Hematopoiesis as a competitive exclusion process: Estimation of a stem cell selective advantage |
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Authors: | Email author" target="_blank">Sandra?N?CatlinEmail author Peter?Guttorp Monica?T?McCallie Janis?L?Abkowitz |
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Institution: | (1) Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, 300 AHB, 3307 North Broad Street, Philadelphia, PA 19140, USA;(2) Present address: Laboratory of Developmental Genetics and Imprinting, Developmental Genetics Programme, The Babraham Institute, Babraham Research Campus, Cambridge, CB2 4AT, UK;(3) Department of Obstetrics and Gynecology, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, QC, Canada, H3G 1A4;(4) The Eccles Institute of Human Genetics, University of Utah Medical Center, Salt Lake City, UT 4112, USA;(5) Phillips Academy, 180 Main Street, Andover, MA 01810, USA;(6) Department of Pathology and Laboratory Medicine, Temple University School of Medicine, 3307 North Broad Street, Philadelphia, PA 19140, USA; |
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Abstract: | Female Safari cats are offspring of domestic and Geoffroy parents, and are balanced heterozygotes with equal numbers of Blood cells containing domestic and Geoffroy-type glucose 6-phosphate dehydrogenase (G6PD),an X-chromosome derived enzyme. In previous
studies, however, we observed increasing percentages of Blood cells with Geoffroy G6PD in cats aged 4–12 years. Similarly, ratios of parental X-chromosome phenotypes greater than three
to one are common in women over age 60, while women under 40 typically exhibit one to one ratios. Using a two-compartment
hidden-Markov model of the distribution of phenotype in samples taken during the second stage of hematopoiesis (Blood cell production), we estimate, through simulation and mathematical calculation, the Geoffroy selective advantages necessary
to reproduce the data obtained from female Safari cats. It is shown that small differences in the kinetics of hematopoietic
stem cells (HSC), less than might be detected by in vitro assays, can explain the “clonal dominance” observed with aging in
cats, and by extension, human females. Conceptually, hematopoiesis in females can be viewed as a competitive exclusion process
in which two populations of HSC (defined by parental X-chromosome phenotype) compete for environmental resources. As in many
ecological examples, dominance may occur only after long periods of time. |
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