POLYSIALIC ACID SYNTHASE (ST8SIA-II STX) MESSENGER-RNA EXPRESSION IN THE DEVELOPING MOUSE CENTRAL-NERVOUS-SYSTEM

A comparative study was undertaken to correlate the immunohistochemica l localization of polysialic acid (PSA) and the in situ localization o f ST8Sia II mRNA. In situ hybridization of postnatal day 3 mouse brain showed high levels of ST8Sia II mRNA expression in the cerebral neoco rtex, striatum, hippocampus, subiculum, medial habenular nucleus, thal amus, pontine nuclei, and inferior colliculus; intermediate-level expr ession in the olfactory bulb, hypothalamus, superior colliculus, and c erebellum; and low-level expression in other regions. The distribution of ST8Sia II mRNA in the neocortex and cerebellum coincided with the immunohistochemical localization of PSA. During brain development, ST8 Sia II mRNA started decreasing and had almost disappeared by postnatal day 14. Comparison between ST8Sia II and IV mRNA expression was also undertaken by northern blot analysis and competitive PCR analysis. Dur ing the late embryonic to early postnatal stages of the mouse CNS, the ST8Sia II mRNA showed abundant mRNA expression compared with the ST8S ia IV mRNA. Competitive PCR analysis of the adult mouse CNS showed wea k expression of the two genes in the olfactory bulb, thalamus, hippoca mpus, and eyes. The regional and transient expression of ST8Sia II mRN A coincides with that of PSA, suggesting that ST8Sia II is closely inv olved in the biosynthesis and expression of PSA in the developing mous e CNS.