Dendritic Spine Ultrastructure in Fragile X syndrome: Evidence for Narrower Neck Widths in Dentate Gyrus Granule Cell Neurons of the Hippocampus
Bibliographic record
Abstract
Fragile X Syndrome (FXS) is a prevalent monogenic disease that presents neurological abnormalities including learning/memory deficits, autism and epilepsy. The Fmr1 gene ‐ transcriptionally silenced in FXS ‐ normally encodes the Fragile X Mental Retardation Protein (FMRP), of which its function is still obscure, but has been shown to localize at dendritic spines of cortical neurons. In an attempt to understand its role, dendritic spines in the dentate gyrus (DG) and cornu ammonis 1 (CA1) hippocampal regions of 21 day FMRP knockout (KO) mice were analyzed and compared to wildtype (WT) littermate controls using electron microscopy. Spines continuous with a parent dendrite were only included in our analyses. There were no significant differences in spine head diameters (DG: 0.529 ±0.014 vs 0.524 ±0.016; CA1: 0.515 ±0.014 vs 0.524 ±0.014µm), postsynaptic density lengths (DG: 6.18 ±0.85 vs 5.69 ±0.30; CA1: 7.55 ±0.87 vs 6.96 ±0.33µm/100µm 2 ) or spine neck lengths (DG: 0.485 ±0.019 vs 0.457 ±0.016; CA1: 0.425 ±0.017 vs 0.421 ±0.015µm) in KO vs WT mice. Spine neck diameters, however, were significantly narrower in the DG of FMRP KO mice (0.193 ±0.0062 vs 0.167 ±0.0064µm) whereas no significant differences were observed in the CA1 (0.162 ±0.0049 vs 0.161 ±0.0061µm). Estimated resistance provided by narrower spine necks in the DG revealed a ~1.7 fold increase in the resistivity of spines. Taken together, these findings suggest that FMRP plays a role in granule cell neuron spine neck structure and may influence signal propagation in a regionally‐specific manner in the hippocampus.
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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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".