ARTEMIS RNA expression of the fibroblasts of the patient with OS. Reverse transcriptase–PCR of ARTEMIS RNA derived from fibroblasts of the patient with OS, an ARTEMIS-deficient patient, a RAG-deficient patient, and an age-matched healthy control. Amplification from a thymic cDNA library and H₂O served as positive and negative controls, respectively. Transcription was performed with (+RT) and without (-RT) reverse transcriptase. Equal usage of cDNA was tested by amplifying HPRT cDNA.