John Park (wisejsm@yahoo.com)
Wednesday, April 6, 2011
Combining ears and eyes?
In page 172 of Your Inner Fish, Neil Shubin talks about the jellyfish and how they have eyes with genes that are similar to both Pax 2 and Pax 6 which are present in modern ears and eyes respectively. After that, he also mentions that some birth defects affect both the eye and the inner ear of the infant. Give some examples to these defects, and how they affect the eyes and the ears of a baby. Then discuss how these defects relates to the Pax 2 and Pax 6 genes.
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Primitive animals like the stinging box jellyfish don’t have the Pax 6 or Pax 2 genes. They arose before these genes did. However, in the eyes of the jellyfish, “the gene that forms the eyes is…a sort of mosaic that has the structure of both Pax 6 and Pax 2” (172). So, in other words, “the major genes that control our eye and ear correspond to a single gene in more primitive creatures” (172). In the jellyfish Cladonema, this gene is known as Pax-A (Suga). Another type of jellyfish, the Tripedelia, uses the gene, Pax-B. These genes, connecting both the Pax 6 and the Pax 2, help scientists to understand connections seen between the eyes and the ears in humans today. These connections are seen in some birth defects, as Shubin said. One example of a birth defect affecting both the eyes and the ears is Congenital Rubella (German measles). This usually occurs in children when the mother is infected with Rubella. This birth defect can cause problems in the sensory organs like the eyes and the ears. The children born with this disease can suffer from hearing loss or deafness and they can also suffer from cataracts. A cataract is a clouding that occurs in the crystalline lens of the eye or in its envelope and obstructs the passage of light into the eye. The Pax 6 gene produces 2 major proteins: PAX6 and PAX6(5a). Cataracts is a dysfunction in the eye that can be caused by an increase in the PAX6(5a) to PAX6 ratio.
ReplyDeleteSources:
http://www.medic8.com/healthguide/birth-defects/sensory/index.html
http://blogs.discovermagazine.com/notrocketscience/2010/07/27/jellyfish-eye-genes-suggest-a-common-origin-for-animal-eyes/
http://www.ncbi.nlm.nih.gov/pubmed/10954416
Danielle Webb (dwebb456@gmail.com)
This comment has been removed by the author.
ReplyDeleteIn discussing the Pax2 and Pax6 gene and their interactions, besides simply possible defects resulting from the pax2 and pax6 gene, we can further explore the interactions of genes and how they work together for a function in our body.
ReplyDeleteAs of now, research shows that Pax2 and Pax6 gene work to downregulate one another's genes or act as corepressors. Specifically, Pax6 gene influences the transcriptional aspect of the Pax2 gene where the gene is transcribed into RNA. In addition to Pax6's role in the developement and formation of the Central Nervous System and numerous ocular tissues, it also represses the promoter of Pax2 gene. (http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B8JDD-4R16S79-R&_user=10&_coverDate=06%2F30%2F2003&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=346d990a24dc66de9370b73563e0e6d5&searchtype=a)
Scientist attribute many defects in optics such as aniridia, papillorenal syndrome and others to the relationship between these two genes. Based on the findings that mutation in either of the Pax2 and Pax6 gene resulted in phenotypic defect lead scientists to conlude that the two genes had similar or shared function in the optic-nerve formation. Scientists were able to also conclude that these two genes function as either trascriptional inhibitor or activator of other genes.
Most often studied mutation that many scientists believe affect the defects in the optics region is attributed to missense. (http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1000870) Missense is where only a single nucleotide is changed. Although in usual case, protein becomes nonfunctional, research showed that the protein coded by Pax2 gene is hypomorphic or only partial loss of function rather than losing the function of the protein as a whole; however, this partial functioning protein still results in phenotypic malformation or defects as those mentioned previously. http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1000870)
Kevin Jeon
bboybyung@gmail.com
As Danielle mentioned, Shubin explains a very interesting evolutionary discovery that scientists uncovered in the stinging box jellyfish. Danielle explained how the mosaic structure is present in this animal, and how the genes pax 6 and Pax 2 were connected. The reason for this is that because the box jellyfish arose before the development of these specific genes, we don't exactly see the Pax 2 and Pax 6 genes themselves. However, the mosaic gives us insight because it displays a look of a primitive version of the two genes, which shows that some time in evolutionary history, these two genes split off from an original one. This gene directly connects us to primitive creatures such as jelly fish.
ReplyDeleteIn addition, both the PAX6 and PAX2 genes are part of the PAX gene family, which is involved in regulation during the embryonic stage of development, by providing instructions for proteins that are linked in DNA, and to help control the expression of certain genes, which is why certain PAX proteins are called transcription factors. After birth, most PAX genes are turned off, but can be activated to help "aid in tissue regrowth protect against cell death caused by cellular stress (such as increased sodium levels in the cell)"(Genetics Home Reference). These genes, although are mostly involved in the development of the eye and inner ear, can also help maintain homeostasis in the body by combating stresses on our cells.
In addition to seeing the linkage of the genes by examining the box jellyfish, we are able to understand the connection between the PAX2 and PAX6 genes because of birth defects in humans that affect the eyes and inner ear, which shows a correlation between the two genes. As Danielle pointed out, congenital rubella is one of the most common birth defects that links PAX2 and PAX6. Results of this birth defect are possible deafness and/or cataracts, which affect the inner ears and lens of the eyes, respectively. When the viral cells infect and destroy cells containing DNA coding that helps in the expressions of genes for hearing and eyesight, the children can lose their hearing, and the altered DNA can cause PAX genes to produce to little or too many proteins, which changes the functions of cells, thus causing loss of eyesight or hearing. These defects allow us to see how the PAX gene family, specifically PAX2 and PAX6 are linked in the genome of humans and other animals on the path of evolutionary history.
Sources:
http://ghr.nlm.nih.gov/geneFamily/pax
http://www.ncbi.nlm.nih.gov/pubmed/10869107
http://www.nlm.nih.gov/medlineplus/ency/article/001658.htm
"Your Inner Fish"
Matt Kim
ReplyDelete(matthewkim0803@gmail.com)
put you comment and plaOyK
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