Generation and characterization of NGLY1 patient-derived midbrain organoids

hPSCs-derived brain organoids for disease modeling, toxicity testing and drug evaluation

Due to the differences and variances in genetic background, in vitro and animal models cannot meet the modern medical exploration of real human brain structure and function. Recently, brain organoids generated by human pluripotent stem cells (hPSCs) can mimic the structure and physiological function of human brain, being widely used in medical research. Brain organoids generated from normal hPSCs or patient-derived induced pluripotent stem cells offer a more promising approach for the study of diverse human brain diseases. More importantly, the use of the established brain organoid model for drug evaluation is conducive to shorten the clinical transformation period. Herein, we summarize methods for the identification of brain organoids from cellular diversity, morphology and neuronal activity, brain disease modeling, toxicity testing, and drug evaluation. Based on this, it is hoped that this review will provide new insights into the pathogenesis of brain diseases and drug research and development, promoting the rapid development of brain science.

Development of new NGLY1 assay systems - toward developing an early screening method for NGLY1 deficiency

Cytosolic peptide: N-glycanase (PNGase/NGLY1 in mammals) is an amidase (EC:3.5.1.52) widely conserved in eukaryotes. It catalyzes the removal of N-glycans on glycoproteins, converting N-glycosylated Asn into Asp residues. This enzyme also plays a role in the quality control system for nascent glycoproteins. Since the identification of a patient with an autosomal recessive genetic disorder caused by NGLY1 gene dysfunction, known as NGLY1 deficiency or NGLY1 congenital disorder of deglycosylation (OMIM: 615273), in 2012, more than 100 cases have been reported worldwide. NGLY1 deficiency is characterized by a wide array of symptoms, such as global mental delay, intellectual disability, abnormal electroencephalography findings, seizure, movement disorder, hypolacrima or alacrima, and liver dysfunction. Unfortunately, no effective therapeutic treatments for this disease have been established. However, administration of adeno-associated virus 9 (AAV9) vector harboring human NGLY1 gene to an NGLY1-deficient rat model (Ngly1-/- rat) by intracerebroventricular injection was found to drastically improve motor function defects. This observation indicated that early therapeutic intervention could alleviate various symptoms originating from central nervous system dysfunction in this disease. Therefore, there is a keen interest in the development of facile diagnostic methods for NGLY1 deficiency. This review summarizes the history of assay development for PNGase/NGLY1 activity, as well as the recent progress in the development of novel plate-based assay systems for NGLY1, and also discusses future perspectives.

Chronic Opioid Treatment Arrests Neurodevelopment and Alters Synaptic Activity in Human Midbrain Organoids

Understanding the impact of long-term opioid exposure on the embryonic brain is critical due to the surging number of pregnant mothers with opioid dependency. However, this has been limited by human brain inaccessibility and cross-species differences in animal models. Here, a human midbrain model is established that uses hiPSC-derived midbrain organoids to assess cell-type-specific responses to acute and chronic fentanyl treatment and fentanyl withdrawal. Single-cell mRNA sequencing of 25,510 cells from organoids in different treatment groups reveals that chronic fentanyl treatment arrests neuronal subtype specification during early midbrain development and alters synaptic activity and neuron projection. In contrast, acute fentanyl treatment increases dopamine release but does not significantly alter gene expression related to cell lineage development. These results provide the first examination of the effects of opioid exposure on human midbrain development at the single-cell level.

Midbrain organoids for Parkinson's disease (PD) - A powerful tool to understand the disease pathogenesis

Brain Organiods (BOs) are a promising technique for researching disease progression in the human brain. These organoids, which are produced from human induced pluripotent stem cells (HiPSCs), can construct themselves into structured frameworks. In the context of Parkinson's disease (PD), recent advancements have been made in the development of Midbrain organoids (MBOs) models that consider key pathophysiological mechanisms such as alpha-synuclein (α-Syn), Lewy bodies, dopamine loss, and microglia activation. However, there are limitations to the current use of BOs in disease modelling and drug discovery, such as the lack of vascularization, long-term differentiation, and absence of glial cells. To address these limitations, researchers have proposed the use of spinning bioreactors to improve oxygen and nutrient perfusion. Modelling PD utilising modern experimental in vitro models is a valuable tool for studying disease mechanisms and elucidating previously unknown features of PD. In this paper, we exclusively review the unique methods available for cultivating MBOs using a pumping system that mimics the circulatory system. This mechanism may aid in delivering the required amount of oxygen and nutrients to all areas of the organoids, preventing cell death, and allowing for long-term culture and using co-culturing techniques for developing glial cell in BOs. Furthermore, we emphasise some of the significant discoveries about the BOs and the potential challenges of using BOs will be discussed.

Induced pluripotent stem cells (iPSCs): molecular mechanisms of induction and applications

The induced pluripotent stem cell (iPSC) technology has transformed in vitro research and holds great promise to advance regenerative medicine. iPSCs have the capacity for an almost unlimited expansion, are amenable to genetic engineering, and can be differentiated into most somatic cell types. iPSCs have been widely applied to model human development and diseases, perform drug screening, and develop cell therapies. In this review, we outline key developments in the iPSC field and highlight the immense versatility of the iPSC technology for in vitro modeling and therapeutic applications. We begin by discussing the pivotal discoveries that revealed the potential of a somatic cell nucleus for reprogramming and led to successful generation of iPSCs. We consider the molecular mechanisms and dynamics of somatic cell reprogramming as well as the numerous methods available to induce pluripotency. Subsequently, we discuss various iPSC-based cellular models, from mono-cultures of a single cell type to complex three-dimensional organoids, and how these models can be applied to elucidate the mechanisms of human development and diseases. We use examples of neurological disorders, coronavirus disease 2019 (COVID-19), and cancer to highlight the diversity of disease-specific phenotypes that can be modeled using iPSC-derived cells. We also consider how iPSC-derived cellular models can be used in high-throughput drug screening and drug toxicity studies. Finally, we discuss the process of developing autologous and allogeneic iPSC-based cell therapies and their potential to alleviate human diseases.

Development of a fluorescence and quencher-based FRET assay for detection of endogenous peptide:N-glycanase/NGLY1 activity

Cytosolic peptide:N-glycanase (PNGase/NGLY1 in mammals) catalyzes deglycosylation of N-glycans on glycoproteins. A genetic disorder caused by mutations in the NGLY1 gene leads to NGLY1 deficiency with symptoms including motor deficits and neurological problems. Effective therapies have not been established, though, a recent study used the administration of an adeno-associated viral vector expressing human NGLY1 to dramatically rescue motor functions in young Ngly1-/- rats. Thus, early therapeutic intervention may improve symptoms arising from central nervous system dysfunction, and assay methods for measuring NGLY1 activity in biological samples are critical for early diagnostics. In this study, we established an assay system for plate-based detection of endogenous NGLY1 activity using a FRET-based probe. Using this method, we revealed significant changes in NGLY1 activity in rat brains during aging. This novel assay offers reliable disease diagnostics and provides valuable insights into the regulation of PNGase/NGLY1 activity in diverse organisms under different stress conditions.

Genetic disruption of mammalian endoplasmic reticulum-associated protein degradation: Human phenotypes and animal and cellular disease models

Endoplasmic reticulum-associated protein degradation (ERAD) is a stringent quality control mechanism through which misfolded, unassembled and some native proteins are targeted for degradation to maintain appropriate cellular and organelle homeostasis. Several in vitro and in vivo ERAD-related studies have provided mechanistic insights into ERAD pathway activation and its consequent events; however, a majority of these have investigated the effect of ERAD substrates and their consequent diseases affecting the degradation process. In this review, we present all reported human single-gene disorders caused by genetic variation in genes that encode ERAD components rather than their substrates. Additionally, after extensive literature survey, we present various genetically manipulated higher cellular and mammalian animal models that lack specific components involved in various stages of the ERAD pathway.