ATM Expression and Activation in Ataxia Telangiectasia Patients with and without Class Switch Recombination Defects

Area of Science:

• Genetics and Molecular Biology
• Immunology
• Cellular Biology

Background:

• Ataxia telangiectasia mutated (ATM) kinase is vital for DNA double-strand break (DSB) repair.
• Ataxia telangiectasia (A-T) patients display immune system abnormalities, including issues with immunoglobulin isotype expression and class switch recombination (CSR).
• This research examines how residual ATM kinase expression and activity influence A-T disease severity.

Purpose of the Study:

• To investigate the correlation between ATM protein expression and activity and the clinical severity of Ataxia telangiectasia (A-T).
• To assess the relationship between ATM protein levels and defects in class switch recombination (CSR) in A-T patients.

Main Methods:

• Classified A-T patients based on genetic diagnosis, CSR status, and medical complication severity.
• Analyzed peripheral blood mononuclear cells from A-T patients and healthy controls before and after ionizing radiation exposure.
• Utilized Western blotting to quantify ATM and phosphorylated ATM (p-ATM) protein expression.

Main Results:

• ATM and p-ATM protein expression were significantly lower in all A-T patients compared to healthy controls, irrespective of radiation exposure.
• Lower ATM and p-ATM protein levels were associated with increased clinical severity in A-T patients.
• While A-T patients with CSR defects showed elevated IgM and reduced switched immunoglobulins, ATM/p-ATM levels did not correlate with these CSR defects.

Conclusions:

• ATM protein expression and activation are impaired in A-T patients.
• Defective ATM and p-ATM protein expression may serve as a clinical indicator for prognostic evaluation and symptom severity assessment in A-T individuals.