Comprehensive expression analysis of glypicans and syndecans in the mouse embryonic brain

Glypicans and syndecans are heparan sulfate proteoglycans that are associated with the cell membrane. They regulate neural progenitor proliferation and differentiation, as well as neuronal migration, axon guidance, and synaptogenesis in the developing nervous system. The glypican family consists of 6 members encoded by the Gpc1 to Gpc6 genes, and the syndecan family consists of 4 members encoded by the Sdc1 to Sdc4 genes. To understand their roles, precise knowledge of their spatiotemporal gene expression is essential. In this study, their expression patterns in the mouse embryonic brain were examined by use of RT-PCR and in situ hybridization. RT-PCR revealed that expression of Gpc1, Gpc2, Gpc3, Gpc4, Gpc6, Sdc1, and Sdc3 was higher in the embryonic brain than in the adult brain, whereas expression of Gpc5 and Sdc4 was higher in the adult brain. In situ hybridization revealed that at embryonic days 13.5 (E13.5), E15.5, and E17.5, Gpc1, Gpc2, Gpc6, and Sdc3 were highly expressed throughout the brain, whereas Gpc3, Gpc4, Gpc5, and Sdc1 expression was more localized. According to their expression profiles, glypicans and syndecans can be divided into 5 groups: Gpc1, Gpc4, Gpc6, and Sdc1 showed high expression in the ventricular/subventricular zone and low expression in the adult brain. Gpc2 and Sdc3 showed high expression outside the ventricular/subventricular zone and lower expression in the adult brain. Gpc3 showed high expression in the meninges and choroid plexus of the embryonic brain and low expression in the adult brain. Gpc5 and Sdc4 showed low expression in the embryonic brain and high expression in the adult brain. Sdc2 showed low expression in both the embryonic and the adult brains. These expression profiles suggest that different groups of genes may play distinct roles in the developing brain.