Splicing mutations, mainly IVS6‐1(G>T), account for 70% of fumarylacetoacetate hydrolase (FAH) gene alterations, including 7 novel mutations, in a survey of 29 tyrosinemia type I patients
Universidad Autónoma de Madrid, Madrid, Madrid, SpainHuman Mutation (Impact Factor: 5.14). 09/2002; 20(3):180-8. DOI: 10.1002/humu.10084
Hereditary tyrosinemia type I (HTI) is an autosomal recessive disease characterized by a deficiency in fumarylacetoacetate hydrolase (FAH) activity. In this work, the FAH genotype was established in a group of 29 HTI patients, most of them from the Mediterranean area. We identified seven novel mutations-IVS8-1(G>A, IVS10-2(A>T), 938delC, E6/I6del26, W78X, Q328X, and G343W-and two previously described mutations-IVS6-1(G>T) and IVS12+5(G>A). Fully 92.8% of the patients were carriers of at least one splice site mutation, with IVS6-1(G>T) accounting for 58.9% of the total number of alleles. The splice mutation group of patients showed heterogeneous phenotypic patterns ranging from acute forms with severe liver malfunction to chronic forms with renal manifestations and slow progressive hepatic alterations. Qualitative FAH cDNA expression was the same in all IVS6-1(G>T) homozygous patients regardless of their clinical picture. One patient with a heterozygous combination of a nonsense (Q328X) and a frameshift (938delC) mutation showed an atypical clinical picture of hypotonia and repeated infections. Despite the high prevalence of IVS12+5(G>A) in the northwestern European population, we found only two patients with this mutation in our group.
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- "c.982C>T p.Gln328X Nonsense Spain 2 2 Arranz et al. (2002) c.1001 C>T p.Ser334>Phe Missense Saudi Arabia 1 2 Imtiaz et al. (2011) "
ABSTRACT: Hereditary tyrosinemia type 1 (HT1) (OMIM 276700) is a severe inherited metabolic disease affecting mainly hepatic and renal functions that leads to a fatal outcome if untreated. HT1 results from a deficiency of the last enzyme of tyrosine catabolism, fumarylacetoacetate hydrolase (FAH). Biochemical findings include elevated succinylacetone in blood and urine; elevated plasma concentrations of tyrosine, methionine and phenylalanine; and elevated tyrosine metabolites in urine. The HT1 frequency worldwide is about 1 in 100,000 individuals. In some areas, where the incidence of HT1 is noticeably higher, prevalence of characteristic mutations has been reported, and the estimated incidence of carriers of a specific mutation can be as high as 1 out of 14 adults. Because the global occurrence of HT1 is relatively low, a considerable number of cases may go unrecognized, underlining the importance to establish efficient prenatal and carrier testing to facilitate an early detection of the disease. Here we describe the 95 mutations reported so far in HT1 with special emphasis on their geographical and ethnic distributions. Such information should enable the establishment of a preferential screening process for mutations most predominant in a given region or ethnic group.
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- "The fah coding gene located on chromosome 15 in the q23–q25 region  spans over 35 kb and contains 14 exons . Forty-seven naturally occurring mutations have been identified so far, including 7 nonsense mutations   . "
ABSTRACT: Messenger RNAs containing premature stop codons are generally targeted for degradation through the nonsense-mediated mRNA decay (NMD) pathway. The subcellular localization of the NMD process in higher eukaryotes remains controversial. While many mRNAs are subjected to NMD prior to their release from the nucleus, a few display cytoplasmic NMD. To understand the possible impact of NMD on the pathogenesis of hereditary tyrosinemia type I, a severe metabolic disease caused by fumarylacetoacetate hydrolase (FAH) deficiency, we examined the metabolism of FAH mRNA harboring a nonsense mutation, W262X, in lymphoblastoid cell lines derived from patients and their parents. W262X-FAH transcripts show a approximately 20-fold reduction in abundance in mutant cells, which is translation-dependent. Cellular fractionation shows that this down-regulation of the W262X transcript occurs in the cytoplasm. Thus, the W262X FAH is another example of nonsense mRNAs subjected to the NMD pathway in the cytoplasm.
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