RESUMEN
In optic neuropathies, including glaucoma, retinal ganglion cells (RGCs) die. Cell transplantation and endogenous regeneration offer strategies for retinal repair, however, developmental programs required for this to succeed are incompletely understood. To address this, we explored cellular reprogramming with transcription factor (TF) regulators of RGC development which were integrated into human pluripotent stem cells (PSCs) as inducible gene cassettes. When the pioneer factor NEUROG2 was combined with RGC-expressed TFs (ATOH7, ISL1, and POU4F2) some conversion was observed and when pre-patterned by BMP inhibition, RGC-like induced neurons (RGC-iNs) were generated with high efficiency in just under a week. These exhibited transcriptional profiles that were reminiscent of RGCs and exhibited electrophysiological properties, including AMPA-mediated synaptic transmission. Additionally, we demonstrated that small molecule inhibitors of DLK/LZK and GCK-IV can block neuronal death in two pharmacological axon injury models. Combining developmental patterning with RGC-specific TFs thus provided valuable insight into strategies for cell replacement and neuroprotection.
RESUMEN
Axon injury is a hallmark of many neurodegenerative diseases, often resulting in neuronal cell death and functional impairment. Dual leucine zipper kinase (DLK) has emerged as a key mediator of this process. However, while DLK inhibition is robustly protective in a wide range of neurodegenerative disease models, it also inhibits axonal regeneration. Indeed, there are no genetic perturbations that are known to both improve long-term survival and promote regeneration. To identify such a neuroprotective target, we conducted a set of complementary high-throughput screens using a protein kinase inhibitor library in human stem cell-derived retinal ganglion cells (hRGCs). Overlapping compounds that promoted both neuroprotection and neurite outgrowth were bioinformatically deconvoluted to identify specific kinases that regulated neuronal death and axon regeneration. This work identified the role of germinal cell kinase four (GCK-IV) kinases in cell death and additionally revealed their unexpected activity in suppressing axon regeneration. Using an adeno-associated virus (AAV) approach, coupled with genome editing, we validated that GCK-IV kinase knockout improves neuronal survival, comparable to that of DLK knockout, while simultaneously promoting axon regeneration. Finally, we also found that GCK-IV kinase inhibition also prevented the attrition of RGCs in developing retinal organoid cultures without compromising axon outgrowth, addressing a major issue in the field of stem cell-derived retinas. Together, these results demonstrate a role for the GCK-IV kinases in dissociating the cell death and axonal outgrowth in neurons and their druggability provides for therapeutic options for neurodegenerative diseases.
Asunto(s)
Axones/enzimología , Axones/patología , Sistema Nervioso Central/patología , Quinasas del Centro Germinal/metabolismo , Regeneración Nerviosa , Animales , Secuencia de Bases , Sistemas CRISPR-Cas/genética , Muerte Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Dependovirus/metabolismo , Modelos Animales de Enfermedad , Humanos , Ratones Endogámicos C57BL , Regeneración Nerviosa/efectos de los fármacos , Proyección Neuronal/efectos de los fármacos , Traumatismos del Nervio Óptico/metabolismo , Traumatismos del Nervio Óptico/patología , Organoides/metabolismo , Inhibidores de Proteínas Quinasas/farmacología , Células Ganglionares de la Retina/efectos de los fármacos , Células Ganglionares de la Retina/metabolismo , Transducción de Señal/efectos de los fármacosRESUMEN
Despite the proliferation of proteins that can form filaments or phase-separated condensates, it remains unclear how this behavior is distributed over biological networks. We have found that 60 of the 440 yeast metabolic enzymes robustly form structures, including 10 that assemble within mitochondria. Additionally, the ability to assemble is enriched at branch points on several metabolic pathways. The assembly of enzymes at the first branch point in de novo purine biosynthesis is coordinated, hierarchical, and based on their position within the pathway, while the enzymes at the second branch point are recruited to RNA stress granules. Consistent with distinct classes of structures being deployed at different control points in a pathway, we find that the first enzyme in the pathway, PRPP synthetase, forms evolutionarily conserved filaments that are sequestered in the nucleus in higher eukaryotes. These findings provide a roadmap for identifying additional conserved features of metabolic regulation by condensates/filaments.
Asunto(s)
Proteínas Luminiscentes/metabolismo , Redes y Vías Metabólicas , Proteínas Mitocondriales/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Regulación Enzimológica de la Expresión Génica , Regulación Fúngica de la Expresión Génica , Proteínas Luminiscentes/genética , Microscopía Fluorescente , Proteínas Mitocondriales/genética , Ribosa-Fosfato Pirofosfoquinasa/genética , Ribosa-Fosfato Pirofosfoquinasa/metabolismo , Saccharomyces cerevisiae/enzimología , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genéticaRESUMEN
The proper regulation of the localization, translation, and stability of maternally deposited transcripts is essential for embryonic development in many organisms. These different forms of regulation are mediated by the various protein subunits of the ribonucleoprotein (RNP) complexes that assemble on maternal mRNAs. However, while many of the subunits that regulate the localization and translation of maternal transcripts have been identified, relatively little is known about how maternal mRNAs are stockpiled and stored in a stable form to support early development. One of the best characterized regulators of maternal transcripts is Cup - a broadly conserved component of the maternal RNP complex that in Drosophila acts as a translational repressor of the localized message oskar. In this study, we have found that loss of cup disrupts the localization of both the oskar mRNA and its associated proteins to the posterior pole of the developing oocyte. This defect is not due to a failure to specify the oocyte or to disruption of RNP transport. Rather, the localization defects are due to a drop in oskar mRNA levels in cup mutant egg chambers. Thus, in addition to its role in regulating oskar mRNA translation, Cup also plays a critical role in controlling the stability of the oskar transcript. This suggests that Cup is ideally positioned to coordinate the translational control function of the maternal RNP complex with its role in storing maternal transcripts in a stable form.
Asunto(s)
Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Oogénesis/genética , Estabilidad del ARN/genética , Alelos , Animales , Drosophila melanogaster/citología , Sitios Genéticos , Mutación/genética , Oocitos/citología , Oocitos/metabolismo , Fenotipo , Subunidades de Proteína/metabolismo , Ribonucleoproteínas/metabolismoRESUMEN
The discovery of large supramolecular complexes such as the purinosome suggests that subcellular organization is central to enzyme regulation. A screen of the yeast GFP strain collection to identify proteins that assemble into visible structures identified four novel filament systems comprised of glutamate synthase, guanosine diphosphate-mannose pyrophosphorylase, cytidine triphosphate (CTP) synthase, or subunits of the eIF2/2B translation factor complex. Recruitment of CTP synthase to filaments and foci can be modulated by mutations and regulatory ligands that alter enzyme activity, arguing that the assembly of these structures is related to control of CTP synthase activity. CTP synthase filaments are evolutionarily conserved and are restricted to axons in neurons. This spatial regulation suggests that these filaments have additional functions separate from the regulation of enzyme activity. The identification of four novel filaments greatly expands the number of known intracellular filament networks and has broad implications for our understanding of how cells organize biochemical activities in the cytoplasm.