Eukaryotic Elongation Factor 1A (eEF1A) plays a key role in protein synthesis by delivering aminoacylated tRNAs to the A site of the ribosome. In higher vertebrates, two isoforms of eEF1A exist called eEF1A1 and eEF1A2, with eEF1A2 being expressed in adult brain, heart and skeletal muscle. Since 2012, several different de novo heterozygous missense mutations in EEF1A2 have been identified in humans and these cause epilepsy, intellectual disability and autism. Before considering treatment options, it is vital to determine whether these mutations cause loss or gain of protein function. I performed a battery of behavioural tests using two mouse lines with heterozygous loss of function mutations in eEF1A2. The aim was to determine whether there were any behavioural phenotypes consistent with intellectual disability and/or autism. Using heterozygous wasted mice (Eef1a2+/wst), I analysed the effects of aging on behaviour and found that Eef1a2+/wst mice showed reduced marble burying activity and reduced movement in the open field test with age. In a test of social behaviour, Eef1a2+/wst mice showed a significantly reduced preference for social novelty at all ages tested. The second heterozygous null line, Del22.ex3, was generated on a pure C57BL/6J genetic background. This new line was made in order to reduce the level of variation observed in data from the wasted line, which was on a mixed genetic background. The genetic background was shown to have an influence on behaviour as the results differed between this line and the wasted line. Del22.ex3 Eef1a2+/- mice showed significantly reduced engagement in repetitive behaviours compared with wild-type littermates and normal preference for social novelty. Using CRISPR/Cas9, a mouse line with the D252H missense mutation was generated and I repeated my behavioural testing on heterozygotes from this line. I found no behavioural abnormalities in this line suggesting a mouse-human difference in the ability to tolerate eEF1A2 missense mutations. Previous attempts to make a line with the G70S missense mutation were unsuccessful but as a product of this experiment, it was found that mice expressing G70S eEF1A2 had a comparable phenotype to and died at the same age as complete knockouts. This suggested that the G70S protein is non-functional and cannot compensate for loss of wild-type eEF1A2. These experiments have improved our understanding of the phenotypic effects of Eef1a2 mutations in mice and have shown, for the first time, that mutations in Eef1a2 affect mouse behaviour.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:743712 |
| Date | January 2018 |
| Creators | Hope, Jilly Evelyn |
| Contributors | Abbott, Catherine ; Jackson, Mandy |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/29620 |
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