Biology subjects

Kvist, J.

Publications and source records attributed to Kvist, J..

9 recordsLinked to original sources

bioRxiv2026

Metabolic commitment to human motor neurons is characterized by mitochondrial depletion and pyruvate rewiring

Mitochondrial remodelling is a key feature of neurogenesis in cortical and hippocampal neuronal lineages, yet the temporal control of organellar homeostasis in developing human motor neurons remains poorly understood. Here, we generated a high-resolution temporal resource integrating proteomics, metabolomics, and mitochondrial characterization across human iPSC-to-motor neuron differentiation. This analysis revealed prolonged mitochondrial depletion during early neurogenesis, characterized by reduced mitochondrial content, mitochondrial fragmentation, and lysosome-dependent turnover. This state persisted throughout the neural progenitor stage and was followed by recovery of mitochondrial content during neuronal maturation. During this transition, pyruvate utilization shifted from pyruvate carboxylation towards pyruvate dehydrogenase-dependent oxidation. Pharmacological manipulation of pyruvate partitioning demonstrated that this metabolic switch is required for human neuronal differentiation. Our findings establish a temporal framework for the metabolic control of human motor neuron differentiation and reveal a progenitor-specific state linking mitochondrial depletion to pyruvate metabolism.

cell biology↗

bioRxiv2026

Loss of mitochondrial co-chaperone GRPEL2 protects mice from age- and diet-induced obesity

Mitochondrial protein homeostasis intersects with metabolic control, but the in vivo roles of specific mitochondrial co-chaperones remain unclear. The chaperone mtHSP70 plays a key role in import and folding of nuclear-encoded proteins targeted to mitochondrial matrix. Its protein folding cycle is regulated by the GrpE-like nucleotide exchange factor GRPEL1. Vertebrates also have a GRPEL2 paralog, postulated as the stress-sensitive counterpart, but its physiological relevance is not known. We show here that GRPEL2 is not essential for viability in mice, and its absence does not induce proteotoxic stress responses in stark contrast to GRPEL1. However, we find that GRPEL2 has a role in regulating body weight homeostasis. GRPEL2 knockout mice are protected from age- and diet-induced weight gain and maintain a better metabolic health and insulin sensitivity. Transcriptional profiling revealed minimal changes in liver and skeletal muscle, whereas white adipose tissue from Grpel2-deficient mice lacked the obesity-associated remodeling seen in controls. We propose that GRPEL2 fine-tunes metabolic setpoints without broadly perturbing mitochondrial protein import, thereby maintaining adipose tissue health during nutritional excess. These findings show that subtle alterations in mitochondrial chaperone systems reshape systemic metabolism and could suggest strategies to mitigate obesity and insulin resistance through targeted modulation of mitochondrial proteostasis.

physiology↗

bioRxiv2023

RFX6 haploinsufficiency predisposes to diabetes through impaired beta cell functionality

Regulatory factor X 6 (RFX6) is indispensable for pancreatic endocrine development and differentiation. The RFX6 protein-truncating variant p.His293LeufsTer7 is significantly enriched in the Finnish population with almost 1:250 individuals as a carrier. Importantly, the FinnGen study indicates a high predisposition for heterozygous carriers to develop type 2 diabetes (T2D) and gestational diabetes. To understand the role of this variant in {beta}-cell development and function, we generated allelic series of isogenic pluripotent stem cell models and directed them into pancreatic islet lineages (SC-islets). Expectedly, in-vitro models of the homozygous RFX6-/- variant failed to generate pancreatic endocrine cells, recapitulating the phenotype in Mitchell-Riley syndrome. Notably, heterozygous RFX6+/- derived SC-islets showed reduced {beta}-cell maturation markers and calcium oscillations, resulting in defective insulin secretion, without affecting {beta}-cell number or insulin content. The reduced insulin secretion is sustained during in-vivo implantation studies, consistent with the susceptibility of the carriers to develop diabetes. TeaserModeling RFX6-assocciated neonatal and type-2 diabetes using allelic series stem cell-derived islets in-vitro and in-vivo.

cell biology↗

bioRxiv2022

The type 1 diabetes gene TYK2 regulates β-cell development and its responses to interferon-α

Type 1 diabetes (T1D) is an autoimmune disease that results in the destruction of insulin producing pancreatic {beta}-cells. One of the genes associated with T1D is TYK2, which encodes a Janus kinase with critical roles in type-I interferon (IFN) mediated intracellular signaling. To study the role of TYK2 in human pancreatic {beta}-cell development and response to IFN, we generated TYK2 knockout human iPSCs and directed them into the pancreatic endocrine lineage. Here we show that loss of TYK2 compromised the emergence of endocrine precursors by regulating KRAS expression while mature stem cell-islets (SC-islets) function was not affected. In the maturing SC-islets, the loss or inhibition of TYK2 prevented IFN-induced antigen processing and presentation, including MHC Class I expression in pancreatic endocrine and progenitor cells. Furthermore, in a CD8+ cytotoxic T-cell co-culture model, the survival of {beta}-cells was enhanced by a selective TYK2 inhibitor. These results identify an unsuspected role for TYK2 on {beta}-cell development and support TYK2 inhibition in adult {beta}-cells as a potent therapeutic target to halt T1D progression.

molecular biology↗

bioRxiv2021

Peripheral neuropathy linked mRNA export factor GANP reshapes gene regulation in human motor neurons

Loss-of-function of the mRNA export protein GANP (MCM3AP gene) cause early-onset sensorimotor neuropathy, characterised by axonal degeneration in long peripheral nerves. GANP functions as a scaffold at nuclear pore complexes, contributing to selective nuclear export of mRNAs. Here, we aimed to identify motor neuron specific transcripts that are regulated by GANP and may be limiting for local protein synthesis in motor neuron axons. We compared motor neurons with a gene edited mutation in the Sac3 mRNA binding domain of GANP to isogenic controls. We also examined patient-derived motor neurons. RNA sequencing of motor neurons as well as nuclear and axonal subcompartments showed that mutant GANP had a profound effect on motor neuron transcriptomes, with alterations in nearly 40 percent of all expressed genes and broad changes in splicing. Expression changes in multiple genes critical for neuronal functions, combined with compensatory upregulation of protein synthesis and early-stage metabolic stress genes, indicated that RNA metabolism was abnormal in GANP-deficient motor neurons. Surprisingly, limited evidence was found for large-scale nuclear retention of mRNA. This first study of neuropathy-linked GANP defects in human motor neurons shows that GANP has a wide gene regulatory role in a disease-relevant cell type that requires long-distance mRNA transport.

neuroscience↗

bioRxiv2021

Functional, metabolic and transcriptional maturation of stem cell derived beta cells

Transplantation of pancreatic islet cells derived from human pluripotent stem cells is a promising treatment for diabetes. Despite progress in stem cell-derived islet (SC-islet) generation, detailed characterization of their functional properties has not been conducted. Here, we generated functionally mature SC-islets using an optimized protocol and comprehensively benchmarked them against primary adult islets. Biphasic glucose stimulated insulin secretion developed during in vitro maturation, associated with cytoarchitectural reorganization and increased alpha cells. Electrophysiology and exocytosis of SC-islets were comparable to adult islets. Glucose-responsive insulin secretion was achieved despite differences in glycolytic and mitochondrial glucose metabolism. Single-cell transcriptomics of SC-islets in vitro and throughout 6 months of murine engraftment revealed a continuous maturation trajectory culminating in a transcriptional landscape closely resembling that of primary islets. Our thorough evaluation of SC-islet maturation highlights their advanced degree of functionality and supports their use in further efforts to understand and combat diabetes.

developmental biology↗

bioRxiv2021

Small mitochondrial protein NERCLIN regulates cardiolipin homeostasis and mitochondrial ultrastructure.

Cardiolipin (CL) is an essential phospholipid for mitochondrial structure and function. Here we present a small mitochondrial protein, NERCLIN, as a negative regulator of CL homeostasis and mitochondrial ultrastructure. Primate-specific NERCLIN is expressed ubiquitously from GRPEL2 locus on a tightly regulated low level, but induced by heat stress. NERCLIN overexpression severely disrupts mitochondrial cristae structure and induces mitochondrial fragmentation. Proximity labeling suggested interactions of NERCLIN with CL synthesis and prohibitin complexes on the matrix side of the inner mitochondrial membrane. Lipid analysis indicated that NERCLIN regulates mitochondrial CL content. The regulation may occur directly through interaction with PTPMT1, a proximal partner on the CL synthesis pathway, as its product phosphatidylglycerol was also reduced by NERCLIN. We propose that NERCLIN contributes to stress-induced adaptation of mitochondrial dynamics and turnover by regulating the mitochondrial CL content. Our findings add NERCLIN to the group of recently identified small mitochondrial proteins with important regulatory functions.

cell biology↗

bioRxiv2019

CHCHD10 OR CHCHD2 ARE NOT REQUIRED FOR HUMAN MOTOR NEURON DIFFERENTIATION IN VITRO BUT MODIFY SYNAPTIC TRANSCRIPTOMES

Mitochondrial intermembrane space proteins CHCHD2 and CHCHD10 have roles in diseases affecting motor neurons such as amyotrophic lateral sclerosis, spinal muscular atrophy and axonal neuropathy and in Parkinsons disease, and form a complex of unknown function. Here we address the importance of these two proteins in human motor neurons. We show that gene edited human induced pluripotent stem cells (iPSC) lacking either CHCHD2 or CHCHD10 are viable and can be differentiated into functional motor neurons that fire spontaneous and evoked action potentials. Knockout iPSC and motor neurons sustain mitochondrial ultrastructure and show reciprocal compensatory increases in CHCHD2 or CHCHD10. Knockout motor neurons have largely overlapping transcriptome profiles compared to isogenic control line, in particular for synaptic gene expression. Our results show that absence of CHCHD2 or CHCHD10 does not disrupt functionality, but induces similar modifications in human motor neurons. Thus pathogenic mechanisms may involve loss of synaptic function.

neuroscience↗

bioRxiv2019

Maturation of Neuronal Activity in Caudalized Human Brain Organoids

Human brain organoids are an emerging tool to study functional neuronal networks in health and disease. A critical challenge is the engineering of brain organoids with defined regional identity and developmental stage. Here we describe a protocol for generating hindbrain-like organoids from human pluripotent stem cells. We first generated a stable pool of caudalized stem cells that expressed hindbrain identity transcription factors and differentiated into tissue containing neurons and astrocytes. After maturation, caudalized brain organoids presented synaptically connected networks consisting of glutamate-, GABA-, and serotoninergic postmitotic neurons. These mature neurons displayed electric properties and dendritic trees resembling medulla oblongata neurons. They fired spontaneous and evoked repetitive action potentials, released serotonin and displayed excitatory and inhibitory synaptic currents, functionally resembling the activity patterns observed in normal human fetal brain. Reminiscent of infected human fetal brain, infection with Zika virus hampered organoid development, while the treatment with anticonvulsant drugs - carbamazepine and valproic acid - reduced organoid growth. Neuronal maturation also occurred in the grafted organoids in vivo. In conclusion, our approach enables efficient derivation of caudalized neuronal stem cells that differentiate into mature and functional neurons in organoids with hindbrain identity following human developmental trajectory. The organoids provide excellent model to study congenital abnormalities in brain development and for drug testing.

neuroscience↗