Wr. Atchley et al., Cellular consequences in the brain and liver of age-specific selection forrate of development in mice, GENETICS, 155(3), 2000, pp. 1347-1357
Changes in cell number (hyperplasia) and cell size (hypertrophy) in the bra
in and liver are described for mice subjected to 24 generations of age-spec
ific restricted index selection for rate of development in body weight. One
selection treatment (E) altered rate of development between birth and 10 d
ays of age, another treatment (L) involved changes in rate of development b
etween 28 and 56 days of age, while a third control treatment (C) involved
random selection. Each selection treatment was replicated three times. Thes
e age-specific selection treatments focused on intervals during ontogeny wh
en different developmental processes (hypertrophy or hyperplasia) were more
predominant in the control of growth. Significant changes in brain and liv
er weight occurred at both 28 and 70 days of age. Early selection (E) gener
ated significant changes in the number of cells in the brain while later se
lection (L) had no effect since the brain had stopped growth before selecti
on was initiated. For the liver, early and late selection produced signific
ant effects on both cell number and cell size. These results describe the d
ynamic and multidimensional aspects of selection in terms of its ability to
alter different cellular and developmental components of complex morpholog
ical traits.