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Updated: Mar 27, 2026
A Phenotyping Regimen for Genetically Modified Mice Used to Study Genes Implicated in Human Diseases of Aging
Published on: July 14, 2016
Exome-wide single-base substitutions in tissues and derived cell lines of the constitutive Fhit knockout mouse
Carolyn A Paisie1, Morgan S Schrock1, Jenna R Karras1
1Department of Molecular Virology, Immunology and Medical Genetics, Columbus, Ohio, USA.
Abstract:
Loss of expression of Fhit, a tumor suppressor and genome caretaker, occurs in preneoplastic lesions during development of many human cancers. Furthermore, Fhit-deficient mouse models are exquisitely susceptible to carcinogen induction of cancers of the lung and forestomach. Due to absence of Fhit genome caretaker function, cultured cells and tissues of the constitutive Fhit knockout strain develop chromosome aneuploidy and allele copy number gains and losses and we hypothesized that Fhit-deficient cells would also develop point mutations. On analysis of whole exome sequences of Fhit-deficient tissues and cultured cells, we found 300 to >1000 single-base substitutions associated with Fhit loss in the 2% of the genome included in exomes, relative to the C57Bl6 reference genome. The mutation signature is characterized by increased C>T and T>C mutations, similar to the "age at diagnosis" signature identified in human cancers. The Fhit-deficiency mutation signature also resembles a C>T and T>C mutation signature reported for human papillary kidney cancers and a similar signature recently reported for esophageal and bladder cancers, cancers that are frequently Fhit deficient. The increase in T>C mutations in -/- exomes may be due to dNTP imbalance, particularly in thymidine triphosphate, resulting from decreased expression of thymidine kinase 1 in Fhit-deficient cells. Fhit-deficient kidney cells that survived in vitro dimethylbenz(a)anthracene treatment additionally showed increased T>A mutations, a signature generated by treatment with this carcinogen, suggesting that these T>A transversions may be evidence of carcinogen-induced preneoplastic changes.
Insights
Loss of the FHIT tumor suppressor leads to increased mutations, particularly C>T and T>C changes, in mouse models. This mutation signature resembles those found in human cancers, suggesting FHIT
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Loss of FHIT (Fragile Histidine Triad) expression, a known tumor suppressor and genome caretaker, is observed in preneoplastic lesions across various human cancers.
- FHIT-deficient mouse models exhibit heightened susceptibility to carcinogen-induced lung and forestomach cancers.
- Constitutive FHIT knockout cells and tissues display chromosomal aneuploidy and copy number alterations due to the absence of FHIT's genome caretaker function.
Purpose of the Study:
- To investigate whether FHIT-deficient cells develop point mutations.
- To characterize the mutation signature associated with FHIT loss.
- To explore the potential mechanisms underlying FHIT-deficiency-associated mutations.
Main Methods:
- Whole exome sequencing of FHIT-deficient tissues and cultured cells.
- Comparative analysis against the C57Bl6 reference genome.
- Analysis of mutation signatures, including base substitutions and their frequencies.
Main Results:
- FHIT loss was associated with 300 to over 1000 single-base substitutions per exome.
- The predominant mutation types were C>T and T>C, mirroring the 'age at diagnosis' signature in human cancers.
- A similar C>T and T>C mutation signature was observed in FHIT-deficient kidney, esophageal, and bladder cancers.
- Increased T>C mutations may stem from dNTP imbalance, specifically thymidine triphosphate, due to reduced thymidine kinase 1 expression.
- In vitro carcinogen treatment (dimethylbenz(a)anthracene) of FHIT-deficient kidney cells revealed increased T>A mutations, indicative of carcinogen-induced changes.
Conclusions:
- FHIT deficiency significantly increases point mutation rates, characterized by C>T and T>C substitutions.
- The observed mutation signature in FHIT-deficient cells has implications for understanding the development of various human cancers.
- Potential mechanisms involving dNTP imbalance and carcinogen interactions contribute to the mutation spectrum in FHIT-deficient cells.
