Scientists discover master regulator of skin development

December 2, 2012

The surface of your skin, called the epidermis, is a complex mixture of many different cell types—each with a very specific job. The production, or differentiation, of such a sophisticated tissue requires an immense amount of coordination at the cellular level, and glitches in the process can have disastrous consequences. Now, researchers at the Stanford University School of Medicine have identified a master regulator of this differentiation process.

"Disorders of epidermal differentiation, from to eczema, will affect roughly one-half of Americans at some point in their lifetimes," said Paul Khavari, MD, PhD. "Understanding how this differentiation occurs has enormous implications, not just for the treatment of disease, but also for studies of and even stem ." Khavari is the Carl J. Herzog Professor and chair of the Department of Dermatology.

Khavari and his colleagues have found that, like a traffic cop motioning cars to specific parking spaces in a large, busy lot, a newly identified molecule called TINCR is required to direct down pathways toward particular developmental fates. It does so by binding to and stabilizing differentiation-specific called messenger RNAs. Blocking TINCR activity, the researchers found, stopped the differentiation of all .

"This is an entirely unique mechanism, which sheds light on a previously invisible portion of the regulation of this process," said Khavari, who is also a member of the Stanford Cancer Institute and chief of the dermatology service at the Veterans Affairs Palo Alto . He is the senior author of the research, which will be published online Dec. 2 in Nature. Former Stanford postdoctoral scholar Markus Kretz, PhD, is the first author. Kretz is now an assistant professor of biology at the University of Regensburg in Germany.

Surprisingly, this coordinator extraordinaire is not a protein. (Proteins have traditionally been thought to be the primary movers and shakers in a cell, although that view is now changing somewhat.) Instead, it belongs to a relatively new, and increasingly influential, class of regulatory molecules called long, non-coding RNAs, or lncRNAs. These molecules are so named because they do not carry instructions to make proteins. They are also longer than other regulatory RNAs known as microRNAs.

But even among lncRNAs, TINCR, and its role in epidermal differentiation, is unique.

"This work revealed a new role for regulatory RNAs in gene activation—by stabilizing select transcripts," said co-author Howard Chang, MD, PhD, professor of dermatology. "This finding highlights the ability of regulatory RNAs to fine-tune gene expression."

The researchers identified the molecule by looking for RNAs that are more highly expressed in differentiating epidermal cells called keratinocytes than in progenitor cells. They found that levels of TINCR (short for "terminal differentiation-induced non-coding RNA") expression were 150 times greater in the keratinocytes. But to figure out what TINCR was doing, they had to develop two new assays: one to help researchers identify interactions between RNA molecules, and another to suss out interactions between a regulatory RNA and its protein partners. Such techniques will become increasingly important as researchers continue to identify the critical regulatory roles played by RNA molecules.

"These long, non-coding RNAs don't have recognizable, classic motifs like proteins do," said Khavari. "And yet, we really need to know with what other molecules they may be physically interacting to truly understand their biological roles."

The first approach, which the researchers termed RIA-Seq, couples an RNA interaction assay with a deep-sequencing technique to identify RNA partners of TINCR. Using RIA-Seq, the researchers found that TINCR and its RNA partners—many of which encode instructions for proteins essential to the differentiation process—share a common, short sequence that mediates their binding.

"These conserved, complementary motifs may help TINCR pair up with and stabilize its partner messenger RNAs," said Khavari. "In this way, TINCR may serve as a scaffold for many mRNAs involved in epidermal differentiation."

The second approach used a grid, or microarray, of 9,400 human proteins to which the researchers exposed TINCR. One of the proteins, termed STAU1, bound strongly to TINCR. STAU1 had not previously been implicated in epidermal differentiation, but the researchers found that blocking its activity prevented differentiation in a manner similar to blocking TINCR.

"This effect is quite specific for epidermal tissue," said Khavari, "and it suggests that nature has evolved a simple mechanism to control the tissue-specific expression of a large number of genes. We'd like to understand more about this TINCR-STAU1 complex to get a better idea of how it acts at a biochemical level."

In addition to identifying a unique role for a new lncRNA in epidermal differentiation, Khavari and Chang said they are excited to have developed new tools to understand how these regulatory RNAs function in the cells. "This really helps substantially expand our tool kit that we can use to analyze how RNAs and proteins interact," said Khavari.

Explore further: The key (proteins) to self-renewing skin

Related Stories

The key (proteins) to self-renewing skin

July 5, 2012
In the July 6 issue of Cell Stem Cell, researchers at the University of California, San Diego School of Medicine describe how human epidermal progenitor cells and stem cells control transcription factors to avoid premature ...

RNA regulator of melanoma could be a new target for cancer therapy

May 10, 2012
Melanoma is the most deadly form of skin cancer, estimated by the National Cancer Institute to afflict more than 70,000 people in the United States annually and the incidence rate continues to rise. In a study published online ...

Long non-coding RNA prevents the death of maturing red blood cells

December 7, 2011
A long non-coding RNA (lncRNA) regulates programmed cell death during one of the final stages of red blood cell differentiation, according to Whitehead Institute researchers. This is the first time a lncRNA has been found ...

Recommended for you

Make way for hemoglobin

August 18, 2017
Every cell in the body, whether skin or muscle or brain, starts out as a generic cell that acquires its unique characteristics after undergoing a process of specialization. Nowhere is this process more dramatic than it is ...

Two-step process leads to cell immortalization and cancer

August 17, 2017
A mutation that helps make cells immortal is critical to the development of a tumor, but new research at the University of California, Berkeley suggests that becoming immortal is a more complicated process than originally ...

New Pathology Atlas maps genes in cancer to accelerate progress in personalized medicine

August 17, 2017
A new Pathology Atlas is launched today with an analysis of all human genes in all major cancers showing the consequence of their corresponding protein levels for overall patient survival. The difference in expression patterns ...

Female mouse embryos actively remove male reproductive systems

August 17, 2017
A protein called COUP-TFII determines whether a mouse embryo develops a male reproductive tract, according to researchers at the National Institutes of Health and their colleagues at Baylor College of Medicine, Houston. The ...

New technique overcomes genetic cause of infertility

August 17, 2017
Scientists have created healthy offspring from genetically infertile male mice, offering a potential new approach to tackling a common genetic cause of human infertility.

Inhibiting a protein found to reduce progression of Alzheimer's and ALS in mice

August 17, 2017
(Medical Xpress)—A team of researchers with Genetech Inc. and universities in Hamburg and San Francisco has found that inhibiting the creation of a protein leads to a reduction in the progression of Alzheimer's disease ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.