Investigating the role of <i>SORL1</i> in mediating AD‐specific endolysosomal phenotypes in neurons and microglia
Bibliographic record
Abstract
Abstract Background Dysregulation of endolysosomal trafficking is a major pathogenic mechanism in Alzheimer’s disease (AD). From the family of AD‐linked endosomal pathway genes, SORL1 stands out as one of the highest risk factors. SORL1 encodes an endocytic sorting receptor that mediates endosomal trafficking and processing of key AD‐associated molecules, including pathogenic forms of amyloid‐β (e.g., Aβ42) and amyloid precursor protein (APP). Using complementary cell‐based model systems, we investigated the role of a protein‐truncating SORL1 variant on endolysosomal trafficking and APP processing. Method Induced pluripotent stem cell (iPSC) lines were derived from two siblings affected with early onset AD (EOAD) who carried a rare protein‐truncating deletion in SORL1 (rs1343336951; p.C1431fs). SORL1+/+ isogenic control iPSC lines were created from the patient lines using CRISPR/Cas9. After validation, the iPSC lines were differentiated into forebrain neurons and analyzed for endosomal trafficking defects. Additional analyses were completed in HEK293‐APPswe cells overexpressing SORL1 wild‐type (WT) or the C1431fs variant. Studies are underway that examine SORL1+/C1431fs microglia for defects in endolysosomal function. Result SORL1+/C1431fs neurons have increased localization of APP in early endosomes (p = 0.002), endosomal swelling (p = 0.004), and greater numbers of early endosomes per cell (p = 0.018). We additionally observe SORL1+/C1431fs neurons trending toward increased secretion of Aβ42 compared to controls. In HEK293 cells, C1431fs increased secretion of Aβ42 (p < 0.01), Aβ40 (p < 0.01), as well as APP soluble α‐secretase (sAPPα; p < 0.01) and β‐secretase (sAPPβ; p < 0.01) cleavage products. We additionally found C1431fs led to increased secretion of soluble SORL1 (p < 0.01). Surface biotinylation revealed C1431fs led to lower levels of SORL1 detected at the cell surface (p < 0.05). Conversely, C1431fs increased the amount of surface APP (p < 0.05). Conclusion Our results indicate that a single gene copy of the SORL1 C1431fs variant is sufficient to induce neuronal defects in endosomal trafficking and APP processing. Our findings are consistent with previously reported results from similar studies of SORL1 in cultured neurons. Ongoing studies in SORL1+/C1431fs microglia and neurons will help broaden our understanding of the role SORL1 plays in regulating endolysosomal phenotypes in multiple cell types implicated in AD.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".