis of patients with HF. Methods: We genotyped a cohort of 881 patients with HF and 1259 individuals from a cohort of individuals from the general population for the alteration -36A>C in the PLN gene. Allele and genotype frequencies were compared between groups (patients and control). In addition, frequencies or mean values of different phenotypes associated with cardiovascular disease were compared between genotypic groups. Finally, patients were prospectively followed-up for death incidence and genotypes for the -36A>C were compared regarding mortality incidence in HF patients. Results: No significant association was found between the study polymorphism and HF in our population. In addition, no association between PLN -36A>C polymorphism and demographic, clinical and functional characteristics and mortality incidence in this sample of HF patients was observed. Conclusion: Our data do not support a role for the PLN -36A>C alteration in modulating the heart failure phenotype, including its clinical course, in humans.

Heat and chemical stress modulate the expression of the alpha-RYR gene in broiler chickens

The biological cause of Pork Stress syndrome, which leads to PSE (pale, soft, exudative) meat, is excessive release of Ca(2+) ions, which is promoted by a genetic mutation in the ryanodine receptors (RyR) located in the sarcoplasmic reticulum of the skeletal muscle cells. We examined the relationship between the formation of PSE meat under halothane treatment and heat stress exposure in chicken alpha RYR hot spot fragments. Four test groups were compared: 1) birds slaughtered without any treatment, i.e., the control group (C); 2) birds slaughtered immediately after halothane treatment (H); 3) birds slaughtered immediately after heat stress treatment (HS), and 4) birds exposed to halothane and to heat stress (H+HS), before slaughtering. Breast muscle mRNA was extracted, amplified by RT-PCR, and sequenced. PSE meat was evaluated using color determination (L*value). The most common alteration was deletion of a single nucleotide, which generated a premature stop codon, resulting in the production of truncated proteins. The highest incidence of nonsense transcripts came with exposure to halothane; 80% of these abnormal transcripts were detected in H and H+HS groups. As a consequence, the incidence of abnormal meat was highest in the H+HS group (66%). In HS, H, and C groups, PSE meat developed in 60, 50, and 33% of the samples, respectively. Thus, halothane apparently modulates alpha RYR gene expression in this region, and synergically with exposure to heat stress, causes Avian Stress syndrome, resulting in PSE meat in broiler chickens.