Impaired Levels of Gangliosides in the Corpus Callosum of Huntington Disease Animal Models

Abstract

Huntington Disease (HD) is a genetic neurodegenerative disorder characterized by broad types of cellular and molecular dysfunctions that may affect both neuronal and non-neuronal cell populations. Among all the molecular mechanisms underlying the complex pathogenesis of the disease, alteration of sphingolipids has been identified as one of the most important determinants in the last years. In the present study, besides the purpose of further confirming the evidence of perturbed metabolism of gangliosides GM1, GD1a, and GT1b the most abundant cerebral glycosphingolipids, in the striatal and cortical tissues of HD transgenic mice, we aimed to test the hypothesis that abnormal levels of these lipids may be found also in the corpus callosum white matter, a ganglioside-enriched brain region described being dysfunctional early in the disease. Semi-quantitative analysis of GM1, GD1a, and GT1b content indicated that ganglioside metabolism is a common feature in two different HD animal models (YAC128 and R6/2 mice) and importantly, demonstrated that levels of these gangliosides were significantly reduced in the corpus callosum white matter of both models starting from the early stages of the disease. Besides corroborating the evidence of aberrant ganglioside metabolism in HD, here, we found out for the first time, that ganglioside dysfunction is an early event in HD models and it may potentially represent a critical molecular change influencing the pathogenesis of the disease.

Keywords: Corpus Callosum White Matter (CC-WM); GD1a; GM1; GT1b; Gangliosides; HD.

Figure 1

Brain ganglioside content is reduced in CC-WM of symptomatic YAC128 HD mice. Representative dot blotting and densitometric analysis of gangliosides GM1 (A), GD1a (B), and GT1b (C) in CC-WM from symptomatic YAC128 (9 month old) mice and age-matched WT littermates. Ganglioside spots were visualized by ECL. Data are represented as the mean ± SD, n = 5 for each group of mice. ^**P < 0.001; ^***P < 0.0001 (non-parametric Mann–Whitney U-test).

Figure 2

Levels of ganglioside GD1a are reduced in the striatum of symptomatic R6/2 mice. Representative dot blotting and densitometric analysis of GD1a (A) and GT1b (B) in striatal tissues isolated from symptomatic R6/2 mice and WT controls. Ganglioside spots were visualized by ECL. Data are represented as the mean ± SD, n = 7 for each group of mice. ^***P < 0.0001 (non-parametric Mann–Whitney U-test).

Figure 3

Levels of brain gangliosides are aberrant also in the cortex and CC-WM from symptomatic R6/2 HD mice. Representative dot blotting and densitometric analysis of gangliosides GM1, GD1a, and GT1b in cortex (A–C) and CC-WM (D–F) from symptomatic (12 week old) R6/2 mice and age-matched WT littermates. Ganglioside spots were visualized by ECL. Data are represented as the mean ± SD, n = 7 for each group of mice. ^*P < 0.05; ^**P < 0.001; ^***P < 0.0001 (non-parametric Mann–Whitney U-test).

Figure 4

Levels of ganglioside GD1a are reduced in CC-WM levels from pre-symptomatic R6/2 HD mice. Representative dot blotting and densitometric analysis of gangliosides GM1, GD1a, and GT1b in CC-WM from pre-symptomatic R6/2 (4 week old) (A–C) and YAC128 (2.5 month old) (D–F) and age-matched WT littermates. Ganglioside spots were visualized by ECL. Data are represented as the mean ± SD, n = 5 for each group of mice. ^**P < 0.001 (non-parametric Mann–Whitney U-test).

Figure 5

Levels of gangliosides GD1a and GT1b are reduced in CC-WM from early symptomatic R6/2 and YAC128 HD mice. Representative dot blotting and densitometric analysis of gangliosides GM1, GD1a, and GT1b in CC-WM from early symptomatic R6/2 (6 week old) (A–C) and YAC128 (5 month old) (D–F) and age-matched WT littermates. Ganglioside spots were visualized by ECL. Data are represented as the mean ± SD, n = 5 for each group of mice. ^**P < 0.001; ^***P < 0.0001 (non-parametric Mann–Whitney U-test).