Specific staining of human chromosomes in Chinese hamster x man hybrid cell lines demonstrates interphase chromosome territories

In spite of Carl Rabl's (1885) and Theodor Boveri's (1909) early
hypothesis that chromosomes occupy discrete territories or domains
within the interphase nucleus, evidence in favor pf this hypothesis
has been limited and indirect so far in higher plants and animals.
The alternative possibility that the chromatin fiber of single
chromosomes might be extended throughout the major part of even the
whole interphase nucleus has been considered for many years. In the
latter case, chromosomes would only exist as discrete chromatin
bodies during mitosis but not during interphase. Both possibilities
are compatible with Boveri's well established paradigm of
chromosome individuality. Here we show that an active human X
chromosome contained as the only human chromosome in a Chinese
hamster x man hybrid cell line can be visualized both in metaphse
plates and in interphase nuclei after in situ hybridization with
either 3H- or biotin-labeled human genomic DNA. We demonstrate that
this chromosome is organized as a distinct chromatin body
throughout interphase. In addition, evidence for the territorial
organization of human chromosomes is also presented for another
hybrid cell line containing several autosomes and the human X
chromosome. These findings are discussed in the context of our
present knowledge of the organization and topography of interphase
chromosomes. General applications of a strategy aimed at specific
staining of individual chromosomes in experimental and clinical
cytogenetics are briefly considered.