Objectives: To find whether chromosomes 13, 16, 18, 21, 22, X and Y in blastomeres of human embryos are nonrandomly localized, whether their aneuploidy affects their localization and if eventual early inactivation of chromosome X with peripheral localization is present.
Methods: Relative distances from the nucleus center and edge of 1,198 fluorescence in situ hybridization signals in 98 human blastomeres were measured in digital images for comparison with a mathematical model of random distribution in spherical nucleus.
Results: Comparison with the mathematical model revealed that localization of chromosomes 13, 16, 21, 22, X and Y in normal and aneuploid blastomeres and that of chromosome 18 in normal blastomeres was not significantly different from random distribution. Similarly, chromosome X in blastomeres with more than one X did not appear to have a preferential localization. Only chromosome 18 in aneuploid blastomeres was differently distributed (p < 0.0001) with a shift to the nuclear periphery (p =or < 0.0001).
Conclusions: Peripheral localization of chromosome 18 in aneuploid blastomeres is related to embryo aneuploidy. Conversely, a peripheral localization of the inactive X chromosome was not found in blastomeres from 3-4 day old embryos. These results open the possibility to improve embryo selection after pre-implantation diagnosis.
Copyright (c) 2007 John Wiley & Sons, Ltd.