Disease Models & Mechanisms最新文献

Stem cell-derived β-cells (SCβ-cell) are a renewable and scalable alternative to cadaveric islets as a cell-replacement therapy for type 1 diabetes (T1D). However, heterogeneity within SCβ-cell cultures remains problematic for graft safety and function. Magnetic selection of SCβ-cells expressing a unique cell-surface marker may help deplete undesirable cell types and facilitate functional maturation. Here, we explored the transmembrane glycoprotein CD19 as a potential cell-surface marker for the enrichment of insulin-expressing SCβ-cells. Using CRISPR/Cas9 technology, we created a knock-in add-on of CD19-mScarlet downstream of insulin (INS) coding sequence exon 2 in human embryonic stem cells (hESCs). We developed and optimized a magnetic-activated cell sorting protocol for CD19-mScarlet-expressing cells, forming enriched SCβ-cell clusters with improved glucose-stimulated C-peptide secretion. This strategy holds promise to facilitate large-scale production of functional SCβ-cells for disease modeling and cell-replacement therapy.

Uremic cardiomyopathy (UC) represents a leading cause of mortality in patients with chronic kidney disease (CKD), characterized by left ventricular hypertrophy (LVH) and fibrosis. The underlying mechanisms of UC pathogenesis remain incompletely understood. This study developed two methods to simulate human UC - modified nephrectomy (MNx) and adenine-normal combinational diet - and compared these approaches across several rodent strains. Transcriptomic analysis was performed on left ventricular tissues from these models. The analysis revealed global changes in UC, including dysregulated cell cycle processes, enhanced extracellular matrix remodeling and metabolic abnormalities, while also highlighting molecular distinctions between MNx- and adenine-induced UC. Notably, this study identified C-C-motif receptor 2 (CCR-2) as a novel potential antifibrotic target in UC. CCR-2 blockade substantially reversed fibrosis without affecting LVH. The mechanism through which CCR-2 inhibition suppresses cardiac fibrosis development in UC appears to involve the promotion of cardiac residual macrophage expansion. These findings establish a central role for CCR-2 in cardiac fibrosis and suggest CCR-2 inhibition as a promising therapeutic target for UC.

PTEN hamartoma tumour syndrome (PHTS), a rare disease caused by germline heterozygous PTEN variants, is associated with multi-organ/tissue overgrowth, autism spectrum disorder and increased cancer risk. Phenotypic variability in PHTS is partly due to diverse PTEN variants and the protein's multifaceted functions. PTEN is primarily a phosphatidylinositol(3,4,5)trisphosphate (PIP3) phosphatase regulating PI3K/AKT signalling but also maintains chromosomal stability through nuclear functions such as double-stranded (ds)DNA damage repair. Here, we show that PTEN-R173C, a pathogenic variant frequently found in PHTS and somatic cancer, has elevated PIP3 phosphatase activity that effectively regulates canonical PI3K/AKT signalling. However, PTEN-R173C is unstable and excluded from the nucleus. We generated Pten+/R173C mice which developed few tumours during their lifetime, aligning with normal PI3K/AKT signalling. However, they exhibited lymphoid hyperplasia, macrocephaly and brain abnormalities, associated with impaired nuclear functions of PTEN-R173C, demonstrated by reduced dsDNA damage repair. We integrated PHTS patient data with our mouse model results, and propose that defective nuclear functions of PTEN variants can predict the onset of PHTS phenotypes and that late-onset cancer in these individuals may arise from secondary genetic alterations, facilitated by compromised dsDNA repair.

Collagen VI related dystrophies (COL6-RD) are congenital muscle diseases, typically inherited as an autosomal dominant trait. A frequent type of pathogenic variant involves glycine substitutions in the triple helical domain of collagen VI alpha chains, exerting a dominant-negative effect on the unaltered protein. Despite this, no prior animal model captured this mutation type. By using CRISPR/Cas9, we generated transgenic mice with the equivalent of the human COL6A1 c.877 G>A; p. Gly293Arg pathogenic variant. We characterized their skeletal muscle phenotype over time, utilizing computer-aided tools applied to standardized parameters of muscle pathology and function. Knock-in mice exhibited early-onset reduced muscle weight, myopathic histology, increased fibrosis, reduced collagen VI expression, muscle weakness and impaired respiratory function. These features provide adequate outcome measures to assess therapeutic interventions. Different automated image analysis methods deployed here are able analyze thousands of features simultaneously, enhancing accuracy in describing muscle disease models. Overall, the Col6a1 Ki Gly292Arg mouse model offers a robust platform to deepen our understanding of COL6-RD and advance its therapeutic landscape.

Cortical bone is highly porous and composed of an interconnecting network of vascular canals and osteocyte lacunae. Our understanding of the mechanisms coupling vascular: lacunar spatial organisation in cortical bone is poorly understood. Defining cellular cross-talk mechanisms could be key in identification of reciprocal molecular signals driving increased cortical porosity with age. Driven by the hypothesis that porosity within bone is heterogeneous and influenced by region-specific spatial cues, we utilised synchrotron X-ray computed tomography to characterise intracortical canal and osteocyte lacunae distribution, morphology and spatial arrangements in healthy and pathological murine bone. We found that the posterior region of the tibiofibular junction (TFJ) exhibited the highest levels of cortical porosity and highest canal number density compared to other regions. The volume of osteocyte lacunae positioned proximal to cortical vascular canals was highest in the posterior region. Following deletion of bone-derived VEGF, the region-specific effects on lacunar: vascular arrangements described in the wild-type TFJ were lost. Our results describe spatial diversity in osteocyte lacunae size within the bone cortex, which associates with vascular canal arrangements maintained by VEGF.

The cohesin complex performs essential cellular functions including regulation of chromatin organization and DNA repair. Somatic pathogenetic variants in cohesin genes, such as STAG2, have been associated with cancer, but their contribution to brain tumorigenesis is unclear. Here, we report the presence of STAG2 variants in patients with glioblastoma and medulloblastoma and determined the effects of loss of STAG2 in human cells and of the homolog SA1 in Drosophila tissues. Reduction of SA1 expression during fly brain development led to defects in neural stem cell differentiation and promotion of tumorigenesis, both in the presence and absence of oncogenic activity. Treatment with inhibitors of poly ADP-ribose polymerase (PARP), which are used to treat forms of cancer with defects in DNA repair, in combination with STAG2/SA1 depletion resulted in apoptosis in vitro and in vivo. In flies, reduction of PARP activity ameliorated the tumor-associated phenotypes of SA1-deficient tissue. Our in vivo and in vitro data suggest that impairment of PARP activity compensates for reduced cohesin activity, highlighting a vulnerability that could be pharmacologically exploited in brain tumors.

Primary cilia play a pivotal role in cellular signaling and development. Human primary microcephaly is strongly associated with pathogenic variants in primary cilia genes. Here, we examine the role of Ttc21b, a component of the intraflagellar transport-A complex, during mouse forebrain development by using a Ttc21balien null allele. Our findings reveal that significant microcephaly in homozygous mutants is caused by disrupted neural progenitor proliferation and differentiation. Histological and immunohistochemical analyses show an enlarged ventricular zone and reduced cortical plate thickness accompanied by altered mitotic spindle angles, suggesting defects in symmetric versus asymmetric cell divisions. Embryonic expression patterns suggest that perdurant TTC21B protein underlies these phenotypes. Progenitor proliferation kinetics were disrupted along with changes in TBR2-positive intermediate progenitors and TBR1-positive early-developing neurons. Neuronal processes in the cortical plate were significantly shortened. Our findings support a model in which early expression of Ttc21b in neural precursor cells destined for the forebrain is critical to ensure TTC21B protein levels to sustain subsequent neural progenitor proliferation and differentiation. These results advance our understanding of the role primary cilia have in cortical development.

Our understanding of mechanisms underlying familial Parkinson's disease (PD) have benefitted from studies in Drosophila models of PD. However, in a majority of patients with PD, the disease occurs sporadically, and cellular phenotypes that arise early in sporadic PD are not yet fully understood. A genetic predisposition, arising from variants in pathways that impact dopaminergic neuron health could be one cause of sporadic PD. Here, we studied Drosophila with single-copy mutation of the recessive IP3R-encoding gene (itpr) in combination with a recessive null mutation of the parkin gene. Whereas individual mutants appeared normal, in combination, the genes synergised so that flies exhibited flight motor deficits with a focus in a subset of central dopaminergic neurons. Surprisingly, mitophagy and mitochondrial Ca2+ were barely affected. Instead, flight motor deficits correlated with elevated levels of mitochondrial H2O2, and reducing H2O2 levels by genetic means restored mitochondrial function and flight to a significant extent. This study underlines the importance of mitochondrial oxidative stress as an early phenotype in PD and suggests that humans with recessive variants in either pathway have a higher chance of developing sporadic PD.

Epilepsy is a mechanistically complex, incompletely understood neurological disorder. To uncover novel converging mechanisms in epilepsy, we used Drosophila whole-brain single-cell RNA sequencing to refine and characterize a previously proposed human epilepsy-associated gene co-expression network (GCN). We identified a conserved co-expressed module of 26 genes, which comprises fly orthologs of 13 epilepsy-associated genes and integrates synaptic and metabolic functions. Over one-third of the Drosophila pan-neuronal knockdown models targeting this module exhibited altered seizure-like behaviors in response to mechanical or heat stress. These knockdown models recapitulated seizures associated with four epilepsy-associated genes and identified two novel epilepsy candidate genes and three genes for which knockdown conferred seizure protection. Most knockdown models with altered seizure susceptibility showed changes in metabolic rate and levels of phosphorylated adenosine monophosphate-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis. Enhancing AMPK activity increased seizure resistance in a dose-dependent manner. Our findings show that Drosophila single-cell expression data and behavior can aid functional validation of human GCNs and highlight a role for metabolism in modifying seizure susceptibility.