Fig. 3.

Cardiac niches, integrin receptors, and extracellular ligands. Apical (A–D) and atrial (E–H) niches contain integrin subunits and laminin. (A–D) The same niche is illustrated at two distinct levels: One (A and B) and two (C and D). c-kit⁺ cells (A, green), which do not express GATA-4 in their nuclei (A and B, white dots), possess α₄-integrin on the cell surface (B, magenta, arrows). However, c-kit⁺ cells (C, green), which express or do not express GATA-4 (C and D, white dots) possess β₁-integrin (D, yellow). (E–H) The α₂-chain of laminin (E, F, and H, yellow) is associated with α₄-integrin (F–H, magenta) in four of the nine c-kit⁺ cells (G and H, green, arrows). The four α₂-laminin α₄-integrin c-kit⁺ cells are negative for GATA-4; GATA-4 is present in the other five c-kit⁺ cells (H, white dots). (Scale bars, 10 μm.)