The Mother of all Humans... (?)

I read an article about a study which was attempting to age the "Mitochondrial Eve" by using Mitochondrial DNA.  The article said that mitochondria, the tiny organelles that serve as energy factories inside all human cells, have their own genome.  Besides containing 37 genes that rarely change, they contain a "hypervariable" region, which changes fast enough to provide a molecular clock calibrated to times comparable to the age of modern humanity.  Since each person's mitochondrial genome is inherited from his or her mother, all mitochondrial lineages are maternal.  By studying the changes in mitochondria they are able to discern some basic evolutionary time periods. The next part of the study is harder for me to understand, they took blood samples from different donors and determined relatedness based on their blood samples, which somehow allowed the scientists to age the mitochondrial DNA.  It was interesting to read about mitochondrial DNA and that it is only passed down through the mother, and using such processes scientists have traced and aged the mitochondrial DNA, estimating that DNA originated 200,000 years ago.

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Pain Gene... Owch

A gene which may help explain why some people are more sensitive to and less able to tolerate pain has been discovered by scientists. The gene in question for this study was a2d3 or straightjacket, which is a unique sensory gene because its pathway is in the brain, instead of being in the peripheral nerves, which is usually the "norm" for pain sensory genes. To test this gene they inserted the genetic sequence into fruit flies and exposed the flies to an excessive heat wave, those who were under the influence of the gene failed to move away from the heat. To test where the gene was being affected (brain or peripheral nervous system) they had to isolate the gene, induce pain then observe activity in the mouse, which they observed in the brain. Mapping of other genetic pathways allowed the researchers to conclude it was indeed a2d3 that had the brain pathway. Why we should care is this gene is found in the flies, mice as well as in humans and the mutant of gene a2d3 causes synesthesia which is where one sense triggers the others (including pain). Research on this gene may allow the development of a pain reliever that would be able to counteract the brain pathway and intercept the pain signal


Article

There is More Than Meets the Eye

Heterochromia is a condition where the irises in the eyes of a person or animal are two different colors. This condition can also occur in the color of hair or of the skin, but is most common in the eyes. Heterochromia occurs when a person or animal has too much or too little of the compound melanin in the body. Melanin is a compound found in plants and animals that creates pigment.

Heterochromia can occur from disease, injury, genetic mosaicism, or an inherited genetic trait. Different colored eyes can also occur due to a hemorrhage or foreign object in the eye, glaucoma, or neurofibromatosis. Even mild  inflammation in one eye can cause this condition.When it affects the eyes, this condition may also be called heterochromia iridis or heterochromia iridum. The eyes can have either complete heterochromia, meaning each eye is a different color, partial or sectoral heterochromia, meaning that there are two different colors within one iris. Complete heterochromia is the more common variety. The partial or sectoral version usually come from inherited conditions, such as Waardenburg syndrome and Hirschsprung's disease.

Genetics, and signaling pathway
The neural crest (NC) is a unique embryonic structure and contains a multipotent stem cell population that arises during vertebrate embryogenesis.  NC stem cells arise from the dorsal neural tube during neurolation in early development and then migrate out from the neural tube and along defined pathways throughout the body, where they contribute to numerous cell types and tissues, including melanocytes, ocular and periocular structures, bone and cartilage cells of the cranial skeleton, sensory neurons, enteric neurons, smooth muscle, endocrine cells, chromaffin cells, and glial cells.  Understanding NC development is medically important because defective NC cell development lead to numerous human diseases known as neurocristopathies and heterochromia is an example of one.



The following link is an in-depth explanation of the many transcriptional and signaling pathways for neural crest cells, very interesting!  This article shows many combined cell research results of how melanocyte deficiency arises during development.  The genes PAX3,SOX10, MITF, SNAI2, EDNRB, EDN3, KIT, and KITL are especially followed and  new insights into a central role of MITF in the complex network of interacting genes in melanocyte development is revealed.

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FIGURE: A simplified schematic showing the features of key signaling pathways in melanocyte development. Green lines represent three major signaling pathways, WNT, KIT, and EDNRB, which are all connected to Mitf. WNT/-catenin signaling promotes melanoblast development by regulating MITF transcription. KIT and EDNRB signal pathways are not required for the initial expression of Mitf in melanocyte development, but both pathways induce the phosphorylation of MITF in mature melanocytes.