GROUP LEADER: Isabelle Vernos (ICREA Research Professor and member of the ERC Scientific Council)

POSTDOCTORAL FELLOWS: Mónica Rodríguez (until June), Georgina Garrido, Álvaro Aranguren, Claudia Conte (until September)

PhD STUDENTS: Miquel Rosas, Krystal Timón, Farners Amargant, Alejandra Laguillo, Aitor Modol, Ivan Zadra.

TECHNICIANS: Nuria Mallol, Leonor Ávila

SUMMARY

The development and growth of multicellular organisms as well as the renewal and homeostasis of their tissues rely on the controlled proliferation of their cells. Errors during cell division are deleterious for a cell and an organism as they can generate aneuploidies, a hallmark of particularly aggressive tumours and one of the main causes of spontaneous abortions.

Cell division entails a dramatic reorganization of most cellular components and the assembly of the bipolar spindle, a microtubule (MT) based apparatus that provides the forces and mechanical support for moving and segregating the chromosomes accurately. Most animal cells enter mitosis with duplicated centrosomes that provide an active source of dynamic MTs but spindle assembly relies largely on the nucleation of acentrosomal MTs occurring in a RanGTP dependent manner around the chromosomes after nuclear envelope breakdown. During the last year, we used a mass spectrometry proteomic approach to look into spindle self-organisation. We obtained the proteome of RanGTP induced mini-spindles as they self-organise over time. Our results show that these microtubule assemblies are similar to the bipolar spindles from cells and that their self-organisation involves specific dynamic changes in their associated proteome.  In collaboration with Clinica EUGIN we also showed that the Xenopus egg extract system can be used to obtain relevant functional information about human sperm samples from patients.

Proteomic analysis of microtubule assemblies induced over time by addition of RanGTP to M-phase Xenopus egg extracts. Microtubules initially organize into asters, and become shorter before organizing spindle like structures as shown in the upper images. The total proteome of these microtubule assemblies consists of 1263 human proteins including 324 ‘spindle proteins’. We found that 447 of all the proteins associate non-stochiometrically with microtubule assemblies over time of incubation. The profiles of association of these proteins are illustrated in the lower part of the figure according to their function groups. Spindle self-organisation involves changes in microtubule dynamics. (see Rosas and Cavazza et al, 2018)

Fig. 1

Proteomic analysis of microtubule assemblies induced over time by addition of RanGTP to M-phase Xenopus egg extracts. Microtubules initially organize into asters, and become shorter before organizing spindle like structures as shown in the upper images. The total proteome of these microtubule assemblies consists of 1263 human proteins including 324 ‘spindle proteins’. We found that 447 of all the proteins associate non-stochiometrically with microtubule assemblies over time of incubation. The profiles of association of these proteins are illustrated in the lower part of the figure according to their function groups. Spindle self-organisation involves changes in microtubule dynamics. (see Rosas and Cavazza et al, 2018)

RESEARCH PROJECTS

  • Understanding the regulation of microtubule minus-end dynamics during mitosis (Alejandra Laguillo, Claudia Conte)
  • Role of microtubule polyglutamylation during mitosis (Monica Rodriguez, Ivan Zadra)
  • Identification and functional characterization of the RanGTP microtubule proteome and novel SAFs (Spindle Assembly Factors) regulated by RanGTP (Miquel Rosas, Tommaso Cavazza)
  • Spatial and temporal control of microtubule assembly during mitosis and its role in spindle assembly and chromosome segregation (Krystal Timon)
  • The role of the sperm centrosome in fertility (Farners Amargant in collaboration with Clinica EUGIN))
  • Identification of the TPX2 and Aurora A interactomes in mitotic cells (Georgina Garrido, Alvaro Aranguren)
  • The role of RanGTP in cilia assembly and function (Aitor Modol)

SELECTED PUBLICATIONS

Amargant F, García D, Barragán M, Vassena R, Vernos I.
“Functional Analysis of Human Pathological Semen Samples in an Oocyte Cytoplasmic Ex Vivo System.”
Sci Rep, 8(1):15348, 2018.

Amargant F, Barragan M, Vassena R, Vernos I.
“Insights of the tubulin code in gametes and embryos: from basic research to potential clinical applications in humans.”
Biol Reprod, doi: 10.1093/biolre/ioy203, 2018. [Epub ahead of print]

Rosas-Salvans M, Cavazza T, Espadas G, Sabido E, Vernos I.
“Proteomic Profiling of Microtubule Self-organization in M-phase.”
Mol Cell Proteomics, 10:1991-2004, 2018.

Eibes S, Gallisà-Suñé N, Rosas-Salvans M, Martínez-Delgado P, Vernos I, Roig J.
“Nek9 Phosphorylation Defines a New Role for TPX2 in Eg5-Dependent Centrosome Separation before Nuclear Envelope Breakdown.”
Curr Biol, 28(1):121-129.e4, 2018.