| In clinics,though infertile patients turn to in vitro fertiliztion technology(IVF)for pregnancy,about 10%to 15%patients fail to attain their goal because of preimplantation embryo development failure.The mechanism of embryonic developmental arrest,especially at morula stage,is unclear.After many studies in mouse and human,chromatin dynamics is closely related with development potential.When the transcription of chromatin structure regulators was inhibited,many cell lineage decision genes,including Cdx2,Oct4,Sox2 and Nanog,were repressed during 8-cell and morula stage,and then spcecification of inner mass(ICM)and trophectoderm(TE)was blocked.However,up to now,the mechanism of chromatin structure regulating cell development potential was unclear.We previously reported that CRL4 E3 ubiquitin ligase was essential for female fertility,which forms many E3 complexes by interacting with different DDB1/CUL4-associated factors(DCAFs)as substrate adaptors.In order to identify a specific adaptor in oocytes,a small-scale RNAi screen was conducted in C.elegans.DCAF13,a highly conserved protein from C.elegans to human,was identified essential for worm fertility.Dcaf13 knockout mice were successfully generated by TALEN technology,and were early embryonic lethal with developmental arrest at morula stage.DCAF13 was undetectable in zygote and 2-cell,and was observed in 4-cell with increase thereafter to blastocyst.This indicated DCAF13 is a key regulator in early embryo development and probabley regulates cell developmental potential.Mechanistically,CRL4DCAF13 directs SUV39H1 for polyubiquitination and degradation,therefore,attenuating histone H3 lysine 9 trimethylation.By injecting Dcafl3 siRNA in zygotes,both H3K9me3 and SUV39H1 increase in Dcaf13-knockdown embryos by immunostaining,which suggests DCAF13 depletion results in heterochromatin.Overexpression of mCherry-SUV39H1 in mouse zygotes phenocopied the embryo defects caused by Dcafl3 knockout.Some cell lineage relative genes beginning to express during 8-cell to morula,such as Nanog and Cdx2,decreased dramatically in Dcaf13-knockdown 8-cells and morulas.Taken together,we suggested that CRL4DCAF13 directs SUV39H1 for polyubiquitination and degradation,therefore attenuating histone lysine 9 trimethylation,which making sure open state chromatins and the cell lineage decision genes expression successfully during mouse early embryo development. |
