Phospho-SMC1 in-Cell ELISA based Detection of Ataxia Telangiectasia

BackgroundAtaxia telangiectasia (A-T) is a common genetically inherited cause of early childhood-onset ataxia. The infrequency of this disease, vast phenotype variation, disorders with features similar to those of A-T, and lack of definite laboratory test, make diagnosis difficult.  In addition, there is no rapid reliable laboratory method for identifying A-T heterozygotes, who susceptible to ionizing radiation (IR), atherosclerosis, diabetes, and cancers. We used SMC1pSer966 (pSMC1) in-cell colorimetric ELISA to diagnosis and screen in A-T families.Materials and Methods: With informed consent, 2cc peripheral blood was collected from the 15 A-T patients, their parents, and 24 healthy controls with no family history of malignancy, diabetes, and atherosclerosis. Extracted peripheral blood mononuclear cells (PBMCs) were cultured in poly-L-Lysine treated 96-well plate with density of 70,000 cells per well. SMC1 phosphorylation was evaluated with cell-based ELISA kit 1 hour after 5 Gy IR and the pSMC1data normalized with Glyceraldehyde-3-phosphate dehydrogenase (GAPDH).Results: SMC1 phosphorylation was significantly low in A-T`s PBMC (mean + standard deviation [SD]: 0.075 + 0.034) in comparison to carriers (mean + SD: 0.190 + 0.060) and healthy controls (mean + SD: 0.312 +0.081), but unluckily could only discriminate A-T patients (Area Under the Curve -receiver operating characteristic [AUC-ROC]: 1.00, 1.00-1.00). This method in spite of rapidness and simplicity showed poor imprecision (22.49% coefficient of variation [CV] for intraday imprecision).Conclusion: It seems pSMC1 assessment by in-cell ELISA can be used for detection of A-T patients, but it may not sensitive enough for identification of carriers. This ELISA test is very simple, rapid, and requires less than 2cc blood. Thus it may be proposed for the early differential diagnosis of A-T as an alternative method.