title: Constitutional telomerase mutations are genetic risk factors for cirrhosis.
abstract: Some patients with liver disease progress to cirrhosis, but the risk factors for cirrhosis development are unknown. Dyskeratosis congenita, an inherited bone marrow failure syndrome associated with mucocutaneous anomalies, pulmonary fibrosis, and cirrhosis, is caused by germline mutations of genes in the telomerase complex. We examined whether telomerase mutations also occurred in sporadic cirrhosis. In all, 134 patients with cirrhosis of common etiologies treated at the Liver Research Institute, University of Arizona, between May 2008 and July 2009, and 528 healthy subjects were screened for variation in the TERT and TERC genes by direct sequencing; an additional 1,472 controls were examined for the most common genetic variation observed in patients. Telomere length of leukocytes was measured by quantitative polymerase chain reaction. Functional effects of genetic changes were assessed by transfection of mutation-containing vectors into telomerase-deficient cell lines, and telomerase activity was measured in cell lysates. Nine of the 134 patients with cirrhosis (7%) carried a missense variant in TERT, resulting in a cumulative carrier frequency significantly higher than in controls (P = 0.0009). One patient was homozygous and eight were heterozygous. The allele frequency for the most common missense TERT variant was significantly higher in patients with cirrhosis (2.6%) than in 2,000 controls (0.7%; P = 0.0011). One additional patient carried a TERC mutation. The mean telomere length of leukocytes in patients with cirrhosis, including six mutant cases, was shorter than in age-matched controls (P = 0.0004).
  
  
  CONCLUSIONS
  Most TERT gene variants reduced telomerase enzymatic activity in vitro. Loss-of-function telomerase gene variants associated with short telomeres are risk factors for sporadic cirrhosis.
authors.affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA. calador@nhlbi.nih.gov
authors.forename: Rodrigo T
authors.initials: RT
authors.lastname: Calado
authors.forename: Jennifer
authors.initials: J
authors.lastname: Brudno
authors.forename: Paulomi
authors.initials: P
authors.lastname: Mehta
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Kovacs
authors.forename: Colin
authors.initials: C
authors.lastname: Wu
authors.forename: Marco A
authors.initials: MA
authors.lastname: Zago
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Chanock
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Boyer
authors.forename: Neal S
authors.initials: NS
authors.lastname: Young
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008103:Liver Cirrhosis / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D012307:Risk Factors; D019098:Telomerase / Q000235:genetics*; D055815:Young Adult
chemical_list: D019098:Telomerase