Figure 7. Deficient and Decreased Number of Stellate Synapses in CHL1−/− Mice.
(A) Single stellate cell axons (A1) labeled in WT PV-GFP mice showed large and distinct boutons that colocalized with GAD65 (A2)..
(B) Higher magnification view showed that nearly all of these boutons (B1) contained GAD65 ([B2], arrowheads).
(C and D) In CHL1−/−::PV-GFP mice, stellate boutons appeared smaller (white arrowheads), and many of them did not contain detectable levels of GAD65 (blue arrowheads). Note the normal GAD65 signal at pinceau synapses in (C2) (arrows).
(E) Quantification of the percentage of stellate boutons colocalization with GAD65 showed a 43% reduction in CHL1−/− compared to WT mice (p ≤ 0.001.
(F) Quantification of stellate bouton size revealed a 40% reduction in CHL1−/− compared to WT mice (p ≤ 0.01).
(G and H) Ultrastructural analysis showed stellate cell synapses along Purkinje dendritic shafts in the ML of CHL1−/− mice (H), with largely normal morphology and organelle organization as compared to those in WT mice (G).
(I) Quantification of stellate cell synapse density along Purkinje dendritic surface in the upper ML of CHL1 −/− mice revealed a approximately 40% reduction compared to WT mice at P30 (p < 0.03), and a 60% reduction compared to WT mice at P40 (p ≤ 0.001).
(J) Ultrastructural analysis showed atrophy of stellate axon terminals in 3-mo-old CHL1−/− mice. Purkinje dendrites (Pd) were often apposed by degenerating profiles exhibiting electron-dense membrane accumulations (arrows) and electron-lucent empty spaces (stars). (J1) and (J2) are two different examples. Note a symmetrical synapse from most likely a stellate cell axon terminal (St).