Julie Leana-Cox

Molecular cytogenetic evidence for a common breakpoint in the largest inverted duplications of chromosome 15.

Chromosomes from 20 patients were used to delineate the breakpoints of inverted duplications of chromosome 15 (inv dup[15]) that include the Prader-Willi syndrome/Angelman syndrome (PWS/AS) chromosomal region (15q11-q13). YAC and cosmid clones from 15q11-q14 were used for FISH analysis, to detect the presence or absence of material on each inv dup(15). We describe two types of inv dup(15): those that break between D15S12 and D15S24, near the distal boundary of the PWS/AS chromosomal region, and those that share a breakpoint immediately proximal to D15S1010. Among the latter group, no breakpoint heterogeneity could be detected with the available probes, and one YAC (810f11) showed a reduced signal on each inv dup(15), compared with that on normal chromosomes 15. The lack of breakpoint heterogeneity may be the result of a U-type exchange involving particular sequences on either homologous chromosomes or sister chromatids. Parent-of-origin studies revealed that, in all the cases analyzed, the inv dup(15) was maternal in origin.

What's in a name? Chromosome 22q abnormalities and the DiGeorge, velocardiofacial, and conotruncal anomalies face syndromes.

The recent advances in our understanding of the phenotype associated with deletion of the DiGeorge Chromosome Region (DGCR) at 22q11.2 are in many ways analogous to the fable about the blind men and the elephant. Originally described as three distinct phenotypes (DiGeorge (DG) syndrome, velocardiofacial (VCF) syndrome, and the conotruncal anomalies face (CTAF) syndrome), it is now clear that there is only a single broad and variable phenotype associated with deletion of the DGCR. As in the fable, distinguished clinicians approached this phenotypic {open_quotes}elephant{close_quotes} from different perspectives and provided three separate, although overlapping descriptions. Our analogy to this fable is not to imply some {open_quotes}blindness{close_quotes} on the part of these clinicians, but rather to point out the well-known difficulty in delineating the indistinct phenotypic boundaries of a syndrome until a genetic or biochemical marker for the condition is available. The recent availability of a fluorescent in situ hybridization (FISH) probe to detect deletion of the DGCR now allows delineation of the broad phenotype of our {open_quotes}elephant{close_quotes} which spans from lethal DG phenotypes through the intermediate VCF and CTAF phenotypes to the newly recognized {open_quotes}mild{close_quotes} phenotype consisting of only developmental delays and subtle facial abnormalities. 33 refs.

Sex chromosome markers: Characterization using fluorescence in situ hybridization and review of the literature

Fluorescence in situ hybridization (FISH) using biotin labeled X- and Y-chromosome DNA probes was utilized in the analysis of 23 sex chromosome-derived markers. Specimens were obtained through prenatal diagnosis, because of a presumptive diagnosis of Ullrich-Turner syndrome, mental retardation, and minor anomalies or ambiguous genitalia; three were spontaneous abortuses. Twelve markers were derived from the X chromosome and eleven from the Y chromosome; this demonstrates successfully the value and necessity of FISH utilizing DNA probes in the identification of sex chromosome markers. Both fresh and older slides, some of which had been previously G-banded, were used in these determinations. We have also reviewed the literature on sex chromosome markers identified using FISH.

Cytogenetic studies of primary cultures of esophageal squamous cell carcinoma.

Cytogenetic analysis was performed on primary cultures of 21 squamous cell carcinomas of the esophagus (SCCE). Seven cases exhibited mosaic clonal chromosome abnormalities distributed as follows: two contained tetraploid cell populations, one with t(3;7)(p21;q11); two showed loss of the Y chromosome, one with double minutes; single cases demonstrated der(11)t(4;11)(q?27;q23); add(1)(p35) and del(4)(p12); and del(7)(p13), del(7)(q22q34), and der(11)t(7;11)(p?15;p?13). The remaining 14 cases had apparently normal karyotypes, possibly derived from stromal elements. These results demonstrate numerical abnormalities and the multiple occurrence of rearrangements involving chromosomes 7 and 11 in SCCE.

Application of FISH to complex chromosomal rearrangements associated with chronic myelogenous leukemia

Identification of complex chromosomal rearrangements can be difficult, due either to the limited number and sometimes poor quality of metaphases in bone marrow preparations or to the nature of the rearrangements. Fluorescence in situ hybridization (FISH) using chromosome-specific DNA libraries in conjunction with a cosmid probe for the c-ABL oncogene was performed to substantiate the preliminary G-banded karyotypes of six patients with chronic myelogenous leukemia (CML). Our results indicate that FISH is sufficiently sensitive to detect complex and subtle rearrangements, even in bone marrow preparations with suboptimal metaphases, and can provide valuable corroborative information.