Regional and Cellular Distribution of Nuclear Phosphorylated Tau (AT100) in the Frontal Cortex and Cerebellum of Cetaceans.

This study investigates the nuclear distribution of phosphorylated tau (AT100) in the frontal cortex and cerebellum of 12 cetaceans stranded along the Galician coast (NW Spain). Using Bayesian beta regression, we identified a suggestive positive trend between aging and tau phosphorylation, with posterior probabilities of 85.7% in the cortex and 89.7% in the cerebellum. Although the 95% credible intervals include zero in both models, reflecting the limited sample size, the direction and magnitude of the age effect were stable across multiple prior specifications and outlier-exclusion sensitivity analyses, suggesting a consistent age-related pattern rather than a data artefact. We hypothesize that the translocation of tau to the nucleus may act as a "nuclear shield" against cumulative oxidative stress, a process potentially intensified by the intermittent hypoxia characteristic of diving in these mammals; this hypothesis awaits direct empirical validation. A strong inter-regional correlation (r=0.932; Spearman ρ=0.923) points to a potentially coordinated regulation of tau phosphorylation across brain regions. Furthermore, markedly elevated AT100 levels in a subadult with cerebral necrosis suggest its potential as a marker of acute neuronal distress. These findings provide a preliminary baseline for understanding neuroprotection in cetaceans, with tau phosphorylation as a candidate mechanism for preserving neuronal genomic integrity under extreme physiological conditions.