Corpora amylacea are cell-derived structures that appear physiologically in the aged human brain. While their histological identification is straightforward, their ultrastructural composition and microenvironment at the nanoscale have remained unclear so far, as has their relevance to aging and certain disease states that involve the sequestration of toxic cellular metabolites. Here, we apply correlative serial block-face scanning electron microscopy and transmission electron tomography to gain three-dimensional insight into the ultrastructure and surrounding microenvironment of cerebral Corpora amylacea in the human brainstem and hippocampal region. We find that cerebral Corpora amylacea are composed of dense labyrinth-like sheets of lipid membranes, contain vesicles as well as morphologically preserved mitochondria, and are in close proximity to blood vessels and the glymphatic system, primarily within the cytoplasm of perivascular glial cells. Our results clarify the nature of cerebral Corpora amylacea and provide first hints on how they may arise and develop in the aging brain.

Clearance of damaged mitochondria through mitophagy is critical for maintaining mitochondrial fidelity and the prevention of neurodegeneration. Here, we report on the UBX domain-containing, p97/VCP cofactor UBXD1/UBXN6/UBXDC2 and its role in mitophagy. Recognizing depolarized mitochondria via its C-terminal UBX domain, UBXD1 translocates to mitochondria in a Parkin-dependent manner. During Parkin-independent mitophagy, UBXD1 shows no mitochondrial translocation. Once translocated, UBXD1 recruits p97 to mitochondria via a bipartite binding motif consisting of its N-terminal VIM and PUB domains. Recruitment of p97 by UBXD1 only depends on the presence of UBXD1 on mitochondria without the need for further mitochondrial signals. Following translocation of UBXD1 to CCCP-depolarized mitochondria and p97 recruitment, formation of LC3-positive autolysosomes is strongly enhanced and autophagic degradation of mitochondria is significantly accelerated. Diminished levels of UBXD1 negatively impact mitophagic flux in Parkin-expressing cells after CCCP treatment. Thus, our data supports a model, whereby the p97 cofactor UBXD1 promotes Parkin-dependent mitophagy by specifically recognizing damaged mitochondria undergoing autophagic clearance.

EPNs comprise a heterogeneous group of neuroepithelial tumors, accounting for about 10% of all intracranial tumors in children and up to 30% of brain tumors in those younger than 3 years. Actually, the pattern therapy for low-grade EPNs includes complete surgical resection followed by radiation therapy. Total surgical excision is often not possible due to tumor location. The aim of this study was to evaluate, for the first time, the anti-tumor activity of Amblyomin-X in 4 primary cultures derived from pediatric anaplastic posterior fossa EPN, Group A (anaplastic, WHO grade III) and one primary culture of a high grade neuroepithelial tumor with MN1 alteration, which was initially misdiagnosed as EPN: i) by in vitro assays: comparisons of temozolomide and cisplatin; ii) by intracranial xenograft model. Amblyomin-X was able to induce cell death in EPN cells in a more significant percentage compared to cisplatin. The cytotoxic effects of Amblyomin-X were not detected on hFSCs used as control, as opposed to cisplatin-treatment, which promoted a substantial effect in the hAFSCs viability. TEM analysis showed ultrastructural alterations related to the process of cell death: mitochondrial degeneration, autophagosomes and aggregate-like structures. MRI and histopathological analyzes demonstrated significant tumor mass regression. Our results suggest that Amblyomin-X has a selective effect on tumor cells by inducing apoptotic cell death and may be a therapeutic option for Group AEPNs.