Fig 5. Loss of DSCAM impairs the growth of ChC axon cartridges and boutons.
(A) Representative images of single ChCs in layer II/III of ACC. Shown are ChCs of DSCAM2j/+ (+/−) and DSCAM2j/2j (−/−) mice at P28. All ChC images in this paper are from this brain region of P28 mice. Scale bar, 20 μm. (B) Quantification of the total cartridge length (A). For each ChC, all axon cartridges (approximately 15–40) innervating the AIS of PyNs in a volume of 120 μm (length) × 80 μm (width) × 30 μm (thickness) with the ChC cell body in the top middle were analyzed (S6 Fig). For each mouse, 4–6 ChCs were analyzed, and 4 DSCAM+/− and 4 DSCAM−/− mice were analyzed. (C) Representative images of ChC axon cartridges innervating the AIS of PyNs. Cartridges of single ChCs were labeled with tdTomato (Red). The AIS of PyNs were labeled by anti-phospho-IκB (pIκB, green). The arrows point to presynaptic boutons of ChCs in the boxed regions. (D, E) Quantification of bouton number (D) and size (E). For each ChC, all boutons in axon cartridges that innervate AIS in the defined volume (S6 Fig) were analyzed for bouton numbers; boutons in the 10 cartridges nearest to the cell body were analyzed for bouton sizes. In each mouse, 4–6 ChCs were analyzed. A total of 4 DSCAM+/− and 4 DSCAM−/− mice were analyzed. Each dot represents 1 mouse. Student t test *: p < 0.05; ***: p < 0.001. The data underlying this Figure can be found in https://doi.org/10.5281/zenodo.7714234. ACC, anterior cingulate cortex; AIS, axon initial segment; ChC, chandelier cell; DSCAM, Down syndrome cell adhesion molecule; PyN, pyramidal neuron; P28, postnatal day 28.