Research

Unexpected structural complexity of supernumerary marker chromosomes characterized by microarray comparative genomic hybridization

Karen D Tsuchiya^1,2 , Kent E Opheim^1,2 , Mark C Hannibal³ , Anne V Hing³ , Ian A Glass³ , Michael L Raff³ , Thomas Norwood⁴ and Beth A Torchia⁵

¹Department of Laboratories, Children's Hospital & Regional Medical Center, Seattle, WA, USA

²Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA, USA

³Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, USA

⁴Department of Pathology, University of Washington School of Medicine, Seattle, WA, USA

⁵Signature Genomic Laboratories, LLC, Spokane, WA, USA

author email corresponding author email

Molecular Cytogenetics 2008, 1:7doi:10.1186/1755-8166-1-7

Published:	21 April 2008

Abstract

Background

Supernumerary marker chromosomes (SMCs) are structurally abnormal extra chromosomes that cannot be unambiguously identified by conventional banding techniques. In the past, SMCs have been characterized using a variety of different molecular cytogenetic techniques. Although these techniques can sometimes identify the chromosome of origin of SMCs, they are cumbersome to perform and are not available in many clinical cytogenetic laboratories. Furthermore, they cannot precisely determine the region or breakpoints of the chromosome(s) involved. In this study, we describe four patients who possess one or more SMCs (a total of eight SMCs in all four patients) that were characterized by microarray comparative genomic hybridization (array CGH).

Results

In at least one SMC from all four patients, array CGH uncovered unexpected complexity, in the form of complex rearrangements, that could have gone undetected using other molecular cytogenetic techniques. Although array CGH accurately defined the chromosome content of all but two minute SMCs, fluorescence in situ hybridization was necessary to determine the structure of the markers.

Conclusion

The increasing use of array CGH in clinical cytogenetic laboratories will provide an efficient method for more comprehensive characterization of SMCs. Improved SMC characterization, facilitated by array CGH, will allow for more accurate SMC/phenotype correlation.