CLONING, CHARACTERIZATION AND DEVELOPMENTAL EXPRESSION OF ALPHA-2,8 SIALYLTRANSFERASE (GD3 SYNTHASE, ST8SIA-I) GENE IN CHICK BRAIN AND RETINA

GD3 and GM2 synthases act on ganglioside GM3 al the branching point of the pathway of synthesis of gangliosides in which the ''a'', ''b'' an d ''c'' families are produced. The relative activities of these enzyme s are important for regulating the ganglioside composition of a given tissue. In the present work, we report the cloning and characterizatio n of a chick GD3 synthase cDNA. The cloned cDNA directed the synthesis of a functionally active enzyme in transiently transfected CHO-K1 cel ls and was highly homologous to mammalian GD3 synthases. In Northern b lot experiments the cDNA detected a single specific GD3 synthase mRNA of about 9.0 kb both in the chicken brain and retina. The abundance of the specific mRNA transcript declined steadily from E7-E9 to very low values around PN2. The levels of enzyme activities measured at the sa me developmental stages roughly followed the changes of specific mRNA levels in both tissues. In situ hybridization of embryonic neural reti na cells in culture showed that both glial-and neuron-like cells expre ssed the specific GD3 synthase mRNA, although with different intensiti es. Results indicate that transcription and/or stability of the specif ic GD3 synthase mRNA constitute a level of control of the expression o f GD3 synthase and indirectly of the ganglioside composition in the de veloping chicken central nervous system (CNS). (C) 1997 ISDN.