Down syndrome critical region 2 protein inhibits the transcriptional activity of peroxisome proliferator-activated receptor β in HEK293 cells

Effects of small molecules on neurogenesis: Neuronal proliferation and differentiation

Neurons are believed to be non-proliferating cells. However, neuronal stem cells are still present in certain areas of the adult brain, although their proliferation diminishes with age. Just as with other cells, their proliferation and differentiation are modulated by various mechanisms. These mechanisms are foundational to the strategies developed to induce neuronal proliferation and differentiation, with potential therapeutic applications for neurodegenerative diseases. The most common among these diseases are Parkinson's disease and Alzheimer's disease, associated with the formation of β -amyloid (Aβ ) aggregates which cause a reduction in the number of neurons. Compounds such as LiCl, 4-aminothiazoles, Pregnenolone, ACEA, harmine, D2AAK1, methyl 3,4-dihydroxybenzoate, and shikonin may induce neuronal proliferation/differentiation through the activation of pathways: MAPK ERK, PI3K/AKT, NFκ B, Wnt, BDNF, and NPAS3. Moreover, combinations of these compounds can potentially transform somatic cells into neurons. This transformation process involves the activation of neuron-specific transcription factors such as NEUROD1, NGN2, ASCL1, and SOX2, which subsequently leads to the transcription of downstream genes, culminating in the transformation of somatic cells into neurons. Neurodegenerative diseases are not the only conditions where inducing neuronal proliferation could be beneficial. Consequently, the impact of pro-proliferative compounds on neurons has also been researched in mouse models of Alzheimer's disease.

Regulation of PPARα by APP in Alzheimer disease affects the pharmacological modulation of synaptic activity

Among genetic susceptibility loci associated with late-onset Alzheimer disease (LOAD), genetic polymorphisms identified in genes encoding lipid carriers led to the hypothesis that a disruption of lipid metabolism could promote disease progression. We previously reported that amyloid precursor protein (APP) involved in Alzheimer disease (AD) physiopathology impairs lipid synthesis needed for cortical networks' activity and that activation of peroxisome proliferator-activated receptor α (PPARα), a metabolic regulator involved in lipid metabolism, improves synaptic plasticity in an AD mouse model. These observations led us to investigate a possible correlation between PPARα function and full-length APP expression. Here, we report that PPARα expression and activation were inversely related to APP expression both in LOAD brains and in early-onset AD cases with a duplication of the APP gene, but not in control human brains. Moreover, human APP expression decreased PPARA expression and its related target genes in transgenic mice and in cultured cortical cells, while opposite results were observed in APP-silenced cortical networks. In cultured neurons, APP-mediated decrease or increase in synaptic activity was corrected by a PPARα-specific agonist and antagonist, respectively. APP-mediated control of synaptic activity was abolished following PPARα deficiency, indicating a key function of PPARα in this process.

miR-484 is associated with disease recurrence and promotes migration in prostate cancer

BACKGROUND: microRNAs (miRs) regulate the expression of protein-coding genes and play key roles in various biological processes, including development and immunity. However, dysregulation of miR expression is also involved in disease biology, including cancer.

METHODS: We utilized The Cancer Genome Atlas (TCGA) and other publicly available databases for miRs and mRNA expression in prostate cancer, selected miR-484 and investigated its role in prostate cancer biology and disease progression using in vitro studies.

RESULTS: Our data mining efforts revealed that increased miR-484 in prostate tumors associates with early disease recurrence, while miR-484 expression in human prostate cancer cells enhances cancer cell mobility. Using RNAseq and bioinformatics, we identified candidate target genes of miR-484 and generated a list of potential tumor suppressors. One candidate in this list was PSMG1. We applied luciferase assays and immunoblotting to confirm that miR-484 directly targets PSMG1. Additional in vitro assays with cancer cell lines showed that PSMG1 knockdown rescued the reduction in mobility brought on by miR-484 inhibition, pointing toward the existence of a miR-484–PSMG1 axis in prostate cancer.

CONCLUSIONS: We hypothesize that miR-484 is an oncogene in the prostate that increases cancer cell mobility, with PSMG1 being a mir-484 target in this process.

Genetic and epigenetic pathways in Down syndrome: Insights to the brain and immune system from humans and mouse models

The presence of an extra copy of human chromosome 21 (Hsa21) leads to a constellation of phenotypic manifestations in Down syndrome (DS), including prominent effects on the brain and immune system. Intensive efforts to unravel the molecular mechanisms underlying these phenotypes may help developing effective therapies, both in DS and in the general population. Here we review recent progress in genetic and epigenetic analysis of trisomy 21 (Ts21). New mouse models of DS based on syntenic conservation of segments of the mouse and human chromosomes are starting to clarify the contributions of chromosomal subregions and orthologous genes to specific phenotypes in DS. The expression of genes on Hsa21 is regulated by epigenetic mechanisms, and with recent findings of highly recurrent gene-specific changes in DNA methylation patterns in brain and immune system cells with Ts21, the epigenomics of DS has become an active research area. Here we highlight the value of combining human studies with mouse models for defining DS critical genes and understanding the trans-acting effects of a simple chromosomal aneuploidy on genome-wide epigenetic patterning. These genetic and epigenetic studies are starting to uncover fundamental biological mechanisms, leading to insights that may soon become therapeutically relevant.

Treatment with corn oil improves neurogenesis and cognitive performance in the Ts65Dn mouse model of Down syndrome

Individuals with Down syndrome (DS), a genetic condition due to triplication of Chromosome 21, are characterized by intellectual disability that worsens with age. Since impairment of neurogenesis and dendritic maturation are very likely key determinants of intellectual disability in DS, interventions targeted to these defects may translate into a behavioral benefit. While most of the neurogenesis enhancers tested so far in DS mouse models may pose some caveats due to possible side effects, substances naturally present in the human diet may be regarded as therapeutic tools with a high translational impact. Linoleic acid and oleic acid are major constituents of corn oil that positively affect neurogenesis and neuron maturation. Based on these premises, the goal of the current study was to establish whether treatment with corn oil improves hippocampal neurogenesis and hippocampus-dependent memory in the Ts65Dn model of DS. Four-month-old Ts65Dn and euploid mice were treated with saline or corn oil for 30 days. Evaluation of behavior at the end of treatment showed that Ts65Dn mice treated with corn oil underwent a large improvement in hippocampus-dependent learning and memory. Evaluation of neurogenesis and dendritogenesis showed that in treated Ts65Dn mice the number of new granule cells of the hippocampal dentate gyrus and their dendritic pattern became similar to those of euploid mice. In addition, treated Ts65Dn mice underwent an increase in body and brain weight. This study shows for the first time that fatty acids have a positive impact on the brain of the Ts65Dn mouse model of DS. These results suggest that a diet that is rich in fatty acids may exert beneficial effects on cognitive performance in individuals with DS without causing adverse effects.

Global gene expression changes in the prefrontal cortex of rabbits with hypercholesterolemia and/or hypertension

Although many studies have identified a link between hypercholesterolemia or hypertension and cognitive deficits, till date, comprehensive gene expression analyses of the brain under these conditions is still lacking. The present study was carried out to elucidate differential gene expression changes in the prefrontal cortex (PFC) of New Zealand white rabbits exposed to hypercholesterolemia and/or hypertension with a view of identifying gene networks at risk. Microarray analyses of the PFC of hypercholesterolemic rabbits showed 850 differentially expressed genes (DEGs) in the cortex of hypercholesterolemic rabbits compared to controls, but only 5 DEGs in hypertensive rabbits compared to controls. Up-regulated genes in the PFC of hypercholesterolemic rabbits included CIDEC, ODF2, RNASEL, FSHR, CES3 and MAB21L3, and down-regulated genes included FAM184B, CUL3, LOC100351029, TMEM109, LOC100357097 and PFDN5. Comparison with our previous study on the middle cerebral artery (MCA) of the same rabbits showed many differentially expressed genes in common between the PFC and MCA, during hypercholesterolemia. Moreover, these genes tended to fall into the same functional networks, as revealed by IPA analyses, with many identical node molecules. These include: proteasome, insulin, Akt, ERK1/2, histone, IL12, interferon alpha and NFκB. Of these, PSMB4, PSMD4, PSMG1 were chosen as representatives of genes related to the proteasome for verification by quantitative RT-PCR. Results indicate significant downregulation of all three proteasome associated genes in the PFC. Immunostaining showed significantly increased number of Aβ labelled cells in layers III and V of the cortex after hypercholesterolemia and hypertension, which may be due to decreased proteasome activity and/or increased β- or γ-secretase activity. Knowledge of altered gene networks during hypercholesterolemia and/or hypertension could inform our understanding of the link between these conditions and cognitive deficits in vascular dementia or Alzheimer's disease.

Genetic dissection of the Down syndrome critical region

Down syndrome (DS), caused by trisomy 21, is the most common chromosomal disorder associated with developmental cognitive deficits. Despite intensive efforts, the genetic mechanisms underlying developmental cognitive deficits remain poorly understood, and no treatment has been proven effective. The previous mouse-based experiments suggest that the so-called Down syndrome critical region of human chromosome 21 is an important region for this phenotype, which is demarcated by Setd4/Cbr1 and Fam3b/Mx2. We first confirmed the importance of the Cbr1-Fam3b region using compound mutant mice, which carry a duplication spanning the entire human chromosome 21 orthologous region on mouse chromosome 16 [Dp(16)1Yey] and Ms1Rhr. By dividing the Setd4-Mx2 region into complementary Setd4-Kcnj6 and Kcnj15-Mx2 intervals, we started an unbiased dissection through generating and analyzing Dp(16)1Yey/Df(16Setd4-Kcnj6)Yey and Dp(16)1Yey/Df(16Kcnj15-Mx2)Yey mice. Surprisingly, the Dp(16)1Yey-associated cognitive phenotypes were not rescued by either deletion in the compound mutants, suggesting the possible presence of at least one causative gene in each of the two regions. The partial rescue by a Dyrk1a mutation in a compound mutant carrying Dp(16)1Yey and the Dyrk1a mutation confirmed the causative role of Dyrk1a, whereas the absence of a similar rescue by Df(16Dyrk1a-Kcnj6)Yey in Dp(16)1Yey/Df(16Dyrk1a-Kcnj6)Yey mice demonstrated the importance of Kcnj6. Our results revealed the high levels of complexities of gene actions and interactions associated with the Setd4/Cbr1-Fam3b/Mx2 region as well as their relationship with developmental cognitive deficits in DS.