Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers find genes connected to seasonal reproductive clock in hamsters

03.12.2002


Researchers at Ohio State University have identified three genes that are involved in the seasonal clock that determines when hamsters reproduce.



While researchers have learned a lot about reproductive clocks in some animals, this study is unique in helping uncover at least part of the genetic basis for determining how the reproductive system shuts off in the fall and restarts in time for spring.

“This study offers some of the first insights into how changes in gene expression are associated with a seasonal clock,” said Brian Prendergast, co-author of the study and a post-doctoral fellow in psychology at Ohio State University.


The study was published online last month and will appear in the Dec. 10 issue of the Proceedings of the National Academy of Science.

The researchers found that the three genes – transthyretin, T4-binding globulin, and albumin – were turned on or off as part of an internal clock in hamsters. These genes help regulate levels of thyroid hormones in the hypothalamus, which is involved in controlling the hamsters’ reproductive cycle.

Hamster reproductive cycles are tied to day length and the amount of daylight they are exposed to during part of the year, Prendergast said. But there’s an interesting catch.

As daylight shortens in the late fall and early winter, the reproductive organs of the hamsters respond by shutting down. In the male hamsters used in this study, the testes regress as daylight shortens. However, the reproductive system begins to turn back on in mid-winter – long before daylight starts to lengthen. The reason why this has to happen is simple: it takes one to two months for the reproductive system to redevelop and if the hamsters had to wait for the lengthening days of spring to start the process of regrowth, it would be too late.

“The short days of winter triggers a timer that shuts off the reproductive cycle,” Prendergast said. “But the timer ends in mid-winter and tells the brain to stop responding to the short days. That’s when the reproductive cycle starts again.”

The researchers found part of the genetic basis for why the reproductive system is able to turn back on in the middle of winter.

In their experiments, the researchers had three groups of hamsters. One group was kept in long days – such as they would have during the summer when they are reproducing – for the whole 32-week experiment. Others were kept in short days during the whole experiment. The third group was kept in long days for 20 weeks, then moved to short days for the final 12 weeks.

The researchers were interested to see what was happening in a part of the brain – called the hypothalamus – that plays an important role in controlling reproduction in hamsters.

After the 32 weeks, the researchers sacrificed the hamsters to see which genes were active in the hypothalamus and which were not, and whether it differed depending on what season the hamsters were kept in.

The results showed that the three genes were being expressed – in other words, they were turned on – in the hamsters that were kept constantly in short days or in long days. These genes produce proteins that help the hypothalamus take in thyroid hormones involved in the regulation of reproduction. In other words, the animals in both long and short days had high levels of thyroid hormones in the brain and therefore were able to respond to changes in day length.

That’s because hamsters need these thyroid hormones both when they are breeding and when the reproduction system shuts down in the winter. Prendergast explained that a different process – separate from the thyroid hormones examined in this study – seemed to be involved in shutting the reproductive system down for the winter.

But the researchers found that the hamsters also need thyroid hormones in the hypothalamus to keep the reproductive system shut down during the winter. If the hypothalamus does not continue to get these hormones, the reproductive system beings to automatically re-grow. So when mid-winter comes the internal clock of the hamsters stops these thyroid hormones from entering the hypothalamus – resulting in the re-growth of the reproductive system in time for the spring breeding season.

The researchers found that the three genes they studied were not being expressed significantly (in other words, they were turned off) in the hamsters who had been housed in short days for 32 weeks – the equivalent of normal hamsters in mid- to late winter. This means the hypothalamus in the hamsters would not be taking in thyroid hormones and their reproductive systems would begin to turn back on.

“These hamsters had lost their ability to respond to the signals of short days. This means that levels of thyroid hormones will drop in the hypothalamus and initiate the recovery of the reproductive system in mid-winter,” he said.

Overall, the studies show how the genes transthyretin, T4-binding globulin, and albumin allow the brain to regulate the levels of thyroid hormones in the hypothalamus, Prendergast said. This in turn regulates how the hamsters’ reproductive systems respond to changing seasons throughout the year.

“The availability of thyroid hormones influences the seasonal timekeeping mechanism,” he said.

Prendergast conducted the study with Bedrich Mosinger, a researcher at Ohio State’s Neurobiotechnology Center; Pappachan Kollattukudy, director of the Neurobiotechnology Center and professor of biochemistry; and Randy Nelson, professor of psychology.


Contact: Contact: Brian Prendergast, (614) 538-9540;
Brianp@psy.ohio-state.edu

Randy Nelson, (614) 247-6408; Rnelson@osu.edu

Brian Prendergast | EurekAlert!
Further information:
http://www.osu.edu/researchnews/archive/geneseas.htm
http://www.acs.ohio-state.edu/units/research/
http://www.psy.ohio-state.edu/nelson/Brian.htm

More articles from Life Sciences:

nachricht A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>