Sunday, 20 May 2012

Ciliopathies


By Blake Kelly 42934011

The ever-evolving field of genetic research delves into a multitude of interesting biological areas. One of these areas is the recently uncovered branch of developmental genetic disorders known as Ciliopathies. Ciliopathies, as mentioned, are genetic disorders, which are dictated by the behaviour and growth of a relatively novel organelle known as the primary Cilium.

Primary Cilia (Electron Microscope Image)
The primary cilium is a single cellular protrusion extending from the exterior of the cell. Its role in cellular processes was unknown until the last decade whereby research has boomed. Although discovered originally over a century ago, it was passed aside simply as a futile growth on the cell with no actual use, however, this is not the case. This structure is integral to correct cell development and embryonic growth. Without this organelle, eukaryotic organisms would cease to exist.

Basically, the role of this organelle is to relay messages from its environment back to the cell via a process of moving particular proteins along various signaling pathways. Certain genes found in the cell code for these particular proteins. Based on the environment and situation the cilium detects, the genes get to work producing certain concentrations of these proteins to which the cilia then moves up and down the organelle and back to the cell. In doing so, the organelle can regulate the position and concentration of the proteins produced which, in turn, assists to differentiate the cells in their embryonic stage.

As you can see, this is an important role when it comes to tissue and organ development. Now, imagine if one or more of the genes, which code for the proteins involved, was defective. The entire system would be altered and this is how ciliopathies are caused. An example of a gene mutation in this organelle is the common defect in the intraflagellar transport gene 88, which codes for a particular protein required to pass a message to the cell. As a result of this proteins absence, the organism develops malformed cilia in its kidney tubules and will suffer from polycystic kidney disease as well as many other defects throughout the body. The biggest issue with ciliopathies is the vast collection of effects across numerous organ systems they have on the organism. Common defects include polycystic kidney disease, cleft palate, polydactyly (extra digits) and numerous other craniofacial and neural disorders.

Hedgehog Signalling Pathway Movement
As this is such a new and fresh branch of research, little is known currently about the causes of these defective genes however, scientists are working on identifying the genes involved in these disorders and mapping the pathways in which the proteins move along in a healthy functioning cell. With this knowledge they hope to be able to identify at a pre-birth embryonic stage whether the organism will suffer from these diseases and hopefully produce treatment strategies to deal with these disorders.

Phenotypic Characteristics Of Mutant versus Wild-type
At this stage however, it seems research is limited ethically as embryonic investigations pose a controversial dilemma. Tampering with genes at this early stage of life to some is considered ‘playing god’ and hence has certain barriers in which scientists mustn’t cross. This means that although they will soon be able to identify all the genes and pathways, it seems a treatment for these diseases is still not in the near future.

References

Abou Alaiwi, W, Lo, S, Nauli, S 2009, ‘Primary Cilium: Highly Sophisticated Biological Sensors’, Sensors, Vol 9, 7003-7020. www.mdpi.com/1424-8220/9/9/7003/pdf

Reece, J Meyers, N Urry, L Cain, M Wasserman, S Minorsky, P Jackson, R Cooke, B 2011, Campbell Biology, Pearson, Australia.

Ashe A, Courtney A, Town E, Butterfield N, Cooper A, Ferguson C, Barry R, Olsson F, Liem K, Parton R, Wainwright B, Anderson K, Whitelaw E, Wicking K 2012, ‘Mutations in mouse Ift144 model the craniofacial, limb and rib defects in skeletal ciliopathies’, Human Molecular Genetics, HMG.

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