First name
Sara
Last name
Gallini
Year of Study
Research Center
Thesis Title
Molecular contribution of the Aurora-A kinase and the junctional protein Afadin to oriented cell divisions
Thesis Abstract
Spindle positioning is essential for tissue morphogenesis and homeostasis. The orientation of the
mitotic spindle is determined by force generators, Dynein/Dynactin, formed on cortical
NuMA:LGN:Gαi complexes, which anchor astral microtubules at specialized domains of the
cortex. In this context, my PhD project aimed to study the molecular mechanisms accounting for the
spindle orientation functions of the Aurora-A kinase and the junctional protein Afadin. To
understand the implication of Aurora-A in spindle orientation, I partially inhibited its activity.
Under these conditions, in metaphase NuMA accumulates abnormally at the spindle poles without
reaching the cell cortex. FRAP experiments revealed that Aurora-A governs the dynamic exchange
between the cytoplasmic and the spindle-pole-localized pools of NuMA. At molecular level,
Aurora-A phosphorylates directly the C-terminus of NuMA on three serine residues, among which
Ser-1969 is the determinant for the dynamic behaviour of NuMA at the spindle poles. Collectively,
my studies demonstrate that Aurora-A activity on NuMA controls its cell localization, and that this
is the major event underlying the spindle orientation functions of Aurora-A in cultured cells. Part of
my PhD studies addressed the role of Afadin in spindle orientation; I demonstrated that Afadin is
required for spindle positioning, and epithelial morphogenesis of Caco-2 cysts. Molecularly, Afadin
binds directly and concomitantly to F-actin and to LGN. Indeed, in mitotic HeLa cells, Afadin is
required for cortical accumulation of LGN, NuMA and Dynein above the spindle poles, in a F-actin
dependent manner. These results depicted Afadin as the first mechanical anchor between Dynein
and cortical F-actin.
mitotic spindle is determined by force generators, Dynein/Dynactin, formed on cortical
NuMA:LGN:Gαi complexes, which anchor astral microtubules at specialized domains of the
cortex. In this context, my PhD project aimed to study the molecular mechanisms accounting for the
spindle orientation functions of the Aurora-A kinase and the junctional protein Afadin. To
understand the implication of Aurora-A in spindle orientation, I partially inhibited its activity.
Under these conditions, in metaphase NuMA accumulates abnormally at the spindle poles without
reaching the cell cortex. FRAP experiments revealed that Aurora-A governs the dynamic exchange
between the cytoplasmic and the spindle-pole-localized pools of NuMA. At molecular level,
Aurora-A phosphorylates directly the C-terminus of NuMA on three serine residues, among which
Ser-1969 is the determinant for the dynamic behaviour of NuMA at the spindle poles. Collectively,
my studies demonstrate that Aurora-A activity on NuMA controls its cell localization, and that this
is the major event underlying the spindle orientation functions of Aurora-A in cultured cells. Part of
my PhD studies addressed the role of Afadin in spindle orientation; I demonstrated that Afadin is
required for spindle positioning, and epithelial morphogenesis of Caco-2 cysts. Molecularly, Afadin
binds directly and concomitantly to F-actin and to LGN. Indeed, in mitotic HeLa cells, Afadin is
required for cortical accumulation of LGN, NuMA and Dynein above the spindle poles, in a F-actin
dependent manner. These results depicted Afadin as the first mechanical anchor between Dynein
and cortical F-actin.
Students representatives
Off
Curricula Term