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Dominant inheritance of sialuria, an inborn error of feedback inhibition.

ABSTRACT: "French type" sialuria, a presumably dominant disorder that, until now, had been documented in only five patients, manifests with mildly coarse facies, slight motor delay, and urinary excretion of large quantities (>1 g/d) of free N-acetylneuraminic acid (NeuAc). The basic defect consists of the very rare occurrence of failed feedback inhibition of a rate-limiting enzyme, in this case uridinediphosphate-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase, by a downstream product, in this case cytidine monophosphate (CMP)-NeuAc. We report a new patient with sialuria who has a heterozygous G-->A substitution in nucleotide 848 of the epimerase gene, which results in an R266Q change. The proband's other allele, as expected, had no mutation. However, the heterozygous R266Q mutation was detected in the patient's mother, who has similarly increased urinary levels of free NeuAc, thereby confirming, for the first time, the dominant mode of inheritance of this inborn error. The biochemical diagnosis of the proband was verified by the greatly increased level of free NeuAc in his cultured fibroblasts, the NeuAc distribution, mainly (59%) in the cytoplasm, and by the complete failure of 100 microM CMP-NeuAc to inhibit UDP-GlcNAc 2-epimerase activity in the mutant cells. These findings call for expansion of the phenotype to include adults and for more-extensive assaying of free NeuAc in the urine of children with mild developmental delay. The prevalence of sialuria is probably grossly underestimated.

SUBMITTER: Leroy JG

PROVIDER: S-EPMC1226128 | biostudies-other | 2001 Jun

REPOSITORIES: biostudies-other

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Dominant inheritance of sialuria, an inborn error of feedback inhibition.

Leroy J G JG Seppala R R Huizing M M Dacremont G G De Simpel H H Van Coster R N RN Orvisky E E Krasnewich D M DM Gahl W A WA

American journal of human genetics 20010418 6

"French type" sialuria, a presumably dominant disorder that, until now, had been documented in only five patients, manifests with mildly coarse facies, slight motor delay, and urinary excretion of large quantities (>1 g/d) of free N-acetylneuraminic acid (NeuAc). The basic defect consists of the very rare occurrence of failed feedback inhibition of a rate-limiting enzyme, in this case uridinediphosphate-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase, by a downstream product, in this case cytidine ...[more]

PMID: 11326336

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Project description:PHARC is a neurodegenerative disease comprising early onset cataract and hearing loss, retinitis pigmentosa, and involvement of both the central and peripheral nervous systems; including demyelinating sensorimotor polyneuropathy and cerebellar ataxia. Previously, we mapped this Refsum-like disorder to a 16 Mb region on chromosome 20. Here we report that mutations in the ABHD12 gene cause PHARC disease and we describe the clinical manifestations in a total of 19 patients from four different countries. The ABHD12 enzyme was recently shown to hydrolyse 2-arachidonoyl glycerol (2-AG), the main endocannabinoid lipid transmitter that acts on cannabinoid receptors CB1 and CB2. Our data therefore represent an example of an inherited disorder related to endocannabinoid metabolism. The endocannabinoid system is involved in a wide range of physiological processes including neurotransmission, mood, appetite, pain appreciation, addiction behaviour and inflammation, and several potential drugs targeting these pathways are in development for clinical applications. Our findings show that ABHD12 performs essential functions in both the central and peripheral nervous systems and the eye. Any future drug-mediated interference with this enzyme should consider the potential risk of long-term adverse effects. Homozygosity mapping using Affymetrix 250K SNP arrays were performed according to the manufacturer's directions on DNA extracted from peripheral blood samples. This accession number contains the data for families 1-5 plus 7 in the article. Supplementary files linked below. The region of interest on chromosome 20 was found using families 1 and 2. The patients in families 3,4 and 5 were then recruited and the patients were homozygous for the same region on chromosome 20 as those in families 1 and 2, showing that all these patients are distantly related. All affected are homozygous for the same mutation. The rest of the chromosomes fall outside the scope of our study. Mutations in ABHD12 Cause the Neurodegenerative Disease PHARC: An Inborn Error of Endocannabinoid Metabolism, Fiskerstrand et al. The American Journal of Human Genetics, 26 August 2010 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B8JDD-50W2K9M-3&_user=6129429&_coverDate=08%2F26%2F2010&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000000150&_version=1&_urlVersion=0&_userid=6129429&md5=234296648f66debd3e2b08e795f2179f

Dataset Information

Dominant inheritance of sialuria, an inborn error of feedback inhibition.

Publications

Dominant inheritance of sialuria, an inborn error of feedback inhibition.

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