Knockdown of SBDS expression recapitulates ribosomal changes seen in SDS patients. (A) Healthy bone marrow stromal cells were infected with lentivirus encoding either a Scrambled (Scr) shRNA or an SBDS shRNA. Two different RNAi sequences targeting SBDS were assayed (no. 1, no. 2). SBDS knockdown was confirmed by immunoblot. Tubulin was assayed as a loading control. (B) The ribosomal profiles were analyzed by sucrose gradient centrifugation. Representative polysome profile overlays are shown for Scr versus SBDS RNAi experiments. 80S:40S ratios were quantitated for 3 independent experiments. 80S:40S ratios represent the average results for 3 independent experiments for each condition; *P < .05.