Thursday, 26 April 2012


Hey guys,


I Google’d some scientific discoveries made in the last few months and I came across an article published on Science Daily. It features a discovery related to how sperm movement works in species that reproduce sexually. This can have genetic implications in terms of the genetic content passed on to offspring. While perhaps a more modest discovery than a silver bullet for cancer and not strictly related to genetics, this new knowledge helps us better understand the means through which genetic information is passed on to successive generations. I figured it’d be somewhat relevant.


For those of you who can’t be bothered, you’re in luck, as I just so happen to be giving an overview of what we already know about sperm movement, what was discovered, and how it could benefit Science. All you have to do is scroll down below J

Why should we pay attention to discoveries in this field?
      Spermatozoa (Sperm Cells) are the male type of haploid cell, the other being Ova (Egg Cells). Fusion of haploid gametes is of importance to sexually reproductive forms of life. Has special relevance to humans.

      Understanding our own reproductive processes helps us to better understand our own species.

      Knowing how biochemical factors influence sperms ability to move and track the egg can further this understanding. This has implications on our ability to track the transaction of genetic information.
What do we know so far? Quite a bit:
      Processes such as Spermatogenesis and Oogenesis have been studied at length. We also know there is an intense competition between millions of sperm to be the first to fertilize the ova. Fertilization of the egg and subsequent embryonic development are also understood.

      We know that sperm take in Fructose produced by various male glands, and use it to generate ATP to power the axenome reaction, which causes tail movement.

Structure of a sperm cell, taken from D. W. Fawcett, The Cell, Ch 14, pg 605, W. B. Saunders, 1981.
 
          

                         
Structure of flagella, taken from D. W. Fawcett, The Cell, Ch 14, pg 608, W. B. Saunders, 1981.
 
      



Enhanced structure of flagella, taken from D. W. Fawcett, The Cell, Ch 14, pg 610, W. B. Saunders, 1981.
 
       


Structure of axenome, taken from Wikipedia: http://en.wikipedia.org/wiki/Axoneme, Published: May 2009, Last updated; 21/10/11, Accessed: 19/03/12
 
           


      We know theres a type of Progesterone signaling between Ova and Sperm called chemotaxis (like a GPS telling the sperm where to go). Progesterone is released by cumulus cells, which surround the ova.
Chemical structure of Progesterone, taken from AddexBio Technologies: http://www.addexbio.com/productdetail?pid=229, Published: 2011, Last Updated: Unknown, Accessed: 15/03/12.
 
                   



      Calcium ions have been found to be responsible for regulating the magnitude of tail whip and direction.
      Researchers have found Progesterone to open Calcium ion (CatSper) channels on the principal piece of mammalian flagella at receptor sites (Max-Planck-Gesellschaft 2011), which regulate the flow of Ca ions into sperm cell. Mutations in the genes coding for CatSper channels are closely tied to infertility in males (Nature, 2011).

      The coupling of progesterone and Calcium ion thus determines sperm movement.

Depicts progesterone action on CatSper channels. Taken from the C.A.E.S.A.R institute, http://www.caesar.de/495.html?&L=2,  Published 16/03/11, accessed 13/03/12.
 




What knowledge about sperm movement has escaped us?
      Up until recently, no one has really known how Sperm respond to Progesterone at different levels, despite knowing it plays a major role.

      For a long time scientists have thought sperm cells to set the beat of their flagella and their direction proportional to Calcium ion influx as a consequence of Progesterone action on CatSper channels.

That’s exactly where this new discovery comes in:
      A study recently done in collaboration between the Max Planck and C.A.E.S.A.R. (Center for Advanced European Studies and Research) Institutes has delivered some surprising findings.

      Researchers found that sperm pretty much react to changes in calcium ion concentration, and not the absolute concentration as previously thought (Science Daily, 2012).

      How did they figure this out? The researchers found the sperm of sea urchin and three invertebrate species to have maintained paths regardless of exposures to a variety of set Calcium ion concentration levels. It was only when the concentration of Calcium ion was altered in real time that each species of sperm changed movement (Science Daily, 2012)

      The rate of calcium increase was shown to determine the degree to which the sperm turned, while path changed based on the gradient of calcium decline (Science Daily, 2012). While the specimens were not human, the responses across the four different test species present the likelihood that human sperm may exhibit similar behaviour.

How could this discovery contribute to Science?
      Other cellular processes can be investigated for similar chemical responses, could potentially cause revision of present models of some biochemical reactions.

      Future studies could explore CatSper channel response in humans, which could subsequently lead to development of new drugs to trigger openings in non - responsive channels (providing they aren’t structurally flawed).

      New contraceptive drugs could be pioneered to replace hormonal drugs and their inconvenient side effects, such as organic compounds that the body can easily deal with.

Reference List:

AddexBio Technologies, published: 2011, Last Updated: Unknown, Accessed: 15/03/12, from: http://www.addexbio.com/productdetail?pid=229

C.A.E.S.A.R institute, published 16/03/11, accessed 13/03/12, from: http://www.caesar.de/495.html?&L=2,

Clapham, D.E, 2011: ‘A novel gene required for male fertility and functional CATSPER channel formation in spermatozoa’, Nature, issue 153, viewed: 12/03/12, from: http://www.nature.com/ncomms/journal/v2/n1/full/ncomms1153.html

Fawcett, D.W., 1981: ‘The Cell’, W. B. Saunders, Philadelphia.

Max-Planck-Gesellschaft, 2011:’Female sex hormone controls human sperm’, Max-Planck-Gesellschaft, viewed: 15/03/12, from:

Science Daily, 2012:‘Sperm can do 'calculus' to calculate calcium dynamics and react accordingly.’ Science Daily, viewed: 15/03/12, from: http://www.sciencedaily.com­ /releases/2012/03/120307094421.htm

Wikipedia, published: May 2009, Last updated; 21/10/11, Accessed: 19/03/12, from: http://en.wikipedia.org/wiki/Axoneme





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