Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

“Bouncer”, the gate-keeper of the egg, controls sperm entry

07.09.2018

A newly found protein restricts fertilisation between species

Fertilisation is a pivotal process underlying all sexual reproduction, yet its molecular mechanisms are poorly understood. Scientists at the Research Institute of Molecular Pathology (IMP) in Vienna have now identified a protein they called “Bouncer” as a crucial factor for sperm entry into the egg. Remarkably, this protein is sufficient to allow fertilisation between different species. The study is published in the current issue of the journal Science.


“Adult medaka (Oryzias latipes, top) and zebrafish (Danio rerio, bottom)”.

IMP


Zebrafish (Danio rerio) and medaka (Oryzias latipes) embryos shortly after fertilization.

IMP

Fertilisation, the fusion of egg and sperm to form the single-cell zygote, is highly efficient yet species-restricted. This strategy ensures reproductive success and the survival of distinct species. However, it is far from understood how these seemingly contradictory requirements are met at the molecular level. Over the years, researchers have identified numerous proteins in vertebrates that seemed to play an essential role in fertilisation. However, the majority of them turned out to be dispensable.

IMP Group Leader Andrea Pauli and her team have turned to zebrafish to identify factors required for fertilisation. Of all the short, uncharacterised genes the group identified (Pauli et al., 2014), one clearly stood out: it was highly expressed in the fish egg, and similar genes were present in other vertebrates. Given its crucial function in ensuring that only the correct sperm can enter the egg, the authors named the gene ‘bouncer’ in analogy to the security guard at a bar.

Experiments with zebrafish revealed that Bouncer enables sperm to enter the egg by promoting stable egg-sperm binding. Thus, its function is essential for successful reproduction in zebrafish. Because the Bouncer homologs differ substantially among fish species, the researchers speculated that the protein might play a role in ensuring that only sperm of the correct species can enter the egg, thus preventing crossbreeding. To test this hypothesis, they constructed transgenic zebrafish that expressed the Bouncer homolog from the Japanese rice fish medaka.

Under natural conditions, the medaka cannot cross-hybridise with zebrafish. After all, the evolutionary paths of the two species diverged over 200 million years ago, long before the ancestral lines of humans and whales split up. Remarkably, when female zebrafish expressed the medaka Bouncer protein, their eggs could be fertilised by medaka sperm. The resulting embryos were medaka-zebrafish hybrids, meaning they contained DNA from both species. These hybrid embryos started to develop and underwent several rounds of cell division and gastrulation movements before dying, usually within two days.

These results demonstrate that Bouncer is necessary and sufficient for mediating species-specific fertilisation in fish. Like a security guard, the protein is decisive for allowing sperm of the same species to enter the egg, while keeping foreign sperm out – hence the chosen name. “Our study is the first report of a protein in any organism allowing entry of another species’ sperm”, says Sarah Herberg, a VBC PhD Student at the IMP and first author of the publication. She also points out that the results suggest the existence of a direct species-specific interaction partner of Bouncer on sperm. The identification of this interaction partner will be the next step towards understanding the mechanism behind Bouncer’s function.

Intriguingly, Bouncer also has a close homolog in humans, a gene called SPACA4. However, unlike in fish and other externally fertilising species such as amphibians, where Bouncer is expressed exclusively in the egg, humans and other internally fertilising species express SPACA4 in the male reproductive system. Whether the mammalian version of Bouncer has a similarly important role in fertilisation will be an exciting line of future investigation to uncover the molecular machinery that mediates this fundamental yet so poorly understood process.

About the IMP
The Research Institute of Molecular Pathology (IMP) in Vienna pursues world-class research in basic molecular biology. It is located at the Vienna BioCenter and largely sponsored by Boehringer Ingelheim. With over 200 scientists from 40 countries, the IMP is committed to scientific discovery of fundamental molecular and cellular mechanisms underlying complex biological phenomena. www.imp.ac.at

About Vienna BioCenter
Vienna BioCenter is a leading life sciences hub in Europe, offering an extraordinary combination of research, business and education in a single location. About 1,700 employees, 86 research groups, 20 biotech companies, 1,300 students and scientists from 70 countries create a highly dynamic and stimulating environment. www.viennabiocenter.org

Wissenschaftliche Ansprechpartner:

Dr. Andrea Pauli, IMP Group Leader
andrea.pauli@imp.ac.at

Originalpublikation:

Sarah Herberg, Krista R. Gert, Alexander Schleiffer, and Andrea Pauli: The Ly6/uPAR protein Bouncer is necessary and sufficient for species-specific fertilization. Science, 7 Sep 2018.

Weitere Informationen:

http://www.imp.ac.at/supplements

Dr. Heidemarie Hurtl | idw - Informationsdienst Wissenschaft

Further reports about: Molekulare Pathologie Pathology Zebrafish fertilisation security guard sperm

More articles from Life Sciences:

nachricht Russian scientists show changes in the erythrocyte nanostructure under stress
22.02.2019 | Lobachevsky University

nachricht How the intestinal fungus Candida albicans shapes our immune system
22.02.2019 | Exzellenzcluster Präzisionsmedizin für chronische Entzündungserkrankungen

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: (Re)solving the jet/cocoon riddle of a gravitational wave event

An international research team including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has combined radio telescopes from five continents to prove the existence of a narrow stream of material, a so-called jet, emerging from the only gravitational wave event involving two neutron stars observed so far. With its high sensitivity and excellent performance, the 100-m radio telescope in Effelsberg played an important role in the observations.

In August 2017, two neutron stars were observed colliding, producing gravitational waves that were detected by the American LIGO and European Virgo detectors....

Im Focus: Light from a roll – hybrid OLED creates innovative and functional luminous surfaces

Up to now, OLEDs have been used exclusively as a novel lighting technology for use in luminaires and lamps. However, flexible organic technology can offer much more: as an active lighting surface, it can be combined with a wide variety of materials, not just to modify but to revolutionize the functionality and design of countless existing products. To exemplify this, the Fraunhofer FEP together with the company EMDE development of light GmbH will be presenting hybrid flexible OLEDs integrated into textile designs within the EU-funded project PI-SCALE for the first time at LOPEC (March 19-21, 2019 in Munich, Germany) as examples of some of the many possible applications.

The Fraunhofer FEP, a provider of research and development services in the field of organic electronics, has long been involved in the development of...

Im Focus: Regensburg physicists watch electron transfer in a single molecule

For the first time, an international team of scientists based in Regensburg, Germany, has recorded the orbitals of single molecules in different charge states in a novel type of microscopy. The research findings are published under the title “Mapping orbital changes upon electron transfer with tunneling microscopy on insulators” in the prestigious journal “Nature”.

The building blocks of matter surrounding us are atoms and molecules. The properties of that matter, however, are often not set by these building blocks...

Im Focus: University of Konstanz gains new insights into the recent development of the human immune system

Scientists at the University of Konstanz identify fierce competition between the human immune system and bacterial pathogens

Cell biologists from the University of Konstanz shed light on a recent evolutionary process in the human immune system and publish their findings in the...

Im Focus: Transformation through Light

Laser physicists have taken snapshots of carbon molecules C₆₀ showing how they transform in intense infrared light

When carbon molecules C₆₀ are exposed to an intense infrared light, they change their ball-like structure to a more elongated version. This has now been...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Global Legal Hackathon at HAW Hamburg

11.02.2019 | Event News

The world of quantum chemistry meets in Heidelberg

30.01.2019 | Event News

Our digital society in 2040

16.01.2019 | Event News

 
Latest News

JILA researchers make coldest quantum gas of molecules

22.02.2019 | Physics and Astronomy

Understanding high efficiency of deep ultraviolet LEDs

22.02.2019 | Materials Sciences

Russian scientists show changes in the erythrocyte nanostructure under stress

22.02.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>