Investigation into the function and structure of Peptidyl Arginine Deiminase 6 in early embryonic development
File(s)
Author(s)
Williams, Jack
Type
Thesis
Abstract
Peptidyl arginine deiminase 6 (PADI6) is a maternal-effect gene essential for early embryo development and female fertility. Despite its clear biological and clinical significance, the function of PADI6 remains elusive. PADI6 belongs to a family of enzymes, that catalyse the post-translational conversion of arginine to citrulline, however, there is currently no reported catalytic activity of PADI6.
The work described in this thesis aimed to expand our understanding of the function of PADI6 in early embryo development, in particular, the question of whether PADI6 has a catalytic function. Using biophysical experiments, I have shown that human PADI6 is dimeric in solution and unlike other PADIs does not bind calcium. We have solved a 2.44 Å X-ray crystal structure of human PADI6, the first high resolution structure of PADI6 to date. Analysis of this structure showed the active site cleft of PADI6 was closed and provided further insight on the structural significance of reported pathogenic PADI6 variants. In search of interacting proteins, I have confirmed interactions with five key early embryonic proteins and shown that these proteins do not have an activating effect on PADI6. Using two mouse models, I have shown that embryonic genome activation (EGA) is defective in embryos from Padi6 knock-out mothers, and that there may be an additional non-essential catalytic function of PADI6 during EGA. Finally, I have shown that knocking out Padi6 in mice has little to no effect on the establishment of the maternal imprinted methylation signature. Together this thesis answers outstanding questions regarding the function of PADI6 and offers new perspectives on its function in early embryonic development.
The work described in this thesis aimed to expand our understanding of the function of PADI6 in early embryo development, in particular, the question of whether PADI6 has a catalytic function. Using biophysical experiments, I have shown that human PADI6 is dimeric in solution and unlike other PADIs does not bind calcium. We have solved a 2.44 Å X-ray crystal structure of human PADI6, the first high resolution structure of PADI6 to date. Analysis of this structure showed the active site cleft of PADI6 was closed and provided further insight on the structural significance of reported pathogenic PADI6 variants. In search of interacting proteins, I have confirmed interactions with five key early embryonic proteins and shown that these proteins do not have an activating effect on PADI6. Using two mouse models, I have shown that embryonic genome activation (EGA) is defective in embryos from Padi6 knock-out mothers, and that there may be an additional non-essential catalytic function of PADI6 during EGA. Finally, I have shown that knocking out Padi6 in mice has little to no effect on the establishment of the maternal imprinted methylation signature. Together this thesis answers outstanding questions regarding the function of PADI6 and offers new perspectives on its function in early embryonic development.
Version
Open Access
Date Issued
2023-12-01
Date Awarded
2024-03-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Walport, Louise
Tate, Edward
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Rights Embargo Date
2026-02-28