Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA.
It has been shown previously that the migration of granule neurons in neonatal cerebellum can be inhibited by a monoclonal antibody (Mab) JONES. Because the inhibition is presumed to be mediated through binding of the JONES antibody to 9-O-acetyl GD3, we used GD3-synthase knockout (GD3S-/-) mice that do not express 9-O-acetyl GD3 and also have no detectable defect in brain development, to examine the mechanism of the inhibitory effect. We found no difference between the migration of granule neurons in the neonatal cerebellar explant culture in GD3S-/- mice and in wild-type mice. Addition of the Mab JONES, but not Mab R24 or A2B5, in the culture medium blocked the neuronal migration in the explant culture of the wild-type mice. The inhibitory effect of Mab JONES was also observed, however, in the explant culture of GD3S-/- mice. Immuno-HPTLC analysis showed at least two JONES-positive glycolipids bands in the lipid extract of GD3S+/+ mice, and none was detected in that of GD3S-/- mice. Western blot analysis of the cerebellum homogenate of wild-type and GD3S-/- mice identified at least 3 JONES-positive protein bands, one of which is beta1-integrin. Because the JONES antibody also blocked neuronal migration in the cerebellar explant culture of GD3S-/- mice that do not express 9-O-acetyl-GD3, it suggested an alternative mechanism for the inhibitory effect of the antibody, at least in the GD3S knockout mice, and the inhibitory effect of the JONES antibody on neuronal migration could be mediated through its binding to beta1-integrin.