HOX9 expression and potential functions during early embryo development in mammals : a special emphasis on HOXB9

Sauvegarde, Caroline
(2016)

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Authors
  • Sauvegarde, CarolineUCLouvain
    author
Supervisors
Rezsohazy, René
 ;
Donnay, Isabelle
Abstract
HOX genes encode transcription factors whose functions in embryonic development have been well studied from gastrulation onward. However, HOX expression has also been detected at earlier stages. In particular, HOXB9 expression profile in the mouse and bovine suggests specific regulations and supports the hypothesis that HOXB9 could fulfil uncharacterised roles during oocyte maturation and early development. In addition, data concerning the presence and localisation of HOX proteins are lacking for the majority of developmental stages in most mammals. The main objectives of this work were thus to characterise the early HOXB9 expression pattern at the protein level and to investigate the potential roles it could play at those stages. Two mammalian models were compared: the mouse and the bovine. The pattern of HOXB9 protein localisation was established for the first time from oocytes to the peri-gastrulation period. HOXB9 was detected at all stages. Its distribution, mainly nuclear, was well conserved between species until blastocysts where differences appeared between lineages and between species, with mouse HOXB9 being more restrictively distributed. Moreover, variations in subcellular localisation of the protein depending on the cell lineage suggested that possible HOXB9 activity is not restricted to its role as transcription factor. HOXB9 knock-down was achieved through RNA interference applied on bovine oocytes, zygotes and on a trophectoderm cell line. However, no significant reduction of the protein abundance could be observed. Finally, since HOX proteins from a given paralog group can exert similar functions, the expression study was extended to the other HOX9 genes. All four HOX9 genes were shown to be expressed, which support that their potential functions in early development could be conserved among mammals.
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Sauvegarde, C. (2016). HOX9 expression and potential functions during early embryo development in mammals : a special emphasis on HOXB9. https://hdl.handle.net/2078.5/181766