To eventually use stem cells in regenerative medicine, scientists need to understand how stem cells become organized into particular tissue patterns and shapes. With that in mind, researchers at USC recently found clues by studying the cellular and molecular basis of complex pigment patterns in bird feathers.
Keck School of Medicine of USC researchers uncovered several fundamental rules of morphogenesis ─ the organizational process of functional cellular patterning. Their study appeared on April 25 in Science Express, the online version of the journal Science.
“Feathers are a good research model because they are unique, able to regenerate repetitively under normal conditions and are positioned at the surface of the body so that we can see their patterns,” said Cheng-Ming Chuong, the study’s team leader and professor of pathology at the Keck School. “Therefore their cellular and molecular composition can be experimentally manipulated to test the hypothesis that certain molecular components may enhance or suppress pigment differentiation.”
Chuong served as the corresponding author for the study. Joining him were first author Sung-Jan Lin from Taiwan University, who spent two years on the work in Chuong’s laboratory and was supported by a visiting fellowship from Taiwan’s National Health Research Institute.
The second author was John Foley, associate professor of anatomy/cell biology and dermatology at Indiana University, Bloomington.
Among the researchers’ findings were:
• For the first time, follicle melanocyte progenitors, cells similar to stem cells that give rise to pigmentation cells in feathers, were identified.
• Fewer than 50 progenitor cells (depending on the feather size) sit in a ring configuration at the base of the feather root.
• The ring of progenitor cells can be regulated by the micro-environment within the feather’s follicle (the stem cell niche) to create different color patterns.
• Progenitor cells produce different pattern outcomes at different ages of birds, from unmarked downy feathers in chicks to elaborately colorful plumage in adult birds.
• Complex feather patterns are not directly coded by DNA; instead, DNA provides coding for gene networks that govern tissue interactions, thereby giving much more flexibility and patterning freedom.
• Systemic factors, such as the level of hormones or seasonal changes, can regulate pigmentation patterns at different stages of a bird’s life.
“With so many layers of factors that can play a role in the basic melanocyte differentiation pathway, the combination and complexity of potential patterns are enormous,” Chuong said. “Now we want to find out more about how other events control the processes we found. Together with other investigators’ research, our findings in the feather study will contribute to the ability of scientists to conduct tissue engineering of human cells in the future.”
The Chuong lab also has been studying the principles of morphogenesis in other organs and has worked on generating fully functional skin and hair from stem cells.
The research team, which included additional multidisciplinary investigators, was supported by the National Institutes of Health (grant number AR 047364).