Although the FAM83 family is highly conserved in vertebrates, little is known of the functions of these proteins beyond a correlation with oncogenesis. Of the family, FAM83F is of particular interest because its over-expression activates canonical Wnt signalling in
Xenopus embryos, a pathway often dysregulated in disease. Insights into gene function can often be gained by studying the roles they play during development, so I decided to investigate the role of FAM83F in zebrafish embryos. The primary zebrafish orthologue,
fam83fa, is expressed maternally, declines, and is then expressed strongly in the pre-polster and hatching gland, an observation that may underlie the fact that mutant
fam83fa lines created using CRISPR-Cas9 hatch earlier than their wild-type counterparts. Widespread over-expression of
fam83fa causes a p53-mediated DNA damage response, consistent with my observation that Fam83fa interacts with, and stabilises, p53. However, the prediction that
fam83fa-/- mutants would show decreased sensitivity to genotoxic stress did not hold. Rather, these embryos show increased sensitivity to ionising radiation, with no difference in the p53-mediated DNA damage response. To gain insight into these observations, I used transcriptomic analysis to show that loss of
fam83fa causes impairment of cellular degradation pathways, and, using western blotting, I show that Fam83fa itself is targeted for destruction by a C’ terminal degradation motif. I propose that Fam83fa modulates autophagic processes, including larval hatching, and that it is impairment of autophagy and not of the DNA damage response, that causes increased sensitivity to genotoxic stress in
fam83fa-/- embryos. I also suggest that overexpression of Fam83fa induces canonical Wnt signalling in
Xenopus by increased autophagic endocytosis of the Wnt signalosome.
| Date of Award | 1 Jan 2021 |
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| Original language | English |
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| Awarding Institution | |
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| Supervisor | Jim Smith (Supervisor) |
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