Scientists ID the genetic makeup of hair
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Despite a $56 billion industry devoted to caring for and styling hair, we know surprisingly little about how it forms. A new paper in last week’s edition of Public Library of Science Biology from Elaine Fuchs’ laboratory at Rockefeller University begins to tease apart the genes, and the cells, that are important for its growth.
“There are many different cell types involved in hair formation,” says Michael Rendl, first author and postdoctoral fellow in the Fuchs lab. “And these cells engage in very intricate signaling exchanges to form the hair follicle.”
“Once stem cells have been activated, the action in making a hair follicle takes place at the base of the follicle, called the hair bulb, where rapidly dividing progeny of the stem cells, called matrix cells, differentiate to form the hair,” explains Fuchs. “In the center of the bulb is a pocket of specialized dermal cells, called the dermal papilla, which stimulate the matrix cells to divide and differentiate. As the matrix cells begin to differentiate, they also pinch off bits of melanocytes to provide pigment to the hair. Thus, the bulb of the hair follicle is rich in different kinds of cells, each of which is important to the process.”
In order to understand the complex signals that trigger these processes, Fuchs and Rendl focused on devising a method to isolate each of the major cell types in the hair bulb and determine the pattern of genes it expresses. They engineered mice that labeled each of the cells differently with colored markers like green and red fluorescent proteins. Together with various antibodies, they were able to use a cell sorter – which divides the cells according to their different labels – to separate each population of cells.
Once the cells were isolated, then Rendl used a technique called microarray profiling to determine which genes were only made in one out of the five different cell types they had isolated. “By comparing all of the global gene profiles, we could say what was unique for each cell type,” Rendl says. “We also looked for what was shared between all of the cells, it gives us an idea of what is the common molecular backbone needed just to be a cell.” Lisa Lewis, a research technician, worked with Rendl to further characterize these expression profiles.
They uncovered many genes specific to each of the five cell types. Some were already known, but others don’t even have names yet. Genes involved in many different hair diseases also appeared in their profiles. Fuchs hopes the new research will aid in the understanding of these and other human skin disorders.
“Knowing which cell types express the genes involved in hair and skin genetic disorders makes a large contribution to our understanding of the biology underlying the conditions,” says Fuchs. “Hopefully it will provide a framework from which functional studies examining the diseases can be carried out. In addition, by knowing the complete repertoire of signals that different cells within the hair bulb use to communicate with each other, we can now begin to dissect out which are the key ones in promoting hair growth.”
