Col6a1^−/− Mks and platelets display increased mTORC1 signaling. (A) In situ staining of phosphorylated (p)S6 protein (i), p4E-BP1 protein (ii), and pAkt (iii) in WT and Col6a1^−/− CD41⁺ BM Mks. Staining intensities were quantified and expressed relative to WT. A minimum of 40 Mks were analyzed per section. Data are mean ± SD (n = 3). Student t test. (Bi) Western blot of pAkt, pS6, and p4E-BP1 in WT and Col6a1^−/− platelets. Total Akt, total S6, total 4E-BP1, and β-actin were used as loading controls. (Bii) Band densities were quantified and expressed relative to WT. Data are mean ± SD (n = 6). Student t test. *P < .05; ** P < .01.