Biology subjects

Kurian, M. A.

Publications and source records attributed to Kurian, M. A..

5 recordsLinked to original sources

bioRxiv2024

A humanized neuronal model system reveals key roles for manganese in neuronal endocytosis, calcium flux and mitochondrial bioenergetics

Manganese (Mn) is an essential trace metal that is necessary for life. Its duality as both a crucial micronutrient and potential neurotoxicant necessitates tight control of intracellular and extracellular Mn levels. Dysregulation of Mn is implicated in a broad range of human diseases, from neurodevelopmental sequelae related to Mn levels in drinking water, to acquired forms of manganism, rare inherited Mn transportopathies and more common disorders such as Parkinsons and Alzheimers disease. Despite the clear association between Mn dysregulation and neurodevelopmental or neurodegenerative diseases, the underlying cellular mechanisms that govern neuropathology remain poorly understood. We established an induced pluripotent stem cells-derived midbrain neuronal system from SLC39A14, SLC39A8, and SLC30A10 patients to better understand the neuronal sequelae of Mn dysregulation. By integrating transcriptomic and functional approaches, we show that Mn dyshomeostasis leads to dysregulation of key cellular pathways that are crucial to normal neuronal function, including defects in mitochondrial bioenergetics, calcium signalling, endocytosis, and glycosylation, as well as cellular stress and early neurodegeneration. Our humanized model has enhanced understanding of the role of Mn in the human brain, and the consequences of both acquired and genetic disorders associated with Mn dysregulation. Better understanding of these underlying pathophysiological processes will identify potential targets for future therapeutic intervention.

neuroscience↗

bioRxiv2024

An in vivo and in vitro spatiotemporal atlas of human midbrain development

The dopaminergic system has key roles in human physiology and is implicated in a broad range of neurological and neuropsychiatric conditions that are increasingly investigated using induced pluripotent stem cell-derived midbrain models. To determine the similarity of such models to human systems, we undertook single cell and spatial profiling of first and second trimester fetal midbrain and compared it to in vitro midbrain models. Our initial histological analysis of second trimester fetal midbrain revealed structural complexity already similar to that of adult tissue, although this similarity did not fully extend to transcriptional activity. Moreover, we show that in vitro models recapitulate the transcriptional activity of late first trimester fetal midbrain, while 3D models replicate the spatial organization and cellular microenvironments of first and second trimester fetal midbrain. Understanding the extent of human tissue recapitulation in midbrain laboratory models is essential to justify their use as biological proxies.

neuroscience↗

bioRxiv2021

Enhanced cGAS-STING-dependent interferon signaling associated with mutations in ATAD3A

Mitochondrial DNA (mtDNA) has been suggested to drive immune system activation, but the induction of interferon signaling by mtDNA has not been demonstrated in a Mendelian mitochondrial disease. We initially ascertained two patients, one with a purely neurological phenotype, and one with features suggestive of systemic sclerosis in a syndromic context, and found them both to demonstrate enhanced interferon-stimulated gene (ISG) expression in blood. We determined each to harbor a previously described de novo dominant-negative heterozygous mutation in ATAD3A, encoding ATPase family AAA domain-containing protein 3A (ATAD3A). We identified five further patients with mutations in ATAD3A, and recorded up-regulated ISG expression and interferon alpha protein in four of them. Knockdown of ATAD3A in THP-1 cells resulted in increased interferon signaling, mediated by cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). Enhanced interferon signaling was abrogated in THP-1 cells and patient fibroblasts depleted of mtDNA. Thus, mutations in the mitochondrial membrane protein ATAD3A define a novel type I interferonopathy. SummaryDominant-negative mutations in ATAD3A, a ubiquitously expressed mitochondrial protein, cause mitochondrial DNA-dependent up-regulation of type I interferon signaling in the context of neurological disease and autoimmunity, thereby defining a novel type I interferonopathy.

immunology↗

bioRxiv2021

Psychomotor impairments and therapeutic implications revealed by a mutation linked with Infantile Parkinsonism-Dystonia

Parkinson disease (PD) is a progressive, neurodegenerative disorder affecting over 6.1 million people worldwide. Although the cause of PD remains unclear, studies of highly-penetrant mutations identified in early-onset familial parkinsonism have contributed to our understanding of the molecular mechanisms underlying disease pathology. Dopamine (DA) transporter (DAT) deficiency syndrome (DTDS) is a distinct type of infantile parkinsonism-dystonia that shares key clinical features with PD, including motor deficits (progressive bradykinesia, tremor, hypomimia) and altered DA neurotransmission. Here, we define structural, functional, and behavioral consequences of a Cys substitution at R445 in human DAT (hDAT R445C), identified in a patient with DTDS. We found that this R445 substitution disrupts a phylogenetically conserved intracellular (IC) network of interactions that compromise the hDAT IC gate. This is demonstrated by both Rosetta molecular modeling and fine-grained simulations using hDAT R445C, as well as EPR analysis and X-ray crystallography of the bacterial homolog leucine transporter. Notably, the disruption of this IC network of interactions supported a channel-like intermediate of hDAT and compromised hDAT function. We demonstrate that Drosophila melanogaster expressing hDAT R445C show impaired hDAT activity, which is associated with DA dysfunction in isolated brains and with abnormal behaviors monitored at high-speed time resolution. We show that hDAT R445C Drosophila exhibit motor deficits, lack of motor coordination (i.e. flight coordination) and phenotypic heterogeneity in these behaviors that is typically associated with DTDS and PD. These behaviors are linked with altered dopaminergic signaling stemming from loss of DA neurons and decreased DA availability. We rescued flight coordination through enhanced DAT surface expression via the lysosomal inhibitor chloroquine. Together, these studies shed light on how a DTDS-linked DAT mutation underlies DA dysfunction and, more broadly, the clinical phenotypes shared by DTDS and PD.

neuroscience↗

bioRxiv2019

Structural analysis of pathogenic missense mutations in GABRA2 and identification of a novel de novo variant in the desensitization gate

Cys-loop receptors are vital for controlling neuronal excitability in the brain and their dysfunction results in numerous neurological disorders. Recently, six de novo missense variants in GABRA2 gene, a member of this family, have been associated with early infantile epileptic encephalopathy (EIEE) and intellectual disability with seizures. Here, using whole-genome sequencing we identified a de novo missense variant in GABRA2 gene in a patient with EIEE and developmental delay. We perform protein structural analysis of the seven variants and show that all the mutations are in the transmembrane domain, either close to the desensitization gate, the activation gate or in inter-subunit interfaces. Further investigations demonstrated that the majority of pathogenic variants reported are at equivalent positions in other Cys-loop receptors, emphasizing the importance of these residues for the adequate function of the receptor. Also, a comparison of the distribution of the mutations in all the Cys-loop receptors showed that pathogenic variants are more common in the transmembrane helices, more specifically in the M2 helix, highlighting the importance of this segment. Our study expands the clinical spectrum of individuals with pathogenic missense mutations in GABRA2, defines the regions where pathogenic mutations are in the protein structure, and highlights the value of considering sequence, evolutionary, and structural information from other Cys-loop receptors as a strategy for variant interpretation of novel missense mutations in GABRA2.

genetics↗