• Polysialyltransferase ST8SIA4 adds sialic acids by α2,8-linkage on α2,3- or α2,6-linked sialic acid
• Polysialic acid on NCAM in the brain is synthesized by two polysialyltransferases, ST8SIA2 and ST8SIA4
• The majority of polysialic acid expressed in adult brain is lost in ST8SIA4-deficient mice, but polysialic acid is remained in premature neurons and migrating neurons expressing ST8SIA2. Lack of polysialic acid in double-knockout mice causes severe abnormalities in brain development such as neural cell death, aberrant neural cell migration, and differentiation.
• Polysialic acid is detected in many cancer cell lines. ST8SIA4 mRNA is detectable in human neuroblastoma, small and non-small cell lung carcinoma, and glioma. Here, polySia is thought to affect adhesive property of tumor cells and promote metastasis and migration of cancer cells in vivo. Thus, polysialic acid regulation may be an important target on tumor cells.
• Restricted to selected proteins (NCAM, SynCAM-1)