In AD, a reduction in ST8Sia4 mRNA expression has been observed in the entorhinal cortex using multiplex in situ hybridization (Highet et al., 2023), complementing prior evidence of decreased PSA-NCAM protein levels in the same region (Murray et al., 2016), suggesting both transcriptional and post-translational disruptions of this regulatory axis. This evidence concerns the gene PROS1 and Alzheimer disease.