| Summary: | Glypican are a family of conserved cell surface Heparan Sulfate Proteoglycans (HSPGs) attached to the cell surface by glycosylphosphatidylinositol (GPI) anchor. Six members (Gpcl-Gpc6) have been identified in mammal so far. They are expressed in spatiotemporally regulated manner in developing and adult tissues which are known to be regulated by signalling growth factors pathways including Fgf, Bmps, Wnt and Shh. Genetic and embryological studies link glypicans to the regulation of signalling pathways during morphogenesis, pattering formation and adult physiology. We showed here that chicken Gallus-gallus glypicans (Gpcl-Gpc6) and No/urn a gene encoding a master regulator of glypican activity are differentially expressed during embryonic developmental stages and adult tissues. This finding suggested that glypicans act as modulator of developmental signalling pathways. Furthermore we show the expression of glypicans in adult chicken tissues and propose a role as regulator of stem cell homeostasis in brain and skeletal muscle. In developing embryo we highlight glypicans expression in some tissue like limb bud, feather bud and neural tube that are known as good models for tissue patterning sites. We provided novel data showing that the inhibition of the signalling pathways altered glypicans expression during early embryonic development. We demonstrated that Notum regulate the pattering of neural tube by regulating the activity and distribution of Shh in the neural tube and alters in the dorsal and ventral boundaries. We concluded that Notum regulate the activity of Shh during neural tube pattering via regulation of glypicans.
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