Understanding how elephants use their trunk

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The elephant proboscis (trunk) exhibits an extraordinary kinematic versatility as it can manipulate a single blade of grass but also carry loads up to 270 kilograms. Using motion-capture technologies developed for the movie industry, Pr Milinkovitch‘s group demonstrates that the complex behaviours of the elephant trunk emerge from the combination of a finite set of basic movements such as the propagation of an inward curvature and the formation of pseudo-joints. In addition, the Swiss team demonstrates that the elephant trunk velocity obeys a mathematical law observed in human hand drawing movements.

The article was published in the journal Current Biology, on August 23rd 2021.

Check out the UNIGE press release.

Induction of a chromatin boundary in vivo upon insertion of a TAD border

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Proposed mechanistic model of Btg1 expression changes.

In mammals, the genome is spatially segmented in three-dimensional domains called TADs, which are separated by more or less strict boundaries. This organization seems to be important to properly implement gene regulation through the action of long-distance enhancers. Nevertheless, genome-wide studies on this relationship are not easy to resolve, and the relevance of each TAD boundary often needs to be taken on a case-by-case basis.

Andréa Willemin and Lucille Lopez-Delisle, from the laboratories of Denis Duboule, showed that a TAD boundary, when randomly inserted in a different chromosome, retained its ability to reshape the chromatin landscape and disturb gene expression.

This work co-supervised by Eddie Rodríguez-Carballo, led Andréa Willemin to obtain the Prix Arditi for the best Master Thesis in Biology in 2020.

The article was published in PLoS Genetics on July 22nd, 2021.

Chromosomes separation under focus

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Representation of the separase-secretin and separase-CCC complexes, with artistic representation of the DNA in the background.

During cell division, chromosomes are duplicated and separated so that one copy of each chromosome is inherited by each of the two emerging daughter cells. Correct distribution of chromosomes requires high accuracy and defects in this process can cause aberrant distribution of chromosomes and facilitate cancer development. By analyzing the structure of the protein responsible for chromosome separation, an international team, led by Andreas Boland from the department of molecular biology, has shed light on the mechanisms controlling this essential player in cell division.

The article was published in the journal Nature, on July 21st 2021.

Check out the UNIGE press release.

DNA reveals the evolutionary history of museum specimens

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Museum specimens held in natural history collections around the world represent a wealth of underutilized genetic information due to the poor state of preservation of the DNA, which often makes it difficult to sequence. An international team, including Nadir Alvarez from the GenEv department and the Museum of Natural History of the City of Geneva, has optimized a method developed for analyzing ancient DNA to identify the relationships between species on a deep evolutionary scale.

The article was published in the journal Genome Biology and Evolution.

Check out the UNIGE press release.

Inherited memories of a chromosomal site

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Most biological traits are inherited through genes, but there are exceptions to this rule. Florian Steiner‘s and Monica Gotta‘s groups have been investigating the location of centromeres – specific sites on chromosomes that are essential for cell division. They found that in the small worm Caenorhabiditis elegans, the transmission of the correct location of these sites to the offspring is not mediated by genes, but by an epigenetic memory mechanism.

The article was published in the journal PLOS Biology, on July 6th 2021.
Check out the UNIGE press release and Reinier Prosée’s short animated video.

How diet controls RNA maturation

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Particularly sensitive to chemical modifications, messenger RNAs (mRNAs) are molecules responsible for transmitting the information encoded in our genome, allowing for the synthesis of proteins, which are necessary for the functioning of our cells. Two teams from the department of molecular biology, Ramesh Pillai and Florian Steiner ‘s labs, have focused on a specific type of chemical modification – called methylation – of mRNA molecules in the small worm Caenorhabditis elegans. They found that methylation on a particular sequence of an mRNA leads to its degradation and that this control mechanism depends on the worm’s diet.

The article was published in Cell, on April 29th 2021.

Check the UNIGE press release.

3D numerical simulations of the ocellated lizard skin colour patterning

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The last study from the Milinkovitch’s lab uses reaction-diffusion (RD) numerical simulations in three-dimension on realistic lizard skin geometries and demonstrates that skin thickness variation on its own is sufficient to cause scale-by-scale coloration and cellular automaton dynamics during RD patterning. In addition, Anamarija Fofonjka and Michel Milinkovitch show that this phenomenon is robust to RD model variation. Finally, they show that animal growth affects the scale-colour flipping dynamics.

The article was published in the journal Nature Communications, on April 23rd 2021.

How the fly selects its reproductive male

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Even a well-characterized genome, such as that of the Drosophila the so-called fruit fly, still holds surprises. Researchers from the Department of Genetics and Evolution, in collaboration with Cornell University (USA) and the University of Groningen (Netherlands), have discovered an RNA coding for a micro-peptide – a very small protein – that plays a crucial role in the competition between spermatozoa from different males with which the female mates. In addition to shedding new light on this biological mechanism, Robert Maeda and collaborators’ work highlights the importance of small peptides, a class of proteins that is now emerging as a key player in complex biological processes.

The article was published in the journal Proceedings of the National Academy of Sciences (PNAS), on April 5th 2021.

UNIGE Press release