Figure 9.

Embryoid bodies lacking the laminin γ1 subunit fail to produce intact laminin but do secrete a truncated α1 subunit and free nidogen. (A) Immunoprecipitation with anti–laminin-1 antibodies and 3% SDS-PAGE under nonreducing conditions of ³⁵S-labeled laminin from cell extracts (1, 3, and 5) and media (2, 4, and 6) of embryoid bodies +/+ (1 and 2), +/− (3 and 4) and −/− (5 and 6) for the γ1 subunit. (B) 5% SDS-PAGE under nonreducing (1–4) and reducing conditions (5–8) of immunoprecipitated ³⁵S-labeled laminin from cell extracts (1, 3, 5, and 7) and media (2, 4, 6, and 8) obtained from +/− (1, 2, 5, and 6) and −/− (3, 4, 7, and 8) embryoid bodies. (C) Immunoprecipitation and electrophoresis under reducing conditions of ³⁵S-labeled protein from culture media of +/− (1 and 2) and −/− (3 and 4) embryoid bodies with antibodies specific for the laminin α1 subunit (2 and 4) and nidogen (1 and 3). (D) Anti–laminin α1 subunit immunoblots of proteins from +/− (1) and −/− (2 and 3) embryoid bodies after electrophoresis under reducing conditions. (1 and 3) Proteins present in the media; (2) proteins present in cell extracts.