The colonic aganglionosis phenotype of miRet51/miRet51 is reproduced in organ culture. Guts were removed from +/+ and miRet51/miRet51 (51/51) E11.5 embryos, cultured for 4 d and processed for immunostaining with PGP9.5. (a,b) Fluorescent images of segments of the small intestine of +/+ and miRet51/miRet51 gut. (c,d) The corresponding colonic segments. Note the absence of a ganglionic plexus from the colon of explants derived from miRet51/miRet51 embryos. +/+, n = 5; 51/51, n = 4.