Heterochromia (also known as a heterochromia iridis or heterochromia iridium) is an ocular condition in which one iris is a different color from the other iris (complete heterochromia), or where the part of one iris is a different color from the remainder (partial heterochromia or sectoral heterochromia). It is a result of the relative excess or lack of pigment within an iris or part of an iris, which may be inherited or acquired by disease or injury. This uncommon condition usually results due to uneven melanin content. A number of causes are responsible, including genetic, such as chimerism, Horners Syndrome and Waardenburg syndrome.
A gene that is associated with regeneration of injured nerve cells has been identified by a team of researchers led by Prof Melissa Rolls of Penn State University.
The team has found that a mutation in a single gene can entirely shut down the process by which axons – the parts of the nerve cell that are responsible for sending signals to other cells – regrow themselves after being cut or damaged.
“We are hopeful that this discovery will open the door to new research related to spinal-cord and other neurological disorders in humans,” said Prof Rolls, who co-authored a paper published online in the journal Cell Reports.
“Axons, which form long bundles extending out from nerve cells, ideally survive throughout an animal’s lifetime. To be able to survive, nerve cells need to be resilient and, in the event of injury or simple wear and tear, some can repair damage by growing new axons,” Prof Rolls explained.
Previous studies suggested that microtubules – the intracellular ‘highways’ along which basic building blocks are transported – might need to be rebuilt as an important step in this type of repair.
“In many ways this idea makes sense: in order to grow a new part of a nerve, raw materials will be needed, and the microtubule highways will need to be organized to take the new materials to the site of growth,” Prof Rolls said.
The team therefore started to investigate the role of microtubule-remodeling proteins in axon regrowth after injury. In particular, they focused on a set of proteins that sever microtubules into small pieces. Out of this set, a protein named spastin emerged as a key player in axon regeneration.
Above: In fruit flies with two normal copies of the spastin gene, a team of scientists led by Prof Melissa Rolls of Penn State University found that severed axons were able to regenerate. However, in fruit flies with two or even only one abnormal spastin gene, the severed axons were not able to regenerate (Melissa Rolls / Penn State University)
Original paper here.
The governing board of the California Institute for Regenerative Medicine (CIRM) has announced that six investigators from the University of California, San Diego Stem Cell Research program have received a total of more than $7 million in the latest round of CIRM funding. This brings UC San Diego’s total to more than $128 million in CIRM funding since the first awards in 2006.
UC San Diego scientists funded by the newly announced CIRM Basic Biology Awards IV include Maike Sander, MD, professor of Pediatrics and Cellular and Molecular Medicine; Miles Wilkinson, PhD, professor, Division of Reproductive Endocrinology; Gene Yeo, PhD, MBA, assistant professor with the Department of Cellular and Molecular Medicine and the Institute for Genomic Medicine; George L. Sen, PhD, assistant professor of cellular and molecular medicine; David Traver, PhD, associate professor with the Department of Cellular and Molecular Medicine and Ananda Goldrath, PhD, associate professor in the Division of Biological Sciences.
pictured: Human stem cells, false color.
The American paddlefish — known for its bizarre, protruding snout and eggs harvested for caviar — duplicated its entire genome about 42 million years ago, according to a new study published in the journal Genome Biology and Evolution. This finding may add a new twist to the way scientists study how fins evolved into limbs since the paddlefish is often used as a proxy for a more representative ancestor shared by humans and fishes.
“We found that paddlefish have had their own genome duplication,” said Karen Crow, assistant professor of biology at San Francisco State University. “This creates extra genetic material that adds complexity to comparative studies. It may change the way we interpret studies on limb development.”
In order to study how human limbs develop, scientists compare the limb-building genes found in mice with fin-building genes found in fishes. Previous research on paddlefish has suggested that fishes possessed the genetic toolkit required to grow limbs long before the evolution of the four-limbed creatures (tetrapods) that developed into reptiles, birds, amphibians and mammals.
In the last decade, paddlefish have become a useful benchmark in evolutionary studies because their position on the evolutionary tree makes them a reasonably good proxy for the ancestor of the bony fishes that evolved into tetrapods such as humans. However, the fact that paddlefish underwent a genome duplication could complicate what its genes tell us about the fin-to-limb transition, says Crow.