Mode of inheritance of the higher degree of megakaryocyte polyploidization
in C3H mice. I. Evidence for a role of genomic imprinting in megakaryocyte
polyploidy determination
TP McDonald and CW Jackson
Department of Animal Science, College of Veterinary Medicine, University of
Tennessee, Knoxville 37901-1071.
C3H mice have higher average ploidy megakaryocytes than all other mouse
strains tested, but the mode of inheritance of this anomaly is unknown.
Therefore, to clarify the genetics of high ploidy megakaryocytes in C3H
mice, we measured megakaryocyte DNA content from both male and female
offspring from F1, as well as backcross matings. In all, offspring from
seven different matings of mice were studied: (1) C57BL X C57BL (the first
strain listed is the male parent in each case), (2) B6C3F1 (offspring from
C57BL X C3H mating) X C57BL, (3) C57BL X B6C3F1, (4) C57BL X C3H, (5) C3H X
B6C3F1, (6) B6C3F1 X C3H, and (7) C3H X C3H. The polyploid megakaryocyte
DNA content distributions of the offspring from these matings show that C3H
mice have higher percentages of high ploidy megakaryocytes than did all
other mice. Also, male mice had significantly higher percentages of high
ploidy (32N and 64N) megakaryocytes than did female mice for all matings,
except backcross mating no. 6. The megakaryocyte DNA content for individual
offspring of a given backcross appeared to form a single, continuous
distribution, rather than segregate into two distinct groups, suggesting
that the higher megakaryocyte DNA content of C3H mice is caused by
involvement of multiple allelles. This conclusion is further supported by
our finding that the frequency of high ploidy megakaryocytes among
offspring of the various matings was related to the proportion of C3H
genotype contributed by the parents, ie, average megakaryocyte DNA content
increased linearly (r2 = .88 for male mice and .84 for female mice. P <
.0001) with increasing C3H gene dosage; the correlations for both male and
female mice were essentially parallel (slope = 0.08 and 0.09,
respectively). In addition, we found an effect of genomic imprinting on
megakaryocyte DNA content in backcross offspring. The genetic imprinting
was characterized by the female parent having a greater influence on the
offspring's megakaryocyte DNA content than the male parent, ie, although
the overall genetic makeup was the same, female offspring from backcross
no. 6 (in which the female was C3H) had higher average megakaryocyte ploidy
values than those from backcross no. 5 (in which the female was
B6C3F1).(ABSTRACT TRUNCATED AT 400 WORDS)
Volume 83,
Issue 6,
pp. 1493-1498,
03/15/1994
Copyright © 1994 by The American Society of Hematology
