Dual-specificity histone demethylase KIAA1718 （KDM7A） regulates neural differentiation through FGF4

Dimethylations of histone H3 lysine 9 and lysine 27 are important epigenetic marks associated with transcription repression. Here, we identified KIAA1718 （KDM7A） as a novel histone demethylase specific for these two repressing marks. Using mouse embryonic stem cells, we demonstrated that KIAA1718 expression increased at the early phase of neural differentiation. Knockdown of the gene blocked neural differentiation and the effect was rescued by the wild-type human gene, and not by a catalytically inactive mutant. In addition, overexpression of KIAA1718 accelerated neural differentiation. We provide the evidence that the pro-neural differentiation effect of KDM7A is mediated through direct transcriptional activation of FGF4, a signal molecule implicated in neural differentiation. Thus, our study identified a dual-specificity histone demethylase that regulates neural differentiation through FGF4.

Visualization of bHLH transcription factor interactions in living mammalian cell nuclei and developing chicken neural tube by FRET

Members of the basic helix-loop-helix （bHLH） gene family play important roles in vertebrate neurogenesis. In this study, confocal microscopy-based fluorescence resonance energy transfer （FRET） is used to monitor bHLH protein-protein interactions under various physiological conditions. Tissue-specific bHLH activators, NeuroD 1, Mash 1, Neurogenin 1 （Ngn 1）, Neurogenin2 （Ngn2）, and ubiquitous expressed E47 protein are tagged with enhanced yellow fluorescence protein （EYFP） and enhanced cyan fluorescence protein （ECFP）, respectively. The subcellular localization and mobility ofbHLH fusion proteins are examined in HEK293 cells. By transient transfection and in ovo electroporation, four pairs of tissue-specific bHLH activators and E47 protein are over-expressed in HEK293 cells and developing chick embryo neural tube. With the acceptor photobleaching method, FRET could be detected between these bHLH protein pairs in the nuclei of transfected cells and developing neural tubes. Mashl/E47 and Ngn2/E47 FRET pairs show higher FRET efficiencies in the medial and the lateral half of chick embryo neural tube, respectively. It suggests that these bHLH protein pairs formed functional DNA-protein complexes with regulatory elements of their downstream target genes in the specific regions. This work will help one understand the behaviours of bHLH factors in vivo.

rSac3, a novel Sac domain phosphoinositide phosphatase, promotes neurite outgrowth in PC12 cells

Sac domain-containing proteins belong to a newly identified family of phosphoinositide phosphatases （the PIPPase family）. Despite well-characterized enzymatic activity, the biological functions of this mammalian Sac domain PIPPase family remain largely unknown. We identified a novel Sac domain-containing protein, rat Sac3 （rSac3）, which is widely expressed in various tissues and localized to the endoplasmic reticulum, Golgi complex and recycling endosomes, rSac3 displays PIPPase activity with PI（3）P, PI（4）P and PI（3,5）P2 as substrates in vitro, and a mutation in the catalytic core of the Sac domain abolishes its enzymatic activity. The expression of rSac3 is upregulated during nerve growth factor （NGF）-stimulated PC 12 cell neuronal differentiation, and overexpression of this protein promotes neurite outgrowth in PC 12 cells. Conversely, inhibition ofrSac3 expression by antisense oligonucleotides reduces neurite outgrowth of NGF- stimulated PC 12 cells, and the active site mutation of rSac3 eliminates its neurite-outgrowth-promoting activity. These results indicate that rSac3 promotes neurite outgrowth in differentiating neurons through its PIPPase activity, suggesting that Sac domain PIPPase proteins may participate in forward membrane trafficking from the endoplasmic reticulum and Golgi complex to the plasma membrane, and may function as regulators of this crucial process of neuronal cell growth and differentiation.

The molecular and cellular choreography of early mammalian lung development

Mammalian lung development starts from a specific cluster of endodermal cells situated within the ventral foregut region.With the orchestrating of delicate choreography of transcription factors,signaling pathways,and cell–cell communications,the endodermal diverticulum extends into the surrounding mesenchyme,and builds the cellular and structural basis of the complex respiratory system.This review provides a comprehensive overview of the current molecular insights of mammalian lung development,with a particular focus on the early stage of lung cell fate differentiation and spatial patterning.Furthermore,we explore the implications of several congenital respiratory diseases and the relevance to early organogenesis.Finally,we summarize the unprecedented knowledge concerning lung cell compositions,regulatory networks as well as the promising prospect for gaining an unbiased understanding of lung development and lung malformations through stateof-the-art single-cell omics.

Comments on ‘Molecular architecture of lineage allocation and tissue organization in early mouse embryo’

Single-cell RNA-seq,with its capability to align cells of continuously changed status by pseudo-time reconstruction,has greatly revolutionized the understanding of cell fate transition during embryo development(Shapiroetal.,2013;Hoppeetal.,2014).

Mouse knockout models reveal largely dispensable but context-dependent functions of IncRNAs during development

Dear Editor, In mammalian genomes, pervasive transcription produces thousands of long non-coding RNA （IncRNA） transcripts （Olebali et al., 2012; Hon et al., 2017）. Compared to protein-coding mRNAs, IncRNAs are less conserved, and often exhibit low-level, developmental stage-and tissue-specific expression （Pauli et al., 2011; Hu et al., 2012; Lee, 2012; Ulitsky and Bartel, 2013; Cech and Steitz, 2014; Hon et al., 2017）. Many IncRNAs are strongly correlated with their neighboring mRNA genes in terms of expression and function, and tend to regulate nearby transcription （Orom et al., 2010; Engreitz et al., 2016; Luo etal., 2016）. It has been implicated that IncRNAs play versatile roles in regulating diverse aspects of cell biology through mechanisms at multiple levels （Pauli et al., 2011; Lee.

BMP signaling pathway and spinal cord development

The development of spinal cord is a precisely and sequentially regulated process, which is controlled bysignaling pathways and transcription factors in each stage. Overwhelming data have shown the essential roles of BMP signaling in different stages of this developmental process. It is also clear that the proper functions of BMP signaling require its cross-talk with several other signaling pathways including Notch, Wnt and retinoic acid （RA） pathways. Here, we highlight the recent advancement in understanding the roles of BMP signaling during neurogenesis, neural tube patterning, axon development and glial differentiation in the spinal cord, and emphasize its integrations with other pathways during these processes.

TGFβ signaling hyperactivation-induced tumorigenicity during the derivation of neural progenitors from mouse ESCs

Clinical therapies of pluripotent stem cells （PSCs）-based transplantation have been hindered by frequent development of terato- mas or tumors in animal models and clinical patients. Therefore, clarifying the mechanism of carcinogenesis in stem cell therapy is of great importance for reducing the risk of tumorigenicity. Here we differentiate Oct4-GFP mouse embryonic stem cells （mESCs） into neural progenitor cells （NPCs） and find that a minority of Oct4＋ cells are continuously sustained at Oct4＋ state. These cells can be enriched and proliferated in a standard ESC medium. Interestingly, the differentiation potential of these enriched cells is tightly restricted with much higher tumorigenic activity, which are thus defined as differentiation-resistant ESCs （DR-ESCs）. Transcriptomic and epigenomic analyses show that DR-ESCs are characterized by primordial germ cell-like gene sig- natures （Dazl, Rec8, Stro8, BUmp1, etc.） and specific epigenetic patterns distinct from mESCs. Moreover, the DR-ESCs possess germ cell potential to generate Sycp3＋ haploid cells and are able to reside in sperm-free spermaduct induced by busulfan. Finally, we find that TGFβ signaling is overactivated in DR-ESCs, and inhibition of TGFβ signaling eliminates the tumorigenicity of mESC-derived NPCs by inducing the full differentiation of DR-ESCs. These data demonstrate that these TGFβ-hyperactivated germ ceU-like DR-ESCs are the main contributor for the tumorigenicity of ESCs-derived target cell therapy and that inhibition of TGFβ signaling in ESC-derived NPC transplantation could drastically reduce the risk of tumor development. Keywords： embryonic stem cells, differentiation-resistant ESCs, tumorigenicity, germ cell, TGFβ signaling

The promise of stem cells in the therapy of Alzheimer’s disease

Alzheimer’s disease(AD),a common neurodegenerative disorder associated with gradually to dramatic neuronal death,synaptic loss and dementia,is considered to be one of the most obscure and intractable brain disorders in medicine.Currently,there is no therapy clinically available to induce marked symptomatic relief in AD patients.In recent years,the proof-of-concept studies using stem cell-based approaches in transgenic AD animal models provide new hope to develop stem cell-based therapies for the effective treatment of AD.The degeneration of basal forebrain cholinergic neurons(BFCNs)and the resultant cholinergic abnormalities in the brain contribute substantially to the cognitive decline of AD patients.The approches using stem cell-derived BFCNs as donor cells need to be developed,and to provide proof of principle that this subtype-specific neurons can induce functional recovery of AD animal models.With the continuous scientific advances in both academic and industrial fields,the potentials of stem cells in cellular neuroprotection and cell replacement in vivo have been elucidated,and stem cell-based therapy for repairing degenerative brains of AD is promising.

The therapeutic prospects and challenges of human neural stem cells for the treatment of Alzheimer’s Disease

Alzheimer’s disease(AD)is a multifactorial neurodegenerative disorder associated with aging.Due to its insidious onset,protracted progression,and unclear pathogenesis,it is considered one of the most obscure and intractable brain disorders,and currently,there are no effective therapies for it.Convincing evidence indicates that the irreversible decline of cognitive abilities in patients coincides with the deterioration and degeneration of neurons and synapses in the AD brain.Human neural stem cells(NSCs)hold the potential to functionally replace lost neurons,reinforce impaired synaptic networks,and repair the damaged AD brain.They have therefore received extensive attention as a possible source of donor cells for cellular replacement therapies for AD.Here,we review the progress in NSC-based transplantation studies in animal models of AD and assess the therapeutic advantages and challenges of human NSCs as donor cells.We then formulate a promising transplantation approach for the treatment of human AD,which would help to explore the disease-modifying cellular therapeutic strategy for the treatment of human AD.

The genome-wide molecular regulation of mouse gastrulation embryo

The diverse morphologies among vertebrate species stems from the evolution of a basic body plan that is constituted by a spatially organized ensemble of tissue lineage progenitors. At gastrulation, this body plan is established through a coordinated morphogenetic process and the delineation of tissue lineages that are driven by the activity of the genome. To explore the molecular mechanisms, in a comprehensive context, it is imperative to glean an understanding of the region-and population-specific genetic activity underpinning this fundamental developmental process. In this review, we outline the recent progress and the future directions in studies of genome activity for the regulation of mouse embryogenesis at gastrulation.

Derivation of Haploid Neurons from Mouse Androgenetic Haploid Embryonic Stem Cells

Dear Editor,Haploid embryonic stem cells（ha ESCs）hold great potential for genetic screening and the analysis of recessive phenotypes.Several studies have recently reported the generation of mammalian ha ESCs through gamete manipulation,and evaluated the benefits of using them for studying functional genomics in different mammals[1–4].

Integration of Computational Analysis and Spatial Transcriptomics in Single-cell Studies

Recent advances of single-cell transcriptomics technologies and allied computational methodologies have revolutionized molecular cell biology.Meanwhile,pioneering explorations in spatial transcriptomics have opened up avenues to address fundamental biological questions in health and diseases.Here,we review the technical attributes of single-cell RNA sequencing and spatial transcriptomics,and the core concepts of computational data analysis.We further highlight the challenges in the application of data integration methodologies and the interpretation of the biological context of the findings.

Ectodermal progenitors derived from epiblast stem cells by inhibition of Nodal signaling

The ectoderm has the capability to generate epidermis and neuroectoderm and plays imperative roles during the early embryonic development.Our recent study uncovered a region with ectodermal progenitor potential in mouse embryo at embryonic day 7.0 and revealed that Nodal inhibition is essential for its formation.Here,we demonstrate that through brief inhibition of Nodal signaling in vitro,mouse embryonic stem cell(ESC)-derived epiblast stem cells(ESD-EpiSCs)could be committed to transient ectodermal progenitor populations,which possess the ability to give rise to neural or epidermal ectoderm in the absence or presence of BMP4,respectively.Mechanistic studies reveal that BMP4 recruits distinct transcriptional targets in ESD-EpiSCs and ectoderm-like cells.Furthermore,FGF–Erk signaling may also be alleviated during the generation of ectoderm-like cells.Thus,our data suggest that instructive interactions among several extracellular signals participate in the commitment of ectoderm from ESD-EpiSCs,which shed new light on the understanding of the formation of ectoderm during the gastrulation in early mouse embryo development.

Generation of functional posterior spinal motor neurons from hPSCs-derived human spinal cord neural progenitor cells

Spinal motor neurons deficiency results in a series of devastating disorders such as amyotrophic lateral sclerosis(ALS),spinal muscular atrophy(SMA)and spinal cord injury(SCI).These disorders are currently incurable,while human pluripotent stem cells(hPSCs)-derived spinal motor neurons are promising but suffered from inappropriate regional identity and functional immaturity for the study and treatment of posterior spinal cord related injuries.In this study,we have established human spinal cord neural progenitor cells(hSCNPCs)via hPSCs differentiated neuromesodermal progenitors(NMPs)and demonstrated the hSCNPCs can be continuously expanded up to 40 passages.hSCNPCs can be rapidly differentiated into posterior spinal motor neurons with high efficiency.The functional maturity has been examined in detail.Moreover,a co-culture scheme which is compatible for both neural and muscular differentiation is developed to mimic the neuromuscular junction(NMJ)formation in vitro.Together,these studies highlight the potential avenues for generating clinically relevant spinal motor neurons and modeling neuromuscular diseases through our defined hSCNPCs.