Origin of Climbing Fiber Neurons and Their Developmental Dependence on Ptf1a

Dynamics of Ptf1a lineage cells in the caudal hindbrain of the heterozygous and homozygous animals for Ptf1a during embryogenesis. A–L, X-gal-stained transverse sections of the caudal hindbrain. M, N, Double staining with Brn3a and β-gal in the regions indicated by rectangles in O and P, respectively. Yellow arrowheads indicate double-positive cells. O–V, Transverse sections stained with Brn3a. White arrows indicate putative migrating neurons that give rise to CF neurons. White arrowheads indicate CF neurons in the ION. W, X, Double staining with Brn3b and β-gal around the regions indicated by rectangles in O and P, respectively. Yellow arrowheads indicate double-positive cells. White arrows indicate β-gal-positive cells that do not express Brn3b. Y, Top, A ventrolateral quarter of caudal hindbrain at E13.5 immunostained with an anti-activated Caspase-3. Bottom, High-magnification pictures of rectangular regions in the top. Arrowheads indicate apoptotic cells. Z, Quantification of the numbers of cleaved Caspase-3-positive cells located in the ventral half of a caudal hindbrain section. The numbers are 0.54 ± 0.16 and 1.25 ± 0.27 in heterozygotes and homozygotes, respectively (mean ± SEM). *p = 0.015, Student's t test. n = 24 in Ptf1a^cre/+, n = 36 in Ptf1a^cre/cre. Developmental stages and genotypes are indicated. Scale bars: A–L, O–V, Y, 100 μm; M, N, W, X, 20 μm.