Fig. 2: TcMAC21 cerebella feature disproportionally reduced anterior and nodular zones, altered pre- and postsynaptic morphology.

A Representative euploid (top) and trisomy (bottom) midsagittal cerebellar sections. The green fluorescence represents GFP expression from the artificial human chromosome 21 present in TcMAC21 mice but absent in euploid controls; all other labeling represents specific antibody immunoreactivity (VGluT1, magenta; DAPI counterstain, blue). Fissures separate the vermis into lobes (left panels, designated by roman numerals). Anterior vermis (AZ) located anterior to the primary fissure, central vermis (CZ) located between the primary fissure and the horizontal fissure, and nodular vermis (NZ) included the nodulus, which is separated from the posterior vermis (PZ) by the posterolateral fissure (right panels). B The analysis of cerebellum morphology. Total cross- sectional area (top) of the molecular layer (ML) and granule cell layer (GCL) measured in the cerebella of TcMAC21 (n = 8) and euploid (n = 8) mice. Each data point represents one mouse, with solid symbols indicating males and open symbols indicating females. Data from the AZ, CZ, PZ, and NZ were discretely represented by (middle) the ML size or (bottom) the GCL size showed a significant decrease in AZ in TcMAC21 cerebella. C Confocal image showing an example of a Purkinje neuron transfected with AAV expressing tdTomato and double stained with vGluT2 (top panels); a high magnification view of a three-dimensional reconstruction of presynaptic vesicle clusters and dendritic shafts from the same neuron (bottom). Scale bar: 50 μm. D Example of a stretch of synaptic vesicle clusters of climbing fiber synapses, labelled using VGluT2 antibody staining (magenta). Scale bar: 10 μm. Quantifications of E VGluT2 staining puncta size and intensity distribution, and F VGAT staining puncta size and intensity distribution were obtained from 9 – 14 mice of each genotype. Both showed a significant trisomy effect of size enlargement. Each data point represents a mouse, and solid data points represent males; open data points represent females. Bars represent mean ± SEM. ***p < 0.001 by t test. G A Confocal image showing an example of two Purkinje neurons transfected with AAV.L7- Cre/AAV.FLEX-tdTomato (red) (left), and a high magnification view of a dendritic segment from the neuron on the right with a three-dimensional reconstruction of spine heads and shafts (right). H Quantifications were obtained from n = 4 mice of each genotype, showing trisomy effects on an increased spine density and a decreased spine shaft length in TcMAC21 Purkinje neurons. 2-3 representative fields of view were measured per mouse; each data point represents a field of view (left panel). Tukey boxplots represent median, the minimum and maximum values (right panel).