Protein tyrosine phosphatase PTPN9 regulates erythroid cell development through STAT3 dephosphorylation in zebrafish

Abstract

Protein tyrosine phosphatases (PTPs) are involved in hematopoiesis, but the function of many PTPs is not well characterized in vivo. Here, we have identified Ptpn9a, an ortholog of human PTPN9, as a crucial regulator of erythroid cell development in zebrafish embryos. ptpn9a, but not ptpn9b, was expressed in the posterior lateral plate mesoderm and intermediate cell mass -two primitive hematopoietic sites during zebrafish embryogenesis. Morpholino-mediated knockdown of ptpn9a caused erythrocytes to be depleted by inhibiting erythroid cell maturation without affecting erythroid proliferation and apoptosis. Consistently, both dominant-negative PTPN9 (with mutation C515S) and siRNA against PTPN9 inhibited erythroid differentiation in human K562 cells. Mechanistically, depletion of ptpn9 in zebrafish embryos in vivo or in K562 cells in vitro increased phosphorylated STAT3, and the hyper-phosphorylated STAT3 entrapped and prevented the transcription factors GATA1 and ZBP-89 (also known as ZNF148) from regulating erythroid gene expression. These findings imply that PTPN9 plays an important role in erythropoiesis by disrupting an inhibitory complex of phosphorylated STAT3, GATA1 and ZBP-89, providing new cellular and molecular insights into the role of ptpn9a in developmental hematopoiesis.

Chromatin-remodelling factor Brg1 regulates myocardial proliferation and regeneration in zebrafish

“…8a–c), suggesting the minimal effects of heat shock on the index of proliferating cardiomyocytes. As previously reported734, Gata4-positive cardiomyocytes appeared near the injured area in wild-type Tg( gata4 :EGFP) hearts at 14 d.p.a. (Fig.…”

“…The ventricular resection was performed according to a well-established procedure534. Briefly, adult zebrafish were anaesthetized with tricaine and the pericardial sac was exposed by removing surface scales and a small piece of skin.…”

“…In situ hybridization and AFOG staining were performed on paraffin sections34. Adult zebrafish hearts were fixed in 4% paraformaldehyde at room temperature for 2 h, dehydrated and then embedded in paraffin and sectioned at 5 μm.…”

Spliceosomal protein eftud2 mutation leads to p53-dependent apoptosis in zebrafish neural progenitors

“…Digoxigenin-labeled probes were synthesized using T7 RNA polymerase (Roche). The RNA probes of pax2a, myoD, cmyb, lyzC, amhc and vmhc were synthesized as previously reported (40). …”

“…The embryos were ground and incubated in RIPA lysis buffer with protease and phosphatase inhibitors (42). Anti-Eftud2 (1:1000, Sigma HPA022021), anti-tubulin (BE0031, EASYBIO) and anti-β-actin (1:1000, Cell Signaling 4967L) were used for western blots as previously described (40). …”