Cell surface marker proteins during mouse spermatogenesis: two-dimensional electrophoretic analysis.
Purified plasma membranes isolated from separated highly homogenous populations of mouse pachytene spermatocytes, round spermatids (step I-8), and residual bodies have been compared using 2-dimensional polyacrylamide gel electrophoresis. Two polypeptides apparently specific to pachytene spermatocytes have been identified. Component Pa has a molecular weight of 90 k daltons (K) and pI of 5.6. Component Pb has a molecular weight of 56.5 K and a pI of 6.0. Four polypeptides detected only in plasma membranes of round spermatids have been identified as follows: RSa, 90-95 K and pI 5.9; RSb, also 90-95 K and pI 5.9; RSc, approximately 88 K and pI 5.5; RSd, 58 K and pI 6.0-6.3. No polypeptides unique to residual body membranes were identified. Short-term culture experiments have established that separated adult mouse spermatogenic cells survive short-term culture in vitro. These cells actively synthesize numerous cellular proteins as determined by the incorporation of [3H]leucine. Investigations concerning the effect of the cell separation procedure on mouse spermatogenic cell membranes indicate that only 7 of 110-120 total plasma membrane constituents are degraded enzymically during cell purification. Only one of these constituents may correspond to the presumptive cell differentiation markers described for pachytene spermatocytes and round spermatids. These results indicate, therefore, that plasma membranes obtained immediately after cell separation are suitable for the detailed biochemical analysis of the most integral surface proteins during spermatogenesis in the mouse.