GPM6A and early-onset autosomal dominant Alzheimer disease: It is of interest to note that S256 was indeed identified as a site of phosphorylation by the phosphoproteome analysis of postmortem Alzheimer’s disease brain tissue (Xia et al., 2008) and phosphorylation of the zebrafish ortholog M6Ab at serine 263, which corresponds to serine 256 of mouse Gpm6a, was shown to contribute to filopodium formation in PC12 cells and neurite outgrowth in zebrafish embryos (Huang et al., 2011).