A Population of CRES Resides in the Outer Dense Fibers of Spermatozoa1
Bibliographic record
Abstract
Cystatin-related epididymal spermatogenic protein (CRES, also CST8) is expressed in both the testis and epididymis and found associated with spermatozoa. It appears as nonglycosylated (14 and 12 kDa) and glycosylated isoforms (19 and 17 kDa). The role of CRES remains enigmatic and is dependent on localization of its isoforms, which is the objective of this study. Our initial approach was to investigate testicular origins of these isoforms by immunohistochemistry and immunogold electron microscopy. We confirmed previous reports that CRES was expressed in the cytoplasm of elongating spermatids from step 8 to step 16. However, we noticed that the pattern of testicular expression was reminiscent of outer dense fiber (ODF) and fibrous sheath (FS) proteins. Western blot analysis of extracts of cauda epididymal sperm revealed a nonionic, detergent-insoluble 14-kDa CRES isoform. To further pinpoint and confirm CRES localization we separated sperm heads and tails and extracted the tails with progressively harsher protein solubilizing agents. Western blots of these sequential extracts, designed to progressively remove the mitochondrial sheath and the ODFs or FS, detected a CRES-immunoreactive 14-kDa band associated with the accessory fibers of the tail. Immunogold labeling was concentrated over growing ODFs in the testes and persisted in spermatozoa. This study discovers a CRES isoform that assembles as part of the ODFs during the elongation and maturation phases of spermiogenesis and is retained as a covalently bound component of the ODFs in spermatozoa.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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) | 0.000 | 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 teacher head, 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".