Reassignment 1 of Mycs gene to mouse chromosome XA1.2-2 by radiation hybrid mapping and fluorescence in situ hybridization

The mouse Mycs gene is a member of the intronless Myc gene family. Both human and rat Mycs genes have been mapped to chromosome X (Moton et al., 1989; Serikawa et al., 1992), while the mouse Mycs was initially localized by fluorescence in situ hybridization (FISH) to chromosome 19B (Sugiyama et al., 1999). The apoptosis-inducing activity of intronless Myc genes is evolutionarily conserved in mammalian cells but is somewhat distinct from c-myc although both require activation of caspase-3 like proteases (Asai et al., 1994; Kagaya et al., 1997, Sugiyama et al., 1999). As a part of our attempt to identify the genes amplified from double minute chromosomes originating from mouse chromosome 19 identified in a hepatocellular carcinoma developed in Myc transgenic mice (Zimonjic et al., 2001), we found by FISH and radiation hybrid (RH) mapping that the mouse Mycs gene is located on the X chromosome. This localization confirms the recent correct assignment of Mycs gene on the X chromosome by RH only (Yamasaki et al., 2001) and places the Mycs gene locus at region XA1.2-2 (Fig. 1). Furthermore, this mapping provides evidence that Mycs genes are conserved in vertebrates, consistent with their similar biological function. Materials and methods