Northern blot analysis of RNA extracted from mouse BM and spleen. Total RNA was extracted from nonadherent wild-type BM and from spleens obtained from wild-type (WT) mice, X-CGD (CGD) mice, and X-CGD mice 13 to 15 weeks after transplantation with MSCV-m91Neo–transduced X-CGD BM. Total cellular RNAs (20 μg per lane) were probed with a radiolabeled murine gp91^phox cDNA (top), and then reprobed with radiolabeled actin cDNA (bottom). The position of the 28S and 18S ribosomal RNAs (top) and actin RNA (bottom) are indicated. The arrows indicate the position of the unspliced and spliced LTR-driven transcripts.