Biology subjects

Ahuja, K.

Publications and source records attributed to Ahuja, K..

4 recordsLinked to original sources

bioRxiv2024

A deep phenotyping study in mouse and iPSC models to understand the role of oligodendroglia in optic neuropathy in Wolfram syndrome

Wolfram syndrome (WS) is a rare childhood disease characterized by diabetes mellitus, diabetes insipidus, blindness, deafness, neurodegeneration and eventually early death, due to autosomal recessive mutations in the WFS1 (and WFS2) gene. While it is categorized as a neurodegenerative disease, it is increasingly becoming clear that other cell types besides neurons may be affected and contribute to the pathogenesis. MRI studies in patients and phenotyping studies in WS rodent models indicate white matter/myelin loss, implicating a role for oligodendroglia in WS-associated neurodegeneration. In this study, we sought to determine if oligodendroglia are affected in WS and whether their dysfunction may be the primary cause of the observed optic neuropathy and brain neurodegeneration. We demonstrate that 7.5-month-old Wfs1{Delta}exon8 mice display signs of abnormal myelination and a reduced number of oligodendrocyte precursor cells (OPCs) as well as abnormal axonal conduction in the optic nerve. An MRI study of the brain furthermore revealed grey and white matter loss in the cerebellum, brainstem, and superior colliculus, as is seen in WS patients. To further dissect the role of oligodendroglia in WS, we performed a transcriptomics study of WS patient iPSC-derived OPCs and pre-myelinating oligodendrocytes. Transcriptional changes compared to isogenic control cells were found for genes with a role in ER function. However, a deep phenotyping study of these WS patient iPSC-derived oligodendroglia unveiled normal differentiation, mitochondria-associated endoplasmic reticulum (ER) membrane interactions and mitochondrial function, and no overt signs of ER stress. Overall, the current study indicates that oligodendroglia functions are largely preserved in the WS mouse and patient iPSC-derived models used in this study. These findings do not support a major defect in oligodendroglia function as the primary cause of WS, and warrant further investigation of neurons and neuron-oligodendroglia interactions as a target for future neuroprotective or -restorative treatments for WS.

neuroscience↗

bioRxiv2023

Mitochondrial calcium signaling mediated transcriptional regulation of keratin filaments is a critical determinant of melanogenesis

Mitochondria are versatile organelles that regulate several physiological functions. Many mitochondria-controlled processes are driven by mitochondrial Ca2+ signaling. However, role of mitochondrial Ca2+ signaling in melanosome biology remains unknown. Here, we show that pigmentation requires mitochondrial Ca2+ uptake. In vitro gain and loss of function studies demonstrated that Mitochondrial Ca2+ Uniporter (MCU) is crucial for melanogenesis while the MCU rheostats, MCUb and MICU1 negatively control melanogenesis. Zebrafish and mouse models showed that MCU plays a vital role in pigmentation in vivo. Mechanistically, MCU controls activation of transcription factor NFAT2 to induce expression of three keratins (keratin 5, 7 and 8), which we report as positive regulators of melanogenesis. Interestingly, keratin 5 in turn modulates mitochondrial Ca2+ uptake thereby this signaling module acts as a negative feedback loop that fine-tunes both mitochondrial Ca2+ signaling and melanogenesis. Mitoxantrone, an FDA approved drug that inhibits MCU, decreases physiological melanogenesis. Collectively, our data demonstrates a critical role for mitochondrial Ca2+ signaling in vertebrate pigmentation and reveal the therapeutic potential of targeting MCU for clinical management of pigmentary disorders. Given the centrality of mitochondrial Ca2+ signaling and keratin filaments in cellular physiology, this feedback loop may be functional in a variety of other pathophysiological conditions. HighlightsO_LIMCU complex mediated mitochondrial Ca2+ uptake is a novel regulator of vertebrate pigmentation C_LIO_LIKeratin filaments bridge mitochondrial Ca2+ signaling to melanosome biogenesis and maturation C_LIO_LITranscription factor NFAT2 connects mitochondrial Ca2+ dynamics to keratins expression C_LIO_LIMCU-NFAT2-Keratin 5 signaling module generates a negative feedback loop to maintain mitochondrial Ca2+ homeostasis and to ensure optimal melanogenesis C_LIO_LIInhibiting MCU with mitoxantrone, an FDA approved drug, leads to reduction in physiological pigmentation C_LI

cell biology↗

bioRxiv2023

Methotrimeprazine exerts antiviral and neuroprotective effects in Japanese encephalitis virus infection through activation of adaptive ER stress and autophagy

Japanese encephalitis virus (JEV) is the leading global cause of virus-induced encephalitis. Its pathogenesis is driven by a combination of neuronal cell death and neuroinflammation. We hypothesized that pharmacological upregulation of autophagy could exert a neuroprotective antiviral effect, and tested a panel of forty-two FDA-approved drugs that were shown to induce autophagy. Four drugs were tested in the JE mouse model based on in vitro protective effects on neuronal cell death, inhibition of viral replication, and anti-inflammatory effects in microglial cells. The antipsychotic phenothiazines Methotrimeprazine (MTP) and Trifluoperazine (TFP) showed a significant survival benefit with reduced virus titers in the brain, prevention of blood-brain barrier (BBB) breach, and inhibition of neuroinflammation. Both drugs were potent mTOR-independent autophagy flux inducers. Mechanistically MTP inhibited SERCA channel functioning, thereby resulting in rise in cytosolic calcium levels, and induction of a unique adaptive ER stress response. In virus infected drug treated cells, there was a strong transcriptional downregulation of type I interferon and interferon-stimulated genes and upregulation of cholesterol metabolic pathway genes. The drugs exerted an autophagy-dependent antiviral effect at the level of JEV protein translation/replication complex formation in diverse cell types. Inhibition of inflammatory cytokine/chemokine release from mouse microglial cells was partly autophagy-dependent. Our study suggests that MTP exerts a combined antiviral and anti-inflammatory effect in JEV infection, and has therapeutic potential to be repurposed for JE treatment.

microbiology↗

bioRxiv2022

Meiotic and mitotic aneuploidies drive arrest of in vitro fertilized human preimplantation embryos

The high incidence of aneuploidy in early human development, arising either from errors in meiosis or postzygotic mitosis, is the primary cause of pregnancy loss, miscarriage, and still birth following natural conception as well as in vitro fertilization (IVF). Preimplantation genetic testing for aneuploidy (PGT-A) has confirmed the prevalence of meiotic and mitotic aneuploidies among blastocyst-stage IVF embryos that are candidates for transfer. However, only about half of normally fertilized embryos develop to the blastocyst stage in vitro, while the others arrest at cleavage to late morula or early blastocyst stages. To achieve a more complete view of the impacts of aneuploidy, we applied a validated method of PGT-A to a large series (n = 909) of arrested embryos and trophectoderm biopsies. We then correlated observed aneuploidies with abnormalities of the first two cleavage divisions using time lapse imaging (n = 843). The combined incidence of meiotic and mitotic aneuploidies was strongly associated with blastocyst morphological grading, with the proportion ranging from 20% to 90% for the highest to lowest grades, respectively. In contrast, the incidence of aneuploidy among arrested embryos was exceptionally high (94%), dominated by mitotic aneuploidies affecting multiple chromosomes. In turn, these mitotic aneuploidies were strongly associated with abnormal cleavage divisions, such that 51% of abnormally dividing embryos possessed mitotic aneuploidies compared to only 23% of normally dividing embryos. We conclude that the combination of meiotic and mitotic aneuploidies drives arrest of human embryos in vitro, as development increasingly relies on embryonic gene expression at the blastocyst stage.

genetics↗