Neuronal Modeling of Alternating Hemiplegia of Childhood Reveals Transcriptional Compensation and Replicates a Trigger-Induced Phenotype

ABSTRACTAlternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disease caused by heterozygous de novo missense mutations in the ATP1A3 gene that encodes the neuronal specific α3 subunit of the Na,K-ATPase (NKA) pump. Mechanisms underlying patient episodes including environmental triggers remain poorly understood, and there are no empirically proven treatments for AHC. In this study, we generated patient-specific induced pluripotent stem cells (iPSCs) and isogenic controls for the E815K ATP1A3 mutation that causes the most phenotypically severe form of AHC. Using an in vitro iPSC-derived cortical neuron disease model, we found elevated levels of ATP1A3 mRNA in AHC lines compared to controls, without significant perturbations in protein expression. Microelectrode array analyses demonstrated that in cortical neuronal cultures, ATP1A3+/E815K iPSC-derived neurons displayed a non-significant trend toward less overall activity than neurons differentiated from isogenic mutation-corrected and unrelated control cell lines. However, induction of cellular stress by elevated temperature revealed a hyperactivity phenotype following heat stress in ATP1A3+/E815K lines compared to control lines. Treatment with flunarizine, a drug commonly used to prevent AHC episodes, did not impact this stress-triggered phenotype. These findings support the use of iPSC-derived neuronal cultures for studying complex neurodevelopmental conditions such as AHC and provide a potential route toward future therapeutic screening and mechanistic discovery in a human disease model.

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Diseases caused by mutations in the Na+/K+ pump α1 gene ATP1A1

AJP Cell Physiology ◽

10.1152/ajpcell.00059.2021 ◽

2021 ◽

Author(s):

Elisa D. Biondo ◽

Kerri Spontarelli ◽

Giovanna Ababioh ◽

Lois Mendez ◽

Pablo Artigas

Keyword(s):

De Novo ◽

Neuromuscular Disorder ◽

Secondary Hypertension ◽

Review Literature ◽

Patient Specific ◽

Future Research ◽

Heterologous Protein Expression ◽

Missense Mutations ◽

Α Subunit ◽

Charcot Marie Tooth Disease

Human cell survival requires function of the Na+/K+ pump; the heteromeric protein that hydrolyzes ATP to extrude Na+ and import K+ across the plasmalemma, thereby building and maintaining their electrochemical gradients. Numerous dominant diseases caused by mutations in genes encoding for Na+/K+ pump catalytic (α) subunit isoforms highlight the importance of this protein. Here, we review literature describing disorders caused by missense mutations in ATP1A1, the gene encoding the ubiquitously expressed α1 isoform of the Na+/K+ pump. These various maladies include primary aldosteronism with secondary hypertension, an endocrine syndrome, Charcot-Marie-Tooth disease, a peripheral neuropathy, complex spastic paraplegia, another neuromuscular disorder, as well as hypomagnesemia accompanied by seizures and cognitive delay, a condition affecting the renal and central nervous systems. This article focuses on observed commonalities among these mutations' functional effects, as well as on the special characteristics that enable each particular mutation to exclusively affect a certain system, without affecting others. In this respect, it is clear how somatic mutations localized to adrenal adenomas increase aldosterone production without compromising other systems. However, it remains largely unknown how and why some but not other de novo germline or familial mutations (where the mutant must be expressed in numerous tissues) produce a specific disease and not the others. We propose hypotheses to explain this observation and the approaches that we think will drive future research on these debilitating disorders to develop novel patient-specific treatments by combining the use of heterologous protein-expression systems, patient-derived pluripotent cells, and gene-edited cell and mouse models.

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Neurodevelopmental disease genes implicated by de novo mutation and CNV morbidity

10.1101/209908 ◽

2017 ◽

Cited By ~ 1

Author(s):

Bradley P. Coe ◽

Holly A.F. Stessman ◽

Arvis Sulovari ◽

Madeleine Geisheker ◽

Fereydoun Hormozdiari ◽

...

Keyword(s):

Developmental Delay ◽

De Novo ◽

Gene Dosage ◽

De Novo Mutation ◽

Disease Genes ◽

Missense Mutations ◽

Genomic Disorder ◽

Network Analyses ◽

Neurodevelopmental Disease ◽

Deletion Syndromes

ABSTRACTWe combined de novo mutation (DNM) data from 10,927 cases of developmental delay and autism to identify 301 candidate neurodevelopmental disease genes showing an excess of missense and/or likely gene-disruptive (LGD) mutations. 164 genes were predicted by two different DNM models, including 116 genes with an excess of LGD mutations. Among the 301 genes, 76% show DNM in both autism and intellectual disability/developmental delay cohorts where they occur in 10.3% and 28.4% of the cases, respectively. Intersecting these results with copy number variation (CNV) morbidity data identifies a significant enrichment for the intersection of our gene set and genomic disorder regions (36/301, LR+ 2.53, p=0.0005). This analysis confirms many recurrent LGD genes and CNV deletion syndromes (e.g., KANSL1, PAFAH1B1, RA1, etc.), consistent with a model of haploinsufficiency. We also identify genes with an excess of missense DNMs overlapping deletion syndromes (e.g., KIF1A and the 2q37 deletion) as well as duplication syndromes, such as recurrent MAPK3 missense mutations within the chromosome 16p11.2 duplication, recurrent CHD4 missense DNMs in the 12p13 duplication region, and recurrent WDFY4 missense DNMs in the 10q11.23 duplication region. Finally, we also identify pathogenic CNVs overlapping more than one recurrently mutated gene (e.g., Sotos and Kleefstra syndromes) raising the possibility that multiple gene-dosage imbalances may contribute to phenotypic complexity of these disorders. Network analyses of genes showing an excess of DNMs confirm previous well-known enrichments but also highlight new functional networks, including cell-specific enrichments in the D1+ and D2+ spiny neurons of the striatum for both recurrently mutated genes and genes where missense mutations cluster.

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Pathogenic DDX3X mutations impair RNA metabolism and neurogenesis during fetal cortical development

10.1101/317974 ◽

2018 ◽

Cited By ~ 6

Author(s):

Ashley L. Lennox ◽

Ruiji Jiang ◽

Lindsey Suit ◽

Brieana Fregeau ◽

Charles J. Sheehan ◽

...

Keyword(s):

Molecular Mechanisms ◽

De Novo ◽

Cortical Development ◽

Rna Helicase ◽

Mouse Genetics ◽

Missense Mutations ◽

Neurodevelopmental Disease ◽

Brain Malformations ◽

And Migration ◽

Human And Mouse

AbstractDe novo germline mutations in the RNA helicase DDX3X account for 1-3% of unexplained intellectual disability (ID) cases in females, and are associated with autism, brain malformations, and epilepsy. Yet, the developmental and molecular mechanisms by which DDX3X mutations impair brain function are unknown. Here we use human and mouse genetics, and cell biological and biochemical approaches to elucidate mechanisms by which pathogenic DDX3X variants disrupt brain development. We report the largest clinical cohort to date with DDX3X mutations (n=78), demonstrating a striking correlation between recurrent dominant missense mutations, polymicrogyria, and the most severe clinical outcomes. We show that Ddx3x controls cortical development by regulating neuronal generation and migration. Severe DDX3X missense mutations profoundly disrupt RNA helicase activity and induce ectopic RNA-protein granules and aberrant translation in neural progenitors and neurons. Together, our study demonstrates novel mechanisms underlying DDX3X syndrome, and highlights roles for RNA-protein aggregates in the pathogenesis of neurodevelopmental disease.

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DRP1-mediated mitochondrial fission is essential to maintain cristae morphology and bioenergetics

10.1101/2021.12.31.474637 ◽

2022 ◽

Author(s):

Gabriella L. Robertson ◽

Stellan Riffle ◽

Mira Patel ◽

Andrea Marshall ◽

Heather Beasley ◽

...

Keyword(s):

Cell Fate ◽

De Novo ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Coupling Efficiency ◽

Acid Oxidation ◽

Mitochondrial Morphology ◽

Missense Mutations ◽

Neurodevelopmental Disease ◽

Signaling Organelles

Mitochondria and peroxisomes are both dynamic signaling organelles that constantly undergo fission. While mitochondrial fission is known to coordinate cellular metabolism, proliferation, and apoptosis, the physiological relevance of peroxisome dynamics and the implications for cell fate are not fully understood. DRP1 (dynamin-related protein 1) is an essential GTPase that executes both mitochondrial and peroxisomal fission. Patients with de novo heterozygous missense mutations in the gene that encodes DRP1, DNM1L, present with encephalopathy due to defective mitochondrial and peroxisomal fission (EMPF1). EMPF1 is a devastating neurodevelopmental disease with no effective treatment. To interrogate the mechanisms by which DRP1 mutations cause cellular dysfunction, we utilized human-derived fibroblasts from patients with mutations in DRP1 who present with EMPF1. As expected, patient cells display elongated mitochondrial morphology and lack of fission. Patient cells display a lower coupling efficiency of the electron transport chain, increased proton leak, and upregulation of glycolysis. In addition to these metabolic abnormalities, mitochondrial hyperfusion results in aberrant cristae structure and hyperpolarized mitochondrial membrane potential, both of which are tightly linked to the changes in metabolism. Peroxisome structure is also severely elongated in patient cells and results in a potential functional compensation of fatty acid oxidation. Understanding the mechanism by which DRP1 mutations cause these metabolic changes will give insight into the role of mitochondrial dynamics in cristae maintenance and the metabolic capacity of the cell, as well as the disease mechanism underlying EMPF1.

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De Novo variant in GNB2 associated with neurodevelopmental disease

Molecular Genetics and Metabolism ◽

10.1016/s1096-7192(21)00519-9 ◽

2021 ◽

Vol 132 ◽

pp. S282

Author(s):

Florencia del Viso ◽

Lisa Lansdon ◽

Emily Fleming ◽

Bonnie Sullivan ◽

Carol Saunders

Keyword(s):

De Novo ◽

Neurodevelopmental Disease ◽

De Novo Variant

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On the Need to Tell Apart Fraternal Twins eEF1A1 and eEF1A2, and Their Respective Outfits

International Journal of Molecular Sciences ◽

10.3390/ijms22136973 ◽

2021 ◽

Vol 22 (13) ◽

pp. 6973

Author(s):

Alberto Mills ◽

Federico Gago

Keyword(s):

De Novo ◽

Elongation Factor ◽

Missense Mutations ◽

Developmentally Regulated ◽

High Sequence Identity ◽

80S Ribosome ◽

Cellular Effects ◽

Cellular Processes ◽

Eukaryotic Elongation Factor ◽

A Site

eEF1A1 and eEF1A2 are paralogous proteins whose presence in most normal eukaryotic cells is mutually exclusive and developmentally regulated. Often described in the scientific literature under the collective name eEF1A, which stands for eukaryotic elongation factor 1A, their best known activity (in a monomeric, GTP-bound conformation) is to bind aminoacyl-tRNAs and deliver them to the A-site of the 80S ribosome. However, both eEF1A1 and eEF1A2 are endowed with multitasking abilities (sometimes performed by homo- and heterodimers) and can be located in different subcellular compartments, from the plasma membrane to the nucleus. Given the high sequence identity of these two sister proteins and the large number of post-translational modifications they can undergo, we are often confronted with the dilemma of discerning which is the particular proteoform that is actually responsible for the ascribed biochemical or cellular effects. We argue in this review that acquiring this knowledge is essential to help clarify, in molecular and structural terms, the mechanistic involvement of these two ancestral and abundant G proteins in a variety of fundamental cellular processes other than translation elongation. Of particular importance for this special issue is the fact that several de novo heterozygous missense mutations in the human EEF1A2 gene are associated with a subset of rare but severe neurological syndromes and cardiomyopathies.

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CACNA1A Mutation Linking Hemiplegic Migraine and Alternating Hemiplegia of Childhood

Cephalalgia ◽

10.1111/j.1468-2982.2008.01596.x ◽

2008 ◽

Vol 28 (8) ◽

pp. 887-891 ◽

Cited By ~ 34

Author(s):

B de Vries ◽

AH Stam ◽

F Beker ◽

AMJM van den Maagdenberg ◽

KRJ Vanmolkot ◽

...

Keyword(s):

Clinical Features ◽

Molecular Mechanisms ◽

De Novo ◽

Monozygotic Twin ◽

Familial Hemiplegic Migraine ◽

Hemiplegic Migraine ◽

Mutation Scanning ◽

Alternating Hemiplegia Of Childhood ◽

Neurological Phenotype ◽

Cacna1a Mutation

Familial hemiplegic migraine (FHM) and alternating hemiplegia of childhood (AHC) are severe neurological disorders that share clinical features. Therefore, FHM genes are candidates for AHC. We performed mutation analysis in the CACNA1A gene in a monozygotic twin pair with clinical features overlapping with both AHC and FHM and identified a novel de novo CACNA1A mutation. We provide the first evidence that a CACNA1A mutation can cause atypical AHC, indicating an overlap of molecular mechanisms causing AHC and FHM. These results also suggest that CACNA1A mutation scanning is indicated in patients with a severe neurological phenotype that includes paroxysmal (alternating) hemiplegia.

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An intronic variant disrupts mRNA splicing and causes FGFR3-related skeletal dysplasia

Journal of Pediatric Endocrinology and Metabolism ◽

10.1515/jpem-2020-0679 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Ting Xu ◽

Liang Shi ◽

Weiqian Dai ◽

Xuefan Gu ◽

Yongguo Yu ◽

...

Keyword(s):

De Novo ◽

Clinical Findings ◽

Recurrent Mutation ◽

Mrna Splicing ◽

Additional Patient ◽

Missense Mutations ◽

Splicing Variant ◽

Amino Acid Insertion ◽

Whole Exome ◽

Minigene Assay

Abstract Objectives Achondroplasia and hypochondroplasia are the most common forms of disproportionate short stature, of which the vast majority of cases can be attributed to the hotspot missense mutations in the gene FGFR3. Here we presented cases with a novel cryptic splicing variant of FGFR3 gene and aimed to interrogate the variant pathogenicity. Case presentaiton In whole exome sequencing of two patients with hypochondroplasia-like features, a de novo intronic variant c.1075 + 95C>G was identified, predicted to alter mRNA splicing. Minigene assay showed that this intronic variant caused retention of a 90-nucleotide segment of intron 8 in mRNA, resulting in a 30-amino acid insertion at the extracellular domain of the protein. This is the first likely pathogenic splicing variant identified in the FGFR3 gene and was detected in one additional patient among 26 genetically unresolved patients. Conclustions Our results strongly suggest that c.1075 + 95C>G is a recurrent mutation and should be included in genetic testing of FGFR3 especially for those patients with equivocal clinical findings and no exonic mutations identified.

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