Spontaneous ATM Gene Reversion in A-T iPSC to Produce an Isogenic Cell Line.

A spontaneously reverted iPSC line was identified from an A-T subject with heterozygous ATM truncation mutations. The reverted iPSC line expressed ATM protein and was capable of radiation-induced phosphorylation of CHK2 and H2A.X. Genome-wide SNP analysis confirmed a match to source T cells and also to a distinct， non-reverted iPSC line from the same subject. Rearranged T cell receptor sequences predict that the iPSC culture originated as several independently reprogrammed cells that resolved into a single major clone， suggesting that gene correction likely occurred early in the reprogramming process. Gene expression analysis comparing ATM(-/-) iPSC lines to unrelated ATM(+/-) cells identifies a large number of differences， but comparing only the isogenic pair of A-T iPSC lines reveals that the primary pathway affected by loss of ATM is a diminished expression of p53-related mRNAs. Gene reversion in culture， although likely a rare event， provided a novel， reverted cell line for studying ATM function.