BMP gradient model for NCPC specification.

The Y axis shows BMP signaling levels. The X axis indicates position along the dorsoventral axis. The threshold range of BMP signaling that specifies NCPC is shown in yellow. The intersection of the gradient with the threshold range for NCPC specification leads to NCPC formation in a lateral region in the size domain shown. In WT, the gradient of BMP signaling reaches a high level ventrally and NCPCs are located in a lateral region of the embryo where BMP signaling levels are low. The region of NCPCs specified in WT is shown with black stripes over the yellow area. In snh, the BMP signaling gradient is lower than WT. Therefore, the NCPCs in snh (blue striped area) are slightly expanded compared to wild type and are located in a more ventral region than WT. In sbn, the BMP signaling gradient is lower than snh. The NCPCs are located in a more ventral region than snh and the NCPCs in sbn (red striped area) are greatly expanded compared to wild type. In the swirl/bmp2b mutant, BMP signaling level is absent or very low, leading to the great reduction or absence of NCPCs.