PLZF induces megakaryocytic development, activates Tpo receptor expression and interacts with GATA1 protein

Abstract

We investigated the expression of the PLZF gene in purified human hematopoietic progenitors induced to unilineage erythroid, granulocytic or megakaryocytic differentiation and maturation in serum-free culture. PLZF is expressed in quiescent progenitors: the expression level progressively rises through megakaryocytic development, whereas it gradually declines in erythroid and granulopoietic culture. To investigate the role of PLZF in megakaryopoiesis, we transduced the PLZF gene into the erythro-megakaryocytic TF1 cell line. PLZF overexpression upmodulates the megakaryocytic specific markers (CD42a, CD42b, CD61, PF4) and induces the thrombopoietin receptor (TpoR). The proximal promoter of the TpoR gene is activated in PLZF-expressing TF1 cells: in this promoter region, a PLZF DNA-binding site was identified by deletion constructs studies. Interestingly, PLZF and GATA1 proteins coimmunoprecipitate in PLZF-expressing TF1 cells: enforced expression of both PLZF and GATA1 in TF1 cells results in increased upregulation of megakaryocytic markers, as compared to exogenous PLZF or GATA1 alone, suggesting a functional role for the PLZF/GATA1 complex. Our data indicate that PLZF plays a significant stimulatory role in megakaryocytic development, seemingly mediated in part by induction of TpoR expression at transcriptional level. This stimulatory effect is potentiated by physical interaction of PLZF and GATA1, which are possibly assembled in a multiprotein transcriptional complex.

Thrombopoietin responsiveness reflects the number of doublings undergone by megakaryocyte progenitors

“…Of interest, the expression level of the PLZF gene progressively increases through megakaryocytic development, and, when it is transduced into the erythromegakaryocytic TF1 cell line, its overexpression induces Mpl and up-modulates megakaryocytic-specific glycoproteins as well as platelet factor 4 (PF4). 41 The observation that 7.62% of single megakaryocyte clones survived in the absence of added TPO may even suggest that at least some postmitotic thrombopoietic cells are TPO independent. However, this observation may also be explained by the effects of contaminants that have been demonstrated in Cohn fraction V, and the insulin and transferrin present in the medium.…”

Role of PLZF in melanoma progression

“…For traditional RT-PCR, the sequences of primers, the PCR products and the annealing conditions are reported in Table 2 and in Care`et al (1996) and Labbaye et al (2002). All the amplified fragments were hybridized to a 30-base end-labelled oligonucleotide according to Southern blot standard procedures.…”

“…During normal hematopoiesis, PLZF is expressed in CD34 þ immature cells and declines when cells are induced to erythroid, granulocytic and monocytic differentiation, indicating that PLZF might play a role in the maintenance of the quiescent state of stem/progenitor cells; conversely, PLZF expression is initially unaffected and then upmodulated during megakaryocytic maturation (Krug et al, 2002;Labbaye et al, 2002).…”

The alpha subunit of Go interacts with promyelocytic leukemia zinc finger protein and modulates its functions

“…In particular, previous studies by our group demonstrate that Goα regulates PKA signaling and increases the number of newly formed neurites [3,4], supporting its role as an activator of neuronal differentiation. PLZF induces cell differentiation in megakaryocytes [42], osteoblasts [43], and neurons [44]. Activation of CB also promotes neuronal differentiation [13,45].…”