Ignazio S. Piras

Necroptosis activation in Alzheimer's disease

Alzheimers disease (AD) is characterized by severe neuronal loss; however, the mechanisms by which neurons die remain elusive. Necroptosis, a programmed form of necrosis, is executed by the mixed lineage kinase domain-like (MLKL) protein, which is triggered by receptor-interactive protein kinases (RIPK) 1 and 3. We found that necroptosis was activated in postmortem human AD brains, positively correlated with Braak stage, and inversely correlated with brain weight and cognitive scores. In addition, we found that the set of genes regulated by RIPK1 overlapped significantly with multiple independent AD transcriptomic signatures, indicating that RIPK1 activity could explain a substantial portion of transcriptomic changes in AD. Furthermore, we observed that lowering necroptosis activation reduced cell loss in a mouse model of AD. We anticipate that our findings will spur a new area of research in the AD field focused on developing new therapeutic strategies aimed at blocking its activation.

Whole transcriptome profiling of the human hippocampus suggests an involvement of the KIBRA rs17070145 polymorphism in differential activation of the MAPK signaling pathway.

The rs17070145‐T variant of the WWC1 gene, coding for the KIBRA protein, has been associated with both increased episodic memory performance and lowered risk for late onset Alzheimers disease, although the mechanism behind this protective effect has not been completely elucidated. To achieve a better understanding of the pathways modulated by rs17070145 and its associated functional variant(s), we used laser capture microdissection (LCM) and RNA‐sequencing to investigate the effect of rs17070145 genotypes on whole transcriptome expression in the human hippocampus (HP) of 22 neuropathologically normal individuals, with a specific focus on the dentate gyrus (DG) and at the pyramidal cells (PC) of CA1 and CA3 sub‐regions. Differential expression analysis of RNA‐seq data within the HP based on the rs17070145 genotype revealed an overexpression of genes involved in the MAPK signaling pathway, potentially driven by the T/T genotype. The most important contribution comes from genes dysregulated within the DG region. Other genes significantly dysregulated, and not involved in the MAPK pathway (Adj P < 0.01 and Fold Change > |1.00|) were: RSPO4 (HP); ARC, DUSP5, DNAJB5, EGR4, PPP1R15A, WBP11P1, EGR1, GADD45B (DG); CH25H, HSPA1A, HSPA1B, TNFSF9, and NPAS4 (PC). Several evidences suggested that the MAPK signaling pathway is linked with memory and learning processes. In non‐neuronal cells, the KIBRA protein is phosphorylated by ERK1/2 (involved in the MAPK signaling) in cells as well as in vitro. Several of the other dysregulated genes are involved in memory and learning processes, as well as in Alzheimers Disease. In conclusion, our results suggest that the effect of the WWC1 rs17070145 polymorphism on memory performance and Alzheimers disease might be due to a differential regulation of the MAPK signaling, a key pathway involved in memory and learning processes.

Case Report: Novel mutations in TBC1D24 are associated with autosomal dominant tonic-clonic and myoclonic epilepsy and recessive Parkinsonism, psychosis, and intellectual disability

Mutations disrupting presynaptic protein TBC1D24 are associated with a variable neurological phenotype, including DOORS syndrome, myoclonic epilepsy, early-infantile epileptic encephalopathy, and non-syndromic hearing loss. In this report, we describe a family segregating autosomal dominant epilepsy, and a 37-year-old Caucasian female with a severe neurological phenotype including epilepsy, Parkinsonism, psychosis, visual and auditory hallucinations, gait ataxia and intellectual disability. Whole exome sequencing revealed two missense mutations in the TBC1D24 gene segregating within this family (c.1078C>T; p.Arg360Cys and c.404C>T; p.Pro135Leu). The female proband who presents with a severe neurological phenotype carries both of these mutations in a compound heterozygous state. The p.Pro135Leu variant, however, is present in the proband’s mother and sibling as well, and is consistent with an autosomal dominant pattern linked to tonic-clonic and myoclonic epilepsy. In conclusion, we describe a single family in which TBC1D24 mutations cause expanded dominant and recessive phenotypes. In addition, we discuss and highlight that some variants in TBC1D24 might cause a dominant susceptibility to epilepsy

A de novo splice site mutation in CASK causes FG syndrome-4 and congenital nystagmus.

Mutations in CASK cause X‐linked intellectual disability, microcephaly with pontine and cerebellar hypoplasia, optic atrophy, nystagmus, feeding difficulties, GI hypomotility, and seizures. Here we present a patient with a de novo carboxyl‐terminus splice site mutation in CASK (c.2521‐2A>G) and clinical features of the rare FG syndrome‐4 (FGS4). We provide further characterization of genotype–phenotype correlations in CASK mutations and the presentation of nystagmus and the FGS4 phenotype. There is considerable variability in clinical phenotype among patients with a CASK mutation, even among variants predicted to have similar functionality. Our patient presented with developmental delay, nystagmus, and severe gastrointestinal and gastroesophageal complications. From a cognitive and neuropsychological perspective, language skills and IQ are within normal range, although visual‐motor, motor development, behavior, and working memory were impaired. The c.2521‐2A>G splice mutation leads to skipping of exon 26 and a 9 base‐pair deletion associated with a cryptic splice site, leading to a 28‐AA and a 3‐AA in‐frame deletion, respectively (p.Ala841_Lys843del and p.Ala841_Glu868del). The predominant mutant transcripts contain an aberrant guanylate kinase domain and thus are predicted to degrade CASKs ability to interact with important neuronal and ocular development proteins, including FRMD7. Upregulation of CASK as well as dysregulation among a number of interactors is also evident by RNA‐seq. This is the second CASK mutation known to us as cause of FGS4.

A de novo missense mutation in ZMYND11 is associated with global developmental delay, seizures and hypotonia

Recently, mutations in the zinc finger MYND-type containing 11 (ZMYND11) gene were identified in patients with autism spectrum disorders, intellectual disability, aggression, and complex neuropsychiatric features, supporting that this gene is implicated in 10p15.3 microdeletion syndrome. We report a novel de novo variant in the ZMYND11 gene (p.Ser421Asn) in a patient with a complex neurodevelopmental phenotype. The patient is a 24-yr-old Caucasian/Filipino female with seizures, global developmental delay, sensorineural hearing loss, hypotonia, dysmorphic features, and other features including a happy disposition and ataxic gait similar to Angelman syndrome. In addition, this patient had uncommon features including eosinophilic esophagitis and multiple, severe allergies not described in similar ZMYND11 cases. This new case further supports the association of ZMYND11 with autistic-like phenotypes and suggests that ZMYND11 should be included in the list of potentially causative candidate genes in cases with complex neurodevelopmental phenotypes.

Hippocampal Transcriptomic Profiles: Subfield Vulnerability to Age and Cognitive Impairment

The current study employed next-generation RNA sequencing to examine gene expression differences related to brain aging, cognitive decline, and hippocampal subfields. Young and aged rats were trained on a spatial episodic memory task. Hippocampal regions CA1, CA3, and the dentate gyrus were isolated. Poly-A mRNA was examined using two different sequencing platforms, Illumina, and Ion Proton. The Illumina platform was used to generate seed lists of genes that were statistically differentially expressed across regions, ages, or in association with cognitive function. The gene lists were then retested using the data from the Ion Proton platform. The results indicate hippocampal subfield differences in gene expression and point to regional differences in vulnerability to aging. Aging was associated with increased expression of immune response-related genes, particularly in the dentate gyrus. For the memory task, impaired performance of aged animals was linked to the regulation of Ca2+ and synaptic function in region CA1. Finally, we provide a transcriptomic characterization of the three subfields regardless of age or cognitive status, highlighting and confirming a correspondence between cytoarchitectural boundaries and molecular profiling.

Associations of MAP2K3 Gene Variants With Superior Memory in SuperAgers

Introduction: SuperAgers are adults age 80+ with episodic memory performance that is at least as good as that of average middle-aged adults. Understanding the biological determinants of SuperAging may have relevance to preventing age-related cognitive decline and dementia. This study aimed to identify associations between genetic variations and the SuperAging phenotype using Whole Exome Sequencing (WES). Methods: Sequence Kernel Association Combined (SKAT-C) test was conducted at the gene level including both rare and common variants in 56 SuperAgers and 22 cognitively-average controls from the Alzheimer’s disease Neuroimaging Initiative (ADNI). Results: The SuperAging phenotype was associated with variants in the Mitogen-Activated Protein Kinase Kinase 3 (MAP2K3) gene. Three single nucleotide polymorphisms (SNPs) contributed to the significance (rs2363221 [intron 1], rs2230435 [exon 5], rs736103 [intron 7]). Conclusions: MAP2K3 resides in a biological pathway linked to memory. It is in a signaling cascade associated with beta-amyloid mediated apoptosis and has enriched expression in microglia. This preliminary work suggests MAP2K3 may represent a novel therapeutic target for age-related memory decline and perhaps Alzheimer’s disease (AD).

Pattern of gene expression in different stages of schizophrenia: Down-regulation of NPTX2 gene revealed by a meta-analysis of microarray datasets

Schizophrenia (SCZ) is a severe psychiatric disorder with a genetic susceptibility. Alterations in neurochemical signaling, as well as changes in brain structure and function, manifest during the course of SCZ and are likely causative of the symptoms shown by affected individuals. However, little is known about the timing of these changes, particularly in the pre-morbid and prodromal phases of SCZ. Here, we performed a gene-based and pathway-based meta-analysis of 5 microarray datasets from human induced pluripotent stem cells (hiPSCs)-derived neurons and post-mortem brain tissue from SCZ and healthy controls (HC), with the underlying assumption they might represent the neurobiological make-up of SCZ in the pre-morbid and chronic stages of illness, respectively. Thus, we identified 1 microarray expression profiling dataset of hiPSCs-derived neurons (GSE25673) and performed a systematic search of microarray expression profiling datasets from SCZ post-mortem brain publicly available on the Gene Expression Omnibus (GEO) repository. We selected 4 different SCZ post-mortem brain microarray expression profiling datasets (GSE17612, GSE21935, GSE12649, and GSE21338) according to specific inclusion and exclusion criteria. We downloaded raw data and performed quality controls, differential expression analysis, and gene-based, as well as pathway-based meta-analysis. Neuronal pentraxin 2 (NPTX2) gene was consistently down-regulated across all datasets, with highly significant association in the meta-analysis (FDR<1.0E-04). These results highlight the heuristic value of microarray meta-analysis and suggest a role of NPTX2 as a disease biomarker, provided that it achieves biological validation in future studies examining whether this down-regulation has predictive value with respect to the developmental trajectory of SCZ.

ASSOCIATION OF MAP2K3 GENE VARIATION AND THE SUPERAGING PHENOTYPE DETECTED BY WHOLE EXOME SEQUENCING

Figure 4. Manhattan plots of the genome-wide association study of olfactory identification after adjusting for age, gender, and APOE 4. The blue line indicates the genome-wide suggestive threshold (1*10), The red line indicates the genome-wide significance threshold (5*10). We found that 22 SNPs survived adjustment for age, gender, and APOE 4 carrier status and identified 9 new SPNs for a total of 31 SPNs. Note that 4 SNPs on chromosome 3 and 14 conserved a P<5*10 after adjusting for covariates. Poster Presentations: Wednesday, July 19, 2017 P1290

A novel FBXO28 frameshift mutation in a child with developmental delay, dysmorphic features, and intractable epilepsy: A second gene that may contribute to the 1q41-q42 deletion phenotype

Chromosome 1q41‐q42 deletions have recently been associated with a recognizable neurodevelopmental syndrome of early childhood (OMIM 612530). Within this group, a predominant phenotype of developmental delay (DD), intellectual disability (ID), epilepsy, distinct dysmorphology, and brain anomalies on magnetic resonance imaging/computed tomography has emerged. Previous reports of patients with de novo deletions at 1q41‐q42 have led to the identification of an evolving smallest region of overlap which has included several potentially causal genes including DISP1, TP53BP2, and FBXO28. In a recent report, a cohort of patients with de novo mutations in WDR26 was described that shared many of the clinical features originally described in the 1q41‐q42 microdeletion syndrome (MDS). Here, we describe a novel germline FBXO28 frameshift mutation in a 3‐year‐old girl with intractable epilepsy, ID, DD, and other features which overlap those of the 1q41‐q42 MDS. Through a familial whole‐exome sequencing study, we identified a de novo FBXO28 c.972_973delACinsG (p.Arg325GlufsX3) frameshift mutation in the proband. The frameshift and resulting premature nonsense mutation have not been reported in any genomic database. This child does not have a large 1q41‐q42 deletion, nor does she harbor a WDR26 mutation. Our case joins a previously reported patient also in whom FBXO28 was affected but WDR26 was not. These findings support the idea that FBXO28 is a monogenic disease gene and contributes to the complex neurodevelopmental phenotype of the 1q41‐q42 gene deletion syndrome.