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Are microRNA required for ovarian stem cells? February 20, 2007

Posted by Sacha in Genetics, microRNA, Science.
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A report was published this weekend in the journal Current Biology titled “Dcr-1 Maintains Drosophila Ovarian Stem Cells.”  The authors were Zhigang Jin, Ph.D, and Ting Xie, Ph.D, from Stowers Institute for Medical Research (Missouri) and the Department of Anatomy and Cell Biology (U of Kansas), respectively. 

According to this paper, the ovaries of Drosophila (a type of small fly) contain three types of adult stem cells: 
Germline stem cells (GSCs)
Escort stem cells (ESCs) and
Somatic stem cells (SSCs)

The authors go into much detail about GSCs and SSCs and the role of Dicer-1(Dcr-1) ribonuclease to maintain them in the Drosophila ovary.

So what is this review doing on an miRNA blog?  In the last paragraph of the article, Xie and Jin state “Because Dcr-1 is an essential component of the miRNA pathway in Drosophila, we further propose that miRNAs processed by Dcr-1 are essential for controlling self-renewal of GSCs and SSCs.”  They go on to explain the problems associated with the absence of miRNA generated by Dcr-1, such as depletion of stem cells.

An article on Biology News Net quoted Dr. Xie on the importance of the role of miRNA:

“We are in the process of identifying the microRNAs that are important for stem cell self-renewal,” said Dr. Xie. “Understanding the mechanisms controlling stem cell self-renewal will be crucial to our developing the ability to expand stem cell populations for performing tissue repair.”


Straight from the Nucleus: miR-29b January 13, 2007

Posted by Sacha in Genetics, microRNA, News, Research, Science.
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Another paper on microRNA.  This one is about miR-29 was published in Science‘s Jan. 5, 2007 edition.  It’s titled “A Hexanucleotide Element Directs MicroRNA Nuclear Import.” 

This is basically a note to myself to read it later.  

2 miRs and Cancer January 13, 2007

Posted by Sacha in Genetics, microRNA, News, Research, Science.
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During all this kurfuffle of winter storms and sick kitties I failed to update you on an important microRNA breakthrough.  At Ohio State University, Yuri Pekarsky’s team has found two microRNA (miRs) that regulate the most common human leukemia:  B-cell chronic lymphocytic, or just B-CLL for short.  These two microRNA are miR-29 and miR-181. 

microRNA can function as reverse regulators of disease.  So, when certain microRNA have low levels of expression, their targets genes are not surpressed and aggressive cancer can result.  What the researchers found was that there was an inverse relationship between expression levels of miR-29 and miR-181 and Tcl1, the ocncogene associated with B-CLL. 

The Ohio State team’s paper was titled “Tcl1 Expression in Chronic Lymphocytic Leukemia Is Regulated by miR-29 and miR-181″ and published in the December 15, 2006 edition of Cancer Research.  According to the paper, “Because miR-29 and miR-181 are natural Tcl1 inhibitors, these miRs may be candidates for therapeutic agents in B-CLL-overexpressing Tcl1. ” 

To read the original paper click here.  To read an excellent, non-technical summary from the American Association for Cancer Research click here

New Paper: Human microRNAs transcribed by polymerase III November 14, 2006

Posted by Sacha in Evolution, Genetics, microRNA, Research, Science.
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A new paper out this week in Nature Structural and Molecular Biology presents evidence that Polymerase III is associated with miRNA genomic sequence and sufficient for transcription.  This is as opposed to the privious view that Pol II was required in mammals for expression.  The miRNAs they analyzed (miR-515-1, 517a, 517c, 519a-1) were interspersed among the Alu repeats, which are transcribed through Pol III recruitment.

Now, I had to ask myself after I read the abstract for this article, “What are Alu repeats?” and “Why do I care if they hang out on the chain with miRs?”  If Wikipedia is accurate, and I hope it is, the Alu family is a family of polymorphisms in the human genome, about 300 bp long.  Their repetitive sequences are the most abundant mobile units on the human genome and have been implemented in diseases, such as cancer.  As for the second question, this connection suggests that repetitive elements play an important role in human miRNA origin and expression, according to this new paper.

Return to Oz: microRNA, Sleep, Cotton, Astronomy, and Nature May 8, 2006

Posted by Sacha in microRNA, Science.
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Before this old news gets any older, I must tell you all about my latest adventure in Australia. 

[The following events take place in the month of March, 2006.]

We started out by visiting the University of Sydney/RPAH.  While there, I had the pleasure of meeting Dr. John Rasko, head of the Gene therapy Unit at the Centenary Institute.  Researchers there have developed techniques for identifying and quantifying microRNA expression in cells.  Dr. Rasko has an entire team working on identifying microRNA function, so I look forward to posting news of breakthrough research from this outstanding group in the future. 

Next on the itenerary was lunch with sleep researcher, physician extraordinaire, and friend, Dr. David Joffe.  David has fun depriving people of sleep in the name of science.  Read about it here.

And on to my favorite part of the trip, the whirlwind cotton adventure through the bush (AKA outback), a personal tour from my in-laws.  First, we visited Auscott, where I got to see the latest in cotton ginning technology.  Next we went to the CSIRO cotton fields, where we saw many varieties of experimental stage cotton.  There was even a tiny, old gin that we put seedy cotton in and out came a fluffy ball of cotton! (City slickers are so easy to amuse!!)

A few things I've learned about cotton over the years:

  • Cotton lint comes in colors, including brown, green, and red, but the fiber quality isn't as good as the traditional white.

  • The flowers are pretty, yellow hibiscus.  Egyptian cotton has the prettiest flowers.

  • Researchers breed and genetically modify cotton to be resistant to bugs.  This cool technology is what originally got me interested in doing genetics research.  By making special breeds of cotton, scientists have had a positive impact on farm worker health, the environment (less pesticides), and the economy.

Rounding out the outback portion of the trip, we visited the Australia Telescope Compact Array (ATCA), also in Narrabri and run by CSIRO.  This facility has an array of six 22-meter antennas used for radio astronomy.  Fun fact: The antennas reside on a track that is a truly straight line – it doesn't follow the curvature of the Earth. (For this to make sense, you have to buy into the "Earth isn't flat" theory.)  The site I linked to above has great photos and lots more information.

Australia is a MUST for any science lover with $US1500 to spend on a plane ticket.  Even trumping the great research is the natural beauty and diversity of animals.  In a typical trip, we will see kangaroos, goannas, cockatoos, and many other creatures in the wild.  But, the best part is the warmth, hospitality, and cooking of the people.  Thank you to everyone who made this a memorable trip for us.


Mouse miR155 May 6, 2006

Posted by Sacha in microRNA.
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Here is an excellent example of just how vital microRNAs can be.  According to the lay article on Ohio State University's website, "Scientists in the Ohio State University Comprehensive Cancer Center say that just one, single, malfunctioning microRNA is sufficient to cause cancer in mice."  This microRNA is mouse miR155.

It loks like what they did was create transgenic mice with miR155 and an enhancer, to promote expression.  The mice developed enlarged spleens at 3 weeks of age.  The spleens were enlarged with immature B cells, a hallmark of some leukemia and lymphoma.  

The research was reported in PNAS on April 25, 2006 titled: "Pre-B cell proliferation and lymphoblastic leukemia/high-grade lymphoma in Emu-miR155 transgenic mice" with authors Stefan Costinean, Nicola Zanesi, Yuri Pekarsky, Esmerina Tili, Stefano Volinia, Nyla Heerema, and Carlo M. Croce at the Comprehensive Cancer Center, Ohio State University.