Sensitivity and specificity of whole chromosome paint (WCP) probes are correlated with size of translocated segment.

Abstract

Wiley et al. reported on a de novo {open_quotes}non-reciprocal translocation 1;8{close_quotes} as {open_quotes}confirmed{close_quotes} by whole chromosome paints (WCP). The assumption in this and similar papers is that WCP for one chromosome would light the ends of a derivative chromosome if the derivative chromosome carries such material and that the signal would be missing from donor chromosome. However, it has been our experience that WCP do not rule out reciprocal translocations involving small segments. Our lab has had three recent relevant examples: Case 1: A t(4;5)(p16.3;p15.3)mat. The initial discovery by G-banding was of a small piece of extra material on 4p in mother and child. Initial trials using a paint 4 probe on the mother`s metaphases, both in our laboratory and in another laboratory, failed to show signal on any other chromosome. The reciprocal 4;5 nature was demonstrated later using a cosmid to 4p. Painting with a chromosome 5 probe on metaphases from the mother with the rcp(4;5) showed apparently complete painting of both chromosome 5s in all cells. The signal from the WCP 5 probe on the derivative 4 was seen as a very small signal in only 30% of the cells. 4 refs.