Zebrafish ELL-associated factors Eaf1/2 modulate erythropoiesis via regulating gata1a expression and WNT signaling to facilitate hypoxia tolerance

EAF1 and EAF2,the eleven-nineteen lysine-rich leukemia(ELL)-associated factors which can assemble to the super elongation complex(AFF1/4,AF9/ENL,ELL,and P-TEFb),are reported to participate in RNA polymeraseⅡto actively regulate a variety of biological processes,including leukemia and embryogenesis,but whether and how EAF1/2 function in hematopoietic system related hypoxia tolerance during embryogenesis remains unclear.Here,we unveiled that deletion of EAF1/2(eaf1^(-/-)and eaf2^(-/-))caused reduction in hypoxia tolerance in zebrafish,leading to reduced erythropoiesis during hematopoietic processes.Meanwhile,eaf1^(-/-)and eaf2^(-/-)mutants showed significant reduc-tion in the expression of key transcriptional regulators scl,lmo2,and gata1a in erythropoiesis at both 24 h post fertilization(hpf)and 72 hpf,with gata1a downregulated while scl and lmo2 upregulated at 14 hpf.Mechanistically,eaf1^(-/-)and eaf2^(-/-)mutants exhibited significant changes in the expression of epigenetic modified histones,with a significant increase in the binding enrichment of modified histone H3K27me3 in gata1a promoter rather than scl and lmo2 promoters.Additionally,eaf1^(-/-)and eaf2^(-/-)mutants exhibited a dynamic expression of canonical WNT/β-catenin signaling during erythropoiesis,with significant reduction in p-β-Catenin level and in the binding enrichment of both scl and lmo2 promoters with the WNT transcriptional factor TCF4 at 24 hpf.These findings demonstrate an important role of Eaf1/2 in erythropoiesis in zebrafish and may have shed some light on regeneration medicine for anemia and related diseases and on molecular basis for fish economic or productive traits,such as growth,disease resistance,hypoxia tolerance,and so on.

Transcriptional profiles in zebrafish atp7a mutants and responses of atp7a mutants to Cu stress

As a copper(Cu)transport ATPase,ATP7A plays an important role in maintaining Cu homeostasis in the body,but the developmental and physiological roles of atp7a in zebrafish embryogenesis are rarely studied.In this study,normal morphological phenotypes of atp7a^(−/−)homozygous zebrafish were observed at both embryonic and adult stages,however,atp7a^(−/−)larvae exhibited delayed touch response and obvious transcriptome changes.Compared with the WT(wild type),differentially expressed genes(DEGs)in atp7a^(−/−)larvae showed the enrichment in gene ontology(GO)terms related to several processes including ATPase activity,oxidoreductase activity,active transmembrane transporter activity,ion binding,and the citrate cycle.Furthermore,decreases in both ATP content and Na+/K+-ATPase activity in atp7a^(−/−)embryos and larvae were unveiled.57 overlapping DEGs were found both in WT stressed with Cu and in WT mutated with atp7a,and GO term analysis indicated the enrichment in the genes related to neurexin family protein binding and neuronal cell-cell adhesion.Moreover,42 overlapping DEGs in Cu stressed WT and Cu stressed atp7a^(−/−)were identified.GO term analysis showed an enrichment in the genes related to heme binding,implying that Cu was independent of the integral function of atp7a to affect heme binding.In addition,genes involved in the negative regulation of angiogenesis were down-regulated in atp7a^(−/−)mutants with and without Cu stress,which failed to occur in WT,implying that the integral function of atp7a is required for maintaining the normal expression of angiogenesis genes.The integrative data in this study demonstrated that atp7a is required for ion transport and angiogenesis,and for Cu-induced neurexin family protein binding defects,rather than for Cu-induced heme binding defects,during zebrafish embryogenesis.These findings provide possible clues for human diseases with ATP7A dysfunction and imbalanced Cu homeostasis.