Disruption of GM2/GD2 synthase gene resulted in overt expression of 9‐O‐acetyl GD3 irrespective of Tis21¹

Abstract

GM2/GD2 synthase gene knockout mice lack all complex gangliosides, which are abundantly expressed in the nervous systems of vertebrates. In turn, they have increased precursor structures GM3 and GD3, probably replacing the roles of the depleted complex gangliosides. In this study, we found that 9‐O‐acetyl GD3 is also highly expressed as one of the major glycosphingolipids accumulating in the nervous tissues of the mutant mice. The identity of the novel component was confirmed by neuraminidase treatment, thin layer chromatography‐immunostaining, two‐dimensional thin layer chromatography with base treatment, and mass spectrometry. All candidate factors reported to be possible inducer of 9‐O‐ acetylation, such as bitamine D binding protein, acetyl CoA transporter, or O‐acetyl ganglioside synthase were not up‐regulated. Tis21 which had been reported to be a 9‐O‐acetylation inducer was partially down‐regulated in the null mutants, suggesting that Tis21 is not involved in the induction of 9‐O‐acetyl‐GD3 and that accumulated high amount of GD3 might be the main factor for the dramatic increase of 9‐O‐acetyl GD3. The ability to acetylate exogenously added GD3 in the normal mouse astrocytes was examined, showing that the wild‐type brain might be able to synthesize very low levels of 9‐O‐acetyl GD3. Increased 9‐O‐acetyl GD3, in addition to GM3 and GD3, may play an important role in the compensation for deleted complex gangliosides in the mutant mice.

Ganglioside accumulation in activated glia in the developing brain: comparison between WT and GalNAcT KO mice

“…Table 1 shows the comparison of the effects of ethanol on brain lipid profi les between KO and WT mice. GD3, GM3, and 9-Oacetyl GD3 were major gangliosides in the KO brain because of the deletion of GalNAcT, as previously reported ( 37,38,46 ), and ethanol treatment further increased amounts of these gangliosides. We have shown previously not only GM2, but also other lipids, specifi cally ceramide, TG, ChE, and NAPE, increased in the ethanol-treated P7 mouse brain, and the elevation of these lipids appeared to be correlated with the severity of neural cell damage/ death ( 15,17 ).…”

Structural analysis of brain ganglioside acetylation patterns in mice with altered ganglioside biosynthesis

“…3, B4galnt1 null AH ). The acetylation of GD3, the fraction heavily accumulated in GM2/GD2 synthase-deficient mice, was previously confirmed by immunohistochemical localization and mass spectrometry in studies by Matsuda et al 23 and Furukawa et al 24 We did not detect O-Ac-GD3 in wt mouse brain tissue since it is a very minor ganglioside in the adult brain, while in developing brain, the expression of O-Ac-GD3 has been associated to processes such as neurite outgrowth and neuronal migration in mammalian brain. [31][32][33] Interestingly, it was found that exogenously added GD3 induces its own O-acetylation machinery in different cell types, 34 while other gangliosides fail to induce the same machinery.…”

“…Additional modifications have been reported for both ganglioside fractions present in normal ganglioside pattern as well as for the accumulated gangliosides. 19,23,24 O-acetylation of sialic acid residues is one of the most common covalent modifications of gangliosides. Although acetylation is a relatively small structural change ( Fig.…”

Regulatory Mechanisms of Nervous Systems with Glycosphingolipids

“…In GM2/GD2 synthase KO mice, amounts of the remaining GM3 and GD3 markedly increased, resulting in the maintenance of total ganglioside at almost equivalent levels with those in wild type mice. 9-O-acetyl GD3, that can be scarcely detected in normal tissues, was also accumulated in the mutant mouse brains [12].…”