Your Nomadic Brain
When discussing matters of variability between the behaviour and development of individuals there are two fundamental aspects that come into play; inherited genes and environmental factors. At least that was the belief until Barbara McClintock discovered that, what she termed “controlling elements”, could move along the genome and alter the genotypic and phenotypic characteristics of plants hence altering their development (N. C. Comfort August 2001). This research led on to the work Professor Fred Gage and Professor Alysson Muotri undertook, in which they found ‘Jumping genes’, the same concept as McClintocks, also occurred within mammals. The so called nomadic characteristics of these genes was believed to occur mainly in germ cells or in the early development of somatic cells but has, through Gage and Muotoris’ research, shown a high prevalence in brain cells of the hippocampus, regardless of age (F. H. Gage & A. R. Muotri 14/02/12). ‘Jumping genes’ are also referred to as transposons or retrotransposons and make up the transposable genetic elements within an organisms DNA (Campbell N. 2009).
Jumping genes are segments of our DNA that are copied from one area of the genome to another in two ways. The first of these is the “Copy-and-paste” method in which both strands of a transposon gene are copied and inserted somewhere else along the genome (Campbell N. 2009). The second is termed the retrotransposon method and is more complex. In Retrotransposons a copy of the DNA sequence is transcribed into RNA and then transported into the cytoplasm. From here the RNA undergoes reverse transcriptase, essentially making DNA from RNA. This new double stranded section of DNA re-enters the nucleus and is inserted along the genome.
The ‘jumping gene’ that was of most interest to Professors Gage and Muotri is termed the Long Interspersed Element 1(L1). L1 is unique among human mobile elements as it has encoded within its structure “…machinery for spreading copies of itself far and wide in the cellular genome”( F. H. Gage & A. R. Muotri 14/02/12). The insertion of a ‘jumping gene’ along the genome can have various consequences; it can activate surrounding genes resulting in the creation of a new protein, the increased production of an existing protein or the decreased production of a protein. This results in variability between the cells present within the brain.
The opportunities that this research gives rise to include better understanding of brain physiology which in turn gives rise to a better understanding of psychiatric diseases and brain disorders e.g. autism. With an in depth knowledge of brain tissue genetics, better more efficient methods of diagnosis, treatment and prevention can be developed (F. H. Gage & A. R. Muotri 14/02/12). Essentially understanding the controlling organ of the body would allow for a greater understanding of how the mind and body are interdigitated. Although Gage and Muotri were not the first scientists to discover ‘jumping genes’ they have contributed to our knowledge of them greatly and it is with this knowledge that we are a step closer to understanding the complex and evolving system that is our brain.
Campbell N. (2009) Biology Pearson Education Australia edition 8 pg 437
F. H. Gage & A. R. Muotri (14 February 2012) What Makes Each Brain Unique Scientific American vol 306 pg 26-31 doi:10.1038/scientificamerican0312-26
N. C. Comfort (August 2001) From controlling elements to transposons: Barbara McClintock and the Nobel Prize Trends in Genetics vol 17 no. 8 pg 475-478