title: Homozygosity for the WRN Helicase-Inactivating Variant, R834C, does not confer a Werner syndrome clinical phenotype.
abstract: Loss-of-function mutations in the WRN helicase gene cause Werner syndrome- a progeroid syndrome with an elevated risk of cancer and other age-associated diseases. Large numbers of single nucleotide polymorphisms have been identified in WRN. We report here the organismal, cellular, and molecular phenotypes of variant rs3087425 (c. 2500C > T) that results in an arginine to cysteine substitution at residue 834 (R834C) and up to 90% reduction of WRN helicase activity. This variant is present at a high (5%) frequency in Mexico, where we identified 153 heterozygous and three homozygous individuals among 3,130 genotyped subjects. Family studies of probands identified ten additional TT homozygotes. Biochemical analysis of WRN protein purified from TT lymphoblast cell lines confirmed that the R834C substitution strongly and selectively reduces WRN helicase, but not exonuclease activity. Replication track analyses showed reduced replication fork progression in some homozygous cells following DNA replication stress. Among the thirteen TT homozygotes, we identified a previously unreported and statistically significant gender bias in favor of males (p = 0.0016), but none of the clinical findings associated with Werner syndrome. Our results indicate that WRN helicase activity alone is not rate-limiting for the development of clinical WS.
authors.affiliation: Departments of Pathology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.|Biochemistry, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
authors.forename: Ashwini S
authors.initials: AS
authors.lastname: Kamath-Loeb
authors.affiliation: INMEGEN, National Institute of Genomic Medicine, Periferico Sur No.4809, Col. Arenal Tepepan, Del. Tlalpan Mèxico, D.F, C.P. 14610, Mexico.
authors.forename: Diego G
authors.initials: DG
authors.lastname: Zavala-van Rankin
authors.affiliation: INMEGEN, National Institute of Genomic Medicine, Periferico Sur No.4809, Col. Arenal Tepepan, Del. Tlalpan Mèxico, D.F, C.P. 14610, Mexico.
authors.forename: Jeny
authors.initials: J
authors.lastname: Flores-Morales
authors.affiliation: Biostatistics, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Emond
authors.affiliation: Departments of Pathology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Sidorova
authors.affiliation: INMEGEN, National Institute of Genomic Medicine, Periferico Sur No.4809, Col. Arenal Tepepan, Del. Tlalpan Mèxico, D.F, C.P. 14610, Mexico.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Carnevale
authors.affiliation: National Institute of Medical Science and Nutrition Salvador Zubiran, Vasco de Quiroga 15, Colonia Sección XVI, Tlalpan C.P.14000, México D.F., Mexico.
authors.forename: Maria Del Carmen
authors.initials: MD
authors.lastname: Cárdenas-Cortés
authors.affiliation: Departments of Pathology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Norwood
authors.affiliation: Departments of Pathology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.|Genome Sciences, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Monnat
authors.affiliation: Departments of Pathology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.|Biochemistry, University of Washington, 1959 NE Pacific St, Seattle, WA 98195, USA.
authors.forename: Lawrence A
authors.initials: LA
authors.lastname: Loeb
authors.affiliation: INMEGEN, National Institute of Genomic Medicine, Periferico Sur No.4809, Col. Arenal Tepepan, Del. Tlalpan Mèxico, D.F, C.P. 14610, Mexico.
authors.forename: Gabriela E
authors.initials: GE
authors.lastname: Mercado-Celis
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019943:Amino Acid Substitution; D005190:Family; D005260:Female; D006720:Homozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D010641:Phenotype; D014898:Werner Syndrome / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D000071657:Werner Syndrome Helicase / Q000235:genetics / Q000378:metabolism*
chemical_list: C098785:WRN protein, human; D000071657:Werner Syndrome Helicase