Lymphoblasts from SDS patients exhibit defective ribosome assembly. (A) Comparison of polysome profiles from wild type and SDS patient–derived lymphoblastoid cell lines. Proteins were immunoblotted to visualize eIF6. Ribosomal subunit ratios (605:805) are indicated in the top right corner. SBDS genotypes in the patient-derived lymphoblastoid cell lines (SD74, SD55, and SD18) are provided in supplemental Table 4. (B) Extracts from wild type and 3 SDS patient–derived lymphoblastoid cell lines were immunoblotted to visualize the indicated proteins.