Consistent chromosomal aberration in cell lines transformed with Marek's disease herpesvirus: evidence of genomic DNA amplification.

A specific chromosomal aberration was observed in 14 of 15 avian lymphoblastoid cell lines transformed with Marek's disease herpesvirus. This aberration, designated dup(1p)(p22-p23), appeared as an extra G-positive band and interband on the short arm of one chromosome I homolog. Using fluorescent in situ hybridization, we identified amplified genomic DNA sequences in this region. This amplification involves sequences linked to an endogenous retrovirus locus and genes in the histone multigene family. This aberration was not observed in cells transformed by reticuloendotheliosis virus or by avian leukosis virus, nor has it been observed in untransformed chicken cells. The induction of the 1p+ chromosomal aberration may be an essential event in the transformation of lymphocytes by Marek's disease virus.