The present results demonstrate that GABP is important

The present results demonstrate that GABP is important for myeloid differentiation confirming the recently reported observations by us and others in hematopoietic cell lines and murine models, respectively (Yang et al., 2011; Yu et al., 2011; Ripperger et al., 2015). Here, for the first time, human primary hematopoietic LDC000067 cost were used to address GABP\'s crucial impact on myeloid differentiation and maintenance of hematopoietic stem/progenitor cells. A putative leukemogenic role of GABP was already postulated based upon a murine model, in which GABP was indicated to contribute to the establishment of leukemic stem/progenitor cell clones after transplantation of BCR-ABL1+ leukemic stem cells (Yu et al., 2012; Yang et al., 2013). In line with this, we demonstrated that a properly functioning heteromeric GABP complex is also necessary for human CML HSPCs to give rise to myeloid colonies. Colonies of either healthy or leukemic stem cell origin are usually formed during multiple cell division cycles prior to maturation into respective hematopoietic lineages (Marley and Gordon, 2005). Hence, the colony formation assay used here is a helpful indicator for self-renewal potential and the myeloid differentiation competence of HSPCs. GABP dysfunction resulted in diminished clonogenic capacity of healthy and CML CD34+ HSPCs. This could not be overcome by the intrinsic leukemogenic potency of BCR-ABL1+ cells, thus confirming the importance of GABP as a regulator of crucial effectors in human CML. Several signaling pathways are defined to co-operate with the BCR-ABL1 fusion protein to establish a transforming and anti-apoptotic phenotype (Steelman et al., 2004). However, whether GABP acts downstream of BCR-ABL1 and/or influences BCR-ABL1 co-operating signaling pathways still needs to be addressed. In our former study, we showed expression correlation of protein kinase D2 (PRKD2) to GABP expression levels in the K-562 cell line and CML patients at diagnosis (Manukjan et al., 2015). This was in line with mouse studies showing GABP\'s impact on PRKD2 in the context of murine CML-like disease (Yang et al., 2013). However, by applying qPCR on cells two days after transduction as well as after 14days in methylcellulose, no expression alteration could be detected after overexpression of GABPB1.ΔTAD (data not shown). Possibly, PRKD2-regulation by GABP plays rather a role in the native situation or during progression to blast crisis. However, possible effects on PRKD2 expression in primary human cells should be investigated in more detail to address the question of a druggable target in CML, since PRKD2 is susceptible to kinase inhibitors (Yang et al., 2013).
Acknowledgment
Introduction Over the past few years, significant progress has been made to derive expandable neural progenitor cell (NPC) populations for biomedical research and regenerative medicine. One important cell source comprises pluripotent stem cells such as embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs), which can be efficiently differentiated into expandable NPCs and subsequently into mature neurons and glial cells using established differentiation protocols. In fact, several groups have demonstrated successful application of ESC- or iPSC–NPC-derived neural cells in disease modeling assays or for cell replacement in animal models of neurological disorders (Ehrlich et al., 2015; Hargus et al., 2010; Hargus et al., 2014b; Kriks et al., 2011; Reinhardt et al., 2013; Ross and Akimov, 2014). Further refinements of reprogramming technologies allowed for the derivation of NPCs by direct conversion of fibroblasts into induced neural stem cells (iNSCs) using different combinations of classical reprogramming and neural transcription factors (Cassady et al., 2014; Han et al., 2012; Kim et al., 2011; Kim et al., 2014; Lujan et al., 2012; Ring et al., 2012; Sheng et al., 2012; Thier et al., 2012). These iNSCs carry self-renewing capabilities and were found to resemble neural stem cells (NSCs) from the developing brain. Like NSCs, iNSCs readily differentiate into neuronal and glial derivatives in vitro when appropriate differentiation cues are provided. Similar to the process of iPSC derivation, iNSC generation is a gradual process, which involves silencing of transgenes and of donor cell-type specific transcriptional programs as well as step-wise establishment of stem cell identities during initial propagation of cells (Han et al., 2012). iNSC direct reprogramming technology reduces the potential risk of tumor formation, which may occur when using ESC- or iPSC-derived neural cell populations for cell transplantation. As such, successful engraftment but no tumor formation was seen after transplantation of iNSCs into the brain and spinal cord of adult mice (Han et al., 2012; Hemmer et al., 2014; Hong et al., 2014; Liu et al., 2015).