The Biological Function Of The Rho Guanine Nucleotide Exchange Factor 12(ARHGEF12) In Erythropoiesis

ARHGEF12,also known as LARG,which was initially identified as a fusion partner of MLL in a case of acute myeloid leukemia,is a regulatory protein involved in the GDP/GTP exchange reaction of the RhoA and activates a Rho-GTPasedependent signaling pathway.However,the role of ARHGEF12 in hematopoiesis remains unknown.Here,we first report that ARHGEF12 takes part in erythroid differentiation not only in erythroleukemia cell line K562 but also in zebrafish based on knockdown technology.Although primitive hematopoiesis including erythroid differentiation progressed normally,double silencing of both orthologues arhgef12 aand arhgef12b in Danio rerio with morpholinos caused erythropenia during definitive hematopoiesis.Meanwhile,cytology assay reveal less mature red blood cells with large and loose nuclear in morpholino injected embryos.Our results also illustrate that arhgef12 aand arhgef12bis involved in the different stage of erythoid differentiation.The phenotype of blocked erythroid differentiation can be rescured by mRNA overexpression of RhoA active mutant.On the other hand,injection of mRNA transcripted from the dominant negative mutant of RhoA could replicate the phenotype of arhgef12 silencing.Antibody array screen of kinase phosphorylation suggested p38 MAPK signaling pathway and STAT1 downstream of RhoA may be crucial in our modles,and activation of p38 MAPK with anisomycin reversed the erythropenia induced by morpholino injection.Also,overexpression of stat1 a in zebrafish rescued the phenotype.