BLOS2 negatively regulates Notch signaling during neural and hematopoietic stem and progenitor cell development

Signaling pathways of liver regeneration: Biological mechanisms and implications

The liver possesses a unique regenerative ability to restore its original mass, in this regard, partial hepatectomy (PHx) and partial liver transplantation (PLTx) can be executed smoothly and safely, which has important implications for the treatment of liver disease. Liver regeneration (LR) can be the very complicated procedure that involves multiple cytokines and transcription factors that interact with each other to activate different signaling pathways. Activation of these pathways can drive the LR process, which can be divided into three stages, namely, the initiation, progression, and termination stages. Therefore, it is important to investigate the pathways involved in LR to elucidate the mechanism of LR. This study reviews the latest research on the key signaling pathways in the different stages of LR.

GCN5L1 regulates pulmonary surfactant production by modulating lamellar body biogenesis and trafficking in mouse alveolar epithelial cells

BACKGROUND

The pulmonary surfactant that lines the air-liquid surface within alveoli is a protein-lipid mixture essential for gas exchange. Surfactant lipids and proteins are synthesized and stored in the lamellar body (LB) before being secreted from alveolar type II (AT2) cells. The molecular and cellular mechanisms that regulate these processes are incompletely understood. We previously identified an essential role of general control of amino acid synthesis 5 like 1 (GCN5L1) and the biogenesis of lysosome-related organelle complex 1 subunit 1 (BLOS1) in surfactant system development in zebrafish. Here, we explored the role of GCN5L1 in pulmonary surfactant regulation.

METHOD

GCN5L1 knockout cell lines were generated with the CRISPR/Cas9 system. Cell viability was analyzed by MTT assay. Released surfactant proteins were measured by ELISA. Released surfactant lipids were measured based on coupled enzymatic reactions. Gene overexpression was mediated through lentivirus. The RNA levels were detected through RNA-sequencing (RNA-seq) and quantitative reverse transcription (qRT)- polymerase chain reaction (PCR). The protein levels were detected through western blotting. The cellular localization was analyzed by immunofluorescence. Morphology of the lamellar body was analyzed through transmission electron microscopy (TEM), Lysotracker staining, and BODIPY phosphatidylcholine labeling.

RESULTS

Knocking out GCN5L1 in MLE-12 significantly decreased the release of surfactant proteins and lipids. We detected the downregulation of some surfactant-related genes and misregulation of the ROS-Erk-Foxo1-Cebpα axis in mutant cells. Modulating the activity of the axis or reconstructing the mitochondrial expression of GCN5L1 could partially restore the expression of these surfactant-related genes. We further showed that MLE-12 cells contained many LB-like organelles that were lipid enriched and positive for multiple LB markers. These organelles were smaller in size and accumulated in the absence of GCN5L1, indicating both biogenesis and trafficking defects. Accumulated endogenous surfactant protein (SP)-B or exogenously expressed SP-B/SP-C in adenosine triphosphate-binding cassette transporterA3 (ABCA3)-positive organelles was detected in mutant cells. GCN5L1 localized to the mitochondria and LBs. Reconstruction of mitochondrial GCN5L1 expression rescued the organelle morphology but failed to restore the trafficking defect and surfactant release, indicating specific roles associated with different subcellular localizations.

CONCLUSIONS

In summary, our study identified GCN5L1 as a new regulator of pulmonary surfactant that plays a role in the biogenesis and positioning/trafficking of surfactant-containing LBs.

Active post-transcriptional regulation and ACLY-mediated acetyl-CoA synthesis as a pivotal target of Shuang-Huang-Sheng-Bai formula for lung adenocarcinoma treatment

BACKGROUND

New therapeutic approaches are required to improve the outcomes of lung cancer (LC), a leading cause of cancer-related deaths worldwide. Chinese herbal medicine formulae widely used in China provide a unique opportunity for improving LC treatment, and the Shuang-Huang-Sheng-Bai (SHSB) formula is a typical example. However, the underlying mechanisms of action remains unclear.

PURPOSE

This study aimed to confirm the efficacy of SHSB against lung adenocarcinoma (LUAD), which is a major histological type of LC, unveil the downstream targets of this formula, and assess the clinical relevance and biological roles of the newly identified target.

METHODS

An experimental metastasis mouse model and a subcutaneous xenograft mouse model were used to evaluate the anti-cancer activity of SHSB. Multi-omics profiling of subcutaneous tumors and metabolomic profiling of sera were performed to identify downstream targets, especially the metabolic targets of SHSB. A clinical trial was conducted to verify the newly identified metabolic targets in patients. Next, the metabolites and enzymes engaged in the metabolic pathway targeted by SHSB were measured in clinical samples. Finally, routine molecular experiments were performed to decipher the biological functions of the metabolic pathways targeted by SHSB.

RESULTS

Oral SHSB administration showed overt anti-LUAD efficacy as revealed by the extended overall survival of the metastasis model and impaired growth of implanted tumors in the subcutaneous xenograft model. Mechanistically, SHSB administration altered protein expression in the post-transcriptional layer and modified the metabolome of LUAD xenografts. Integrative analysis demonstrated that SHSB markedly inhibited acetyl-CoA synthesis in tumors by post-transcriptionally downregulating ATP-citrate lyase (ACLY). Consistently, our clinical trial showed that oral SHSB administration declined serum acetyl-CoA levels of patients with LC. Moreover, acetyl-CoA synthesis and ACLY expression were both augmented in clinical LUAD tissues of patients, and high intratumoral ACLY expression predicted a detrimental prognosis. Finally, we showed that ACLY-mediated acetyl-CoA synthesis is essential for LUAD cell growth by promoting G1/S transition and DNA replication.

CONCLUSION

Limited downstream targets of SHSB for LC treatment have been reported in previous hypothesis-driven studies. In this study, we conducted a comprehensive multi-omics investigation and demonstrated that SHSB exerted its anti-LUAD efficacy by actively and post-transcriptionally modulating protein expression and particularly restraining ACLY-mediated acetyl-CoA synthesis.

DNA methylation is associated with prenatal exposure to sulfur dioxide and childhood attention-deficit hyperactivity disorder symptoms

Epigenetic influence plays a role in the association between exposure to air pollution and attention deficit hyperactivity disorder (ADHD); however, research regarding sulfur dioxide (SO₂) is scarce. Herein, we investigate the associations between prenatal SO₂ exposure and ADHD rating scale (ARS) at ages 4, 6 and 8 years repeatedly in a mother-child cohort (n = 329). Whole blood samples were obtained at ages 2 and 6 years, and genome-wide DNA methylation (DNAm) was analyzed for 51 children using the Illumina Infinium HumanMethylation BeadChip. We analyzed the associations between prenatal SO₂ exposure and DNAm levels at ages 2 and 6, and further investigated the association between the DNAm and ARS at ages 4, 6 and 8. Prenatal SO₂ exposure was associated with ADHD symptoms. From candidate gene analysis, DNAm levels at the 6 CpGs at age 2 were associated with prenatal SO₂ exposure levels. Of the 6 CpGs, cg07583420 (INS-IGF2) was persistently linked with ARS at ages 4, 6 and 8. Epigenome-wide analysis showed that DNAm at 6733 CpG sites were associated with prenatal SO₂ exposure, of which 58 CpGs involved in Notch signalling pathway were further associated with ARS at age 4, 6 and 8 years, persistently. DNAm at age 6 was not associated with prenatal SO₂ exposure. Changes in DNAm levels associated with prenatal SO₂ exposure during early childhood are associated with increases in ARS in later childhood.

Borcs6 is required for endo-lysosomal degradation during early development

Early development and differentiation require precise control of cellular functions. Lysosomal degradation is a critical component of normal cellular homeostasis, allowing for degradation of signaling molecules, proteins, and other macromolecules for cellular remodeling and signaling. Little is known about the role of lysosomal function in mammalian embryos before gastrulation. Borcs6 is a protein involved in lysosomal trafficking as well as endo-lysosomal and autophagosome fusion. Here, we show that Borcs6 is necessary for efficient endo-lysosomal degradation in the early embryo. Although embryos lacking Borcs6 are developmentally comparable to control littermates at E5.5, they are characterized by large cells containing increased levels of late endosomes and abnormal nuclei. Furthermore, these embryos display a skewed ratio of extraembryonic and embryonic cell lineages, are delayed by E6.5, and do not undergo normal gastrulation. These results demonstrate the essential functions of lysosomal positioning and fusion with endosomes during early embryonic development and indicate that the early lethality of BORCS6 mutant embryos is primarily due to defects in the HOPS-related function of BORC rather than lysosomal positioning.

DNA methylation safeguards the generation of hematopoietic stem and progenitor cells by repression of Notch signaling

The earliest hematopoietic stem and progenitor cells (HSPCs) are generated from the ventral wall of the dorsal aorta, through endothelial-to-hematopoietic transition during vertebrate embryogenesis. Notch signaling is crucial for HSPC generation across vertebrates; however, the precise control of Notch during this process remains unclear. In the present study, we used multi-omics approaches together with functional assays to assess global DNA methylome dynamics during the endothelial cells to HSPCs transition in zebrafish, and determined that DNA methyltransferase 1 (Dnmt1) is essential for HSPC generation via repression of Notch signaling. Depletion of dnmt1 resulted in decreased DNA methylation levels and impaired HSPC production. Mechanistically, we found that loss of dnmt1 induced hypomethylation of Notch genes and consequently elevated Notch activity in hemogenic endothelial cells, thereby repressing the generation of HSPCs. This finding deepens our understanding of HSPC specification in vivo, which will provide helpful insights for designing new strategies for HSPC generation in vitro.

Summary: Multi-omics approaches and functional assays reveal global DNA methylome dynamics and an indispensable role of DNA methyltransferase 1 in hematopoietic stem/progenitor cell generation through repression of Notch signaling.

Scientific Validation of Human Neurosphere Assays for Developmental Neurotoxicity Evaluation

There is a call for a paradigm shift in developmental neurotoxicity (DNT) evaluation, which demands the implementation of faster, more cost-efficient, and human-relevant test systems than current in vivo guideline studies. Under the umbrella of the Organisation for Economic Co-operation and Development (OECD), a guidance document is currently being prepared that instructs on the regulatory use of a DNT in vitro battery (DNT IVB) for fit-for-purpose applications. One crucial issue for OECD application of methods is validation, which for new approach methods (NAMs) requires novel approaches. Here, mechanistic information previously identified in vivo, as well as reported neurodevelopmental adversities in response to disturbances on the cellular and tissue level, are of central importance. In this study, we scientifically validate the Neurosphere Assay, which is based on human primary neural progenitor cells (hNPCs) and an integral part of the DNT IVB. It assesses neurodevelopmental key events (KEs) like NPC proliferation (NPC1ab), radial glia cell migration (NPC2a), neuronal differentiation (NPC3), neurite outgrowth (NPC4), oligodendrocyte differentiation (NPC5), and thyroid hormone-dependent oligodendrocyte maturation (NPC6). In addition, we extend our work from the hNPCs to human induced pluripotent stem cell-derived NPCs (hiNPCs) for the NPC proliferation (iNPC1ab) and radial glia assays (iNPC2a). The validation process we report for the endpoints studied with the Neurosphere Assays is based on 1) describing the relevance of the respective endpoints for brain development, 2) the confirmation of the cell type-specific morphologies observed in vitro, 3) expressions of cell type-specific markers consistent with those morphologies, 4) appropriate anticipated responses to physiological pertinent signaling stimuli and 5) alterations in specific in vitro endpoints upon challenges with confirmed DNT compounds. With these strong mechanistic underpinnings, we posit that the Neurosphere Assay as an integral part of the DNT in vitro screening battery is well poised for DNT evaluation for regulatory purposes.

New insights into the pathogenesis of Hermansky-Pudlak syndrome

Hermansky-Pudlak syndrome (HPS) is characterized by defects of multiple tissue-specific lysosome-related organelles (LROs), typically manifesting with oculocutaneous albinism or ocular albinism, bleeding tendency, and in some cases with pulmonary fibrosis, inflammatory bowel disease or immunodeficiency, neuropsychological disorders. Eleven HPS subtypes in humans and at least 15 subtypes in mice have been molecularly identified. Current understanding of the underlying mechanisms of HPS is focusing on the defective biogenesis of LROs. Compelling evidences have shown that HPS protein-associated complexes (HPACs) function in cargo transport, cargo recycling, and cargo removal to maintain LRO homeostasis. Further investigation on the molecular and cellular mechanism of LRO biogenesis and secretion will be helpful for better understanding of its pathogenesis and for the precise intervention of HPS.

Biological implications of genetic variations in autism spectrum disorders from genomics studies

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental condition characterized by atypical social interaction and communication together with repetitive behaviors and restricted interests. The prevalence of ASD has been increased these years. Compelling evidence has shown that genetic factors contribute largely to the development of ASD. However, knowledge about its genetic etiology and pathogenesis is limited. Broad applications of genomics studies have revealed the importance of gene mutations at protein-coding regions as well as the interrupted non-coding regions in the development of ASD. In this review, we summarize the current evidence for the known molecular genetic basis and possible pathological mechanisms as well as the risk genes and loci of ASD. Functional studies for the underlying mechanisms are also implicated. The understanding of the genetics and genomics of ASD is important for the genetic diagnosis and intervention for this condition.

Organelle Crosstalk Regulators Are Regulated in Diseases, Tumors, and Regulatory T Cells: Novel Classification of Organelle Crosstalk Regulators

To examine whether the expressions of 260 organelle crosstalk regulators (OCRGs) in 16 functional groups are modulated in 23 diseases and 28 tumors, we performed extensive -omics data mining analyses and made a set of significant findings: (1) the ratios of upregulated vs. downregulated OCRGs are 1:2.8 in acute inflammations, 1:1 in metabolic diseases, 1:1.2 in autoimmune diseases, and 1:3.8 in organ failures; (2) sepsis and trauma-upregulated OCRG groups such as vesicle, mitochondrial (MT) fission, and mitophagy but not others, are termed as the cell crisis-handling OCRGs. Similarly, sepsis and trauma plus organ failures upregulated seven OCRG groups including vesicle, MT fission, mitophagy, sarcoplasmic reticulum–MT, MT fusion, autophagosome–lysosome fusion, and autophagosome/endosome–lysosome fusion, classified as the cell failure-handling OCRGs; (3) suppression of autophagosome–lysosome fusion in endothelial and epithelial cells is required for viral replications, which classify this decreased group as the viral replication-suppressed OCRGs; (4) pro-atherogenic damage-associated molecular patterns (DAMPs) such as oxidized low-density lipoprotein (oxLDL), lipopolysaccharide (LPS), oxidized-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (oxPAPC), and interferons (IFNs) totally upregulated 33 OCRGs in endothelial cells (ECs) including vesicle, MT fission, mitophagy, MT fusion, endoplasmic reticulum (ER)–MT contact, ER– plasma membrane (PM) junction, autophagosome/endosome–lysosome fusion, sarcoplasmic reticulum–MT, autophagosome–endosome/lysosome fusion, and ER–Golgi complex (GC) interaction as the 10 EC-activation/inflammation-promoting OCRG groups; (5) the expression of OCRGs is upregulated more than downregulated in regulatory T cells (Tregs) from the lymph nodes, spleen, peripheral blood, intestine, and brown adipose tissue in comparison with that of CD4⁺CD25⁻ T effector controls; (6) toll-like receptors (TLRs), reactive oxygen species (ROS) regulator nuclear factor erythroid 2-related factor 2 (Nrf2), and inflammasome-activated regulator caspase-1 regulated the expressions of OCRGs in diseases, virus-infected cells, and pro-atherogenic DAMP-treated ECs; (7) OCRG expressions are significantly modulated in all the 28 cancer datasets, and the upregulated OCRGs are correlated with tumor immune infiltrates in some tumors; (8) tumor promoter factor IKK2 and tumor suppressor Tp53 significantly modulate the expressions of OCRGs. Our findings provide novel insights on the roles of upregulated OCRGs in the pathogenesis of inflammatory diseases and cancers, and novel pathways for the future therapeutic interventions for inflammations, sepsis, trauma, organ failures, autoimmune diseases, metabolic cardiovascular diseases (CVDs), and cancers.

A novel BLOC1S5-related HPS-11 patient and zebrafish with bloc1s5 disruption

Hermansky-Pudlak Syndrome (HPS) cases present with a variable degree of OCA and bleeding tendency. HPS is categorized into eleven types based on eleven causative genes, and disease severity varies among different types. By whole-exome sequencing performed on a family trio and Sanger sequencing of candidate variants, we identified a novel homozygous variant (NM_201280.3: c.181delC, p.Val61*) in BLOC1S5 in the patient who presents OCA and mild bleeding diathesis, and his healthy parents are heterozygous carriers. The variant can be considered pathogenic based on the guideline American College of Medical Genetics and Genomics, and the patient is proposed to be affected with HPS-11. In this study, we also explored bloc1s5 in zebrafish. bloc1s5 mRNA can be detected during early development of zebrafish. bloc1s5 knockdown zebrafish present with retinal hypopigmentation, thrombocytes loss and pericardial edema, and dll4/notch1 signaling and vascular integrity signaling are down-regulated at mRNA level in bloc1s5 morphants. The data from the first HPS-11 patient in Chinese population expand phenotypic and genotypic spectrum of HPS-11. Disruption of bloc1s5 in zebrafish recapitulates HPS-11-like phenotypes, and the potential signaling pathways associated with bloc1s5 are proposed. Altogether, this study may facilitate genetic counseling of HPS and investigation about BLOC1S5.

Notch signaling and the emergence of hematopoietic stem cells

The hematopoietic stem cell (HSC) is able to give rise to all blood cell lineages in vertebrates. HSCs are generated in the early embryo after two precedent waves of primitive hematopoiesis. Canonical Notch signaling is at the center of the complex mechanism that controls the development of the definitive HSC. The successful in vitro generation of hematopoietic cells from pluripotent stem cells with the capacity for multilineage hematopoietic reconstitution after transplantation requires the recapitulation of the most important process that takes place in the hemogenic endothelium during definitive hematopoiesis, that is the endothelial-to-hematopoietic transition (EHT). To meet this challenge, it is necessary to thoroughly understand the molecular mechanisms that modulate Notch signaling during the HSC differentiation process considering different temporal and spatial dimensions. In recent years, there have been important advances in this field. Here, we review relevant contributions describing different genes, factors, environmental cues, and signaling cascades that regulate the EHT through Notch interactions at multiple levels. The evolutionary conservation of the hematopoietic program has made possible the use of diverse model systems. We describe the contributions of the zebrafish model and the most relevant ones from transgenic mouse studies and from in vitro differentiated pluripotent cells.

The road to lysosome-related organelles: Insights from Hermansky-Pudlak syndrome and other rare diseases

Lysosome-related organelles (LROs) comprise a diverse group of cell type-specific, membrane-bound subcellular organelles that derive at least in part from the endolysosomal system but that have unique contents, morphologies and functions to support specific physiological roles. They include: melanosomes that provide pigment to our eyes and skin; alpha and dense granules in platelets, and lytic granules in cytotoxic T cells and natural killer cells, which release effectors to regulate hemostasis and immunity; and distinct classes of lamellar bodies in lung epithelial cells and keratinocytes that support lung plasticity and skin lubrication. The formation, maturation and/or secretion of subsets of LROs are dysfunctional or entirely absent in a number of hereditary syndromic disorders, including in particular the Hermansky-Pudlak syndromes. This review provides a comprehensive overview of LROs in humans and model organisms and presents our current understanding of how the products of genes that are defective in heritable diseases impact their formation, motility and ultimate secretion.

Rab5c-mediated endocytic trafficking regulates hematopoietic stem and progenitor cell development via Notch and AKT signaling

It is well known that various developmental signals play diverse roles in hematopoietic stem and progenitor cell (HSPC) production; however, how these signaling pathways are orchestrated remains incompletely understood. Here, we report that Rab5c is essential for HSPC specification by endocytic trafficking of Notch and AKT signaling in zebrafish embryos. Rab5c deficiency leads to defects in HSPC production. Mechanistically, Rab5c regulates hemogenic endothelium (HE) specification by endocytic trafficking of Notch ligands and receptor. We further show that the interaction between Rab5c and Appl1 in the endosome is required for the survival of HE in the ventral wall of the dorsal aorta through AKT signaling. Interestingly, Rab5c overactivation can also lead to defects in HSPC production, which is attributed to excessive endolysosomal trafficking inducing Notch signaling defect. Taken together, our findings establish a previously unrecognized role of Rab5c-mediated endocytic trafficking in HSPC development and provide new insights into how spatiotemporal signals are orchestrated to accurately execute cell fate transition.

Cell-autonomous Notch signaling regulated by the membrane trafficking protein Rab5c plays an instructive role in hematopoietic stem and progenitor cell specification, while the AKT signaling seems to provide a permissive signal to maintain hemogenic endothelium survival.

Genome-wide identification of loci associated with growth in rainbow trout

Background

Growth is a major economic production trait in aquaculture. Improvements in growth performance will reduce time and cost for fish to reach market size. However, genes underlying growth have not been fully explored in rainbow trout.

Results

A previously developed 50 K gene-transcribed SNP chip, containing ~ 21 K SNPs showing allelic imbalances potentially associated with important aquaculture production traits including body weight, muscle yield, was used for genotyping a total of 789 fish with available phenotypic data for bodyweight gain. Genotyped fish were obtained from two consecutive generations produced in the NCCCWA growth-selection breeding program. Weighted single-step GBLUP (WssGBLUP) was used to perform a genome-wide association (GWA) analysis to identify quantitative trait loci (QTL) associated with bodyweight gain. Using genomic sliding windows of 50 adjacent SNPs, 247 SNPs associated with bodyweight gain were identified. SNP-harboring genes were involved in cell growth, cell proliferation, cell cycle, lipid metabolism, proteolytic activities, chromatin modification, and developmental processes. Chromosome 14 harbored the highest number of SNPs (n = 50). An SNP window explaining the highest additive genetic variance for bodyweight gain (~ 6.4%) included a nonsynonymous SNP in a gene encoding inositol polyphosphate 5-phosphatase OCRL-1. Additionally, based on a single-marker GWA analysis, 33 SNPs were identified in association with bodyweight gain. The highest SNP explaining variation in bodyweight gain was identified in a gene coding for thrombospondin-1 (THBS1) (R² = 0.09).

Conclusion

The majority of SNP-harboring genes, including OCRL-1 and THBS1, were involved in developmental processes. Our results suggest that development-related genes are important determinants for growth and could be prioritized and used for genomic selection in breeding programs.

Cooperative evolution of two different TEs results in lineage-specific novel transcripts in the BLOC1S2 gene

BACKGROUND

The BLOC1S2 gene encodes the multifunctional protein BLOS2, a shared subunit of two lysosomal trafficking complexes: i) biogenesis of lysosome-related organelles complex-1 and i) BLOC-1-related complex. In our previous study, we identified an intriguing unreported transcript of the BLOC1S2 gene that has a novel exon derived from two transposable elements (TEs), MIR and AluSp. To investigate the evolutionary footprint and molecular mechanism of action of this transcript, we performed PCR and RT-PCR experiments and sequencing analyses using genomic DNA and RNA samples from humans and various non-human primates.

RESULTS

The results showed that the MIR element had integrated into the genome of our common ancestor, specifically in the BLOC1S2 gene region, before the radiation of all primate lineages and that the AluSp element had integrated into the genome of our common ancestor, fortunately in the middle of the MIR sequences, after the divergence of Old World monkeys and New World monkeys. The combined MIR and AluSp sequences provide a 3' splice site (AG) and 5' splice site (GT), respectively, and generate the Old World monkey-specific transcripts. Moreover, branch point sequences for the intron removal process are provided by the MIR and AluSp combination.

CONCLUSIONS

We show for the first time that sequential integration into the same location and sequence divergence events of two different TEs generated lineage-specific transcripts through sequence collaboration during primate evolution.

Suppression of YAP/TAZ-Notch1-NICD axis by bromodomain and extraterminal protein inhibition impairs liver regeneration

Background and aims: Biological mechanisms that control liver regeneration remain poorly defined. However, these mechanisms are remarkable issues in the clinic that affect management of hepatic loss caused by liver surgery, traumatic injury, chronic infection, or liver poisoning. Increasing evidence has shown that various growth factors, cytokines, and metabolic signaling pathways affect the liver regenerative process. Our aim is to study the effect of bromodomain and extraterminal (BET) protein inhibition on liver regeneration and its mechanism.

Methods: We studied the role of BET protein inhibitor, JQ1, in liver regeneration in a mouse model after 70% partial hepatectomy (PH). We evaluated yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) and Notch signaling pathways, which were affected by BET protein inhibitor in mouse hepatic tissues and primary hepatocytes in vivo and AML12 cell lines in vitro. We evaluated the relationship of YAP/TAZ and Notch signaling pathway using YAP/TAZ pathway inhibitor in liver regeneration in vivo. Moreover, we analyzed the relationship of YAP/TAZ and Notch signaling pathways via overexpression or RNA silencing of Yap in AML12 cells. Furthermore, we used Yap overexpression mouse model to examine whether it can rescue liver regeneration damage caused by inhibition of BET proteins.

Results: In this study, we report that BET protein inhibitor JQ1 molecule impairs the early phase of liver regeneration in a mouse model after 70% PH. Mechanistically, YAP/TAZ and Notch1-NICD pathways were suppressed by BET protein inhibitor in mouse hepatic tissues and primary hepatocytes in vivo and mouse AML12 cell lines in vitro. By using YAP/TAZ pathway inhibitor, we confirmed that the liver regeneration and the activation of Notch pathway were impaired by the inhibition of YAP/TAZ pathway in vivo. Furthermore, the study showed that Yap knockdown by shRNA in normal mouse hepatic cell line downregulated Notch1 signal transduction, whereas Yap overexpression promoted Notch1-NICD signals. Specific overexpression of Yap in mouse liver could rescue the effect of BET protein inhibition on liver regeneration injury.

Conclusion: These results revealed the crucial role of the YAP/TAZ-Notch1-NICD axis in liver regeneration. Therefore, BET protein inhibitors must be used in caution in the treatment of hepatic diseases by reason of its suppressive roles in liver regeneration.

Prediction of causal genes and gene expression analysis of attention-deficit hyperactivity disorder in the different brain region, a comprehensive integrative analysis of ADHD

Recent genome-wide association study (GWAS) identified 12 independent loci for Attention-deficit hyperactivity disorder (ADHD). However, the causal genes expression and pathways of ADHD is still vague. We integrated GWAS, eQTL and genes expression data to find the causal genes, genes expression, and genes prioritization in the different brain tissues and whole blood cells. Overall 47 genes were prioritized, the most promising genes were LSG1, HYAL3, PIDD, PNPLA2, BLOC1S2, PLK1S1, CALN1, KAT2B, CTNNB1 and WDR11. Whereas, the CALN1, KAT2B, and WDR11 were previously associated with schizophrenia (SZ), bipolar (BP) and drug abuse. Gene ontology analysis shows that the glutamate receptor signaling pathway (P = 8.009E-07, with false discovery rate (FDR) < 5%), GRIK5 sub network (P = 2.887E-06, FDR < 5%), abnormal gait (P = 3.657E-06, FDR < 5%), REACTOME_SIGNALING_BY_ERBB2 (P = 5.161E-06, FDR < 5%), and abnormal nervous system physiology (P = 5.239E-06, FDR < 5%) were associated with ADHD. These causal genes were highly expressed in Fetal Astrocytes, Neurons, and Microglia/Macrophage. This study illustrates the comprehensive GWAS integrative approach of ADHD. However, further genetic and functional studies are required to validate the role of these genes in the etiology of ADHD, which should provide novel insights into the understanding of this disease.

The retromer complex safeguards against neural progenitor-derived tumorigenesis by regulating Notch receptor trafficking

The correct establishment and maintenance of unidirectional Notch signaling are critical for the homeostasis of various stem cell lineages. However, the molecular mechanisms that prevent cell-autonomous ectopic Notch signaling activation and deleterious cell fate decisions remain unclear. Here we show that the retromer complex directly and specifically regulates Notch receptor retrograde trafficking in Drosophila neuroblast lineages to ensure the unidirectional Notch signaling from neural progenitors to neuroblasts. Notch polyubiquitination mediated by E3 ubiquitin ligase Itch/Su(dx) is inherently inefficient within neural progenitors, relying on retromer-mediated trafficking to avoid aberrant endosomal accumulation of Notch and cell-autonomous signaling activation. Upon retromer dysfunction, hypo-ubiquitinated Notch accumulates in Rab7⁺ enlarged endosomes, where it is ectopically processed and activated in a ligand-dependent manner, causing progenitor-originated tumorigenesis. Our results therefore unveil a safeguard mechanism whereby retromer retrieves potentially harmful Notch receptors in a timely manner to prevent aberrant Notch activation-induced neural progenitor dedifferentiation and brain tumor formation.

Most cells in the animal body are tailored to perform particular tasks, but stem cells have not yet made their choice. Instead, they have unlimited capacity to divide and, with the right signals, they can start to specialize to become a given type of cells. In the brain, this process starts with a stem cell dividing. One of the daughters will remain a stem cell, while the other, the neural progenitor, will differentiate to form a mature cell such as a neuron. Keeping this tight balance is crucial for the health of the organ: if the progenitor reverts back to being a stem cell, there will be a surplus of undifferentiated cells that can lead to a tumor.

A one-way signal driven by the protein Notch partly controls the distinct fates of the two daughter cells. While the neural progenitor carries Notch at its surface, its neural stem cell sister has a Notch receptor on its membrane instead. This ensures that the Notch signaling goes in one direction, from the cell with Notch to the one sporting the receptor.

When a stem cell divides, one daughter gets more of a protein called Numb than the other. Numb pulls Notch receptors away from the external membrane and into internal capsules called endosomes. This guarantees that only one of the siblings will be carrying the receptors at its surface. Yet, sometimes the Notch receptors can get activated in the endosomes, which may make neural progenitors revert to being stem cells. It is still unclear what tools the cells have to stop this abnormal activation.

Here, Li et al. screened brain cells from fruit fly larvae to find out the genes that might play a role in suppressing the inappropriate Notch signaling. This highlighted a protein complex known as the retromer, which normally helps to transport proteins in the cell. Experiments showed that, in progenitors, the retromer physically interacts with Notch receptors and retrieves them from the endosomes back to the cell surface. If the retromer is inactive, the Notch receptors accumulate in the endosomes, where they can be switched on. It seems that, in fruit flies, the retromer acts as a bomb squad that recognizes and retrieves potentially harmful Notch receptors, thereby preventing brain tumor formation.

Several retromer components are less present in patients with various cancers, including glioblastoma, an aggressive form of brain cancer. The results by Li et al. may therefore shed light on the link between the protein complex and the emergence of the disease in humans.

Notch signaling pathway regulates cell cycle in proliferating hepatocytes involved in liver regeneration

BACKGROUND AND AIM

It has been well documented that Notch signaling is involved in liver regeneration. However, the exact molecular mechanism mediating this process is not fully elucidated. The current study aimed to investigate the role of Notch signaling regulating cell cycle in proliferating hepatocytes in liver regeneration after partial hepatectomy (PHx, 67% resection) and the related molecular mechanism.

METHODS

Partial hepatectomy was performed in Sprague Dawley rats, and remnant livers were harvested 0, 1, 3, 5, and 7 days after operation, and primary hepatocytes were isolated to investigate the molecular mechanism.

RESULTS

Notch signaling activation and hepatocyte proliferation were significantly increased after PHx, while treatment with FLI-06, the inhibitor of γ-secreting enzyme, blocked these trends. Besides, inhibition of Notch signaling led to dysregulation of cell cycle and cell-cycle components. Furthermore, Akti-1/2 (a selective Akt inhibitor) and PX-478 (a selective Hif-1α inhibitor) inhibited hepatocyte proliferation and liver regeneration after PHx, and the effect of downstream molecules activation by Jagged-1 (Notch-1 ligand) in hepatocytes was abolished by FLI-06, Akti-1/2, and PX-478.

CONCLUSION

The current study demonstrated for the first time that Notch signaling regulated cell cycle in proliferating hepatocytes involved in liver regeneration through NICD/Akt Akt/Hif-1α pathway.

A Mutation in the Borcs7 Subunit of the Lysosome Regulatory BORC Complex Results in Motor Deficits and Dystrophic Axonopathy in Mice

Lysosomes play a critical role in maintenance of the integrity of neuronal function, and mutations in genes that contribute to lysosome formation, transport, and activity are associated with neurodegenerative disorders. Recently, the multisubunit complex, BLOC-one-related complex (BORC), has been shown to be involved in positioning lysosomes within the cytoplasm, although the consequences of altered BORC function in adult animals have not been established. We show that a spontaneous truncation mutation in the mouse Borcs7 gene, identified through whole-genome sequencing followed by genetic complementation, results in progressive axonal dystrophy with dramatic impairment of motor function. Furthermore, mice homozygous for deletion of the entire Borcs7 coding sequence die shortly after birth, and neurons cultured from these animals show impaired centrifugal transport of lysosomes. This identifies BORCS7 as a central factor in axonal transport of lysosomes and a possible target for improving disease-related disturbances in this important function.

Development of the Swimbladder Surfactant System and Biogenesis of Lysosome-Related Organelles Is Regulated by BLOS1 in Zebrafish

Hermansky-Pudlak syndrome (HPS) is a human autosomal recessive disorder that is characterized by oculocutaneous albinism and a deficiency of the platelet storage pool resulting from defective biogenesis of lysosome-related organelles (LROs). To date, 10 HPS genes have been identified, three of which belong to the octamer complex BLOC-1 (biogenesis of lysosome-related organelles complex 1). One subunit of the BLOC-1 complex, BLOS1, also participates in the BLOC-1-related complex (BORC). Due to lethality at the early embryo stage in BLOS1 knockout mice, the function of BLOS1 in the above two complexes and whether it has a novel function are unclear. Here, we generated three zebrafish mutant lines with a BLOC-1 deficiency, in which melanin and silver pigment formation was attenuated as a result of mutation of bloc1s1, bloc1s2, and dtnbp1a, suggesting that they function in the same complex. In addition, mutations of bloc1s1 and bloc1s2 caused an accumulation of clusters of lysosomal vesicles at the posterior part of the tectum, representing a BORC-specific function in zebrafish. Moreover, bloc1s1 is highly expressed in the swimbladder during postembryonic stages and is required for positively regulating the expression of the genes, which is known to govern surfactant production and lung development in mammals. Our study identified BLOS1 as a crucial regulator of the surfactant system. Thus, the zebrafish swimbladder might be an easy system to screen and study genetic modifiers that control surfactant production and homeostasis.

Ferritin is secreted via 2 distinct nonclassical vesicular pathways

Ferritin turnover plays a major role in tissue iron homeostasis, and ferritin malfunction is associated with impaired iron homeostasis and neurodegenerative diseases. In most eukaryotes, ferritin is considered an intracellular protein that stores iron in a nontoxic and bioavailable form. In insects, ferritin is a classically secreted protein and plays a major role in systemic iron distribution. Mammalian ferritin lacks the signal peptide for classical endoplasmic reticulum-Golgi secretion but is found in serum and is secreted via a nonclassical lysosomal secretion pathway. This study applied bioinformatics and biochemical tools, alongside a protein trafficking mouse models, to characterize the mechanisms of ferritin secretion. Ferritin trafficking via the classical secretion pathway was ruled out, and a 2:1 distribution of intracellular ferritin between membrane-bound compartments and the cytosol was observed, suggesting a role for ferritin in the vesicular compartments of the cell. Focusing on nonclassical secretion, we analyzed mouse models of impaired endolysosomal trafficking and found that ferritin secretion was decreased by a BLOC-1 mutation but increased by BLOC-2, BLOC-3, and Rab27A mutations of the cellular trafficking machinery, suggesting multiple export routes. A 13-amino-acid motif unique to ferritins that lack the secretion signal peptide was identified on the BC-loop of both subunits and plays a role in the regulation of ferritin secretion. Finally, we provide evidence that secretion of iron-rich ferritin was mediated via the multivesicular body-exosome pathway. These results enhance our understanding of the mechanism of ferritin secretion, which is an important piece in the puzzle of tissue iron homeostasis.

Notch4 inhibition suppresses invasion and vasculogenic mimicry formation of hepatocellular carcinoma cells

Vasculogenic mimicry (VM) is a process by which aggressive tumor cells generate non-endothelial cell-lined channels in malignant tumors including hepatocellular carcinoma (HCC). It has provided new insights into tumor behavior and has surfaced as a potential target for drug therapy. The molecular events underlying the process of VM formation are still poorly understood. In this study, we attempted to elucidate the relationship between Notch4 and VM formation in HCC. An effective siRNA lentiviral vector targeting Notch4 was constructed and transfected into Bel7402, a HCC cell line. VM networks were observed with a microscope in a 3 dimensional cell culture system. Cell migration and invasion were evaluated using wound healing and transwell assays. Matrix metalloproteinases (MMPs) activity was detected by gelatin zymography. Furthermore, the role of Notch4 inhibition in Bel7402 cells in vivo was examined in subcutaneous xenograft tumor model of mice. The results showed that downregulation of Notch4 destroyed VM network formation and inhibited migration and invasion of tumor cells in vitro (P<0.05). In vivo, tumor growth was also inhibited in subcutaneous xenograft model (P<0.05). The potential mechanisms might be related with down-regulation of MT1-MMP, MMP-2, MMP-9 expression and inhibition of the activation of MMP2 and MMP9. These results indicated that Notch4 may play an important role in VM formation and tumor invasion in HCC. Related molecular pathways may be used as novel therapeutic targets for HCC antiangiogenesis therapy.

Notch Signaling in Development, Tissue Homeostasis, and Disease

Notch signaling is an evolutionarily highly conserved signaling mechanism, but in contrast to signaling pathways such as Wnt, Sonic Hedgehog, and BMP/TGF-β, Notch signaling occurs via cell-cell communication, where transmembrane ligands on one cell activate transmembrane receptors on a juxtaposed cell. Originally discovered through mutations in Drosophila more than 100 yr ago, and with the first Notch gene cloned more than 30 yr ago, we are still gaining new insights into the broad effects of Notch signaling in organisms across the metazoan spectrum and its requirement for normal development of most organs in the body. In this review, we provide an overview of the Notch signaling mechanism at the molecular level and discuss how the pathway, which is architecturally quite simple, is able to engage in the control of cell fates in a broad variety of cell types. We discuss the current understanding of how Notch signaling can become derailed, either by direct mutations or by aberrant regulation, and the expanding spectrum of diseases and cancers that is a consequence of Notch dysregulation. Finally, we explore the emerging field of Notch in the control of tissue homeostasis, with examples from skin, liver, lung, intestine, and the vasculature.