PMC4213471_01
G-banded karyotype showing the marker chromosome.
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Fig1
The fetal karyotype was: 47,XY,+mar (Figure 1).
C-banded metaphase showing the marker chromosome (arrow) with a C-band-negative constriction.
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Fig2
The marker was negative for C-banding (Figure 2).
Molecular cytogenetic characterization of the marker chromosome. Arrows indicate the marker chromosome. (A) Spectral karyotyping. (B) Whole chromosome paint 18 green. (C) chromosome 18 arm-specific painting, 18p green/18q red. (D) Multicolor DNA Probe Kit CEP 18 aqua/X green/Y orange.
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Fig3
Multiplex FISH with spectral karyotyping identified the marker as a derivative of chromosome 18 (Figure 3A). This was confirmed using a whole chromosome painting probe specific for chromosome 18 (Figure 3B). Partial chromosome painting probes specific for the long and the short arms of chromosome 18 indicated that the marker derived from the long arm of chromosome 18 (Figure 3C). The multicolor probe panel used to reveal alpha satellite sequences failed to show signals on the marker (Figure 3D).
Electropherogram of the unbalanced marker D18S386 on chromosome 18.
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Fig4
In the case of chromosome 18, the informative microsatellite markers D18S391, D18S1002, D18S535, and D18S858 (18pter 18q21.31) showed two balanced peaks, revealing a normal heterozygote pattern, while the D18S386 marker (18q22.1) showed two unbalanced peaks (peak area ratio 1:2) (Figure 4), suggesting that the markers derived from the distal end of the long arm of chromosome 18.
Co-hybridization experiments using BACs RP11-246I7 (red; centromeric), RP11-177C10 (green) and RP11-715C4 (blue; telomeric). Their mapping position on chromosome 18 is reported in Table 1. For clarity, the original black and white FISH signals for RP11-246I7 (R), RP11-177C10 (G), RP11-715C4 (B), and DAPI are reported separately in the upper left boxes. The partial metaphase in the upper right box shows the telomeric FISH signals of the marker (arrowed).
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Fig5
Examples of FISH experiments are shown in Figure 5. A FISH experiment with a probe specific for the telomeric sequences revealed a clear signal at both ends of the marker (Figure 5T). The pattern of the FISH signals (Figure 5) indicated a symmetrical organization of the marker, the breakpoint likely representing the centromere of an inverted duplicated chromosome.