Summary of early SC development.

<p>The images show VECAD (yellow) immunolabeled cells in the IZ in the plane of the future SC at the developmental ages listed. The cartoons represent the corresponding stages. The development of SC starts by sprouting from the LVP and RV. RV and their sprouts have been left out of the cartoons for the sake of simplicity and in no way are meant to suggest lesser importance of RV. (A) As in angiogenesis, sprouts led by tip cells penetrate into the IZ all around the limbus. (B) However, in contrast to angiogenesis, multiple tip cells interact and form tip cell clusters (TCCs). (C) These local clusters of cells connect with each other to form a continuous structure encircling the entire limbus. We call this structure the rSC. (D) The number of cells in the rSC increases and the cellular chain branches. Scale bar, 20 µm.