Fig. 6. Loss of both Slit2 and Ntn1 and leads to separation of epithelial cell layers in the duct. All ducts are immunostained with antibody generated against SMA. (A,B) Slit2^-/-;Ntn1^-/- ducts. (A) Moderate disruption characterized by sporadic loss of LECs (arrows). (B) Separation of epithelial layer (double arrowhead). (C) Table quantifying the severity of ductal disruption. Ntn1^-/- ducts are normal, whereas Slit2^-/- and Slit2^-/-;Ntn1^-/- ducts display increasingly severe disorganization. (+) Modest disruption is characterized by sporadic loss of LECs in short (50 µm) length of duct. (++) More severe disruption is characterized by significant stretches (50-2000 µm) of separation of myoepithelial and LEC layers. (D) Slit2^+/+;Ntn1^+/+ duct from contralateral transplant shows tight juxtaposition of myoepithelial and LEC layers, and an unobstructed lumen. (E,F) Loss of Slit2 (E) leads to sporadic loss of LECs (arrows) in the duct, compared with Slit2^+/+ duct (F) from contralateral transplant duct. (G,H) Ntn1^-/- duct (G) appears morphologically indistinguishable compared with Ntn1^{-/- +/+} duct (H) from contralateral transplant. L, lumen. Scale bar: 20 µm.