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Two novel mutations in ABHD12: expansion of the mutation spectrum in PHARC and assessment of their functional effects.

ABSTRACT: PHARC (polyneuropathy, hearing loss, ataxia, retinitis pigmentosa, and cataracts) is a recently described autosomal-recessive neurodegenerative disease caused by mutations in the ?-?-hydrolase domain-containing 12 gene (ABHD12). Only five homozygous ABHD12 mutations have been reported and the pathogenesis of PHARC remains unclear. We evaluated a woman who manifested short stature as well as the typical features of PHARC. Sequence analysis of ABHD12 revealed a novel heterozygous c.1129A>T (p.Lys377*) mutation. Targeted comparative genomic hybridization detected a 59-kb deletion that encompasses exon 1 of ABHD12 and exons 1-4 of an adjacent gene, GINS1, and includes the promoters of both genes. The heterozygous deletion was also carried by the patient's asymptomatic mother. Quantitative reverse transcription-PCR demonstrated ?50% decreased expression of ABHD12 RNA in lymphoblastoid cell lines from both individuals. Activity-based protein profiling of serine hydrolases revealed absence of ABHD12 hydrolase activity in the patient and 50% reduction in her mother. This is the first report of compound heterozygosity in PHARC and the first study to describe how a mutation might affect ABHD12 expression and function. The possible involvement of haploinsufficiency for GINS1, a DNA replication complex protein, in the short stature of the patient and her mother requires further studies.

SUBMITTER: Chen DH

PROVIDER: S-EPMC3855015 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Two novel mutations in ABHD12: expansion of the mutation spectrum in PHARC and assessment of their functional effects.

Chen Dong-Hui DH Naydenov Alipi A Blankman Jacqueline L JL Mefford Heather C HC Davis Marie M Sul Youngmee Y Barloon A Samuel AS Bonkowski Emily E Wolff John J Matsushita Mark M Smith Corrine C Cravatt Benjamin F BF Mackie Ken K Raskind Wendy H WH Stella Nephi N Bird Thomas D TD

Human mutation 20131002 12

PHARC (polyneuropathy, hearing loss, ataxia, retinitis pigmentosa, and cataracts) is a recently described autosomal-recessive neurodegenerative disease caused by mutations in the α-β-hydrolase domain-containing 12 gene (ABHD12). Only five homozygous ABHD12 mutations have been reported and the pathogenesis of PHARC remains unclear. We evaluated a woman who manifested short stature as well as the typical features of PHARC. Sequence analysis of ABHD12 revealed a novel heterozygous c.1129A>T (p.Lys3 ...[more]

PMID: 24027063

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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

Two novel mutations in ABHD12: expansion of the mutation spectrum in PHARC and assessment of their functional effects.

Publications

Two novel mutations in ABHD12: expansion of the mutation spectrum in PHARC and assessment of their functional effects.

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