Lg. Koss, Characteristics of chromosomes in polarized normal human bronchial cells provide a blueprint for nuclear organization, CYTOG C GEN, 82(3-4), 1998, pp. 230-237
In normal human terminally differentiated and polarized bronchial cells, th
e fluorescent "painting" technique (FISH) for all chromosomes (except Y) do
cumented that each homologue of each chromosome occupies a distinct, separa
te domain within the nucleus. The homologues are distributed along the nucl
ear membrane. In most cells and chromosomes studied, the two homologues wer
e not identical: one was usually more "compact" than the other which was mo
re "open," displaying fiber-shaped extensions. The differences between the
territories of homologues 1 and 7 were shown to be statistically valid (P <
0.0001 by Wilcoxon sign rank test), as has been previously documented for
the two X chromosomes (Eils et al., 1996).
In some parallel arrays of bronchial cells, the position of the chromosomes
in the nuclei was either identical or formed a mirror image, suggesting th
at the position of the chromosomes in polarized nuclei may be constant. To
confirm this observation, the angles formed by the two homologues in the po
larized oval nuclei were measured for chromosomes I, X, and 7. The measurem
ents disclosed that, in about two-thirds of the nuclei, the two homologues
formed angles of 1.50 degrees, 157 degrees and 148 degrees, nearly identica
l to these formed by the same three chromosomes in prometaphase rosettes of
cultured diploid human fibroblasts (Nagele et al., 1995). In about one thi
rd of the nuclei, the same homologues formed angles of 89 degrees, 72 degre
es, and 94 degrees, and occasionally an angle of 180 degrees. A three-dimen
sional computer reconstruction of the nuclei was performed using the data f
or the X chromosomes. By cinematographic technique, it could be documented
that the angles separating the two homologues depended on the rotation of t
he nucleus along the axes X, Y, and Z. The cause of the rotation is specula
tive at this time. Because of the concordance of these data in terminally d
ifferentiated epithelial cells with prior observations on prometaphases of
human diploid fibroblasts, it is suggested that the position of chromosomes
in all human cells is constant throughout the cell cycle. The possible sig
nificance of these observations is discussed.