Live tissue imaging of BM from A^gfp/A⁺ and A^gfpR702C/A⁺ mice. (A) Representative 3D images of MKs in control A^gfp/A⁺ BM (n = 9). There are 2 MKs (arrows) forming proplatelets (arrowheads indicate some of the proplatelets). The well-developed multiple branches of proplatelets and the multiple buds are similar to those seen in culture. Bar, 30 μm. (B) Representative 3D image from a video showing a MK (arrow) during PPF in A^gfpR702C/A⁺ BM (n = 7). The mouse shown was injected with 1 ng TPO/g of body weight 3 days before imaging to increase possibility of visualizing PPF.²¹  Proplatelets are shorter and thicker than those seen in panel A. White signal is due to bone collagen SHG. Bar, 30 μm. (C) Snapshot from supplemental Video 2 of a MK (arrow) in A^gfp/A⁺ BM. Proplatelets and buds are indicated by arrowheads. Bar, 40 μm. (D) Snapshots from a video showing PPF from a MK (arrow) in A^gfpR702C/A⁺ BM. There are fewer branches and buds on proplatelets (arrowheads; supplemental Video 5). White signal is because of bone collagen SHG. Bar, 30 μm. (E) Fixed BM confirming MK identity by CD41 staining in A^gfp/A⁺ (Ei-ii) and A^gfpR702C/A⁺ (Eiii-iv) BM. (Eii,iv) Shown are increased magnification of panel Ei,iii. Arrows indicate MKs; arrowheads, proplatelets; red, CD41; green, GFP. Bar, 30 μm (Ei,iii) and 20 μm (Eii,iv).