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What do we work with in our laboratory? We work with early stages of Xenopus frog embryos. 🐸

Why frogs? As you may have noticed in nature, frog embryos are generally relatively large and develop outside the mother’s body, making them excellent for observation under a microscope. 🔬

Why Xenopus and not another frog? Xenopus was used as the first reliable test for fertility in humans. It was called the Hogben test, named after the British scientist Lancelot Hogben, and was used in American and English hospitals from the 1930s until World War II. After these tests were replaced by biochemical strips, Xenopus frogs became the subject of study in hospitals and scientific centers, becoming the most commonly used amphibian or frog models in biomedical research. 🧪

What do we study in Xenopus frog embryos? We study the formation of the neural tube and the migration of cells in the so-called neural crest. 🧠

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PRINCIPAL INVESTIGATOR

Group leader:             Assist. Prof. Jakub Harnos, Ph.D.    

Office:                        Campus Bohunice, bldg. D36, rm 1S16

E-mail:                        harnos@sci.muni.cz

Telephone:                  +420 549 49 4465

ORCID ID:                  0000-0002-0752-9260

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Scientific autobiography


I dedicated my scientific career to WNT signaling, a set of pathways that play a vital role in multicellular development and diseases when deregulated.  WNT signaling is traditionally divided into the canonical branch, which regulates cell cycle or cell fate by alternating the gene transcription, and the non-canonical branch, which controls cytoskeleton rearrangements.

As a Master and PhD student, I started to study the key WNT signaling component Dishevelled under the supervision of Prof. Vitezslav Bryja in Brno.  In collaboration with Prof. Carsten Hoffman (University of Wurzburg, Germany), in whose lab I spent several months, I developed FRET biosensors to monitor the dynamics of Dishevelled structural conformations and analyzed their role in WNT signal transduction (published in Nature Communication, 2019).  

Postdoctoral training with Prof. Sergei Sokol in New York in the years 2018-2020 extended my knowledge in developmental biology, vertebrate embryology, and the frog Xenopus model system, and helped me to master expertise in polarity signaling.  I studied polarity proteins during neurulation in Xenopus embryos during this stay using proximity-dependent biotinylation. 

After my return to Czechia in 2020 due to the Covid-19 outbreak, I started a new position as an Assistant Professor at Masaryk University.  Besides neurulation, I became fascinated with cell migration and deeply interested in answering the question of how migrating cells obtain energy.  I have established my research group that focuses on identifying new roles of polarity signaling in bioenergetics & neurulation using cell culture systems and Xenopus embryos. 

 

Fellowships, Grants, and Awards

*2024 – 2026: Grant in the Standard/Senior category (#24-10622S), Czech Science Foundation, Czechia

2023: Hemsley Fellowship (#203103), Xenopus course, Cold Spring Harbor Laboratories, NY, USA (declined due to family reasons)

*2022 – 2024: Grant in the Standard/Senior category (#22-06405S), Czech Science Foundation, Czechia

*2022 – 2024: Science & Humanities Award Junior (#MUNI/J/0004/2021), Grant Agency of Masaryk University, Czechia

2020: “Seal of Excellence” in MSCA-IF-2020 (#101028952), European Commission, Brussels

2018 – 2019: “Excellent Results” Grant (#MUNI/E/0533/2018), Grant Agency of Masaryk University, Czechia

2017 – 2017: EMBO Short-term Fellowship (#ASTF 687-2016), University of Wurzburg, Germany

2016 – 2016: Mobility program “Free mover”, University of Wurzburg, Germany

*Current funding

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RESEARCH TOPIC

Polarity refers to spatial differences in shape, structure, and function within a cell.  Almost all cell types exhibit some form of polarity that enables them to carry out specialized functions.  We focus on planar polarity, which refers to the coordinated alignment of cells across the tissue plane.  Planar polarity is currently viewed as a “passive” compass providing cells with a sense of direction. This feature is important during development when a cell needs to know its position within a multicellular organism, and during homeostasis, when a cell needs to know the direction e.g., for its migration.   

Our primary goal is to demonstrate the active role of planar polarity in neural tube formation during vertebrate development.  Neural tube formation is an early developmental event that involves approximately two hundred proteins.  Although the tube formation is described somewhat well, the factor responsible for its initiation is not yet known.  We have gathered evidence that polarity proteins may be the active triggers for initiating neural tube formation.

Our second aim is related to cell migration.  Migration is the directed movement of a cell from one place to another and requires an increased amount of energy.  The produced energy is utilized for the rearrangement of dedicated regions in a migratory cell, thus allowing its physical movement.  However, what initiates the production of the extra energy needed for rearrangements remains a mystery.  Here, we intend to show the active role of planar polarity as an energy trigger for cell migration.

In short, assigning dynamic behaviors to polarity proteins in Xenopus embryos and tissue culture systems is the core of the research conducted in the Harnos lab.

 

 

LEFT: A developing Xenopus tadpole, whose neural cells have been marked with the green fluorescent protein (GFP). 

 

 

RIGHT: We investigate cellular processes in which proteins can initiate several subsequent events that we can observe using microscopes.

In the picture, there are two cells expressing green fluorescent protein fused to a protein of our interest. The last picture on the right shows that the green fusion protein co-localizes with the red cellular process, suggesting that protein X induces this particular cellular process Y (images were editted in Imaris software v9.8).

Keywords

Planar polarity, neural tube formation, cell migration, bioenergetics, tissue culture cells, Xenopus embryos.

 

 

RESEARCH TEAM

  • Alumni
    • Mgr. Marie Sulcova, Ph.D. (2022-2023; currently a postdoc at the University of Stockholm, Sweden)
    • Alba Hernández Ramos (2022-2023, Erasmus student, a practical 10-month stay, University of Salamanca, Spain)
    • Mgr. Eliska Kohoutkova (2022-2023; currently a Ph.D. student at Vienna Biocenter, Austria)
    • Cristina González Cuevas (2022, Erasmus student, a practical 3-month stay, University UFV in Madrid, Spain)
    • Belén Escalona Pulido (2022, Erasmus student, a practical 4-month stay, University UFV in Madrid, Spain)
    • Miriam Sánchez Calvo (2022, Erasmus student, a practical 4-month stay, University UFV in Madrid, Spain)

 

COLLABORATIONS

  • Germany:      

– Prof. Carsten Hoffmann (Maximilians University,Wurzburg/University Hospital, Jena)

– Prof. Alexandra Schambony (Max Planck Institute for Science of Light, Erlangen)

Previous collaborations led to my first-authored Nat Comm 2019 manuscript about Dishevelled

 

 

  • USA:  

– Prof. Sergei Sokol (Icahn School of Medicine at Mount Sinai, New York):

Active collaboration on neurulation and PCP signaling in developing Xenopus embryos

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– Dr. Giovanna Collu (Icahn School of Medicine at Mount Sinai, New York):

Active collaboration in the context of WNT-Notch crosstalk

 

 

  • Czechia:        

– Assoc. Prof. Lukas Trantirek (CEITEC, Brno): 

The previous collaboration led to my first-authored JBC 2018 manuscript about Axin

Active collaboration on DNA quadruplex structures analyzed by NMR techniques in Xenopus oocytes

 

 

– Prof. Zbynek Zdrahal (CEITEC, Brno): 

The previous collaboration led to my first-authored Nat Comm 2019 manuscript about Dishevelled

Active collaboration on proximity biotinylation approaches using Mass Spectrometry

 

 

– Dr. Jan Masek (Charles University, Prague):

            Active collaboration on cilia formation in Xenopus in the context of WNT-Notch crosstalk

 

 

We are actively recruiting talent of all levels, from Bachelor’s and Master’s students to PhDs and Postdocs. 

Write an email with your CV and a short motivation letter to harnos@sci.muni.cz

 

 


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