Interstitial deletion of chromosome 6q: Precise definition of the breakpoints by microdissection,DNA amplification,and reverse painting |
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Authors: | N Rubtsov G Senger A Neumann C Kelbova K Junker V Beensen U Claussen N Rubtsov H Kuzcera |
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Institution: | (1) Institute of Human Genetics and Anthropology, University Jena, Kollegiengasse 10, D-07740 Jena, Germany Tel. +49-3641-631712; fax +49-3641-631713, DE;(2) Institute of Cytology and Genetics, 630090 Novosibirsk, Russia, RU;(3) Südharz-Hospital Nordhausen, Dr. Robert-Koch-Strasse 39, D-99734 Nordhausen, Germany, DE |
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Abstract: | Routine chromosomal analysis using GTG-banding alone showed a mosaic terminal deletion of 6q in a 14-week-old boy with developmental
retardation, facial anomalies, agenesis of corpus callosum, cleft palate, hypotonia, short neck and pterygium colli, and minor
anomalies of hands and feet. Discrepancies between the clinical findings on our patient and those described in the literature
on patients having terminal deletions led to a more precise analysis of the karyotype. Reverse painting was performed on normal
G-banded metaphases for exact determination of the breakpoints and on metaphases of the patient for evaluation of mosaicism.
A DNA library that was obtained by microdissection of three deleted chromosomes 6 was used as a painting probe. Subsequent
DNA amplification was performed with the help of topoisomerase-pretreated degenerate oligonucleotide primers. Unexpectedly,
the hybridization pattern on normal metaphase chromosomes revealed an interstitial deletion with breakpoints at 6q25.1 and
6q27 instead of a terminal deletion. Hybridization on metaphases of the patient showed one deleted chromosome 6 in all metaphases
analyzed at a higher resolution rather than mosaicism as previously assumed karyotype, 46,XY,del(6)(q25.1→q27)]. We assume
that in the single cases of 6q– described in the literature the deletions are misclassified. This might be due to difficulties in distinguishing between
interstitial and terminal deletions at 6q and in precisely defining chromosomal breakpoints after GTG-banding alone.
Received: 29 November 1995 / Revised: 15 January 1996 |
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