E2F and GATA switches turn off WD repeat domain 77 expression in differentiating cells

Mep50 is essential for embryonic development in medaka fish

Mep50 as a partner promotes the activity and substrate affinity of Prmt5. Prmt5 and Mep50 function together in multiple bioprocesses of the cells. Both Prmt5 and Mep50 are necessary for maintenance of the stem cells and are indispensable in the embryogenesis in the mammals. However, the role of Mep50 is rarely studied in fish. This study was to investigate the role of Mep50 in embryonic development of medaka. Medaka mep50 was mutated by genomic editing with CRISPR-Cas9 technology. Two mutants with a deletion of 22 and 46 bp separately in mep50 caused premature stopping of translation. The homozygotes of these mutant fish were obtained by self-crossing of the heterozygotes. These homozygotic mutants could reproduce embryos but the offspring were not viable. The apoptotic cells were significantly more in the mutant embryos than that in the wild type indicated by TUNEL assay. Quantitative RT-PCR showed that the expression of oct4 and sox2 were significantly decreased, but p53 was increased in the mutant embryos. These results suggest that disruption of mep50 severely interferes with embryogenesis and mep50 is necessary for embryonic development by maintaining stem cells and repression of apoptosis in medaka.

WD Repeat Domain 77 Protein Regulates Translation of E2F1 and E2F3 mRNA

WD repeat domain 77 protein (WDR77) is required for cellular proliferation of lung and prostate epithelial cells during earlier stages of development and is reactivated during prostate and lung tumorigenesis. WDR77 plays an essential role in prostate tumorigenesis and cell growth mediated by growth regulatory factors. Here, we identified E2F1 and E2F3 mRNAs as translational targets of WDR77. We demonstrated that WDR77 regulated the translation of E2F1 and E2F3 mRNAs through the 5' untranslated regions (UTRs) of E2F1 and E2F3 (E2F1/3) mRNAs. WDR77 physically interacted with programmed cell death 4 (PDCD4) that suppresses translation of mRNAs containing structured 5' UTRs by interacting with eukaryotic translation initiation factor 4A (eIF4A) and inhibiting its helicase activity. Further, we demonstrated that the interaction between WDR77 and PDCD4 prevented the binding of PDCD4 to eIF4A and relieved PDCD4's inhibitory effect on eIF4A1. Overall, our work reveals for the first time that WDR77 is directly involved in translational regulation of E2F1/3 mRNAs through their structured 5' UTRs, PDCD4, and eIF4A1 and provides novel insight into the cell growth controlled by WDR77.

GATA transcription factors in development and disease

The GATA family of transcription factors is of crucial importance during embryonic development, playing complex and widespread roles in cell fate decisions and tissue morphogenesis. GATA proteins are essential for the development of tissues derived from all three germ layers, including the skin, brain, gonads, liver, hematopoietic, cardiovascular and urogenital systems. The crucial activity of GATA factors is underscored by the fact that inactivating mutations in most GATA members lead to embryonic lethality in mouse models and are often associated with developmental diseases in humans. In this Primer, we discuss the unique and redundant functions of GATA proteins in tissue morphogenesis, with an emphasis on their regulation of lineage specification and early organogenesis.