Congenital myasthenic syndrome caused by a frameshift insertion mutation in

Objective: Description of a new variant of the glutamine-fructose-6-phosphate transaminase 1 (GFPT1) gene causing congenital myasthenic syndrome (CMS) in 3 children from 2 unrelated families. Methods: Muscle biopsies, EMG, and whole-exome sequencing were performed. Results: All 3 patients presented with congenital hypotonia, muscle weakness, respiratory insufficiency, head lag, areflexia, and gastrointestinal dysfunction. Genetic analysis identified a homozygous frameshift insertion in the GFPT1 gene (NM_001244710.1: c.686dupC; p.Arg230Ter) that was shared by all 3 patients. In one of the patients, inheritance of the variant was through uniparental disomy (UPD) with maternal origin. Repetitive nerve stimulation and single-fiber EMG was consistent with the clinical diagnosis of CMS with a postjunctional defect. Ultrastructural evaluation of the muscle biopsy from one of the patients showed extremely attenuated postsynaptic folds at neuromuscular junctions and extensive autophagic vacuolar pathology. Conclusions: These results expand on the spectrum of known loss-of-function GFPT1 mutations in CMS12 and in one family demonstrate a novel mode of inheritance due to UPD

Identification of Novel Genetic Risk Loci in Maltese Dogs with Necrotizing Meningoencephalitis and Evidence of a Shared Genetic Risk across Toy Dog Breeds

Necrotizing meningoencephalitis (NME) affects toy and small breed dogs causing progressive, often fatal, inflammation and necrosis in the brain. Genetic risk loci for NME previously were identified in pug dogs, particularly associated with the dog leukocyte antigen (DLA) class II complex on chromosome 12, but have not been investigated in other susceptible breeds. We sought to evaluate Maltese and Chihuahua dogs, in addition to pug dogs, to identify novel or shared genetic risk factors for NME development. Genome-wide association testing of single nucleotide polymorphisms (SNPs) in Maltese dogs with NME identified 2 regions of genome-wide significance on chromosomes 4 (chr4:74522353T>A, p = 8.1×10-7) and 15 (chr15:53338796A>G, p = 1.5×10-7). Haplotype analysis and fine-mapping suggests that ILR7 and FBXW7, respectively, both important for regulation of immune system function, could be the underlying associated genes. Further evaluation of these regions and the previously identified DLA II locus across all three breeds, revealed an enrichment of nominal significant SNPs associated with chromosome 15 in pug dogs and DLA II in Maltese and Chihuahua dogs. Meta-analysis confirmed effect sizes the same direction in all three breeds for both the chromosome 15 and DLA II loci (p = 8.6×10-11 and p = 2.5×10-7, respectively). This suggests a shared genetic background exists between all breeds and confers susceptibility to NME, but effect sizes might be different among breeds. In conclusion, we identified the first genetic risk factors for NME development in the Maltese, chromosome 4 and chromosome 15, and provide evidence for a shared genetic risk between breeds associated with chromosome 15 and DLA II. Last, DLA II and IL7R both have been implicated in human inflammatory diseases of the central nervous system such as multiple sclerosis, suggesting that similar pharmacotherapeutic targets across species should be investigated

A cellular model of amyloid precursor protein processing and amyloid-β peptide production

Background: A hallmark pathologic feature of Alzheimer\u27s disease (AD) is accumulation of neuritic senile plaques in the brain parenchyma. Neurotoxic plaque cores are composed predominantly of amyloid-β (Aβ) peptides of 40 and 42 amino acids in length, formed by sequential cleavage of amyloid precursor protein (APP) by β-, and γ-secretases. There is a great interest in approaches to modulate Aβ peptide production and develop therapeutic interventions to reduce Aβ levels to halt or slow the progression of neurodegeneration. New method: We characterized and present the BE(2)-M17 human neuroblastoma cell line as a novel in vitro model of the APP-cleavage cascade to support future (1) functional studies of molecular regulators in Aβ production, and (2) high-throughput screening assays of new pharmacotherapeutics. Results: In BE(2)-M17 cells, both RNA (i.e., RT-PCR, RNA sequencing) and protein analyses (i.e., Western blots, ELISA), show endogenous expression of critical components of the amyloidogenic pathway, APP-cleavage intermediates CTF83 and CTF99, and final cleavage products Aβ40 and Aβ42. We further report effects of retinoic acid-mediated differentiation on morphology and gene expression in this cell line. Comparison with existing method(s): In contrast to primary isolates or other cell lines reported in current literature, BE(2)-M17 not only sustains baseline expression of the full contingent of APP-processing components, but also remains stably adherent during culture, facilitating experimental manipulations. Conclusions: Our evidence supports the use of BE(2)-M17 as a novel, human, cell-based model of the APP processing pathway that offers a potential streamlined approach to dissect molecular functions of endogenous regulatory pathways, and perform mechanistic studies to identify modulators of Aβ production. © 2013 Elsevier B.V

The PKC-β selective inhibitor, Enzastaurin, impairs memory in middle-aged rats

Enzastaurin is a Protein Kinase C-beta selective inhibitor that was developed to treat cancers. Protein Kinase C-beta is an important enzyme for a variety of neuronal functions; in particular, previous rodent studies have reported deficits in spatial and fear-conditioned learning and memory with lower levels of Protein Kinase C-beta. Due to Enzastaurin's mechanism of action, the present study investigated the consequences of Enzastaurin exposure on learning and memory in 12-month-old Fischer-344 male rats. Rats were treated daily with subcutaneous injections of either vehicle or Enzastaurin, and behaviorally tested using the spatial reference memory Morris Water Maze. Rats treated with Enzastaurin exhibited decreased overnight retention and poorer performance on the latter testing day, indicating a mild, but significant, memory impairment. There were no differences during the probe trial indicating that all animals were able to spatially localize the platform to the proper quadrant by the end of testing. RNA isolated from the hippocampus was analyzed using Next Generation Sequencing (lllumina). No statistically significant transcriptional differences were noted. Our findings suggest that acute Enzastaurin treatment can impair hippocampal-based learning and memory performance, with no effects on transcription in the hippocampus. We propose that care should be taken in future clinical trials that utilize Protein Kinase C-SS inhibitors, to monitor for possible cognitive effects, future research should examine if these effects are fully reversible.NIH-NINDS [R01-NS059873]; State of Arizona DHSOpen access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Variants in triggering receptor expressed on myeloid cells 2 are associated with both behavioral variant frontotemporal lobar degeneration and Alzheimer's disease.

Recent evidence suggests that rare genetic variants within the TREM2 gene are associated with increased risk of Alzheimer's disease. TREM2 mutations are the genetic basis for a condition characterized by polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) and an early-onset dementia syndrome. TREM2 is important in the phagocytosis of apoptotic neuronal cells by microglia in the brain. Loss of function might lead to an impaired clearance and to accumulation of necrotic debris and subsequent neurodegeneration. In this study, we investigated a consanguineous family segregating autosomal recessive behavioral variant FTLD from Antioquia, Colombia. Exome sequencing identified a nonsense mutation in TREM2 (p.Trp198X) segregating with disease. Next, using a cohort of clinically characterized and neuropathologically verified sporadic AD cases and controls, we report replication of the AD risk association at rs75932628 within TREM2 and demonstrate that TREM2 is significantly overexpressed in the brain tissue from AD cases. These data suggest that a mutational burden in TREM2 may serve as a risk factor for neurodegenerative disease in general, and that potentially this class of TREM2 variant carriers with dementia should be considered as having a molecularly distinct form of neurodegenerative disease