Bird, Adrian

Cook, Atlanta

Tillotson, Anne Rebekah

Biotechnology and Biological Sciences Research Council (BBSRC)

2018-03-22T11:25:48Z

2018-03-22T11:25:48Z

2017-07-07

MeCP2 was identified by its ability to bind DNA in a methylation-specific manner. Yet, how it interprets the DNA methylome remains unclear. Several mechanisms have been proposed, including a role in transcriptional repression. MeCP2 is highly abundant in the brain, and loss-of-function mutations result in a neurological disorder called Rett syndrome (RTT). Strikingly, RTT-causing missense mutations are almost all located in either the methyl-CpG-binding domain (MBD) or a region that has been shown to bind the NCoR/SMRT co-repressor complex (NID). This suggests that the MBD and the NID are the key functional domains in MeCP2, and that the role of MeCP2 is to form a ‘bridge’ between chromatin and the co-repressor complex to regulate gene expression. To test this ‘bridge’ hypothesis, I have made an allelic series of knock-in mice with truncated forms of MeCP2 to determine whether the other regions are dispensable for protein function. The three other regions of MeCP2 (the N-terminus before the MBD, the Intervening region between the MBD and the NID, and the C-terminus after the NID) were deleted in a step-wise manner to produce progressively smaller truncated proteins. Knock-in mice which lack just the N-terminus or both the N- and C-termini are phenotypically normal. Therefore, these regions, which together make up 46% of the protein sequence, are dispensable for MeCP2 function in vivo. Additional deletion of the Intervening region, retaining only 34% of the original sequence, results in mild RTT-like symptoms in the knock in mice. This is likely to be caused by this protein’s decreased stability and reduced ability to bind the NCoR/SMRT complex in the brain. The most severely truncated protein is nevertheless able to reverse the Mecp2-null phenotype when reactivated after the onset of symptoms. Together, these findings strongly support the ‘bridge’ hypothesis.

http://hdl.handle.net/1842/28917

en

The University of Edinburgh

MeCP2

epigenetic

mouse model

gene expression

Identifying the key functions of MeCP2 via genetic manipulation in mice

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy