Archive for September 15th, 2011

September 15, 2011

Multiple dwarf strikes gave Milky Way its spirals

It’s difficult enough, from inside, to determine in detail what the spiral structure of our galaxy is, but progress has been made recently. It’s also been determined that a nearby dwarf galaxy has passed through our galaxy at least twice in the past, and should have had a large effect on the current spiral structure. Now there is also a simulation that attempts to determine the effects in more detail.

Multiple dwarf strikes gave Milky Way its spirals – NewScientist

A dwarf galaxy called Sagittarius can be credited with giving the Milky Way its signature spiral arms.

Sagittarius struck our galaxy some 1.9 billion years ago. It then looped over the galactic “north pole” and struck again about 900 million years ago. It is heading back right now, on course for a third clash in 10 million years or so.

These impacts must have had a considerable influence on the Milky Way but the effects have been hard to calculate because of uncertainties over the amount of dark matter in Sagittarius.

Further reading:

Milky Way Owes Its Shape to Crashes With Dwarf Galaxy

Milky Way’s spiral arms are the product of an intergalactic collision course

The Sagittarius impact as an architect of spirality and outer rings in the Milky Way

September 15, 2011

Yeast thrives with partially synthetic genome

Synthetic biology is progressing rapidly in making “artificial life” that is actual biological life. Previously this has been accomplished with viruses and prokaryotic cells (bacteria) – both of which do not keep their genetic material in chromosomes. Now, for the first time, engineered DNA has been incorporated in small chromosome segments and introduced into eukaryotic yeast cells – with surprisingly good results.

Yeast thrives with partially synthetic genome – Nature News

Researchers have equipped yeast cells with semi-synthetic chromosomes. It is the first such achievement in eukaryotic, or complex-celled, organisms, and marks a step towards large-scale genome engineering in these cells.

The team publishes its results today in Nature. The study suggests that the engineered yeast strains are as healthy as natural yeast.

“It appears to be fantastically stable,” says Andy Ellington, a biochemist at The University of Texas at Austin, who was not involved in the work. “At least some of us thought that it would fall flat on its face or would mutate quite readily.”

Further reading:

Synthetic chromosome arms function in yeast and generate phenotypic diversity by design

September 15, 2011

Gene therapy kills breast cancer stem cells, boosts chemotherapy

Gene therapy has had a somewhat tortuous history – as well as some fairly recent successes. The key issue is being able to deliver appropriate genes to exactly the cells where they are needed.

The way this therapy works is somewhat complicated. The agent is targeted to cells, such as cancer cells, that overexpress a gene called claudin4, which encodes a cell membrane protein. Cancer therapies such as chemotherapy and radiation therapy work by causing apoptosis (programmed cell death). But some types of cancer overexpress genes for certain members of the Bcl-2 family of proteins, which inhibit apoptosis. Another protein, BIK counteracts the effects of these Bcl-2 proteins, but it falls short if they are overexpressed. However, BIKDD is a mutant form of BIK that is better at the same task. The experimental therapy delivers BIKDD genes to targeted cancer cells, and pre-clinical tests show that it improves the anti-cancer activity of the lapatinib chemotherapy drug.

Gene therapy kills breast cancer stem cells, boosts chemotherapy

Gene therapy delivered directly to a particularly stubborn type of breast cancer cell causes the cells to self-destruct, lowers chance of recurrence and helps increase the effectiveness of some types of chemotherapy, researchers at The University of Texas MD Anderson Cancer Center reported in the Sept. 13 edition of Cancer Cell.

In cellular and mouse studies, scientists found the gene mutation BikDD significantly reduced treatment-resistant breast-cancer initiating cells (BCICs), also known as breast cancer stem cells, by blocking the activity of three proteins in the Bcl-2 family. This genetic approach increased the benefits of lapatinib, one of the most common chemotherapy drugs for breast cancer.

Further reading:

BikDD Eliminates Breast Cancer Initiating Cells and Synergizes with Lapatinib for Breast Cancer Treatment

September 15, 2011

Obscure Organelle in Stem Cells and Cancer

Stem cells and cancer cells seem to have more in common besides an ability to divide much more freely than normal adult cells – the persistence of structures called midbodies that are, as currently understood, important only in cell division. This raises the question of whether midbodies have functions, besides helping in cell division, that are common to both stem cells and cancer cells.

Obscure Organelle in Stem Cells and Cancer – The Scientist

Cellular structures known as midbodies, formed during cell division, appear to accumulate in stem cells and cancer cells, hinting at a potential function for these once-disregarded organelles.

Midbodies, once considered the rubbish of cell division, might have a function beyond their role in getting daughter cells to separate. Researchers show in today’s Nature Cell Biology that stem cells and cancer cells collect used midbodies, whereas differentiated cells digest the organelle through autophagy.

Further reading:

Midbody accumulation through evasion of autophagy contributes to cellular reprogramming and tumorigenicity

September 15, 2011

Skipping Pluripotency

When the production of induced pluripotent stem cells (iPSCs) was achieved about five years ago, it seemed they might provide a good alternative to working with embryonic stem cells, in both research and clinical applications. Then problems showed up, such as potential tumorigenicity, inadvertent DNA damage, and incompatibilities with the source’s immune system. More recently, the alternative of “reprogramming” adult cells directly from one type (such as skin) to another type (such as neurons) has been achieved. But this newer technique has problems of its own.

Skipping Pluripotency – The Scientist

The discovery of induced pluripotent stem cells (iPSC) in 2006 opened the door to promising research and therapeutic techniques, such as the generation of disease models and the potential to replace cells damaged by neurodegenerative diseases like Parkinson’s. Derived from fetal or adult cells, iPSC strategies avoided the ethical issues surrounding embryonic stem cells. But they retained one critical drawback—the propensity for tumor formation. In the last 18 months, however, researchers have discovered a new reprogramming technique that could avoid that problem altogether: the direct conversion of one differentiated cell type to another.

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