Protein tyrosine phosphatases have been recognized as critical components of multiple signaling regulators of fundamental cellular processes, including differentiation, cell death, and migration. In this study, we show that dual specificity phosphatase 4 (DUSP4) is crucial for neuronal differentiation and functions in the neurogenesis of embryonic stem cells (ESCs). The endogenous mRNA and protein expression levels of DUSP4 gradually increased during mouse development from ESCs to postnatal stages. Neurite outgrowth and the expression of neuron-specific markers were markedly reduced by genetic ablation of DUSP4 in differentiated neurons, and these effects were rescued by the reintroduction of DUSP4. In addition, DUSP4 knockdown dramatically enhanced extracellular signal-regulated kinase (ERK) activation during neuronal differentiation. Furthermore, the DUSP4-ERK pathway functioned to balance calcium signaling, not only by regulating Ca(2+)/calmodulin-dependent kinase I phosphorylation, but also by facilitating Cav1.2 expression and plasma membrane localization. These data are the first to suggest a molecular link between the MAPK-ERK cascade and calcium signaling, which provides insight into the mechanism by which DUSP4 modulates neuronal differentiation.

Mitochondria are the major source of intercellular bioenergy in the form of ATP. They are necessary for cell survival and play many essential roles such as maintaining calcium homeostasis, body temperature, regulation of metabolism and apoptosis. Mitochondrial dysfunction has been observed in variety of diseases such as cardiovascular disease, aging, type 2 diabetes, cancer and degenerative brain disease. In other words, the interpretation and regulation of mitochondrial signals has the potential to be applied as a treatment for various diseases caused by mitochondrial disorders. In recent years, mitochondrial transplantation has increasingly been a topic of interest as an innovative strategy for the treatment of mitochondrial diseases by augmentation and replacement of mitochondria. In this review, we focus on diseases that are associated with mitochondrial dysfunction and highlight studies related to the rescue of tissue-specific mitochondrial disorders. We firmly believe that mitochondrial transplantation is an optimistic therapeutic approach in finding a potentially valuable treatment for a variety of mitochondrial diseases.

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Nurr1, a transcription factor belonging to the orphan nuclear receptor, has an essential role in the generation and maintenance of dopaminergic neurons and is important in the pathogenesis of Parkinson' disease (PD). In addition, Nurr1 has a non-neuronal function, and it is especially well known that Nurr1 has an anti-inflammatory function in the Parkinson's disease model. However, the molecular mechanisms of Nurr1 have not been elucidated. In this study, we describe a novel mechanism of Nurr1 function. To provide new insights into the molecular mechanisms of Nurr1 in the inflammatory response, we performed Chromatin immunoprecipitation sequencing (ChIP-Seq) on LPS-induced inflammation in BV2 cells and finally identified the RasGRP1 gene as a novel target of Nurr1. Here, we show that Nurr1 directly binds to the RasGRP1 intron to regulate its expression. Moreover, we also identified that RasGRP1 regulates the Ras-Raf-MEK-ERK signaling cascade in LPSinduced inflammation signaling. Finally, we conclude that RasGRP1 is a novel regulator of Nurr1's mediated inflammation signaling. Nurr1 (NR4A2) belongs to the nuclear receptor (NR)4 family of orphan nuclear receptors 1. NRs are ligand inducible transcription factors that bind to DNA and regulate the expression of target genes 2. Developing mesencephalic dopaminergic cells deficient in Nurr1 are unable to express tyrosine hydroxylase 3,4. Nurr1 deficiency in embryonic ventral midbrain cells causes them not to migrate normally, and they fail to innervate their striatal target areas 5. It has been suggested that the absence of Nurr1 may be a contributing factor in the pathogenesis of PD 6. Recently, two human mutations located in exon 1 of the Nurr1 gene were shown to result in a decreased expression of Nurr1 mRNA and were associated with familial PD 7. Additionally, recent studies have proposed that Nurr1 overexpression or modification of Nurr1 expression in stem cells (and neural stem cells) may have an impact on the future of cell therapy for PD 8-11. It is further supported by a link between altered Nurr1 expression and PD indicating that Nurr1 may have a protection role. Saijo et al. reported that Nurr1 protects dopaminergic neurons from inflammation-induced neurotoxicity through the inhibition of pro-inflammatory mediator expression in microglia and astrocytes 12. Nurr1 functions as a key component of a negative feedback loop in both microglia and astrocytes by recruiting CoREST corepressor complexes to NF-κB target genes 12. They found that a reduction of Nurr1 expression in itself does not affect the death of TH + dopaminergic neurons, but the expression of inflammatory mediators are enhanced, and the survival rate of TH + neurons are decreased in response to inflammatory stimuli in the Nurr1 deficiency condition 12. Moreover, they mentioned that astrocytes can act as amplifying agents of microglia-derived proinflammatory mediators in the production of neurotoxic factors 12-14. Collectively, the expression of LPS-induced pro-inflammatory genes in microglia lead to...

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Astrocytes perform multiple essential functions in the developing and mature brain, including regulation of synapse formation, control of neurotransmitter release and uptake, and maintenance of extracellular ion balance. As a result, astrocytes have been implicated in the progression of neurodegenerative disorders such as Alzheimer’s disease, Huntington’s disease, and Parkinson’s disease. Despite these critical functions, the study of human astrocytes can be difficult because standard differentiation protocols are time-consuming and technically challenging, but a differentiation protocol recently developed in our laboratory enables the efficient derivation of astrocytes from human embryonic stem cells. We used this protocol along with microarrays, luciferase, EMSA and ChIP assays to explore the genes involved in astrocyte differentiation. We demonstrate that paired-like homeodomain transcription factor 1 (PITX1) is critical for astrocyte differentiation. PITX1 overexpression induced early differentiation of astrocytes and its knockdown blocked astrocyte differentiation. PITX1 overexpression also increased and PITX1 knockdown decreased sex-determining region Y box 9 (SOX9), a known initiator of gliogenesis, expression during early astrocyte differentiation. Moreover, we determined that PITX1 activates the SOX9 promoter through a unique binding motif. Taken together, these findings indicate that PITX1 drives astrocyte differentiation by sustaining activation of the SOX9 promoter.

Janus kinase 2 (JAK2), a non-receptor tyrosine kinase, is a critical component of cytokine and growth factor signaling pathways regulating hematopoietic cell proliferation. JAK2 mutations are associated with multiple myeloproliferative neoplasms. Although physiological and pathological functions of JAK2 in hematopoietic tissues are well-known, such functions of JAK2 in the nervous system are not well studied yet. The present study demonstrated that JAK2 could negatively regulate neuronal differentiation of mouse embryonic stem cells (ESCs). Depletion of JAK2 stimulated neuronal differentiation of mouse ESCs and activated glycogen synthase kinase 3ꞵ, Fyn, and cyclin-dependent kinase 5. Knockdown of JAK2 resulted in accumulation of GTPbound Rac1, a Rho GTPase implicated in the regulation of cytoskeletal dynamics. These findings suggest that JAK2 might negatively regulate neuronal differentiation by suppressing the GSK-3β/ Fyn/CDK5 signaling pathway responsible for morphological maturation. [