Health,Stem Cells, and Technology

Saturday, April 27, 2013

DNA Sequences That Change During Aging May Contribute To Age-Related Brain Defects

More evidence for adult somatic cells displaying genetic variability, both over time in one cell, and from cell to cell. Thus the idea of a single genome for an individual is misguided; there are many genomes in an individual and those genomes change in time.

In a journal article published in Nature Neuroscience, CSHL Associate Professor Joshua Dubnau, PhD and colleagues show that so-called “jumping genes,” or transposons, increase in abundance and activity in the brains of fruit flies as they age. Originally discovered at CSHL by Professor Barbara McClintock, a Nobel Laureate, while working on maize (corn) in the 1940s, transposons are typically repeat DNA sequences that insert themselves into the DNA of an animal or plant.

The term “jumping genes” comes from the fact that when activated these gene segments can reinsert themselves, or transpose, into another part of the genome. In the course of doing so they are thought to either provide variations in genetic function or, especially in the germline, induce potentially fatal disruptive defects.

The results in his team’s new paper, Dubnau proposes that a transposon activation may be responsible for age-related neurodegeneration as well as the pathology seen in some neurodegenerative disorders.

However, his studies so far don’t address whether transposons are the cause or an effect of aging-related brain defects. The next step will be to activate transposons by genetically manipulating fruit flies and ask whether they are a direct cause of neurodegeneration.

Thursday, April 25, 2013

Pluripotent Stem Cell Discovered in Adult Tissue

A new study by Dr. Thea Tisty, PhD at UCSF describes rare somatic cells from human breast tissue that exhibit extensive lineage plasticity, and thus appear to be pluripotent adult stem cells. Previously, only embryonic stem cells were thought to be pluripotent. As Ron Leuty described in the San Francisco Business Times, "A new type of stem cell, discovered by UCSF researchers, may open new possibilities for fixing damaged parts of the body while sidestepping the politically and morally thorny issues surrounding embryonic stem cell research."

Some religious organizations oppose embryonic stem cell research because they consider embryos, a small cluster of cells that fit on the tip of a pin, to be human life. As a result, conservative, anti-abortion lawmakers have largely seized on those concerns to block federal funding for research of embryonic stem cells.  The newly discovered endogenous pluripotent stem cells (ePS) described by Dr Tisty obviate these religious and moral problems.

Further, unlike iPSCs or parthenogenetic stem cells, the ePS cells are genetically and epigenetically stable and mortal, which means they will stop growing over time, thus reducing the risk of cells becoming rogue and morphing into cancer tumors.

The discovery by Dr Tisty opens a new path for exploration in the quest to develop stem cell therapies.