Mode of Inheritance of the Higher Degree of Megakaryocyte Polyploidization

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, w e measured megakaryocyte DNA content from both male and female offspring from F1, as well as backcross matings. In all, offspring fmm 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