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Deletion and duplication of the adenomatous polyposis coli gene resulting from an interchromosomal insertion involving 5(q22q23.3) in the father
  4. D WELLS,
  1. *Clinical Cytogenetics, The Galton Laboratory, University College London, Wolfson House, 4 Stephenson Way, London NW1 2HE, UK
  2. †The Galton Laboratory, University College London, Wolfson House, 4 Stephenson Way, London NW1 2HE, UK
  3. ‡Paediatric Department, Whittington Hospital, St Mary's Wing, Highgate Hill, London N19 5NF, UK

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    Editor—Chromosomal rearrangements occur at a low frequency in the general population and chromosomal insertions occur at an estimated frequency of 1 in 5000 newborn infants.1 Adjacent segregation of interchromosomal insertions results in a deletion or duplication of the inserted segment or more complicated imbalances through a recombination event at meiosis. In the case presented here, a balanced interchromosomal insertion between chromosomes 5 and 10, 46,XY,dir ins(10;5)(q25;q22q23.3), was carried by the father. Theoretically this insertion involves less than 1% of the haploid autosomal length and therefore a fetus with either a duplication or deletion is likely to be viable unless there are essential genes in this segment that are deleterious in an aneuploid conceptus. Generally deletions are more deleterious than duplications and there are few published cases where the clinical features of a duplication and deletion for the same chromosomal region have been described within the same family.2 3

    In this paper we report four cases of a 5q22q23.3 deletion and one case of a duplication for the same region which includes theAPC gene. All of the aneuploid offspring were within the same generation and the clinical features associated with 5q22q23.3 deletion with a similar genetic background will be compared with published cases.

    Lymphocytes were cultured by standard methods including semi-synchronisation with thymidine and preparations were analysed using G banding.4 Fluorescence in situ hybridisation (FISH) of the chromosome preparations involved YAC probe 37HG4 containing a 2.3 kb fragment of cDNA from theAPC gene which recognises anMspI polymorphism.5 TheAPC gene has been localised to the subband 5q22.1.5 Standard FISH procedures were used and have been published elsewhere.6 FISH images were viewed using computer enhanced image analysis systems (Vysis).

    The family were investigated on the birth of the proband. The …

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