Contact results in adhesions of cilia membranes. (A) Multiple models could explain the observed coincidence of signal from multiple cilia: one cilium could be resorbed and the other could be making contact with the apical surface, or the membranes of cilia could adhere to one another, or the cilia membranes could be fusing to create an intercellular connection. (B) The formation of the cilia adhesion was monitored by collecting z stacks every 4.6 min. This montage shows the maximum intensity projections of the cilia of two adjacent cells during contact initiation. It appears that a point contact is made (white arrowhead) and maintained for a short time before the area of adhesion starts to spread (yellow arrowhead). Scale bar is 10 μm. (C, D) Scanning EM images of cilia engaged in overlapping (C) and point (D) adhesions (scale bar is 0.2 μm). (E) Pools of cells stably expressing SmoYFP and SmoCFP were mixed and plated on the same transwell. The lowest panel is a maximum intensity projection image of cilia adhesions between cells expressing different fluorophores. Individual z slices make up the montage above and demonstrate that the cilia remain distinct: fluorescence is not shared between the two adjacent cilia.