Human hair genealogies and stem cell latency
- PDF / 594,087 Bytes
- 10 Pages / 610 x 792 pts Page_size
- 78 Downloads / 221 Views
BioMed Central
Open Access
Research article
Human hair genealogies and stem cell latency Jung Yeon Kim1,4, Simon Tavaré2,3 and Darryl Shibata*1 Address: 1Department of Pathology, University of Southern California Keck School of Medicine, Los Angeles, CA 90033, USA, 2Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA, 3Department of Oncology, University of Cambridge, Cambridge, UK and 4Department of Pathology, Inje University Sanggye-Paik Hospital, Sanggye 7 dong 761-7, Nowon-gu, Seoul, Korea Email: Jung Yeon Kim - [email protected]; Simon Tavaré - [email protected]; Darryl Shibata* - [email protected] * Corresponding author
Published: 03 February 2006 BMC Biology 2006, 4:2
doi:10.1186/1741-7007-4-2
Received: 16 October 2005 Accepted: 03 February 2006
This article is available from: http://www.biomedcentral.com/1741-7007/4/2 © 2006 Kim et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: Stem cells divide to reproduce themselves and produce differentiated progeny. A fundamental problem in human biology has been the inability to measure how often stem cells divide. Although it is impossible to observe every division directly, one method for counting divisions is to count replication errors; the greater the number of divisions, the greater the numbers of errors. Stem cells with more divisions should produce progeny with more replication errors. Methods: To test this approach, epigenetic errors (methylation) in CpG-rich molecular clocks were measured from human hairs. Hairs exhibit growth and replacement cycles and "new" hairs physically reappear even on "old" heads. Errors may accumulate in long-lived stem cells, or in their differentiated progeny that are eventually shed. Results: Average hair errors increased until two years of age, and then were constant despite decades of replacement, consistent with new hairs arising from infrequently dividing bulge stem cells. Errors were significantly more frequent in longer hairs, consistent with long-lived but eventually shed mitotic follicle cells. Conclusion: Constant average hair methylation regardless of age contrasts with the age-related methylation observed in human intestine, suggesting that error accumulation and therefore stem cell latency differs among tissues. Epigenetic molecular clocks imply similar mitotic ages for hairs on young and old human heads, consistent with a restart with each new hair, and with genealogies surreptitiously written within somatic cell genomes.
Background One way to organize the billions of cells within an individual is through genealogy, because all cells are related. Each cell has its own genealogy, which starts from the zygote and ends with the current phenotype. Conceptually, the genealogy of a differentiated
Data Loading...
