RESUMEN
BACKGROUND: Tyrosinemia type 1 (HT1, MIM#276700) is caused by a deficiency in fumarylacetoacetate hydrolase (FAH) and it is associated with severe liver and renal disfunction. At present, the mutational FAH (15q25.1, MIM*613871) spectrum underlying HT1 in the Mexican population is unknown. The objective of this study was to determine the FAH genotypes in eight nonrelated Mexican patients with HT1, who were diagnosed clinically. METHODS: Sequencing of FAH and their exon-intron boundaries and in silico protein modeling based on the crystallographic structure of mouse FAH. RESULTS: We identified pathogenic variants in 15/16 studied alleles (93.8%). Nine different variants were found. The most commonly detected HT1-causing allele was NM_000137.2(FAH):c.3G > A or p.(?) [rs766882348] (25%, n = 4/16). We also identified a novel missense variant NM_000137.2(FAH):c.36C > A or p.(Phe12Leu) in a homozygous patient with an early and fatal acute form. The latter was classified as a likely pathogenic variant and in silico protein modeling showed that Phe-12 residue substitution for Leu, produces a repulsion in all possible Leu rotamers, which in turn would lead to a destabilization of the protein structure and possible loss-of-function. CONCLUSION: HT1 patients had a heterogeneous mutational and clinical spectrum and no genotype-phenotype correlation could be established.
Asunto(s)
Hidrolasas/genética , Mutación Missense , Tirosinemias/enzimología , Tirosinemias/genética , Alelos , Preescolar , Exones , Femenino , Genotipo , Humanos , Hidrolasas/metabolismo , Lactante , Intrones , Hígado/patología , Masculino , México/epidemiología , Tirosinemias/patologíaRESUMEN
Tyrosinemia is a rare genetic disease caused by mutations on genes that codify enzymes responsible for tyrosine metabolism. Considering that tyrosinemics patients usually present symptoms associated with central nervous system alterations that ranges from slight decreases in intelligence to severe mental retardation, we decided to investigate whether acute and chronic administration of L-tyrosine in rats would affect acetylcholinesterase mRNA expression and enzymatic activity during their development. In our acute protocol, Wistar rats (10 and 30 days old) were killed one hour after a single intraperitoneal L-tyrosine injection (500 mg/kg) or saline. Chronic administration consisted of L-tyrosine (500 mg/kg) or saline injections 12 h apart for 24 days in Wistar rats (7 days old) and rats were killed 12 h after last injection. Acetylcholinesterase activity was measured by Ellman's method and acetylcholinesterase expression was carried out by a semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) assay. We observed that acute (10 and 30 days old rats) and chronic L-tyrosine administration increased acetylcholinesterase activity in serum and all tested brain areas (hippocampus, striatum and cerebral cortex) when compared to control group. Moreover, there was a significant decrease in mRNA levels of acetylcholinesterase in hippocampus was observed after acute protocol (10 and 30 days old rats) and in striatum after chronic protocol. In case these alterations also occur in the brain of the patients, our results may explain, at least in part, the neurological sequelae associated with high plasma concentrations of tyrosine seen in patients affected by tyrosinemia type II.
Asunto(s)
Acetilcolinesterasa/biosíntesis , Tirosina/farmacología , Acetilcolinesterasa/sangre , Acetilcolinesterasa/genética , Animales , Animales Recién Nacidos , Animales Lactantes , Química Encefálica/efectos de los fármacos , Modelos Animales de Enfermedad , Esquema de Medicación , Inducción Enzimática/efectos de los fármacos , Proteínas Ligadas a GPI/biosíntesis , Proteínas Ligadas a GPI/sangre , Proteínas Ligadas a GPI/genética , Inyecciones Intraperitoneales , Masculino , Proteínas del Tejido Nervioso/biosíntesis , Proteínas del Tejido Nervioso/genética , ARN Mensajero/biosíntesis , Ratas , Ratas Wistar , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Tirosina/administración & dosificación , Tirosinemias/enzimologíaRESUMEN
Mutations in the human HPD gene (encoding 4-hydroxyphenylpyruvic acid dioxygenase) cause hereditary tyrosinemia type 3 (HT3). We deleted the Aspergillus nidulans homologue (hpdA). We showed that the mutant strain is not able to grow in the presence of phenylalanine and that it accumulates increased concentrations of tyrosine and 4-hydroxyphenylpyruvic acid, mimicking the human HT3 phenotype.