No widespread induction of cell death genes occurs in pure motoneurons in an amyotrophic lateral sclerosis mouse model

Abstract

To identify candidate genes that may be involved in motoneuron degeneration, we combined laser capture microdissection with microarray technology. Gene expression in motoneurons was analyzed during the progression of the disease in transgenic SOD1(G93A) mice that develop motoneuron loss. Three major observations were made: first, there was only a small number of genes that were differentially expressed in motoneurons at a pre-symptomatic age (27 out of 34 000 transcripts). Secondly, there is an early specific up-regulation of the gene coding for the intermediate filament vimentin that is increased even further during disease progression. Using in situ hybridization and immunohistochemical analysis, we show that vimentin expression was not only elevated in motoneurons but that the protein formed inclusions in the motoneuron cytoplasm. Thirdly, a time-course analysis of the motoneurons at a symptomatic age (90 and 120 days) showed a modest de-regulation of only a few genes associated with cell death pathways; however, a massive up-regulation of genes involved in cell growth and/or maintenance was observed. This is the first description of the gene profile of SOD1(G93A) motoneurons during disease progression and unexpectedly, no widespread induction of cell death-associated genes was detected in motoneurons of SOD1(G93A) mice.

Toxicity from different SOD1 mutants dysregulates the complement system and the neuronal regenerative response in ALS motor neurons

“…The significance of these findings is amplified by our analysis of the data from an earlier gene array study (12) with an additional dismutase active SOD1 mutant (SOD1 G93A ). The analysis revealed a 43% overlap (49 genes) with our own dismutase active mutant SOD1 G37R data set, including all our major functional candidate groups (SI Tables 4 and 5).…”

“…Because certain aspects of ALS are non-cell autonomous and originate from mutant SOD1 accumulation in non-motor neuronal cells (8,9), cell-type specificity is of high importance when using such an approach. To date, three main gene-expression profiling studies have been reported (10)(11)(12), all of which were restricted to analysis of the adult disease phase in one SOD1 mouse line that accumulates a dismutase active mutant to extraordinarily high levels during disease progression [between 10-and 20-fold over the already abundant endogenous mouse SOD1 (4,13)]. Two studies (10,11) used the entire spinal cord, thus losing cell-type specificity and masking mRNA changes within motor neurons as a consequence of the much more numerous glial cells and their activation before or during disease progression.…”

“…Two studies (10,11) used the entire spinal cord, thus losing cell-type specificity and masking mRNA changes within motor neurons as a consequence of the much more numerous glial cells and their activation before or during disease progression. A more recent effort (12) used profiling by laser microdissection of motor neurons. The major outcome of this study was an elevation of vimentin beginning in the presymptomatic phase.…”

Insights Arising from Gene Expression Profiling in Amyotrophic Lateral Sclerosis

“…The first report described transcriptional analysis of motor neurones isolated from SOD1 G93A mice bred on a mixed background and no differentially expressed genes were detected in the pre-symptomatic mice (Perrin et al 2005). However, in contrast to the whole tissue homogenates, motor neurones did not show activation of apoptotic genes, suggesting that cell death signals derive from other cell types in the spinal cord (Figure 2).…”

“…Several studies have determined the changes in gene expression occurring in motor neurones isolated from the spinal cord of mutant SOD1 G93A mice at different stages during the disease; from the pre-symptomatic stage to paralysis (Ferraiuolo et al 2007;Perrin et al 2005). The first report described transcriptional analysis of motor neurones isolated from SOD1 G93A mice bred on a mixed background and no differentially expressed genes were detected in the pre-symptomatic mice (Perrin et al 2005).…”