Julien Guizetti, Ph.D.

julien.guizetti@med.uni-heidelberg.de

Phone: ++49-(0)6221–56-7877

Nuclear division mechanisms in malaria-causing parasite

Projects

Despite being key to rapid pro­lif­er­a­tion of malar­ia-caus­ing par­a­sites in the human blood the mech­a­nisms of cell divi­sion are still poor­ly under­stood. Our vision is to gen­er­ate a cell bio­log­i­cal and genet­ic frame­work, which details crit­i­cal events dur­ing this atyp­i­cal mode of nuclear divi­sion. The study of this high­ly dynam­ic and small scale process requires exquis­ite tem­po­ral and spa­tial res­o­lu­tion. Hence, we are using a com­bi­na­tion advanced imag­ing tech­niques such as live cell, super-res­o­lu­tion and cor­rel­a­tive light and elec­tron microscopy to inves­ti­gate key struc­tur­al ele­ments of the divi­sion machin­ery. There­by we hope to uncov­er new tar­gets with­in this essen­tial path­way of the par­a­site’s life cycle.

1 | Organization and composition of the atypical plasmodial centrosomes (Caroline Sophie Simon)

Cen­tro­somes are micro­tubule orga­niz­ing cen­ters and mas­ter reg­u­la­tors of mito­sis. Study­ing their func­tion­al­i­ty and com­po­si­tion is crit­i­cal to under­stand cell divi­sion. The plas­modi­al cen­tro­somes, how­ev­er, dis­play a very dis­tinct mor­phol­o­gy when com­pared to any mod­el organ­ism. Based on the poor con­ser­va­tion of canon­i­cal cen­tro­some pro­teins we spec­u­late that diver­gent fac­tors might gov­ern mito­sis in the par­a­site. We aim to build the first detailed work­ing mod­el for cen­tro­some orga­ni­za­tion using advanced imag­ing meth­ods such as STED nanoscopy. To uncov­er the cen­tro­so­mal pro­teome we use in-vivo prox­im­i­ty label­ing and mass spec­trom­e­try.

Fig­ure 1 | STED nanoscopy of divid­ing par­a­site. Image acquired by Res­cueST­ED show­ing late stage P. fal­ci­parum mult­i­n­u­cle­at­ed par­a­site, which has infect­ed a human red blood cell. DNA (blue) is stained by Hoechst and micro­tubules (green) are labeled with anti-Tubu­lin anti­body. Con­fo­cal images and zoomed in region are shown on top. Scale bar, 1µm.

2 | Centrin function in malaria parasite division (Yannik Voß)

Cen­trins are con­served struc­tur­al pro­teins involved in cen­tro­some dupli­ca­tion in mam­mals. P. fal­ci­parum pos­sess­es four homo­logues of which two are spe­cif­ic for the phy­lum of this par­a­site. In mod­el organ­isms cen­trins have been described as cal­ci­um-bind­ing con­trac­tile ele­ments with the poten­tial to poly­mer­ize. We aim to inves­ti­gate the func­tion of those, like­ly essen­tial, pro­teins by inducible knock-out strate­gies. We com­ple­ment our in vivo stud­ies with in-vit­ro bio­chem­i­cal assays using recom­bi­nant cen­trins to test for poly­mer­iza­tion, post-trans­la­tion­al mod­i­fi­ca­tion, and inter­ac­tion part­ners.

Fig­ure 2 | Struc­ture of PfCentrin1‑4. Schemat­ic indi­cat­ing the rel­a­tive size of PfCentrin1‑4, as well as the posi­tion of the EF-hand domains (EFh), phos­pho­ry­la­tion sites ℗ and acety­la­tion sites (Ac) to scale. N‑terminus (N), C‑terminus © (Cob­bold et al., 2016; Gan­ter et al., 2017; Treeck et al., 2011).

 

 

 

Selected Publications

Com­plete pub­li­ca­tion list (PubMed)

Mehn­ert, A.K., Simon C.S., Guizetti, J. (2019). Immuno­flu­o­res­cence stain­ing pro­to­col for STED nanoscopy of Plas­mod­i­um-infect­ed red blood cells. Mol Biochem Par­a­sitol. 229, 47–52.

Müller, L. S. M., Cosenti­no, R. O., Först­ner, K. U., Guizetti, J., Wedel, C., Kaplan, N., … Siegel, T. N. (2018). Genome orga­ni­za­tion and DNA acces­si­bil­i­ty con­trol anti­genic vari­a­tion in try­panosomes. Nature 563(7729), 121–125

Zanghì, G., Vem­bar, S. S., Baum­garten, S., Ding, S., Guizetti, J., Bryant, J. M., … Scherf, A. (2018). A Spe­cif­ic PfEMP1 Is Expressed in P. fal­ci­parum Sporo­zoites and Plays a Role in Hepa­to­cyte Infec­tion. Cell Reports 22(11), 2809–2817.

Bryant J.M., Reg­nault C., Schei­dig-Benatar C., Baum­garten S., Guizetti J.*, Scherf A. (2017). CRISPR/Cas9 Genome Edit­ing Reveals That the Intron Is Not Essen­tial for var2csa Gene Acti­va­tion or Silenc­ing in Plas­mod­i­um fal­ci­parum. MBio 8(4). pii: e00729-17.

Guizetti, J.*, Bar­cons-Simon, A., Scherf, A. (2016). Trans-act­ing GC-rich non-cod­ing RNA at var expres­sion site mod­u­lates gene count­ing in malar­ia par­a­site. Nucle­ic Acids Res 44, 9710–9718.

Zhang, Q., Siegel, T. N., Mar­tins, R. M., Wang, F., Cao, J., Gao, Q., Cheng, X., Jiang, L., Hon, C. C., Schei­dig-Benatar, C., Sakamo­to, H., Turn­er, L., Jensen, A. T., Claes, A., Guizetti, J., Malmquist, N. A., and Scherf, A. (2014). Exonu­cle­ase-medi­at­ed degra­da­tion of nascent RNA silences genes linked to severe malar­ia. Nature 513, 431–435.

Guizetti, J., Mar­tins, R. M., Guadagni­ni, S., Claes, A., and Scherf, A. (2013). Nuclear Pores and Per­in­u­clear Expres­sion Sites of var and Ribo­so­mal DNA Genes Cor­re­spond to Phys­i­cal­ly Dis­tinct Regions in Plas­mod­i­um fal­ci­parum. Eukary­ot Cell 12, 697–702.

Guizetti, J., Scher­melleh, L., Mantler, J., Maar, S., Pos­er, I., Leon­hardt, H., Muller-Reichert, T., and Ger­lich, D. W. (2011). Cor­ti­cal con­stric­tion dur­ing abscis­sion involves helices of ESCRT-III-depen­dent fil­a­ments. Sci­ence 331, 1616–1620.

Guizetti, J., Mantler, J., Muller-Reichert, T., and Ger­lich, D. W. (2010). Cor­rel­a­tive time-lapse imag­ing and elec­tron microscopy to study abscis­sion in HeLa cells. Meth­ods Cell Biol 96, 591–601.

Lacroix, B., van Dijk, J., Gold, N. D., Guizetti, J., Aldri­an-Her­ra­da, G., Rogows­ki, K., Ger­lich, D. W., and Janke, C. (2010). Tubu­lin polyg­lu­tamy­la­tion stim­u­lates spastin-medi­at­ed micro­tubule sev­er­ing. J Cell Biol 189, 945–954.

Lekomt­sev, S., Guizetti, J., Poz­ni­akovsky, A., Ger­lich, D. W., and Petron­cz­ki, M. (2010). Evi­dence that the tumor-sup­pres­sor pro­tein BRCA2 does not reg­u­late cytoki­ne­sis in human cells. J Cell Sci 123, 1395–1400.

Steige­mann, P., Wurzen­berg­er, C., Schmitz, M. H., Held, M., Guizetti, J., Maar, S., and Ger­lich, D. W. (2009). Auro­ra B‑mediated abscis­sion check­point pro­tects against tetraploidiza­tion. Cell 136, 473–484.

Reviews

Guizetti, J.*, and Scherf, A. (2013). Silence, acti­vate, poise and switch! Mech­a­nisms of anti­genic vari­a­tion in Plas­mod­i­um fal­ci­parum. Cell Micro­bi­ol 15, 718–726.

Guizetti, J., and Ger­lich, D. W. (2012). ESCRT-III poly­mers in mem­brane neck con­stric­tion. Trends Cell Biol 22, 133–140.

Guizetti, J., and Ger­lich, D. W. (2010). Cyto­ki­net­ic abscis­sion in ani­mal cells. Semin Cell Dev Biol 21, 909–916.