Ataxia-Telangiectasia (A-T) is a prototypical genomic instability disorder with multi-organ deficiency and it is caused by the defective function of a single gene, ATM (Ataxia-Telangiectasia Mutated). Radiosensitivity, among the pleiotropic symptoms of A-T, reflects the basic physiological functions of ATM protein in the double strand break (DSB)-induced DNA damage response (DDR) and also restrains A-T patients from the conventional radiation therapy for their lymphoid malignancy. In this chapter, we describe two methods that have been developed in our lab to assess the radiosensitivity of A-T patients: (1) Colony Survival Assay (CSA) and (2) Flow Cytometry of phospho-SMC1 (FC-pSMC1). The establishment of these more rapid and reliable functional assays to measure the radiosensitivity, exemplified by A-T, would facilitate the diagnosis of other genomic instability genetic disorders as well as help the treatment options for most radiosensitive patients.
Keywords: Colony survival; DNA damage response; Flow cytometry; Ionizing radiation; Lymphoblastoid cells; Whole blood.