Chondroitin sulphate proteoglycan is involved in lens vesicle morphogenesis in chick embryos

Proteoglycans have been implicated in the invagination and formation of var ious embryonal cavitied primordia. In this paper the expression of chondroi tin sulphate proteoglycan (CSPG) is analysed in the lens primordium during lens vesicle formation, and demonstrate that this proteoglycan has a specif ic distribution pattern with regard to invagination and fusion processes in the transformation of placode into lens vesicle. More specifically. CSPG w as detected in: (1) the apical surface of lens epithelial cells. where earl y CSPG expression was observed in the whole of the lens placode whilst in t he vesicle phase it was restricted to the posterior epithelium: (2) intense CSPG expression in the basal lamina. which remained constant for the entir e period under study; (3) CSPG expression in the intercellular spaces of th e lens primordium epithelium, which increased during the invagination of th e primordium and which at the vesicle stage was more evident in the posteri or epithelium; and (4) CSPG expression on the edges of the lens placode bot h prior to and during fusion. Treatment with beta -D-xyloside causes signif icant CSPG depletion in the lens primordium together with severe alteration s in the invagination and fusion of the lens vesicle; this leads to the for mation of lens primordia which in some cases remain practically flat or sho w partial invagination defects or fusion disruption. Similar results were o btained by enzyme digestion with chondroitinase AC but not with type Il hep arinase, which indicates that alterations induced by beta -D-xyloside were due to interference in CSPG synthesis. The findings demonstrate that CSPG i s a common component of the lens primordium at the earliest developmental s tages during which it undergoes specific modifications. It also includes ex perimental evidence to show that 'in vivo' CSPG plays an important role in the invagination and fusion processes of the lens primordium. (C) 2001 Acad emic Press.