Multicolour spectral karyotyping of mouse chromosomes

Abstract

Murine models of human carcinogenesis are exceedingly valuable tools to understand genetic mechanisms of neoplastic growth. The identification of recurrent chromosomal rearrangements by cytogenetic techniques serves as an initial screening test for tumour specific aberrations. In murine models of human carcinogenesis, however, karyotype analysis is technically demanding because mouse chromosomes are acrocentric and of similar size. Fluorescence in situ hybridization (FISH) with mouse chromosome specific painting probes can complement conventional banding analysis. Although sensitive and specific, FISH analyses are restricted to the visualization of only a few mouse chromosomes at a time. Here we apply a novel imaging technique that we developed recently for the visualization of human chromosomes to the simultaneous discernment of all mouse chromosomes. The approach is based on spectral imaging to measure chromosome-specific spectra after FISH with differentially labelled mouse chromosome painting probes. Utilizing a combination of Fourier spectroscopy, CCD-imaging and conventional optical microscopy, spectral imaging allows simultaneous measurement of the fluorescence emission spectrum at all sample points. A spectrum-based classification algorithm has been adapted to karyotype mouse chromosomes. We have applied spectral karyotyping (SKY) to chemically induced plasmocytomas, mammary gland tumours from transgenic mice overexpressing the c-myc oncogene and thymomas from mice deficient for the ataxia telangiectasia (Atm) gene. Results from these analyses demonstrate the potential of SKY to identify complex chromosomal aberrations in mouse models of human carcinogenesis.

Mammary tumors in mice conditionally mutant for Brca1 exhibit gross genomic instability and centrosome amplification yet display a recurring distribution of genomic imbalances that is similar to human breast cancer

“…The cells were lysed in hypotonic solution (0.06 M KCl) and the chromsomes were fixed in methanol:acetic acid (3:1). Spectral karyotyping was performed as described previously (Liyanage et al, 1996;Weaver et al, 1999). For each tumor, at least five metaphases were analysed.…”

A targeted disruption of the murine Brca1 gene causes γ-irradiation hypersensitivity and genetic instability

“…Spectral karyotyping of the embryonic cell metaphases was performed as described previously for human and mouse (SchroÈ ck et al, 1996;Liyanage et al, 1996). Brie¯y,¯ow-sorted mouse chromosomes were ampli®ed by degenerate oligonucleotide-primed PCR incorporating haptenized or uorochrome-conjugated nucleotides (Telenius et al, 1992).…”

Centrosome abnormalities, recurring deletions of chromosome 4, and genomic amplification of HER2/neu define mouse mammary gland adenocarcinomas induced by mutant HER2/neu

“…Such comparative cytogenetic analyses, however, have been hampered by the intricacy of reliably karyotyping mouse chromosomes. We have therefore used spectral karyotyping (SKY) (Liyanage et al, 1996;SchroÈ ck et al, 1996b) and comparative genomic hybridization (CGH) (Kallioniemi et al, 1992;Weaver et al, 1999), two techniques that overcome these hurdles, to characterize chromosomal aberrations in a mouse model of human breast cancer induced by the expression of an activated mutated HER2/neu under its endogenous promoter (Andrechek et al, 2000). As part of the family of epithelial growth factor receptors, the HER2/neu oncogene is ampli®ed in about 25% of human breast cancers (Revillion et al, 1998).…”