Analysis of histone variant H3.3 function in embryonic development and stem cell differentiation
Tai, Joyce An Yi
Date of Issue2012
School of Biological Sciences
Institute of Medical Biology
Upon fertilization, global epigenetic reprogramming of parental genomes is required for embryonic development. This event involves DNA demethylation and changes in the histone variant compositions. However, little is known about the molecular mechanisms of histone variant incorporation, the function of histone variant H3.3 and of modified residues within the H3.3 in the chromatin. Here, we show that the histone variant H3.3, in particular lysine 27, is required for the establishment of embryonic development. Mutant mRNA H3.3A K4A and H3.3A K27A, which were introduced through microinjection, were overexpressed in mouse zygotes. Preliminary results showed that mutation of H3.3A K27 may delay embryonic development by approximately 1 cleavage-stage while mutation of H3.3A K4 may lead to improper formation of ICM in blastocysts. However, due to the insufficient statistical evidence to support the abnormal ICM formation induced in embryos expressing H3.3A K4A mutants, more experimental repeats have to be performed. Murine embryonic stem cells overexpressing H3.3A K4A, H3.3A K27A, H3.3A K9A and H3.3A K9AK27A were also analyzed for cellular differentiation. We observed no change in gene expression in ES cells expressing histone mutants, indicating no stem cell differentiation was induced. Taken together, our findings suggest a possible functional role for one modifiable lysine residue within histone variant H3.3.
Final Year Project (FYP)
Nanyang Technological University