title: Genetic instability in lymphoblastoid cell lines expressing biallelic and monoallelic variants in the human MUTYH gene.
abstract: The MUTYH DNA glycosylase counteracts mutagenesis by removing adenine misincorporated opposite DNA 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG). Biallelic germline mutations in MUTYH cause the autosomal recessive MUTYH-associated polyposis (MAP). The impact on genetic instability of the p.Tyr179Cys and p.Arg245His MUTYH variants was evaluated in lymphoblastoid cell lines (LCLs) derived from MAP patients and their relatives in comparison to wild-type LCLs. No difference in MUTYH expression was identified between wild type and LCLs with the p.Tyr179Cys, while the p.Arg245His mutation was associated with an unstable MUTYH protein. LCLs homozygous for the p.Tyr179Cys or the p.Arg245His variant contained increased DNA 8-oxodG levels and exhibited a mutator phenotype at the PIG-A gene. The extent of the increased spontaneous mutation frequency was 3-fold (range 1.6- to 4.6-fold) in four independent LCLs carrying the p.Tyr179Cys variant, while a larger increase (6-fold) was observed in two p.Arg245His LCLs. A similar hypermutability and S-phase delay following treatment with KBrO3 was observed in LCLs homozygous for either variant. When genetic instability was investigated in monoallelic p.Arg245His carriers, mutant frequencies showed an increase which is intermediate between wild-type and homozygous cells, whereas the mutator effect in heterozygous p.Tyr179Cys LCLs was similar to that in homozygotes. These findings indicate that the type of MUTYH mutation can affect the extent of genome instability associated with MUTYH inactivation. In addition, the mild spontaneous mutator phenotype observed in monoallelic carriers highlights the biological importance of this gene in the protection of the genome against endogenous DNA damage.
authors.affiliation: Department of Environment and Primary Prevention and.
authors.forename: Francesca
authors.initials: F
authors.lastname: Grasso
authors.affiliation: Experimental Oncology 1, CRO Aviano National Cancer Institute, Aviano, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Giacomini
authors.affiliation: Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Sanchez
authors.affiliation: Department of Translational Oncology and.
authors.forename: Paolo
authors.initials: P
authors.lastname: Degan
authors.affiliation: Unit of Hereditary Cancer, IRCCS AOU San Martino-IST, Genoa, Italy.
authors.forename: Viviana
authors.initials: V
authors.lastname: Gismondi
authors.affiliation: Department of Environment and Primary Prevention and.
authors.forename: Filomena
authors.initials: F
authors.lastname: Mazzei
authors.affiliation: Unit of Hereditary Cancer, IRCCS AOU San Martino-IST, Genoa, Italy.
authors.forename: Liliana
authors.initials: L
authors.lastname: Varesco
authors.affiliation: Experimental Oncology 1, CRO Aviano National Cancer Institute, Aviano, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Viel
authors.affiliation: Department of Environment and Primary Prevention and margherita.bignami@iss.it.
authors.forename: Margherita
authors.initials: M
authors.lastname: Bignami
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D011125:Adenomatous Polyposis Coli / Q000097:blood / Q000235:genetics*; D000328:Adult; D001959:Bromates / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D045647:DNA Glycosylases / Q000235:genetics* / Q000378:metabolism*; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000032:analysis; D014644:Genetic Variation; D042822:Genomic Instability; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D055550:Protein Stability; D055815:Young Adult
chemical_list: D001959:Bromates; D008565:Membrane Proteins; C080086:phosphatidylinositol glycan-class A protein; C019536:potassium bromate; D000080242:8-Hydroxy-2'-Deoxyguanosine; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; D003849:Deoxyguanosine