pCREB is involved in neural induction of mouse embryonic stem cells by RA

JNK signaling and its impact on neural cell maturation and differentiation

C-Jun-N-terminal-kinases (JNKs), members of the mitogen-activated-protein-kinase family, are significantly linked with neurological and neurodegenerative pathologies and cancer progression. However, JNKs serve key roles under physiological conditions, particularly within the central-nervous-system (CNS), where they are critical in governing neural proliferation and differentiation during both embryogenesis and adult stages. These processes control the development of CNS, avoiding neurodevelopment disorders. JNK are key to maintain the proper activity of neural-stem-cells (NSC) and neural-progenitors (NPC) that exist in adults, which keep the convenient brain plasticity and homeostasis. This review underscores how the interaction of JNK with upstream and downstream molecules acts as a regulatory mechanism to manage the self-renewal capacity and differentiation of NSC/NPC during CNS development and in adult neurogenic niches. Evidence suggests that JNK is reliant on non-canonical Wnt components, Fbw7-ubiquitin-ligase, and WDR62-scaffold-protein, regulating substrates such as transcription factors and cytoskeletal proteins. Therefore, understanding which pathways and molecules interact with JNK will bring knowledge on how JNK activation orchestrates neuronal processes that occur in CNS development and brain disorders.

The Role of Retinoic Acid in Spermatogenesis and Its Application in Male Reproduction

Spermatogenesis in mammalian testes is essential for male fertility, ensuring a continuous supply of mature sperm. The testicular microenvironment finely tunes this process, with retinoic acid, an active metabolite of vitamin A, serving a pivotal role. Retinoic acid is critical for various stages, including the differentiation of spermatogonia, meiosis in spermatogenic cells, and the production of mature spermatozoa. Vitamin A deficiency halts spermatogenesis, leading to the degeneration of numerous germ cells, a condition reversible with retinoic acid supplementation. Although retinoic acid can restore fertility in some males with reproductive disorders, it does not work universally. Furthermore, high doses may adversely affect reproduction. The inconsistent outcomes of retinoid treatments in addressing infertility are linked to the incomplete understanding of the molecular mechanisms through which retinoid signaling governs spermatogenesis. In addition to the treatment of male reproductive disorders, the role of retinoic acid in spermatogenesis also provides new ideas for the development of male non-hormone contraceptives. This paper will explore three facets: the synthesis and breakdown of retinoic acid in the testes, its role in spermatogenesis, and its application in male reproduction. Our discussion aims to provide a comprehensive reference for studying the regulatory effects of retinoic acid signaling on spermatogenesis and offer insights into its use in treating male reproductive issues.

The Role of Various Factors in Neural Differentiation of Human Umbilical Cord Mesenchymal Stem Cells with a Special Focus on the Physical Stimulants

Human umbilical cord matrix-derived mesenchymal stem cells (hUCMs) are considered as ideal tools for cell therapy procedures and regenerative medicine. The capacity of these cells to differentiate into neural lineage cells make them potentially important in the treatment of various neurodegenerative diseases. An electronic search was performed in Web of Science, PubMed/MEDLINE, Scopus and Google Scholar databases for articles published from January 1990 to March 2022. This review discusses the current knowledge on the effect of various factors, including physical, chemical and biological stimuli which play a key role in the differentiation of hUCMs into neural and glial cells. Moreover, the currently understood molecular mechanisms involved in the neural differentiation of hUCMs under various environmental stimuli are reviewed. Various stimuli, especially physical stimuli and specifically different light sources, have revealed effects on neural differentiation of mesenchymal stem cells, including hUCMs; however, due to the lack of information about the exact mechanisms, there is still a need to find optimal conditions to promote the differentiation capacity of these cells which in turn can lead to significant progress in the clinical application of hUCMs for the treatment of neurological disorders.

Direct Neuronal Reprogramming: Bridging the Gap Between Basic Science and Clinical Application

Direct neuronal reprogramming is an innovative new technology that involves the conversion of somatic cells to induced neurons (iNs) without passing through a pluripotent state. The capacity to make new neurons in the brain, which previously was not achievable, has created great excitement in the field as it has opened the door for the potential treatment of incurable neurodegenerative diseases and brain injuries such as stroke. These neurological disorders are associated with frank neuronal loss, and as new neurons are not made in most of the adult brain, treatment options are limited. Developmental biologists have paved the way for the field of direct neuronal reprogramming by identifying both intrinsic cues, primarily transcription factors (TFs) and miRNAs, and extrinsic cues, including growth factors and other signaling molecules, that induce neurogenesis and specify neuronal subtype identities in the embryonic brain. The striking observation that postmitotic, terminally differentiated somatic cells can be converted to iNs by mis-expression of TFs or miRNAs involved in neural lineage development, and/or by exposure to growth factors or small molecule cocktails that recapitulate the signaling environment of the developing brain, has opened the door to the rapid expansion of new neuronal reprogramming methodologies. Furthermore, the more recent applications of neuronal lineage conversion strategies that target resident glial cells in situ has expanded the clinical potential of direct neuronal reprogramming techniques. Herein, we present an overview of the history, accomplishments, and therapeutic potential of direct neuronal reprogramming as revealed over the last two decades.

High throughput screening identifies SOX2 as a super pioneer factor that inhibits DNA methylation maintenance at its binding sites

Binding of mammalian transcription factors (TFs) to regulatory regions is hindered by chromatin compaction and DNA methylation of their binding sites. Nevertheless, pioneer transcription factors (PFs), a distinct class of TFs, have the ability to access nucleosomal DNA, leading to nucleosome remodelling and enhanced chromatin accessibility. Whether PFs can bind to methylated sites and induce DNA demethylation is largely unknown. Using a highly parallelized approach to investigate PF ability to bind methylated DNA and induce DNA demethylation, we show that the interdependence between DNA methylation and TF binding is more complex than previously thought, even within a select group of TFs displaying pioneering activity; while some PFs do not affect the methylation status of their binding sites, we identified PFs that can protect DNA from methylation and others that can induce DNA demethylation at methylated binding sites. We call the latter super pioneer transcription factors (SPFs), as they are seemingly able to overcome several types of repressive epigenetic marks. Finally, while most SPFs induce TET-dependent active DNA demethylation, SOX2 binding leads to passive demethylation, an activity enhanced by the co-binding of OCT4. This finding suggests that SPFs could interfere with epigenetic memory during DNA replication.

In-vitro differentiation of early pig spermatogenic cells to haploid germ cells

Spermatogonial stem cells (SSCs) self-renew and contribute genetic information to the next generation. Pig is wildly used as a model animal for understanding reproduction mechanisms of human being. Inducing directional differentiation of porcine SSCs may be an important strategy in exploring the mechanisms of spermatogenesis and developing better treatment methods for male infertility. Here, we established an in-vitro culture model for porcine small seminiferous tubule segments, to induce SSCs to differentiate into single-tail haploid spermatozoa. The culture model subsequently enabled spermatozoa to express the sperm-specific protein acrosin and oocytes to develop to blastocyst stage after round spermatid injection. The addition of retinoic acid (RA) to the differentiation media promoted the efficiency of haploid differentiation. RT-PCR analysis indicated that RA stimulated the expression of Stra8 but reduced the expression of NANOS2 in spermatogonia. Genes involved in post-meiotic development, transition protein 1 (Tnp1) and protamine 1 (Prm1) were upregulated in the presence of RA. The addition of an RA receptor (RAR) inhibitor, BMS439, showed that RA enhanced the expression of cAMP responsive-element binding protein through RAR and promoted the formation of round spermatids. We established an efficient culture system for in-vitro differentiation of pig SSCs. Our study represents a model for human testis disease and toxicology screening. Molecular regulators of SSC differentiation revealed in this study might provide a therapeutic strategy for male infertility.

Induction of Tyrosine Hydroxylase Gene Expression in Embryonal Carcinoma Stem Cells Using a Natural Tissue-Specific Inducer

A large number of studies have focused on the generation of dopaminergic neurons from pluripotent cells. Differentiation of stem cells into distinct cell types is influenced by tissue-specific microenvironment. Since, central nervous system undergoes further development during postnatal life, in the present study neonatal rat brain tissue extract (NRBE) was applied to direct the differentiation of embryonal carcinoma stem cell line, P19 into dopaminergic (DA) phenotypes. Additionally, a neuroprotective drug, deprenyl was used alone or in combination with the extract. Results from morphological, immunofluorescence, and qPCR analyses showed that during a period of one to three weeks, a large percentage of stem cells were differentiated into neural cells. The results also indicated the greater effect of NRBE on the differentiation of the cells into tyrosine hydroxylase-expressing cells. MS analysis of NRBE showed the enrichment of gene ontology terms related to cell differentiation and neurogenesis. Network analysis of the studied genes and some DA markers resulted in the suggestion of potential regulatory candidates such as AVP, ACHE, LHFPL5, and DLK1 genes. In conclusion, NRBE as a natural native inducer was apparently able to simulate the brain microenvironment and support neural differentiation of P19 cells.

Neural stem cell differentiation into mature neurons: Mechanisms of regulation and biotechnological applications

The abilities of stem cells to self-renew and form different mature cells expand the possibilities of applications in cell-based therapies such as tissue recomposition in regenerative medicine, drug screening, and treatment of neurodegenerative diseases. In addition to stem cells found in the embryo, various adult organs and tissues have niches of stem cells in an undifferentiated state. In the central nervous system of adult mammals, neurogenesis occurs in two regions: the subventricular zone and the dentate gyrus in the hippocampus. The generation of the different neural lines originates in adult neural stem cells that can self-renew or differentiate into astrocytes, oligodendrocytes, or neurons in response to specific stimuli. The regulation of the fate of neural stem cells is a finely controlled process relying on a complex regulatory network that extends from the epigenetic to the translational level and involves extracellular matrix components. Thus, a better understanding of the mechanisms underlying how the process of neurogenesis is induced, regulated, and maintained will provide elues for development of novel for strategies for neurodegenerative therapies. In this review, we focus on describing the mechanisms underlying the regulation of the neuronal differentiation process by transcription factors, microRNAs, and extracellular matrix components.

Effects of muscarinic acetylcholine receptor stimulation on the differentiation of mouse induced pluripotent stem cells into neural progenitor cells

Muscarinic acetylcholine receptors (mAchRs), which are expressed in various embryonic cells, may regulate neuronal differentiation. In the present study, we examined the effects of mAchR stimulation on the differentiation of mouse induced pluripotent stem (iPS) cells into neural progenitor cells (NPCs). Mouse iPS cells were cultured on ultra-low attachment dishes to induce embryoid body (EB) formation. All-trans retinoic acid (ATRA, 3 μmol/L) and/or pilocarpine (10 or 100 μmol/L), a mAchR agonist, were added to EB cultures for 4 days, following which the EBs were cultured on gelatin-coated plates for 7 days. Subtype-specific antibody staining revealed that mouse iPS cells predominantly express m₂ - and m₄ -AchR. Treatment with pilocarpine alone did not affect the expression of Nestin (a specific marker for neural progenitor cells). However, additional treatment with pilocarpine significantly suppressed ATRA-induced Nestin expression. Pretreating EBs with either AF-DX116 (an antagonist of both m₂ - and m₄ -AchR) or forskolin (an activator of adenylate cyclase) significantly reversed the pilocarpine-induced suppression of Nestin expression. In addition, treatment with pilocarpine significantly suppressed ATRA-induced phosphorylation of cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB). These findings suggest that the stimulation of m₂ - or m₄ -AchR suppresses ATRA-induced differentiation of mouse iPS cells into NPCs by inhibiting the cAMP/protein kinase A pathway and CREB activation.

Effects of light emitting diode irradiation on neural differentiation of human umbilical cord-derived mesenchymal cells

Recently, light emitting diodes (LEDs) have been introduced as a potential physical factor for proliferation and differentiation of various stem cells. Among the mesenchymal stem cells human umbilical cord matrix-derived mesenchymal (hUCM) cells are easily propagated in the laboratory and their low immunogenicity make them more appropriate for regenerative medicine procedures. We aimed at this study to evaluate the effect of red and green light emitted from LED on the neural lineage differentiation of hUCM cells in the presence or absence of retinoic acid (RA). Harvested hUCM cells exhibited mesenchymal and stemness properties. Irradiation of these cells by green and red LED with or without RA pre-treatment successfully differentiated them into neural lineage when the morphology of the induced cells, gene expression pattern (nestin, β-tubulin III and Olig2) and protein synthesis (anti-nestin, anti-β-tubulin III, anti-GFAP and anti-O4 antibodies) was evaluated. These data point for the first time to the fact that LED irradiation and optogenetic technology may be applied for neural differentiation and neuronal repair in regenerative medicine.

Transient CREB-mediated transcription is key in direct neuronal reprogramming

Combinations of neuronal determinants and/or small-molecules such as Forskolin (Fk) can be used to convert different cell types into neurons. As Fk is known to activate cAMP-dependent pathways including CREB-activity, we aimed here to determine the role of CREB in reprogramming – including its temporal profile. We show that transient expression of the dominant-positive CREB-VP16 followed by its inactivation mediated by the dominant-negative ICER improves neuronal conversion of astrocytes mediated by the neurogenic determinant Ascl1. Contrarily, persistent over-activation by CREB-VP16 or persistent inhibition by ICER interferes with neuronal reprogramming, with the latter enhancing cell death. Taken together our work shows transient CREB activation as a key effector in neuronal reprogramming.

ERK1/2 is a key regulator of Fndc5 and PGC1α expression during neural differentiation of mESCs

Fibronectin type III domain containing 5 (Fndc5) has already been distinguished to be involved in neural differentiation. However, cellular events of Fndc5 function are still ambiguous in the nervous system. One approach to shed light on duty of this protein in the nervous system is to find its cross-talks with various signaling pathways with defined characteristics and roles. Identification of the underlying molecular mechanism which controls Fndc5 expression and switches its activity up and down enables us to find out the Fndc5 functional map in the nervous system and other human body systems. Retinoic acid (RA) is a bio-small molecule which exerts its role as a neural inducer in the neurodevelopmental process of neural tube. RA up-regulates the expression of various genes involved in neural differentiation process via two distinct pathways: the genomic and the non-genomic. Our previous study has revealed that RA induces Fndc5 expression during neural differentiation process. In this study we have evaluated our hypothesis about the non-genomic up regulation of Fndc5 expression by RA. Interestingly we have identified that there is an association between ERK signaling pathway and Fndc5 expression. Furthermore, inhibition of this pathway by PD0325901 dramatically reduced Fndc5 mRNA level, while activating the pathway up-regulated Fndc5 transcription. In addition, it has been proven that ERK1/2 modulation via RA has more significant controlling effect on Fndc5 promoter rather than bFGF. This led us to conclude that RA enhances Fndc5 expression through a non-genomic pathway via the ERK signaling pathway.

Neural differentiation from embryonic stem cells in vitro: An overview of the signaling pathways

Neurons derived from embryonic stem cells (ESCs) have gained great merit in both basic research and regenerative medicine. Here we review and summarize the signaling pathways that have been reported to be involved in the neuronal differentiation of ESCs, particularly those associated with in vitro differentiation. The inducers and pathways explored include retinoic acid, Wnt/β-catenin, transforming growth factor/bone morphogenetic protein, Notch, fibroblast growth factor, cytokine, Hedgehog, c-Jun N-terminal kinase/mitogen-activated protein kinase and others. Some other miscellaneous molecular factors that have been reported in the literature are also summarized and discussed. These include calcium, calcium receptor, calcineurin, estrogen receptor, Hox protein, ceramide, glycosaminioglycan, ginsenoside Rg1, opioids, two pore channel 2, nitric oxide, chemically defined medium, cell-cell interactions, and physical stimuli. The interaction or crosstalk between these signaling pathways and factors will be explored. Elucidating these signals in detail should make a significant contribution to future progress in stem cell biology and allow, for example, better comparisons to be made between differentiation in vivo and in vitro. Of equal importance, a comprehensive understanding of the pathways that are involved in the development of neurons from ESCs in vitro will also accelerate their application as part of translational medicine.

Phospholipase D1 increases Bcl-2 expression during neuronal differentiation of rat neural stem cells

We studied the possible role of phospholipase D1 (PLD1) in the neuronal differentiation, including neurite formation of neural stem cells. PLD1 protein and PLD activity increased during neuronal differentiation. Bcl-2 also increased. Downregulation of PLD1 by transfection with PLD1 siRNA or a dominant-negative form of PLD1 (DN-PLD1) inhibited both neurite outgrowth and Bcl-2 expression. PLD activity was dramatically reduced by a PLCγ (phospholipase Cγ) inhibitor (U73122), a Ca(2+)chelator (BAPTA-AM), and a PKCα (protein kinase Cα) inhibitor (RO320432). Furthermore, treatment with arachidonic acid (AA) which is generated by the action of PLA2 (phospholipase A2) on phosphatidic acid (a PLD1 product), increased the phosphorylation of p38 MAPK and CREB, as well as Bcl-2 expression, indicating that PLA2 is involved in the differentiation process resulting from PLD1 activation. PGE2 (prostaglandin E2), a cyclooxygenase product of AA, also increased during neuronal differentiation. Moreover, treatment with PGE2 increased the phosphorylation of p38 MAPK and CREB, as well as Bcl-2 expression, and this effect was inhibited by a PKA inhibitor (Rp-cAMP). As expected, inhibition of p38 MAPK resulted in loss of CREB activity, and when CREB activity was blocked with CREB siRNA, Bcl-2 production also decreased. We also showed that the EP4 receptor was required for the PKA/p38MAPK/CREB/Bcl-2 pathway. Taken together, these observations indicate that PLD1 is activated by PLCγ/PKCα signaling and stimulate Bcl-2 expression through PLA2/Cox2/EP4/PKA/p38MAPK/CREB during neuronal differentiation of rat neural stem cells.

Generation of neural progenitors from induced Bama miniature pig pluripotent cells

Pig pluripotent cells may represent an advantageous experimental tool for developing therapeutic application in the human biomedical field. However, it has previously been proven to be difficult to establish from the early embryo and its pluripotency has not been distinctly documented. In recent years, induced pluripotent stem (iPS) cell technology provides a new method of reprogramming somatic cells to pluripotent state. The generation of iPS cells together with or without certain small molecules has become a routine technique. However, the generation of iPS cells from pig embryonic tissues using viral infections together with small molecules has not been reported. Here, we reported the generation of induced pig pluripotent cells (iPPCs) using the iPS technology in combination with valproic acid (VPA). VPA treatment significantly increased the expression of pluripotent genes and played an important role in early reprogramming. We showed that iPPCs resembled pig epiblast cells in their morphology and pluripotent markers, such as OCT4, NANOG, and SSEA1. It had a normal karyotype and could form embryoid bodies, which express three germ layer markersin vitro. In addition, the iPPCs might directly differentiate into neural progenitors after being induced with the retinoic acid and extracellular matrix. Our study established a reasonable method to generate pig pluripotent cells, which might be a new donor cell source for human neural disease therapy.

β1-adrenoceptor stimulation enhances the differentiation of mouse induced pluripotent stem cells into neural progenitor cells

The cyclic AMP/protein kinase A signaling pathway is thought to be involved in neural differentiation of mesenchymal stem cells. In the present study, we examined the involvement of β-adrenoceptor signaling on the differentiation of mouse induced pluripotent stem (iPS) cells into neural progenitor cells. Mouse iPS cells were cultured on ultra-low-attachment dishes to induce embryoid body (EB) formation. All-trans retinoic acid (ATRA, 1 μM) and/or the β-adrenoceptor agonist l-isoproterenol (0.3 or 1 μM) were added to the EB cultures for 4 days, then EBs were plated on gelatin-coated plates and cultured for 7 or 14 days. Subtype-specific antibody staining revealed that mouse iPS cells express β(1)-adrenoceptors predominantly. Although treatment with l-isoproterenol alone did not affect the expression of Nestin (a specific marker for neural progenitor cells), l-isoproterenol significantly enhanced ATRA-induced Nestin expression. Pretreatment of EBs with either atenolol (a selective β(1)-adrenoceptor antagonist) or H89 (a protein kinase A inhibitor) significantly inhibited the l-isoproterenol-enhancement of ATRA-induced Nestin expression. In addition, the l-isoproterenol treatment significantly enhanced ATRA-induced expression of NeuN (a neuron-specific nuclear protein). These findings suggest that β(1)-adrenoceptor stimulation enhances ATRA-induced neural differentiation of mouse iPS cells.

Fascin-1 promoter activity is regulated by CREB and the aryl hydrocarbon receptor in human carcinoma cells

Background

Fascin is an actin-bundling protein that is absent from most normal epithelia yet is upregulated in multiple forms of human carcinoma, where its expression correlates clinically with a poor prognosis. How fascin-1 transcription is activated in carcinoma cells is largely unknown, although the hypothesis of regulation by β-catenin signaling has received attention. The question is important because of the clinical significance of fascin expression in human carcinomas.

Methodology/Principal Findings

Through comparative genomics we made an unbiased analysis of the DNA sequence of the fascin-1 promoter region from six mammalian species. We identified two regions in which highly conserved motifs are concentrated. Luciferase promoter reporter assays for the human fascin-1 promoter were carried out in fascin-positive and -negative human breast and colon carcinoma cells, and in human dermal fibroblasts that are constitutively fascin-positive. In all fascin-positive cells, the region −219/+114 that contains multiple highly conserved motifs had strong transcriptional activity. The region −2953/−1582 appeared to contain repressor activity. By examining the effects of single or multiple point mutations of conserved motifs within the −219/+114 region on transcriptional reporter activity, we identified for the first time that the conserved CREB and AhR binding motifs are major determinants of transcriptional activity in human colon carcinoma cells. Chromatin immunoprecipitations for CREB, AhR or β-catenin from extracts from fascin-positive or -negative human colon carcinoma cells identified that CREB and AhR specifically associate with the −219/+114 region of the FSCN1 promoter in fascin-positive colon carcinoma cells. An association of β-catenin was not specific to fascin-positive cells.

Conclusion

Upregulation of fascin-1 in aggressive human carcinomas appears to have a multi-factorial basis. The data identify novel roles for CREB and AhR as major, specific regulators of FSCN-1 transcription in human carcinoma cells but do not support the hypothesis that β-catenin signaling has a central role.