Search

The Faroe Islands are a geographically isolated population in the North Atlantic with a similar prevalence of Alzheimer's disease (AD) and all-cause dementia as other European populations. However, the genetic risk underlying AD and other dementia susceptibility has yet to be elucidated.Forty-nine single-nucleotide polymorphisms (SNPs) were genotyped in 174 patients with AD and other dementias and 159 healthy controls. Single variant and polygenic risk score (PRS) associations, with/without APOE variability, were assessed by logistic regression. Performance was examined using receiver operating characteristic area under the curve (ROC AUC) analysis.APOErs429358 was associated with AD in the Faroese cohort after correction for multiple testing (odds ratio [OR] 6.32, 95% confidence interval [CI] 3.98-10.05, p = 6.31esup-15/sup), with suggestive evidence for three other variants: NECTIN2 rs41289512 (OR 2.05, 95% CI 1.20-3.51, p = 0.01), HLA-DRB1 rs6931277 (OR 0.67, 95% CI 0.48-0.94, p = 0.02) and APOE rs7412 [ε2] (OR 0.28, 95% CI 0.11-0.73, p = 0.01). PRSs were associated with AD with or without the inclusion of APOE (PRSsup+APOE/supOR = 4.5, 95% CI 2.90-5.85, p = 4.56esup-15/sup, and PRSsup-APOE/supOR = 1.53, 95% CI 1.21-1.98, p = 6.82esup-4/sup). AD ROC AUC analyses demonstrated a PRSsup+APOE/supAUC = 80.3% and PRSsup-APOE/supAUC = 63.4%. However, PRSsup+APOE/supwas also significantly associated with all-cause dementia (OR = 3.39, 95% CI 2.51-4.71, p = 2.50esup-14/sup) with an AUC = 76.9%, that is, all-cause dementia showed similar results albeit less significant.In the Faroe Islands, SNP analyses highlighted APOE and immunogenomic variability in AD and dementia risk. PRSsup+APOE/sup, based on 25 SNPs/loci, had excellent sensitivity and specificity for AD with an AUC of 80.3%. High PRSs were also associated with an earlier onset of late-onset AD.

To elucidate the molecular basis of multiple system atrophy (MSA), a neurodegenerative disease, we conducted a genome-wide association study (GWAS) in a Japanese MSA case/control series followed by replication studies in Japanese, Korean, Chinese, European and North American samples. In the GWAS stage rs2303744 on chromosome 19 showed a suggestive association (P= 6.5 × 10−7) that was replicated in additional Japanese samples (P= 2.9 × 10−6. OR = 1.58; 95% confidence interval, 1.30 to 1.91), and then confirmed as highly significant in a meta-analysis of East Asian population data (P= 5.0 × 10-15. Odds ratio= 1.49; 95% CI 1.35 to 1.72). The association of rs2303744 with MSA remained significant in combined European/North American samples (P=0.023. Odds ratio=1.14; 95% CI 1.02 to 1.28) despite allele frequencies being quite different between these populations. rs2303744 leads to an amino acid substitution inPLA2G4Cthat encodes the cPLA2γ lysophospholipase/transacylase. The cPLA2γ-Ile143 isoform encoded by the MSA risk allele has significantly decreased transacylase activity compared with the alternate cPLA2γ-Val143 isoform that may perturb membrane phospholipids and α-synuclein biology.

Extracellular vesicles (EVs) are secreted by myriad cells in culture and also by unicellular organisms, and their identification in mammalian fluids suggests that EV release also occurs at the organism level. However, although it is clearly important to better understand EVs' roles in organismal biology, EVs in solid tissues have received little attention. Here, we modified a protocol for EV isolation from primary neural cell culture to collect EVs from frozen whole murine and human neural tissues by serial centrifugation and purification on a sucrose gradient. Quantitative proteomics comparing brain-derived EVs from nontransgenic (NTg) and a transgenic amyotrophic lateral sclerosis (ALS) mouse model, superoxide dismutase 1 (SOD1)G93A, revealed that these EVs contain canonical exosomal markers and are enriched in synaptic and RNA-binding proteins. The compiled brain EV proteome contained numerous proteins implicated in ALS, and EVs from SOD1G93A mice were significantly depleted in myelin-oligodendrocyte glycoprotein compared with those from NTg animals. We observed that brain- and spinal cord–derived EVs, from NTg and SOD1G93A mice, are positive for the astrocyte marker GLAST and the synaptic marker SNAP25, whereas CD11b, a microglial marker, was largely absent. EVs from brains and spinal cords of the SOD1G93A ALS mouse model, as well as from human SOD1 familial ALS patient spinal cord, contained abundant misfolded and nonnative disulfide-cross-linked aggregated SOD1. Our results indicate that CNS-derived EVs from an ALS animal model contain pathogenic disease-causing proteins and suggest that brain astrocytes and neurons, but not microglia, are the main EV source.

STAC3 is a soluble protein essential for skeletal muscle excitation-contraction (EC) coupling. Through its tandem SH3 domains, it interacts with the cytosolic II-III loop of the skeletal muscle voltage-gated calcium channel. STAC3 is the target for a mutation (W284S) that causes Native American myopathy, but multiple other sequence variants have been reported. Here, we report a crystal structure of the human STAC3 tandem SH3 domains. We analyzed the effect of five disease-associated variants, spread over both SH3 domains, on their ability to bind to the Ca

STAC3 is a soluble protein essential for skeletal muscle excitation-contraction (EC) coupling. Through its tandem SH3 domains, it interacts with the cytosolic II-III loop of the skeletal muscle voltage-gated calcium channel. STAC3 is the target for a mutation (W284S) that causes Native American myopathy, but multiple other sequence variants have been reported. Here, we report a crystal structure of the human STAC3 tandem SH3 domains. We analyzed the effect of five disease-associated variants, spread over both SH3 domains, on their ability to bind to the CaV1.1 II-III loop and on muscle EC coupling. In addition to W284S, we find the F295L and K329N variants to affect both binding and EC coupling. The ability of the K329N variant, located in the second SH3 domain, to affect the interaction highlights the importance of both SH3 domains in association with CaV1.1. Our results suggest that multiple STAC3 variants may cause myopathy.

Extracellular vesicles (EVs) are secreted by myriad cells in culture and also by unicellular organisms, and their identification in mammalian fluids suggests that EV release also occurs at the organism level. However, although it is clearly important to better understand EVs' roles in organismal biology, EVs in solid tissues have received little attention. Here, we modified a protocol for EV isolation from primary neural cell culture to collect EVs from frozen whole murine and human neural tissues by serial centrifugation and purification on a sucrose gradient. Quantitative proteomics comparing brain-derived EVs from nontransgenic (NTg) and a transgenic amyotrophic lateral sclerosis (ALS) mouse model, superoxide dismutase 1 (SOD1)(G93A), revealed that these EVs contain canonical exosomal markers and are enriched in synaptic and RNA-binding proteins. The compiled brain EV proteome contained numerous proteins implicated in ALS, and EVs from SOD1(G93A) mice were significantly depleted in myelin-oligodendrocyte glycoprotein compared with those from NTg animals. We observed that brain- and spinal cord–derived EVs, from NTg and SOD1(G93A) mice, are positive for the astrocyte marker GLAST and the synaptic marker SNAP25, whereas CD11b, a microglial marker, was largely absent. EVs from brains and spinal cords of the SOD1(G93A) ALS mouse model, as well as from human SOD1 familial ALS patient spinal cord, contained abundant misfolded and nonnative disulfide-cross-linked aggregated SOD1. Our results indicate that CNS-derived EVs from an ALS animal model contain pathogenic disease-causing proteins and suggest that brain astrocytes and neurons, but not microglia, are the main EV source.