The relationship of the 15q11-q13 IC to the nuclear matrix depends on
its parental origin. The halo nuclei analyzed were those in which both
copies of the chromosome 15 α satellite repeat (15cen, yellow) are
present within the nuclear matrix (visible on
4′,6-diamidino-2-phenylindole counterstaining, blue), and one of the
two copies of the HPRT probe (HPRT,
green) is confined to the nuclear matrix with the homologue associated,
at least in part, with the surrounding DNA halo. The IC probe is shown
as the red signal in these images. (a) In a normal
female, the majority (16/20) of analyzed halo nuclei show one IC
signal solely within the nuclear matrix, the other partially within the
DNA halo. The remaining DNA haloes (4/20) showed both signals to
be present within the matrix. (b) In a patient with PWS
caused by a deletion of the paternal 15q11-q13 region, the sole signal
is from the maternal chromosome, found only in the matrix in the
majority (18/20) of halo nuclei.