Patterns of GFP expression in the bones of donor mice. (A) Within trabecular bone, 3.6-green is strongly expressed on the bone surface and can extend into regions of recently formed bone. The pink cellular regions surrounded by the GFP-positive cells are bone marrow. (B) The 2.3-green is strongly expressed in bone surface cells and in the osteocytes throughout the bone. (C) The 3.6-blue expression resembles 3.6-green. (D) Nondecalcified trabecular bone of trabecular from a 3.6-green donor mouse labeled with XO 2 days before it was killed. The red label is closely associated with the majority of the GFP-positive cells although there are regions of XO labeling without overlying GFP-positive cells (arrows). (A-D) Original magnification, × 200.