Fig. 7

Infrequent three-fold coordination of mutant retina cone photoreceptors suggests strongly directional interaction.

(See Methods section for details of image processing.) A) To identify rods, we superimposed on the ZO-1 label (white) the signal in the rod GFP reporter channel (green) from a single z-slice per cell chosen to coincide with the level of the OLM. B) Same retina as panel A. Adjacent cone photoreceptors in ventral-temporal retina of adult tbx2b mutant. Red lines join pairs of cones that are classified as adjacent at both low and high threshold (see Methods), while yellow lines indicate pairs that were identified as adjacent only with the less stringent threshold. (C) Histogram showing the fraction of cone photoreceptors with the specified number of identified neighbors in a sample of ventral-temporal retina. (See Table 1 for additional data.) D) Segmented image from the region outlined by the dashed box in panels A and B. Pixels between adjacent cells that were filled in by the morphological closing procedure are colored either red (high threshold) or blue (low threshold); at this magnification, 1 pixel corresponds to 0.1 μm. The two cells flanking each red region were classified as adjacent at the high threshold, but the blue region is too long (along the axis joining the centers of the two cells) and too narrow (along the orthogonal axis) to meet the adjacency criteria at the high threshold. The blue region meets the adjacency criteria at the low threshold. Stars indicate cone cells that are three-fold coordinated, i.e. have 3 adjacent cells. Scale bars are 20 μm for A and B, and 4 μm for D.