CLONING AND IN-SITU HYBRIDIZATION ANALYSIS OF THE EXPRESSION OF POLYSIALYLTRANSFERASE MESSENGER-RNA IN THE DEVELOPING AND ADULT-RAT BRAIN

Polysialyltransferase (PST) is an enzyme that catalyzes the addition o f polysialic acid (PSA), a homopolymer of alpha-2,8-linked sialic acid residues, onto neural cell adhesion molecule (NCAM). The expression o f PSA-NCAM in the brain is developmentally regulated and is of critica l importance; however, the temporal and spatial developmental expressi on of brain PST, a potential key player in the control of PSA-NCAM lev els, remains unclear. In the present study, we have cloned the coding region of rat PST cDNA by reverse transcription-polymerase chain react ion, using primers based on the hamster PST-1 cDNA sequence. A 39-mer oligonucleotide complementary to rat PST cDNA was synthesized to inves tigate the distribution of its mRNA in the developing and adult rat br ain by Northern blot and in situ hybridization. In the embryonic rat b rain, PST mRNA was detected abundantly throughout the neuroepithelia o f most brain regions. At post-natal days 1 and 14, PST was detected th roughout the neocortex, in the pyramidal cells (PC) of the hippocampus proper, the granule cell layer (GCL) of the dentate gyrus, the anteri or ventral nucleus of the thalamus (AVNT) and the GCL and external ger minal layer of the cerebellum. Finally, from PD21 until adulthood, exp ression of PST mRNA was restricted to the PC layer of the hippocampus proper, the GCL of the dentate gyrus, the AVNT, the GCL of the cerebel lum and the dorsal and lateral nucleus of the anterior olfactory bulb. The developmental profile of PST mRNA is paralleled in some structure s by that of the PSA-NCAM, there are, however, notable exceptions. The refore, our results demonstrate that expression of rat PST mRNA is dev elopmentally regulated, is present in the adult rat brain in restricte d areas and may be involved in regulating temporal and spatial express ion of PSA-NCAM. (C) 1997 Elsevier Science B.V.