Cotransduction of hepatocytes in vivo. Hem-A mice were injected with 3 × 10¹¹ vg/mouse of both AAV-cFVIII-HC and AAV-cFVIII-LC. Treated and naive livers were harvested 15 weeks after injection and analyzed by FISH for RNA expression (A-D). Sections were probed sequentially with a heavy-chain–specific probe (green; A) and then with a cocktail of 2 light chain–specific probes (red; B). Colocalization of both transcripts is indicated by the yellow staining (yellow; C). No signal was seen in sections from untreated mice (D). Original magnification, ×40.