Complementation mapping in microcell hybrids: Localization ofFpgs andAk-1 onmus musculus chromosome 2

Abstract

The gene encoding folylpolyglutamyl synthetase (FPGS) was assigned to mouse chromosome 2 by complementation mapping. Chinese hamster ovary cells (AuxBl) deficient in FPGS, and consequently auxotrophic for glycine, adenosine, and thymidine (gat⁻), were employed as recipients in microcell-mediated chromosome transfer experiments. Mouse chromosomes derived from diploid embryo fibroblasts were introduced into hamster AuxBl cells, and gat⁺ microcell hybrids were selected in medium lacking adenosine and thymidine. Mouse chromosome 2 was the only donor chromosome whose presence correlated with expression of FPGS activity. Furthermore, every gat⁺ hybrid clone expressed murine AK-1, a marker previously assigned to chromosome 2. Eight of 20 clones analyzed retained deletion chromosomes derived from mouse chromosome 2. These clones were used to localize murine Fpgs and Ak-1 to a region of this chromosome, namely 2(cen→C1).