Distinct nuclear orientation patterns for mouse chromosome 11 in normal B lymphocytes

Background: Characterizing the nuclear orientation of chromosomes
in the three-dimensional (3D) nucleus by multicolor banding
(mBANDing) is a new approach towards understanding nuclear
organization of chromosome territories. An mBANDing paint is
composed of multiple overlapping subchromosomal probes that
represent different regions of a single chromosome. In this study,
we used it for the analysis of chromosome orientation in 3D
interphase nuclei. We determined whether the nuclear orientation of
the two chromosome 11 homologs was random or preferential, and if
it was conserved between diploid mouse Pre B lymphocytes of BALB/c
origin and primary B lymphocytes of congenic [T38HxBALB/c] N
wild-type mice. The chromosome orientation was assessed visually
and through a semi-automated quantitative analysis of the radial
and angular orientation patterns observed in both B cell types.
Results: Our data indicate that there are different preferential
patterns of chromosome 11 orientation, which are not significantly
different between both mouse cell types (p > 0.05). In the most
common case for both cell types, both copies of chromosome 11 were
oriented in parallel with the nuclear border. The second most
common pattern in both types of B lymphocytes was with one homolog
of chromosome 11 positioned with its telomeric end towards the
nuclear center and with its centromeric end towards the periphery,
while the other chromosome 11 was found parallel with the nuclear
border. In addition to these two most common orientations present
in approximately 50% of nuclei from each cell type, other
orientations were observed at lower frequencies. Conclusions: We
conclude that there are probabilistic, non-random orientation
patterns for mouse chromosome 11 in the mouse B lymphocytes we
investigated (p < 0.0001).