Fig. 10. Accumulation of αSyn aggregates in hippocampal CA2 region associated w ith ATF4 expression in dendrites.
(A) A sagittal section of MPO-A53T brain was immunostained with αSyn505 (green) and ATF4 (red). An arrow points to the hippocampal CA2 region with red and green staining. (B) Higher magnification of the CA2 region shows the dentate gyrus (DG), CA3, and CA2 regions. ATF4 immunostaining (red) is seen in CA2 neurites terminating in a region of αSyn aggregates (green) in the stratum lacunosum moleculare (SLM). (C,D,E) Higher definition confocal image (C) shows two boxed regions in CA2 that are magnified in D and E. (D) ATF4 present in punctate vesicles (red) in CA2 neurites passing through the mossy fiber tract (MF). (E) CA2 neurites with ATF4 (red) passing through larger bead-like aggregates of αSyn (Syn505) (green) in the SLM. (F,G,H) This staining pattern for ATF4 and αSyn aggregates is also seen in A53T brain lacking hMPO, though staining is less intense (F), as well as in the hMPO-Syn61 model (G), and in the PDGF-αSyn model (H). (I) The hMPO-MSA model shows lower level of ATF4 staining in CA2 neurites (red) but lacks the αSyn aggregates (green). (J) CA2 region from wild-type mice lacks both ATF4 staining and αSyn aggregates. (K) The CA2 region of hMPO-A53T brain is stained with hematoxylin and eosin showing pyknotic neurons. (L,M,N) Immunostaining of MPO-A53T CA2 region for MPO (L), CHOP (M), and cleaved caspase-3 (N). (O) A low magnification image of the hippocampus shows ATF4 immunostaining (black) throughout the CA2 and CA3 soma while only CA2 apical dendrites (AP) express significant ATF4. (P,Q,R) Confocal images show immunostaining of the CA2 region for RGS14 (R), a specific marker for CA2 neurons, ATF4 (Q), and the merged images (P). Scale bars A 1 mm, B 40 μm, C 70 μm, D 15 μm, E 15 μm, F-J 100 μm, K 25 μm, O 30 μm P-R 30 μm. All mice used in these studies were males.