RESUMO
PURPOSE: Despite the public health successes of newborn bloodspot screening, uncertainty associated with variant forms of primary screening targets has led to discrepancies in medical management. This study explored health-care providers' approaches to managing atypical forms of inherited metabolic diseases (IMDs) in the absence of evidence-based guidelines. METHODS: Semistructured telephone interviews were conducted with metabolic specialists. 3-Methylcrotonyl CoA deficiency and variant forms of phenylketonuria, biotinidase deficiency, and fatty acid oxidation disorders were considered. Data were analyzed inductively and deductively using a novel taxonomy of uncertainty. RESULTS: Health-care providers (n = 12) navigate diagnostic, prognostic, and therapeutic challenges of uncertainty while interpreting patient and family attitudes, preferences, and ideas in the care of children with these result types. Participants explained the limits of classifying mild and atypical metabolic phenotypes. Participants also described the challenge of finding balance between cautious care and overmedicalization. Developing consistent care plans and honest communication with families were perceived as effective strategies when navigating uncertainty. CONCLUSION: Providers' experiences suggest a need for transparent and accessible guidelines that account for challenges associated with uncertainty generated by screening. Timely consideration of this challenge is warranted with increasing emergence of genotype-first approaches to screening.
Assuntos
Pessoal de Saúde , Doenças Metabólicas/diagnóstico , Triagem Neonatal/normas , Atitude do Pessoal de Saúde , Criança , Feminino , Humanos , Recém-Nascido , Masculino , Doenças Metabólicas/epidemiologia , Doenças Metabólicas/metabolismo , Atenção Primária à Saúde , Pesquisa Qualitativa , IncertezaRESUMO
Mutations in genes encoding proteins that are involved in mitochondrial heme synthesis, iron-sulfur cluster biogenesis, and mitochondrial protein synthesis have previously been implicated in the pathogenesis of the congenital sideroblastic anemias (CSAs). We recently described a syndromic form of CSA associated with B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD). Here we demonstrate that SIFD is caused by biallelic mutations in TRNT1, the gene encoding the CCA-adding enzyme essential for maturation of both nuclear and mitochondrial transfer RNAs. Using budding yeast lacking the TRNT1 homolog, CCA1, we confirm that the patient-associated TRNT1 mutations result in partial loss of function of TRNT1 and lead to metabolic defects in both the mitochondria and cytosol, which can account for the phenotypic pleiotropy.
Assuntos
Anemia Sideroblástica/congênito , Anemia Sideroblástica/genética , Deficiências do Desenvolvimento/complicações , Febre/complicações , Doenças Genéticas Ligadas ao Cromossomo X/genética , Síndromes de Imunodeficiência/complicações , Mutação/genética , RNA Nucleotidiltransferases/genética , Alelos , Anemia Sideroblástica/complicações , Anemia Sideroblástica/enzimologia , Deficiências do Desenvolvimento/genética , Febre/genética , Doenças Genéticas Ligadas ao Cromossomo X/complicações , Doenças Genéticas Ligadas ao Cromossomo X/enzimologia , Células HEK293 , Humanos , Síndromes de Imunodeficiência/genéticaRESUMO
Programmed cell death 4 (PDCD4) is a tumour suppressor implicated in cancer development and progression and was recently identified as a repressor of cap-independent translation of specific genes involved in the regulation of apoptosis. We show that the RNA-binding protein HuR binds to the PDCD4 3'UTR to protect it from miR-21-induced silencing. However, following H2O2 treatment, PDCD4 mRNA is degraded via miR-21 binding. Importantly, we identify HuR as a novel substrate of the ERK8 kinase pathway in response to H2O2 treatment. We show that phosphorylation of HuR by ERK8 prevents it from binding to PDCD4 mRNA and allows miR-21-mediated degradation of PDCD4.
Assuntos
Proteínas Reguladoras de Apoptose/metabolismo , Proteína Semelhante a ELAV 1/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , MicroRNAs/metabolismo , Proteínas de Ligação a RNA/metabolismo , Neoplasias do Colo do Útero/enzimologia , Regiões 3' não Traduzidas , Proteínas Reguladoras de Apoptose/genética , Sítios de Ligação , Proteína Semelhante a ELAV 1/genética , Ativação Enzimática , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Inativação Gênica , Células HeLa , Humanos , Peróxido de Hidrogênio/farmacologia , MicroRNAs/genética , Fosforilação , Interferência de RNA , Estabilidade de RNA , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/genética , Transdução de Sinais , Fatores de Tempo , Transfecção , Neoplasias do Colo do Útero/genética , Neoplasias do Colo do Útero/patologiaRESUMO
BACKGROUND: SIFD (Sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay) is a novel form of congenital sideroblastic anemia associated with B-cell immunodeficiency, periodic fevers, and developmental delay caused by mutations in the CCA-adding enzyme TRNT1, but the precise molecular pathophysiology is not known. RESULTS: We show that the disease causing mutations in patient-derived fibroblasts do not affect subcellular localization of TRNT1 and show no gross morphological differences when compared to control cells. Analysis of cellular respiration and oxidative phosphorylation (OXPHOS) complexes demonstrates that both basal and maximal respiration rates are decreased in patient cells, which may be attributed to an observed decrease in the abundance of select proteins of the OXPHOS complexes. CONCLUSIONS: Our data provides further insight into cellular pathophysiology of SIFD.
Assuntos
Anemia Sideroblástica/metabolismo , Respiração Celular/fisiologia , Fibroblastos/metabolismo , Nucleotidiltransferases/metabolismo , Anemia Sideroblástica/genética , Western Blotting , Respiração Celular/genética , Células Cultivadas , Feminino , Imunofluorescência , Humanos , Potencial da Membrana Mitocondrial , Microscopia Eletrônica de Transmissão , Mitocôndrias/metabolismo , Mutação , Nucleotidiltransferases/genética , Fosforilação OxidativaRESUMO
PEX7 encodes the cytosolic receptor for the set of peroxisomal matrix enzymes targeted to the organelle by the peroxisome targeting signal 2 (PTS2). Mutations in PEX7 cause rhizomelic chondrodysplasia punctata (RCDP), a distinct peroxisome biogenesis disorder. In previous work we described three novel PEX7 mutant alleles, including one, L292X, with a high frequency due to a founder effect. We have now extended our analysis to 60 RCDP probands and identified a total of 24 PEX7 alleles, accounting for 95% of the mutant PEX7 genes in our sample. Of these, 50% are L292X, 13% are IVS9+1G>C, and the remainder are mostly private. IVS9+1G>C occurs on at least three different haplotypes and thus appears to result from recurrent mutation. The phenotypic spectrum of RCDP is broader than commonly recognized and includes minimally affected individuals at the mild end of the spectrum. To relate PEX7 genotype and phenotype, we evaluated the consequence of the disease mutation on PEX7 RNA by Northern analysis and RT/PCR. We evaluated the function of the encoded Pex7 protein (Pex7p) by expressing selected alleles in fibroblasts from RCDP patients and assaying their ability to restore import of a PTS2 marker protein. We find that residual activity of mutant Pex7p and reduced amounts of normal Pex7p are associated with milder and variant phenotypes.
Assuntos
Condrodisplasia Punctata Rizomélica/genética , Análise Mutacional de DNA/métodos , Receptores Citoplasmáticos e Nucleares/genética , Receptores Citoplasmáticos e Nucleares/fisiologia , Adolescente , Sequência de Aminoácidos/genética , Substituição de Aminoácidos/genética , Criança , Pré-Escolar , Efeito Fundador , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Mutação/genética , Receptor 2 de Sinal de Orientação para Peroxissomos , Fenótipo , Estrutura Quaternária de Proteína/genética , Receptores Citoplasmáticos e Nucleares/químicaRESUMO
Phosphorylase kinase-deficient liver glycogenosis manifests in infancy with hepatomegaly, growth retardation, and elevated plasma aminotransferases and lipids. It can be caused by mutations in three different genes of phosphorylase kinase subunits: PHKA2, PHKB, and PHKG2. It is usually a benign condition, often with complete resolution of symptoms during puberty. A minority of patients displays a more severe phenotype with symptomatic fasting hypoglycemia and abnormal liver histology that may progress to cirrhosis. Three patients with liver cirrhosis in childhood analyzed previously all had PHKG2 mutations. This suggested that this genotype may generally cause a more severe clinical manifestation, but to date PHKG2 mutations have been identified in only seven patients. Here, we report mutation analysis in three new patients with liver phosphorylase kinase deficiency and recurrent hypoglycemia, liver fibrosis, and lack of glucagon response but no overt cirrhosis. In all three patients, PHKG2 mutations were found (H89fs[insC], E157K, D215N, W300X). Three of these mutations are novel, bringing the total number of distinct human PHKG2 mutations to 11, found in 10 patients. We conclude that liver phosphorylase kinase deficiency with a severe phenotype, with or without cirrhosis, is indeed often caused by PHKG2 mutations. These patients require active measures to maintain normoglycemia (raw cornstarch, nocturnal tube feeding), which may also alleviate growth retardation and the development of abnormal liver histology.