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Updated: Jun 22, 2026
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A Phenotyping Regimen for Genetically Modified Mice Used to Study Genes Implicated in Human Diseases of Aging
Published on: July 14, 2016
Mice hypomorphic for Atr have increased DNA damage and abnormal checkpoint response
Ryan L Ragland1, Martin F Arlt, Elizabeth D Hughes
1Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-0618, USA. ryanragland@yahoo.com
Summary
Researchers created a novel mouse model for Seckel syndrome-1 (SCKL1) by targeting the ATR gene. These mice exhibit reduced ATR protein levels, leading to increased DNA damage and replication stress, offering new insights into ATR deficiency.
Area of Science:
- Cell Biology
- Genetics
- Cancer Research
Background:
- The ATR (Ataxia Telangiectasia and Rad3-related) checkpoint pathway is crucial for responding to DNA damage during S/G2 phases.
- ATR's role in development and tumorigenesis is challenging to study due to homozygous lethality and limited heterozygous effects.
- A hypomorphic Atr mutation model was needed to overcome limitations in studying ATR deficiency.
Purpose of the Study:
- To create a mouse model with a hypomorphic Atr mutation, mimicking the Seckel syndrome-1 (SCKL1) human disease.
- To investigate the effects of reduced ATR protein levels on DNA damage and replication stress in mice.
Main Methods:
- Targeted knock-in of the SCKL1 A --> G mutation into the mouse Atr gene.
- Western blot and RT-PCR to assess Atr protein levels and splicing.
- Analysis of primary fibroblasts from homozygous mice under APH-induced replication stress.
Main Results:
- The A --> G substitution alone did not reduce Atr protein or increase missplicing in homozygotes.
- Homozygous SCKL1 mice retaining the neo cassette showed a 66-82% reduction in total Atr protein due to missplicing.
- Mutant fibroblasts exhibited increased chromosome damage, gaps, breaks at fragile sites, delayed checkpoint induction, and elevated DNA damage markers (Chk1 phosphorylation, gamma-H2ax).
Conclusions:
- The generated hypomorphic Atr mouse model effectively mimics aspects of ATR deficiency and replication stress.
- These mice serve as a valuable system for studying the consequences of ATR deficiency in a developmental and tumorigenesis context.
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