Dr. Franziska Hentzschel

franziska.hentzschel
(at)med.uni-heidelberg.de
Phone: +49 6221 56–7877

Malaria Research

Projects and research interest

In humans, Plas­mod­i­um par­a­sites cause malar­ia, a dead­ly dis­ease killing hun­dreds of thou­sands of peo­ple each year. The sex­u­al repli­ca­tion of Plas­mod­i­um, how­ev­er, occurs in the mos­qui­to, start­ing with the for­ma­tion of male and female gametes (game­to­ge­n­e­sis). Male game­to­ge­n­e­sis is par­tic­u­lar­ly fas­ci­nat­ing, as with­in only ten min­utes, eight male gametes form and emerge from one sin­gle par­ent cell. In this time the par­ent cell repli­cates its DNA three times to pro­vide eight genomes, but its nucle­us only divides when the eight gametes emerge from the cell. It is thus a chal­lenge for the par­a­site to make sure that each gamete takes up a com­plete genome from the sin­gle nucle­us. Fail­ure to do so results in male gametes with too lit­tle DNA, and while they can still fer­tilise female gametes and form zygotes, these will then stop devel­op­ing at the oocyst stage in the mos­qui­to. A func­tion­al and com­plete male genome is thus essen­tial for the par­a­site to trans­mit through the mosquito.

At the Hentzschel lab, we inves­ti­gate the for­ma­tion and con­tri­bu­tion of the male genome to the sex­u­al repli­ca­tion of Plas­mod­i­um. How does the male game­to­cyte ensure that each gamete takes up a com­plete genome? What does the male gamete con­tribute to the female gamete dur­ing fer­til­i­sa­tion to ini­ti­ate devel­op­ment of a motile zygote? How is repli­ca­tion organ­ised in the oocyst and why does the oocyst require a diploid genome for this? We address these research ques­tions using a com­bi­na­tion of reverse genet­ics, live cell and fixed imag­ing tech­niques, and inter­ac­tome stud­ies to reveal the mol­e­c­u­lar basis for these phe­no­types. In addi­tion, we devel­op nov­el genet­ic tools to enable inves­ti­ga­tion of gene func­tion in the diploid oocyst stages.

Fig­ure 1. Plas­mod­i­um par­a­site devel­op­ment in the mos­qui­to, from game­to­cytes to oocysts. C denotes the genome content.

1 | Deciphering DNA segregation during Plasmodium male gametogenesis

Dur­ing the rapid for­ma­tion of male gametes, the cell must ensure that each of the eight bud­ding gametes takes up one genome from the octo­ploid nucle­us. We have dis­cov­ered that Plas­mod­i­um utilise a atyp­i­cal Actin-relat­ed pro­tein 2/3 com­plex (Arp2/3) to medi­ate this DNA seg­re­ga­tion. We are now inves­ti­gat­ing its mech­a­nis­tic func­tion and how this pro­tein com­plex is assem­bled and acti­vat­ed. We also inves­ti­gate the func­tion of fur­ther inter­ac­tion part­ners to gain a deep­er under­stand­ing of the mol­e­c­u­lar biol­o­gy of male gamete formation.

Fig­ure 2. Male gametes emerg­ing from the par­ent cell. DNA is stained in cyan, micro­tubule are stained in red. While in the wild­type (WT), gametes take up the DNA into the emerg­ing gametes, par­a­sites lack­ing the pro­tein com­plex (KO) fail to do so.

2 | Developing novel CRISPR tools to dissect the mosquito stages of Plasmodium

The mol­e­c­u­lar and genet­ic basis of the devel­op­ment of Plas­mod­i­um in mos­qui­toes is lit­tle under­stood. One rea­son for this is that genet­ic mod­i­fi­ca­tions can only be done in blood stages, and if a gene dele­tion arrests par­a­site devel­op­ment there, the func­tion of this gene can­not be inves­ti­gat­ed in sub­se­quent oocyst stages. Anoth­er rea­son is that oocysts are diploid, car­ry­ing both the mater­nal and the pater­nal genome, which fur­ther com­pli­cates reverse genet­ics. We are work­ing on engi­neer­ing CRISPR-based gene tar­get­ing strate­gies that make use of the sex­u­al repli­ca­tion of Plas­mod­i­um to silence gene expres­sion only in the diploid oocyst.

Fig­ure 3. Scheme of post-tran­scrip­tion­al gene silencing.

3 | Investigating the early replication events in the oocyst

The oocyst is a high­ly unusu­al, under­ex­plored life cycle stage of Plas­mod­i­um. Not only is it the only stage at which the par­a­site grows extra­cel­lu­lar­ly, it also employs an unusu­al mode of repli­ca­tion where DNA repli­ca­tion is not always fol­lowed by nuclear divi­sion, and the oocyst thus con­tains mul­ti­ple nuclei with sev­er­al genomes each. Curi­ous­ly, we found that if oocysts are ane­u­ploid, i.e. miss­ing a sub­set of the pater­nal genome, oocysts arrest ear­ly in devel­op­ment. Using live-cell imag­ing approach­es, sin­gle-cell tran­scrip­tomics and reverse genet­ics, we aim to spa­tiotem­po­ral­ly char­ac­ter­ize ear­ly oocyst devel­op­ment and to under­stand how the pater­nal genome is impor­tant for this development.

Fig­ure 4. Oocyst devel­op­ment. Left: Oocysts grow­ing on a mos­qui­to midgut. Right: Close-up on two oocysts (red), one of which is already pro­duc­ing daugh­ter cells (sporo­zoites). DNA of oocysts and sur­round­ing mos­qui­to cells is stained in cyan.

Research articles

  • Hentzschel, F.*, Binder, A. M.*, Dorner, L. P., Herzel, L., Nug­lish, F., Sema, M., Aguirre-Botero, M. C., Cyrk­laff, M., Funaya, C., & Frischknecht, F. (2023). Micro­tubule inner pro­teins of Plas­mod­i­um are essen­tial for trans­mis­sion of malar­ia par­a­sites. BioRx­iv, 2023.10.19.562943. DOI: 10.1101/2023.10.19.562943 (accept­ed at PNAS)
  • Hentzschel, F., Gib­bins, M. P., Atti­pa, C., Beral­di, D., Mox­on, C. A., Otto, T. D., & Mar­ti, M. (2022). Host cell mat­u­ra­tion mod­u­lates par­a­site inva­sion and sex­u­al dif­fer­en­ti­a­tion in Plas­mod­i­um berghei. Sci Adv, 8(17), 7348. DOI: 10.1126/SCIADV.ABM7348
  • Hentzschel, F., Mitess­er, V., Frasch­ka, S., Krzikalla, D., Car­ril­lo, E., Berk­hout B., Bárt­fai R., Mueller, A.-K., & Grimm, D. (2020) Gene knock­down in malar­ia par­a­sites via non-canon­i­cal RNAi. NAR, 48(1), e2. DOI: 10.1093/nar/gkz927
  • Hentzschel, F.*, Ham­mer­schmidt-Kam­per, C.*, Börn­er, K.*, Heiss, K.*, (…), Mueller, A‑K. M., Grimm, D. (2014) AAV8-medi­at­ed in vivo over­ex­pres­sion of miR-155 enhances the pro­tec­tive capac­i­ty of genet­i­cal­ly-atten­u­at­ed malar­i­al par­a­sites. Mol. Ther., 22(12), 2130–2141. DOI: 10.1038/mt.2014.172

Preprints

  • Hentzschel, F., Jew­an­s­ki, D.*, Sokolows­ki, Y.*, Agar­w­al, P., Kraeft, A., Hilden­brand, K., Dorner, L. P., Singer, M., Frischknecht, F., & Mar­ti, M. (2023). A non-canon­i­cal Arp2/3 com­plex is essen­tial for Plas­mod­i­um DNA seg­re­ga­tion and trans­mis­sion of malar­ia. BioRx­iv, 2023.10.25.563799. DOI: 10.1101/2023.10.25.563799

Reviews

  • Hentzschel, F., & Frischknecht, F. (2022). Still enig­mat­ic: Plas­mod­i­um oocysts 125 years after their dis­cov­ery. Trends in Par­a­sitol­ogy, 38(8), 610–613. DOI: 10.1016/J.PT.2022.05.013 (Review)
  • Venu­gopal, K., Hentzschel, F., Valk­iū­nas, G., Mar­ti, M. (2020) Plas­mod­i­um asex­u­al growth and sex­u­al devel­op­ment in the haematopoi­et­ic niche of the host. Nat Rev Micro, 18(3), 177–189. DOI: 10.1038/s41579-019‑0306‑2 (Review)
  • Ngotho P., Soares AB., Hentzschel F., Achcar F., Bertuc­ci­ni L., Mar­ti M. (2019) Revis­it­ing game­to­cyte biol­o­gy in malar­ia par­a­sites. FEMS Micro­bi­ol Rev., 43(4), 401–414. DOI: 10.1093/femsre/fuz010 (Review)