MANS peptide binds to MARCKS and inhibits proplatelet formation. (A) Live MKs at day 4 were treated with either MANS peptide specific for MARCKS (100 μg/mL) RNS control peptide (100 μg/mL) or Di-8-Anepps to highlight the demarcation membrane. Confocal microscopy was performed with a Leica SP5X Laser Scanning Confocal Microscope equipped with a 63Χ (N.A. = 1.4) Plan-Apo oil immersion objective, and a white light laser. Images were obtained and analyzed using the Leica Applications Suite Advanced Fluorescence, version 2.6.6. MANS and ANEPPS are localized to DMS, whereas the control peptide, RNS, is nonspecific and punctated throughout the MK. (B) Apoptosis and (C) Proplatelet formation after treatment with MANS and RNS peptides (n = 5; *P < .01). (D) Representative images; scale bar represents 10 μm. (E) Immunogold transmission electron microscopy showing MARCKS labeling along the plasma membrane (PM) and demarcation membrane invaginations (DMS). Scale bars represent 500 nm.