Biology subjects

Yangzom, T.

Publications and source records attributed to Yangzom, T..

4 recordsLinked to original sources

bioRxiv2023

Nicotinamide Riboside Supplementation Ameliorates Mitochondrial Dysfunction and Neuronal Loss in POLG Mutant Midbrain Organoids

Mitochondrial dysfunction is associated with many neurodegenerative disorders and is particularly prominent in conditions tied to POLG mutations. POLG encodes DNA polymerase gamma vital for mitochondrial DNA replication. Employing 3D human pluripotent stem cell-derived midbrain organoids (hMOs), harbouring POLG mutations, this study explores their differentiation, transcriptional alterations, and underlying pathways of neurodegeneration associated with POLG mutations. The generated hMOs displayed midbrain specificity and, at three months, a reduced diameter, suggesting growth challenges from POLG mutations. A reduced presence of dopaminergic neurons, particularly in DA2 and ventral midbrain classes, was evident. Intriguingly, post-treatment with 1 mM Nicotinamide Riboside (NR), an NAD+ precursor, the organoids demonstrated an increased count of DA and VMN neurons and an elevated gene expression, especially in processes crucial to mitochondrial and synaptic functions. Our findings spotlight NAD+ supplementation has potential therapeutic value in addressing POLG-associated neuronal and mitochondrial deficits. Moreover, the unique insights garnered from single-cell RNA sequencing, and enrichment analyses further emphasize the significance of mitochondrial disturbances and potential interventions for POLG-related neurodegenerative conditions. In summary, we underscore the transformative potential of NAD+ in managing neurodegenerative diseases associated with POLG mutations. It also establishes the utility of POLG mutant hMOs as a potent research model.

neuroscience↗

bioRxiv2023

Mitochondrial Dysfunction and Neuronal Anomalies in POLG Mutant Midbrain Organoids

Human pluripotent stem cell-derived midbrain organoids offer transformative potential for elucidating brain development, disease representation, and therapeutic innovations. We introduce a novel methodology to generate midbrain-specific organoids from both embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). By employing tailored differentiation cues, notably dual-SMAD inhibition combined with FGF-8b and Sonic hedgehog agonist purmorphamine, we direct pluripotent stem cells towards a midbrain lineage. These organoids, growing beyond 2mm in diameter, house diverse neuroepithelial cell populations. Their midbrain character is affirmed by the pronounced expression of midbrain-specific markers and the absence of forebrain and hindbrain indicators. Critically, these organoids differentiate into dopaminergic neurons characteristic of the midbrain, displaying both morphological sophistication and electrophysiological vigor. Additionally, our experiments with POLG iPSC-derived midbrain organoids revealed a marked loss of dopaminergic neurons and diminished expression of genes governing mitochondrial pathways. This evidence underscores the models potential in simulating mitochondrial diseases and neurodegenerative conditions, notably Parkinsons disease. Our protocol thus emerges as a pivotal instrument for crafting functionally adept, midbrain-centric organoids, paving avenues for advanced studies in midbrain evolution, disorders like Parkinsons disease, and their interplay with mitochondrial dysfunction.

neuroscience↗

bioRxiv2023

Hallmark molecular and pathological features of POLG disease are recapitulated in cerebral organoids

In our research, we developed a 3D brain organoid model to study POLG-related encephalopathy, a mitochondrial disease stemming from POLG gene mutations. We utilized induced pluripotent stem cells (iPSCs) derived from patients with these mutations to generate cortical organoids, which exhibited typical POLG disease features, such as altered morphology, neuronal loss, and mtDNA depletion. We also identified significant dysregulation in pathways crucial for neuronal development and function, alongside upregulated NOTCH and JAK-STAT signaling pathways. Metformin treatment ameliorated many of these abnormalities, except for the persistent affliction of inhibitory DA GLU neurons. This novel model effectively mirrors both the molecular and pathological attributes of POLG disease, providing a valuable tool for mechanistic understanding and therapeutic screening for POLG-related disorders and other conditions characterized by compromised neuronal mtDNA maintenance and complex I deficiency. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/558087v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1759de3org.highwire.dtl.DTLVardef@d0a3dborg.highwire.dtl.DTLVardef@1b58eaborg.highwire.dtl.DTLVardef@a986a8_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIWe have successfully developed cortical organoid model that represents POLG-related disease. C_LIO_LIThis model effectively replicates both histological and molecular signatures seen in the brains of patients. C_LIO_LIThe cortical organoid model displays a range of features common in POLG-related disease, including neurodegeneration, mtDNA depletion, and neuronal complex I deficiency. C_LIO_LIThe use of metformin supplementation in this model improved mitochondria protein and reduced cell death. C_LI

cell biology↗

bioRxiv2023

The NAD+ Precursor Nicotinamide Riboside Rescues Mitochondrial Defects and Neuronal Loss in iPSC derived Cortical Organoid of Alpers' Disease

Alpers syndrome is an early-onset neurodegenerative disorder usually caused by biallelic pathogenic variants in the gene encoding the catalytic subunit of polymerase-gamma (POLG), which is essential for mitochondrial DNA (mtDNA) replication. The disease is progressive, incurable, and inevitably it leads to death from drug-resistant status epilepticus. The neurological features of Alpers syndrome are intractable epilepsy and developmental regression, with no effective treatment; the underlying mechanisms are still elusive, partially due to lack of good experimental models. Here, we generated the patient-derived induced pluripotent stem cells from one Alpers patient carrying the compound heterozygous mutations of A467T (c.1399G>A) and P589L (c.1766C>T), and further differentiated them into cortical organoids and neural stem cells (NSCs) for mechanistic studies of neural dysfunction in Alpers syndrome. Patient cortical organoids exhibited a phenotype that faithfully replicated the molecular changes found in patient postmortem brain tissue, as evidenced by cortical neuronal loss and depletion of mtDNA and complex I (CI). Patient NSCs showed mitochondrial dysfunction leading to ROS overproduction and downregulation of the NADH pathway. More importantly, the NAD+ precursor nicotinamide riboside (NR) significantly ameliorated mitochondrial defects in patient brain organoids. Our findings demonstrate that the iPSC model and brain organoids are good in vitro models of Alpers disease; this first-in-its-kind stem cell platform for Alpers syndrome enables therapeutic exploration and has identified NR as a viable drug candidate for Alpers disease and, potentially, other mitochondrial diseases with similar causes.

neuroscience↗