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Basal forebrain cholinergic neurons are vulnerable in a mouse model of Down syndrome and their molecular fingerprint is rescued by maternal choline supplementation

ABSTRACT: Basal forebrain cholinergic neuron (BFCN) degeneration is a hallmark of Down syndrome (DS) and Alzheimer's disease (AD). Current therapeutics in these disorders have been unsuccessful in slowing disease progression, likely due to poorly understood complex pathological interactions and dysregulated pathways. The Ts65Dn trisomic mouse model recapitulates both cognitive and morphological deficits of DS and AD, including BFCN degeneration and has shown lifelong behavioral changes due to maternal choline supplementation (MCS). To test the impact of MCS on trisomic BFCN, we performed laser capture microdissection to individually isolate choline acetyltransferase-immunopositive neurons in Ts65Dn and disomic littermates, in conjunction with MCS at the onset of BFCN degeneration. We utilized single population RNA sequencing (RNA-seq) to interrogate transcriptomic changes within medial septal nucleus (MSN) BFCN. Leveraging multiple bioinformatic analysis programs on differentially expressed genes (DEGs) by genotype and diet, we identified key canonical pathways and altered physiological functions within Ts65Dn MSN BFCN, which were attenuated by MCS in trisomic offspring, including the cholinergic, glutamatergic and GABAergic pathways. We linked differential gene expression bioinformatically to multiple neurological functions, including motor dysfunction/movement disorder, early onset neurological disease, ataxia and cognitive impairment via Ingenuity Pathway Analysis. DEGs within these identified pathways may underlie aberrant behavior in the DS mice, with MCS attenuating the underlying gene expression changes. We propose MCS ameliorates aberrant BFCN gene expression within the septohippocampal circuit of trisomic mice through normalization of principally the cholinergic, glutamatergic, and GABAergic signaling pathways, resulting in attenuation of underlying neurological disease functions.

ORGANISM(S): Mus musculus

PROVIDER: GSE246245 | GEO | 2023/10/30

REPOSITORIES: GEO

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Project description:Persons with Down syndrome (DS) exhibit low muscle strength that significantly impairs their physical functioning. The Ts65Dn mouse model of DS also exhibits muscle weakness in vivo and may serve as a useful model to examine potential factors responsible for DS-associated muscle dysfunction. Therefore, the purpose of this experiment was to directly assess skeletal muscle function in the Ts65Dn mouse and to reveal potential mechanisms of DS-associated muscle weakness. Soleus muscles were harvested from anesthetized male Ts65Dn and wild-type (WT) colony controls. In vitro muscle contractile experiments revealed normal force generation of unfatigued Ts65Dn soleus, but a 12% reduction in force was observed in Ts65Dn muscle during recovery following fatiguing contractions compared to WT muscle (p<0.05). Oxidative stress may contribute to DS-related pathologies, including muscle weakness, which may be the result of overexpression of chromosome 21 genes (e.g., copper-zinc superoxide dismutase (SOD1)). SOD1 expression was 25% higher (p<0.05) in Ts65Dn soleus compared to WT muscle but levels of other antioxidant proteins were unchanged. Lipid peroxidation (4-hydroxynoneal) was unaltered in Ts65Dn muscle although protein carbonyls were 20% greater compared to muscle of WT animals (p<0.05). Cytochrome c oxidase expression was reduced 22% in Ts65Dn muscle, suggesting a limitation in mitochondrial function may contribute to post-fatigue muscle weakness. Microarray analysis of Ts65Dn soleus revealed alteration of numerous cellular pathways including: proteolysis, glucose and fat metabolism, neuromuscular transmission, and ATP biosynthesis. In summary, the Ts65Dn mouse displays evidence of muscle dysfunction, and the potential role of mitochondria and oxidative stress warrants further investigation. We used microarrays to gain insight into potential mechanisms of DS-associated skeletal muscle weakness. Soleus muscles were obtained from four male Ts65Dn (DS) mice and four male colony control mice. Animals were apparently healthy and approximately five months old. The muscles were harvested in the basal state under anesthesia induced by sodium pentobarbital at approximately the same time of the day.

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Basal forebrain cholinergic neurons are vulnerable in a mouse model of Down syndrome and their molecular fingerprint is rescued by maternal choline supplementation

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