Induced G1 phase arrest of fast-dividing cells improves the quality of genomic profiles generated by array-CGH

SNP array profiling of mouse cell lines identifies their strains of origin and reveals cross-contamination and widespread aneuploidy

BACKGROUND

The crisis of Misidentified and contaminated cell lines have plagued the biological research community for decades. Some repositories and journals have heeded calls for mandatory authentication of human cell lines, yet misidentification of mouse cell lines has received little publicity despite their importance in sponsored research. Short tandem repeat (STR) profiling is the standard authentication method, but it may fail to distinguish cell lines derived from the same inbred strain of mice. Additionally, STR profiling does not reveal karyotypic changes that occur in some high-passage lines and may have functional consequences. Single nucleotide polymorphism (SNP) profiling has been suggested as a more accurate and versatile alternative to STR profiling; however, a high-throughput method for SNP-based authentication of mouse cell lines has not been described.

RESULTS

We have developed computational methods (Cell Line Authentication by SNP Profiling, CLASP) for cell line authentication and copy number analysis based on a cost-efficient SNP array, and we provide a reference database of commonly used mouse strains and cell lines. We show that CLASP readily discriminates among cell lines of diverse taxonomic origins, including multiple cell lines derived from a single inbred strain, intercross or wild caught mouse. CLASP is also capable of detecting contaminants present at concentrations as low as 5%. Of the 99 cell lines we tested, 15 exhibited substantial divergence from the reported genetic background. In all cases, we were able to distinguish whether the authentication failure was due to misidentification (one cell line, Ba/F3), the presence of multiple strain backgrounds (five cell lines), contamination by other cells and/or the presence of aneuploid chromosomes (nine cell lines).

CONCLUSIONS

Misidentification and contamination of mouse cell lines is potentially as widespread as it is in human cell culture. This may have substantial implications for studies that are dependent on the expected background of their cell cultures. Laboratories can mitigate these risks by regular authentication of their cell cultures. Our results demonstrate that SNP array profiling is an effective method to combat cell line misidentification.

Single cell segmental aneuploidy detection is compromised by S phase

BACKGROUND

Carriers of balanced translocations are at high risk for unbalanced gametes which can result in recurrent miscarriages or birth defects. Preimplantation genetic diagnosis (PGD) is often offered to select balanced embryos. This selection is currently mainly performed by array CGH on blastomeres. Current methodology does not take into account the phase of the cell cycle, despite the variable copy number status of different genomic regions in S phase.

RESULTS

Cell lines derived from 3 patients with different chromosomal imbalances were used to evaluate the accuracy of single cell array CGH. The different cell cycle phases were sorted by flow cytometry and 10 single cells were picked per cell line per cell cycle phase, whole genome amplified and analyzed by BAC arrays, the most commonly used platform for PGD purposes. In contrast to G phase, where the imbalances were efficiently identified, less than half of the probes in the regions of interest indicated the presence of the aberration in 17 S-phase cells, resulting in reduced accuracy.

CONCLUSIONS

The results demonstrate that the accuracy to detect segmental chromosomal imbalances is reduced in S-phase cells, which could be a source of misdiagnosis in PGD. Hence, the cell cycle phase of the analyzed cell is of great importance and should be taken into account during the analysis. This knowledge may guide future technological improvements.

A de novo chromosomal abnormality in Cri du Chat syndrome

OBJECTIVE

To find the length and location of the deletions in the short arm of chromosome 5 in one case of Cri du Chat syndrome using oligo array comparative genomic hybridization.

METHODS

Metaphase chromosomes were prepared from peripheral blood lymphocyte cultures using standard cytogenetic protocols. Chromosomal analysis was done in G-banded metaphases. Oligo array comparative genomic hybridization and fluorescence in situ hybridization were performed by the commercially available kits.

RESULTS

Oligonucleotide array comparative genomic hybridization (CGH) analysis revealed a 23.263 Mb deletion at region 5p14.2-->qter, combined with a duplication of 14.602 Mb in size in the area 12p13.1-->pter. Chromosomal aberrations were confirmed by fluorescence in situ hybridization. The male neonate with Cri du Chat syndrome had an unbalanced translocation which was inherited from his father who was a balanced carrier with a karyotype 46, XY, t (5; 12) (p14.2; p13.1).

CONCLUSIONS

This report shows the clinical utility of the oligonucleotide array in the detection of submicroscopic chromosomal aberrations, thus improving the molecular diagnosis of Cri du Chat syndrome.