Fig. 5. Asymmetry in normal lens development and in the phenotype of Alk6^DN transgenic mice. (A-C) Hematoxylin and Eosin stained sections through the ventral eye region of the right eye of an E12.5 wild-type mouse. These are equally spaced serial sections located at 40 µm (A), 80 µm (B) 120 µm (C) from the first ventral lens section. The reference proximodistal axis from the future optic nerve head to the mid point of the developing cornea is marked by the red line in C. These sections show that primary fiber cell elongation begins in a temporally located (T) domain of the posterior wall of the lens vesicle. The nasal (N) aspect of the posterior lens vesicle wall remains undifferentiated at this stage. The relative size of the undifferentiated domains is marked by the broken red lines. It is also observed that there is a larger domain of developing retina on the temporal side of the optic stalk. (D-F) Sections through the ventral eye region of the left eye of the same E12.5 wild-type mouse shown in A-C labeled for the differentiation marker MIP26 (red) and nuclei (green). These are also equally spaced serial sections located at 40 µm (D), 80 µm (E) and 120 µm (F) from the first ventral lens section and serve to emphasize the temporal side (T) primary fiber cell differentiation asymmetry. The relative size of the undifferentiated domains is marked by the broken white lines in F. (G,H) Three dimensional renderings of E13.5 homozygous A-Alk6^DN-11 and wild-type lenses in posterior pole (G) and nasal (H) views. The renderings were reconstructed from serial sections. The glassy sphere represents the lens capsule and the purple surface the boundary between epithelium and fiber cell mass. These renderings indicate clearly the ventronasal location of the primary fiber cell differentiation defect in the A-Alk6^DN-11 homozygous transgenic lenses.