Fig. 4. Western blot assay of CD9-eGFP expression in CD9^–/– eggs injected with either wild-type or F174A mutant mouse CD9-eGFP mRNA. The injected eggs were allowed to develop to the M-II phase, then were lysed in non-reducing SDS-sample buffer. Western blots were carried out as described in Materials and Methods. Each lane contains 20 eggs. Lane 1, CD9^–/– eggs; lane 2, CD9^–/– eggs injected with wild-type CD9-eGFP mRNA; lane 3, CD9^–/– eggs injected with mutant CD9- F174A-eGFP mRNA. The molecular mass (kDa) of protein standards is indicated.