Selective Forces Related to Spinocerebellar Ataxia Type 2.

Spinocerebellar ataxia type 2 (SCA2) is caused by an unstable expanded CAG repeat tract (CAGexp) at ATXN2. Although prone to selective forces such as anticipation, SCA2 frequency seems to be stable in populations. Our aim was to estimate reproductive success, segregation patterns, and role of anticipation in SCA2. Adult subjects from families with molecular diagnosis provided data about all his/her relatives. Affected and unaffected sibs older than 65.7 years of age were used to estimate reproductive success and segregation patterns. Twenty-one SCA2 families were studied, including 1017 individuals (164 affected) who were born from 1840 to 2012. The median number of children of the non-carriers and carriers, among 99 subjects included in the reproductive success analysis, were 2 and 3 (p < 0.025), respectively. Therefore, the reproductive success of carriers was 1.5. There were 137 non-carriers (59.6%) and 93 carriers (40.4%) (p = 0.04), among subjects included in the segregation analysis. Age at onset across generations pointed to anticipation as a frequent phenomenon. We raised evidence in favor of increased reproductive success related to the carrier state at ATXN2, and segregation distortion favoring normal alleles. Since majority of normal alleles analyzed carried 22 repeats, we propose that this distortion segregation can be related to the high frequency of this allele in human chromosomes.

BRCA1 and BRCA2 rearrangements in Brazilian individuals with Hereditary Breast and Ovarian Cancer Syndrome.

Approximately 5-10% of breast cancers are caused by germline mutations in high penetrance predisposition genes. Among these, BRCA1 and BRCA2, which are associated with the Hereditary Breast and Ovarian Cancer (HBOC) syndrome, are the most frequently affected genes. Recent studies confirm that gene rearrangements, especially in BRCA1, are responsible for a significant proportion of mutations in certain populations. In this study we determined the prevalence of BRCA rearrangements in 145 unrelated Brazilian individuals at risk for HBOC syndrome who had not been previously tested for BRCA mutations. Using Multiplex Ligation-dependent Probe Amplification (MLPA) and a specific PCR-based protocol to identify a Portuguese founder BRCA2 mutation, we identified two (1,4%) individuals with germline BRCA1 rearrangements (c.547+240_5193+178del and c.4675+467_5075-990del) and three probands with the c.156_157insAlu founder BRCA2 rearrangement. Furthermore, two families with false positive MLPA results were shown to carry a deleterious point mutation at the probe binding site. This study comprises the largest Brazilian series of HBOC families tested for BRCA1 and BRCA2 rearrangements to date and includes patients from three regions of the country. The overall observed rearrangement frequency of 3.44% indicates that rearrangements are relatively uncommon in the admixed population of Brazil.

Polymorphic variants of UGT1A1 in neonatal jaundice in southern Brazil.

Alterations in the hepatic conjugation of bilirubin due to uridyl-diphosphate-glucuronosyltransferase 1A1 (UGT1A1) polymorphisms have been proposed as risk factors to neonatal jaundice. Herein, we estimated the frequency of genotypes of the promoter region of UGT1A1 gene in newborns and evaluated its association with severe hyperbilirubinemia. Prospective study of cases and controls including all newborns admitted for phototherapy at HCPA, Brazil, during 9 months; 490 babies were enrolled and PCR was performed. Polymorphic genotypes were detected in 16% of the patients and 7 of the 10 possible genotypes were identified with higher prevalence of polymorphisms in Afro-descendants. In this sample, the variants of UGT1A1 were not associated to severe hyperbilirubinemia; other genic factors should be sought in this high miscegenation area of Brazil.

Prevalence of 4977bp deletion in mitochondrial DNA from patients with chronic kidney disease receiving conservative treatment or hemodialysis in southern Brazil.

BACKGROUND: Damage to mitochondrial DNA (mtDNA) has been described in patients with chronic kidney disease (CKD). The presence of mtDNA 4977bp deletion in many different tissues can serve as a marker of this damage. However, no attempt has been made to detect the presence of mtDNA 4977bp in blood cells of patients with CKD. METHODS: Polymerase chain reaction techniques (PCR) were used to detect mtDNA 4977bp deletion in blood samples of 94 CKD patients. RESULTS: The prevalence of 4977bp deletion in mtDNA was 73.1% (38/52) in patients with CKD undergoing hemodialysis, 57.1% (27/42) in patients with CKD receiving conservative treatment, and 27.8% (15/54) in control samples (p < 0.001). Higher prevalence of this mutation was not associated with patient age (p = 0.54) or time on hemodialysis (p = 0.70). CONCLUSION: The higher prevalence of mtDNA 4977bp deletion in patients in this study indicates that the CKD can induce damage to mtDNA in blood cells and could be exacerbated by hemodialysis.

Biochemical properties of beta-glucosidase in leukocytes from patients and obligated heterozygotes for Gaucher disease carriers.

BACKGROUND: Gaucher's disease (GD) is a disorder caused by the deficiency of lysosomal beta-glucosidase, an enzyme that participates in the degradation of glycosphingolipids. Deficiency of this enzyme results in the storage of glucocerebrosides in lysosomes of macrophage. No studies are available in the literature comparing biochemical and kinetic behavior of this enzyme in leukocytes and fibroblasts from normal individuals, obligate heterozygotes and patients with GD. METHODS: The behavior of beta-glu in terms of optimum pH, heat stability, Km and Vmax in leukocytes from patients with GD and obligated heterozygotes with different genotypes and normal individuals were characterized. RESULTS: Optimum pH was similar in all groups analyzed. In terms of Km and Vmax, several differences among heterozygotes and homozygotes groups and among these groups and normal enzyme were observed. Enzyme from all groups were inactivated when preincubated at 60 degrees C, but some enzymes were more stable than other. Results showed a different behavior of the enzyme in the 3 groups under analysis. Such behavior varied according to individual mutation. CONCLUSIONS: The catalytic gradient presented by beta-glu allowed the correlation of N370S mutation-which presented more stable biochemical properties-with the non-neurological clinical condition of the disease and the catalytically less stable mutation (D409H), with the neurological clinical condition of GD. This study contributes to a better understanding of the repercussion of the different mutations on the protein function, thus allowing to predict the severity of such complex metabolic disorder and to anticipate the most appropriate intervention for each case specifically.

Successful therapy of hyperphenylalaninemia due to defective tetrahydrobiopterin metabolism in two siblings

Alguns pacientes com o diagnóstico inicial de fenilcetonúria (PKU) näo apresentam melhora clínica mesmo apesar de tratados com uma dieta pobre em fenilalanina. Inúmeros trabalhos publicados nos últimos dez anos têm atribuído esses casos a erros no metabolismo da tetra hidrobiopterina (BH4), um cofator essencial para a hidroxilaçäo de fenilalanina, tirosina e triptofânio. Descrevem-se duas irmäs que apresentam um defeito na síntese de BH4, nas quais a administraçäo oral de BH4, L-Dopa, Carbidopa e 5-hidróxi-triptofânio foi seguida de significativa melhora clínica, neurofisiológica e bioquímica. Dados obtidos na nossa regiäo permitem supor que a freqüência de defeitos no metabolismo do BH4, entre os pacientes com hiperfenilalaninemia seja maior que a presentemente estimada. Ao contrário dos indivíduos com PKU clássica, alguns pacientes com deficiência de BH4 parecem responder ao tratamento mesmo quando este é introduzido tardiamente. Enfatiza-se a importância de aplicar o teste para o diagnóstico de deficiência de BH4 em todos os pacientes com hiperfenilalaninemia

Mucolipidosis III (pseudo-Hurler polydystrophy): case report and comments on the diagnostic challenge of the Hurler-like patient

Muitos erros inatos do metabolismo dos glicosaminoglicanos, glicoproteinas e esfingolipídios levam a quadros clínicos e radiológicos denominados "Hurler-like". Entre esses distúrbios estäo as mucolipidoses II e III. Um caso de mucolipidose III (polidistrofia pseudo-Hurler) é apresentado com o objetivo de ilustrar as dificuldades apresentadas no diagnóstico específico desses casos. O diagnóstico laboratorial se baseia num conjunto de testes realizados em urina, sangue e leucócitos e/ou tecidos, e deve ser interpretado cuidadosamente junto com os dados clínicos e radiológicos. Os Autores acreditam que a rotina bioquímica executada no presente caso possa ser útil, uma vez que pacientes "Hurler-like" näo säo raros em serviços de genética, pediatria e neurologia

A flow-sheet for the diagnosis of storage diseases

Baseados na sua experiência em diagnosticar erros inatos do metabolismo num país em desenvolvimento, os autores propöem uma rotina para o diagnóstico de doenças de depósito, a qual pode ser empregada mesmo em laboratórios modestamente equipados. A rotina proposta segue um fluxo de complexidade crescente, embora consista de técnicas de execuçäo relativamente simples (cromatografia em camada delgada, separaçäo de leucócitos do sangue periférico e de mucopolissacarídios urinários, determinaçöes colorimétricas e fluorimétricas) que näo requerem procedimentos ou equipamentos sofisticados

Use of the urine uric acid to creatinine ratio for the detection of disorders of purine metabolism: normal values among 0 to 12 year old children

Os erros inatos do metabolismo das purinas näo säo usualmente identificados com a bateria de testes empregados para a detecçäo de distúrbios metabólicos. A aplicaçäo de um método simples de triagem desses distúrbios, a relaçäo ácido úrico/creatinina na urina, tem sido prejudicada pela inexistência de valores normais para a nossa populaçäo infantil e para as nossas condiçöes de laboratório. No presente trabalho, a relaçäo ácido úrico/creatinina é determinada em 72 crianças normais de 0 a 12 anos. O limite superior da normalidade pode ser estabelecido como de 1,22 para esta faixa etária, excluindo-se os recém-nascidos, que apresentaram valores em média mais elevados. Propöem-se que a relaçäo ácido/creatinina na urina seja incluída nos procedimentos usuais de triagem para erros inatos do metabolismo empregados em nosso meio