Science Square

  • Issue 121 / January - February 2018



    Scientists have cloned monkeys; are humans next?

    The Fountain

    Liu, Z. et al. Cloning of macaque monkeys by somatic cell nuclear transfer. Cell, January 2018.


    After two decades of failures, scientists have finally cloned monkeys using somatic cell nuclear transfer (SCNT), the same method that was used for the first animal clone, Dolly the sheep, over 20 years ago. Long-tailed macaques Zhong Zhong and Hua Hua were born in early December at a laboratory in China. SCNT is a type of cloning that involves taking the nucleus from any cell in the adult animal to be cloned and injecting it into the cell of a fertilized egg, whose nucleus has been removed. Since Dolly, 23 other species have also been cloned using SCNT, including cows, horses, cats, and pigs.  However, transitioning from cloning sheep to cloning primates proved far more difficult than expected. Scientists removed the DNA-containing nucleus from monkey eggs and replaced it with DNA from the monkey fetus. The newly reconstituted eggs grew, divided, and finally differentiated into an early embryo, which was then placed into female monkeys to grow until birth. The whole process is extremely inefficient, as it took 127 eggs to get the two babies. While the researchers are optimistic that the ability to have genetically identical monkeys will allow unprecedented insights into human diseases, these experiments prompted concerns that the technical barrier of cloning primate species and humans is now broken.


    An unexpected culprit behind climate change


    Rysgaard S et al. High geothermal heat flux in close proximity to the Northeast Greenland Ice Stream. Scientific Reports, January 2018.


    Greenland is a critical component of the global climate system. The ice sheet covering 80% of the island reflects so much of the sun’s energy back into space that it helps keep the Earth cooler. This is known as the “albedo effect.” But Greenland is particularly vulnerable to climate change, as Arctic air temperatures are currently rising at twice the average global rate. The Greenland ice sheet is up to three kilometers thick; if it melted, sea levels would rise by seven meters. The current rate of melting is adding about 1 millimeter a year to the average global sea level. A new study has revealed yet another force expediting the melting of glaciers. Researchers showed, for the first time, that the deep bottom water of the North-eastern Greenland fjords is being warmed up by heat gradually lost from the Earth's interior. This heat loss triggers the sliding of glaciers from the ice sheet towards the sea. This source of heat, also called the geothermal heat flux, is found all over the planet and dates back to Earth's formation. The warming and melting from below the ice sheets lubricates the interface between the ice and the ground, resulting in a much faster ice flow. ┬áThe findings from the latest study are expected to improve the models of ice sheet dynamics, allowing better predictions of the stability of the Greenland ice sheet, its melting, and the resulting global water rise.


     


     


    The powerhouses of our cells run at a sizzling 50┬░C


    Chr├ętien D. et al. Mitochondria are physiologically maintained at close to 50 ┬░C. PLOS Biology, January 2018.


    Our body temperature runs between 35 to 38 ┬░C, at an average of 37.5 ┬░C. The heat needed to maintain this temperature comes from tiny subcellular structures called mitochondria. A new study presents surprising evidence that mitochondria are optimized to run more than 10┬░C hotter than the body's average temperature. There are tens or hundreds of mitochondria in each cell and their job is to combust nutrients, producing energy and heat at the last stage of food consumption. 40% of the energy released from mitochondria is captured in the form of a chemical compound, ATP, which is used to drive functions of the body such as heartbeats, brain activity, and muscle contractions; the remaining 60% is dissipated as heat. To analyze the internal dynamics of mitochondria, researchers grew human kidney cells and skin cells in tissue cultures at 38 ┬░C, with heat-sensing fluorescent dyes inserted into the cells. When the mitochondria became active, the level of fluorescent signal was rapidly changed to indicate a rise of 10┬░C within the mitochondria. Scientists suggest that mitochondria seem to operate much like radiators in a poorly insulated room, running at a much higher temperature than their surroundings. They also showed that several human mitochondrial enzymes operate at an optimum temperature close to 50┬░C, supporting the scientist’s interpretation of the molecular thermometer data. Researchers now are very interested in answering whether there are correlated temperature fluctuations in health conditions that are caused by mitochondrial dysfunction, such as neurodegenerative diseases and aging.

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