A cluster of protein kinases and phosphatases modulated in fetal Down syndrome (trisomy 21) brain

AKT Hyperphosphorylation and T Cell Exhaustion in Down Syndrome

Down syndrome (DS) is associated with increased susceptibility to infections, auto-immunity, immunodeficiency and haematological malignancies. The exact underlying immunological pathophysiology is still unclear. The immunophenotype and clinical characteristics of DS resemble those of Activated PI3K Delta Syndrome (APDS), in which the PI3K/AKT/mTOR pathway is overactivated. We hypothesized that T cell exhaustion and the hyperactivation of the AKT signalling pathway is also present in immune cells of children with DS. In this observational non-interventional cohort study we collected blood samples of children with DS (n=22) and healthy age-matched controls (n=21) for flowcytometric immunophenotyping, phospho-flow AKT analysis and exhaustion analysis of T cells. The median age was 5 years (range 1-12y). Total T and NK cells were similar for both groups, but absolute values and transitional B cells, naive memory B cells and naive CD4+ and CD8+ T cells were lower in DS. pAKT and AKT were increased for CD3+ and CD4+ T cells and CD20+ B cells in children with DS. Total AKT was also increased in CD8+ T cells. Children with DS showed increased expression of inhibitory markers Programmed cell dealth-1 (PD-1), CD244 and CD160 on CD8+ T cells and increased PD-1 and CD244+ expression on CD4+ T cells, suggesting T cell exhaustion. Children with DS show increased pAKT and AKT and increased T cell exhaustion, which might contribute to their increased susceptibility to infections, auto immunity and haematological malignancies.

Drug-Targeted Genomes: Mutability of Ion Channels and GPCRs

Mutations of ion channels and G-protein-coupled receptors (GPCRs) are not uncommon and can lead to cardiovascular diseases. Given previously reported multiple factors associated with high mutation rates, we sorted the relative mutability of multiple human genes by (i) proximity to telomeres and/or (ii) high adenine and thymine (A+T) content. We extracted genomic information using the genome data viewer and examined the mutability of 118 ion channel and 143 GPCR genes based on their association with factors (i) and (ii). We then assessed these two factors with 31 genes encoding ion channels or GPCRs that are targeted by the United States Food and Drug Administration (FDA)-approved drugs. Out of the 118 ion channel genes studied, 80 met either factor (i) or (ii), resulting in a 68% match. In contrast, a 78% match was found for the 143 GPCR genes. We also found that the GPCR genes (n = 20) targeted by FDA-approved drugs have a relatively lower mutability than those genes encoding ion channels (n = 11), where targeted genes encoding GPCRs were shorter in length. The result of this study suggests that the use of matching rate analysis on factor-druggable genome is feasible to systematically compare the relative mutability of GPCRs and ion channels. The analysis on chromosomes by two factors identified a unique characteristic of GPCRs, which have a significant relationship between their nucleotide sizes and proximity to telomeres, unlike most genetic loci susceptible to human diseases.

Phosphorylated Aβ peptides in human Down syndrome brain and different Alzheimer's-like mouse models

The deposition of neurotoxic amyloid-β (Aβ) peptides in extracellular plaques in the brain parenchyma is one of the most prominent neuropathological features of Alzheimer's disease (AD), and considered to be closely related to the pathogenesis of this disease. A number of recent studies demonstrate the heterogeneity in the composition of Aβ deposits in AD brains, due to the occurrence of elongated, truncated and post-translationally modified Aβ peptides that have peculiar characteristics in aggregation behavior and biostability. Importantly, the detection of modified Aβ species has been explored to characterize distinct stages of AD, with phosphorylated Aβ being present in the clinical phase of AD. People with Down syndrome (DS) develop AD pathology by 40 years of age likely due to the overproduction of Aβ caused by the additional copy of the gene encoding the amyloid precursor protein on chromosome 21. In the current study, we analysed the deposition of phosphorylated and non-phosphorylated Aβ species in human DS, AD, and control brains. In addition, deposition of these Aβ species was analysed in brains of a series of established transgenic AD mouse models using phosphorylation-state specific Aβ antibodies. Significant amounts of Aβ phosphorylated at serine residue 8 (pSer8Aβ) and unmodified Aβ were detected in the brains of DS and AD cases. The brains of different transgenic mouse models with either only human mutant amyloid precursor protein (APP), or combinations of human mutant APP, Presenilin (PS), and tau transgenes showed distinct age-dependent and spatiotemporal deposition of pSer8Aβ in extracellular plaques and within the vasculature. Together, these results demonstrate the deposition of phosphorylated Aβ species in DS brains, further supporting the similarity of Aβ deposition in AD and DS. Thus, the detection of phosphorylated and other modified Aβ species could contribute to the understanding and dissection of the complexity in the age-related and spatiotemporal deposition of Aβ variants in AD and DS as well as in distinct mouse models.