AB2.2 Cells

The AB2.2 cell line is a widely utilized murine embryonic stem (ES) cell line derived from the 129S7 (also known as 129P2/OlaHsd) mouse strain. It has played a prominent role in gene targeting and transgenic mouse generation due to its robust capacity for in vitro expansion and genetic manipulation. AB2.2 cells are pluripotent, capable of contributing to all germ layers, and have been instrumental in producing germline-competent chimeras. However, like many ES cell lines maintained over extended culture periods, AB2.2 is prone to chromosomal instability, especially aneuploidy involving chromosome 8. Cytogenetic analysis of AB2.2 and its sub-lines has revealed a high frequency of chromosomal abnormalities, with mosaic and pure trisomy 8 being particularly common. In one study, AB2.2 displayed a mosaic karyotype involving gains of chromosomes 8 and Y, including configurations such as 42,XY,+Y,+8 / 41,XY,+Y / 40,XY. Among its sub-lines, additional karyotypic anomalies were identified, such as double trisomies involving chromosomes 8 and 11, and complex derivative chromosomes arising from unbalanced translocations involving chromosome 8. These structural and numerical aberrations are associated with decreased germline transmission efficiency, and their presence complicates interpretation of genotype-phenotype relationships in chimeric animals. Given its genetic background and susceptibility to chromosomal instability, AB2.2 remains a powerful tool in mouse genetics, but it requires careful quality control. Routine karyotype screening-including both G-banding and FISH-is recommended before proceeding with blastocyst injection to ensure the chromosomal integrity necessary for reliable germline transmission and accurate phenotypic analyses.