mRNP export kinetics and retrograde transport in mex67-5. (A) Merged and registered images show select frames of a successful export event in a mex67-5 cell (see Video 8). (B) Dot plot showing the distribution of GFA1 mRNP export times in REF (n = 43) and mex67-5 (n = 9) cells, with the mean denoted by a black line. (C) Selected nonconsecutive frames show a retrograde transport event in which an mRNP on the cytoplasmic side of the NE returns to the nucleus (see Video 10). For A and C, cells were imaged at 26°C and 67 Hz with the time from the start of the event given in the bottom right of each image in milliseconds. The last image and inset show an overlay of the mRNP path that is color coded based on position (white, nuclear docked; yellow, transition; blue, cytoplasmic docked/cytoplasm). Each green arrowhead and star denotes mRNP positions at the beginning and end of the track, respectively. Bars, 1 µm.