Publications by authors named "Ashraf Muhaisen"

Article Synopsis
  • ClC-K/barttin channels play a vital role in chloride transport in the kidneys and inner ear, and mutations in their genes can lead to Bartter's syndrome.
  • Research shows that a specific amino acid change in barttin enhances ClC-K currents, but the exact mechanism and significance in living organisms is still unclear.
  • Experiments using Xenopus oocytes and mice indicate that mutations in a particular YxxØ motif on barttin can increase its stability at the plasma membrane and improve function, although these mutations do not change overall protein expression levels under certain diet conditions.
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The function of the chloride channel ClC-1 is crucial for the control of muscle excitability. Thus, reduction of ClC-1 functions by CLCN1 mutations leads to myotonia congenita. Many different animal models have contributed to understanding the myotonia pathophysiology.

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Article Synopsis
  • Axonal guidance is essential for proper brain connectivity and is influenced by guidance cues like Netrin-1, which can attract or repel axons depending on receptor interactions.
  • This study utilized various biochemical and cell biology techniques to explore the mechanisms behind Netrin-1's role in axonal repulsion during brain development.
  • Results indicated that Netrin-1 activates macropinocytosis, facilitated by a protein complex with syntaxin-1, revealing that syntaxin-1 plays a critical role in mediating axonal guidance responses.
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The role of somatic mutations in complex diseases, including neurodevelopmental and neurodegenerative disorders, is becoming increasingly clear. However, to date, no study has shown their relation to Parkinson disease's phenotype. To explore the relevance of embryonic somatic mutations in sporadic Parkinson disease, we performed whole-exome sequencing in blood and four brain regions of ten patients.

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Reelin is an extracellular protein crucial for adult brain plasticity. Moreover, Reelin is protective against amyloid-β (Aβ) pathology in Alzheimer's Disease (AD), reducing plaque deposition, synaptic loss and cognitive decline. Given that Tau protein plays a key role in AD pathogenesis, and that the Reelin pathway modulates Tau phosphorylation, here we explored the involvement of Reelin in AD-related Tau pathology.

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Axonal growth during normal development and axonal regeneration rely on the action of many receptor signaling systems and complexes, most of them located in specialized raft membrane microdomains with a precise lipid composition. Cholesterol is a component of membrane rafts and the integrity of these structures depends on the concentrations present of this compound. Here we explored the effect of cholesterol depletion in both developing neurons and regenerating axons.

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SNARE proteins are essential components of the machinery that regulates vesicle trafficking and exocytosis. Their role is critical for the membrane-fusion processes that occur during neurotransmitter release. However, research in the last decade has also unraveled the relevance of these proteins in membrane expansion and cytoskeletal rearrangements during developmental processes such as neuronal migration and growth cone extension and attraction.

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Reelin regulates neuronal positioning and synaptogenesis in the developing brain, and adult brain plasticity. Here we used transgenic mice overexpressing Reelin (Reelin-OE mice) to perform a comprehensive dissection of the effects of this protein on the structural and biochemical features of dendritic spines and axon terminals in the adult hippocampus. Electron microscopy (EM) revealed both higher density of synapses and structural complexity of both pre- and postsynaptic elements in transgenic mice than in WT mice.

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Background: Although genome-wide association studies have shown that genetic factors increase the risk of suffering late-onset, sporadic Alzheimer's disease (SAD), the molecular mechanisms responsible remain largely unknown.

Objective: The aim of the study was to investigate the presence of somatic, brain-specific single nucleotide variations (SNV) in the hippocampus of SAD samples.

Methods: By using bioinformatic tools, we compared whole exome sequences in paired blood and hippocampal genomic DNAs from 17 SAD patients and from 2 controls and 2 vascular dementia patients.

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DNA is the most stable nucleic acid and most important store of genetic information. DNA sequences are conserved in virtually all the cells of a multicellular organism. To analyze the sequences of various individuals with distinct pathological disorders, DNA is routinely isolated from blood, independently of the tissue that is the target of the disease.

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Psychiatric disorders have been hypothesized to originate during development, with genetic and environmental factors interacting in the etiology of disease. Therefore, developmentally regulated genes have received attention as risk modulators in psychiatric diseases. Reelin is an extracellular protein essential for neuronal migration and maturation during development, and its expression levels are reduced in psychiatric disorders.

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Directed cell migration and axonal guidance are essential steps in neural development that share many molecular mechanisms. The guidance of developing axons and migrating neurons is likely to depend on the precise control of plasmalemma turnover in selected regions of leading edges and growth cones, respectively. Previous results provided evidence of a signaling mechanism that couples chemotropic deleted in colorectal cancer (DCC)/Netrin-1 axonal guidance and exocytosis through Syntaxin1(Sytx1)/TI-VAMP SNARE proteins.

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Directed cell migration and axonal guidance are essential steps in neural development. Both processes are controlled by specific guidance cues that activate the signaling cascades that ultimately control cytoskeletal dynamics. Another essential step in migration and axonal guidance is the regulation of plasmalemma turnover and exocytosis in leading edges and growth cones.

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In these experiments we have tested the effect of bis(acetato)tetrakis (imidazole) copper(II) on the release and uptake of 14C-GABA and 3H-glutamate from brain slices and brain cortical synaptosomes. Cu(OAc)2(Im)4 in concentrations ranging from 1 to 100 microM has increased the release of GABA and glutamate from brain slices and synaptosomal preparations in a dose-related manner when the effect on GABA release is two-fold greater than glutamate and 10-fold greater than alanine. Pretreatment with a GABA uptake inhibitor such as 1-2 mM nipecotic acid has no effect on 14C-GABA release, whereas hydroxy aspartate, the glutamate uptake inhibitor, has elevated the stimulated release of glutamate.

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ATP is an electrically charged molecule that functions both in the supply of energy necessary for cellular activity and as an intercellular signaling molecule. Although controlled ATP secretion occurs via exocytosis of granules and vesicles, in some cells, and under certain conditions, other mechanisms control ATP release. Gap junctions, intercellular channels formed by connexins that link the cytoplasm of two adjacent cells, control the passage of ions and molecules up to 1 kDa.

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Syntaxin 1 and synaptobrevin/VAMP play an essential role in synaptic vesicle exocytosis. Two isoforms for each of these proteins, syntaxins 1A and 1B and synaptobrevin/VAMPs 1 and 2, have been found in nerve endings. Morphological and biochemical studies have revealed a characteristic colocalization and selective interactions patterns of syntaxin 1 and synaptobrevin/VAMP isoforms in nervous and endocrine systems.

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