Mouse molecular cytogenetic resource: 157 BACs link the chromosomal and genetic maps

Abstract

We have established a collection of strong molecular cytogenetic markers that span the mouse autosomes and X chromosome at an average spacing of one per 19 Mb and identify 127 distinct band landmarks. In addition, this Mouse Molecular Cytogenetic Resource relates the ends of the genetic maps to their chromosomal locations. The resource consists of 157 bacterial artificial chromosome (BAC) clones, each of which identifies specific mouse chromosome bands or band borders, and 42 of which are linked to genetic markers that define the centromeric and telomeric ends of the Whitehead/MIT recombinational maps. In addition, 108 randomly selected and 6 STS-linked BACs have been assigned to single chromosome bands. We have also developed a high-resolution fluorescent reverse-banding technique for mouse chromosomes that allows simultaneous localization of probes by fluorescence in situ hybridization (FISH) with respect to the cytogenetic landmarks. This approach integrates studies of the entire mouse genome. Moreover, these reagents will simplify gene mapping and analyses of genomic fragments in fetal and adult mouse models. As shown with the MMU16 telomeric marker for the trisomy 16 mouse model of Down syndrome, these clones can obviate the need for metaphase analyses. The potential contribution of this resource and associated methods extends well beyond mapping and includes clues to understanding mouse chromosomes and their rearrangements in cancers and evolution. Finally it will facilitate the development of an integrated view of the mouse genome by providing anchor points from the genetic to the cytogenetic and functional maps of the mouse as we attempt to understand mutations, their biological consequences, and gene function.

Figure 1

Mouse reverse-banded haploid karyotype produced from a single cell using chromomycin A3/distamycin A. For each chromosome pair, the left one shows the fluorescent R-band pattern; the right shows the typical Giemsa band pattern.

Figure 2

Dual-color FISH mapping of BACs on high-resolution reverse-banded mouse chromosomes. Two differently labeled BACs (biotin and digoxigenin) were cohybridized and detected simultaneously on R-banded chromosomes. (A) BAC 412F6 (green) maps on MMU6F2-3; BAC 412E19 (red) maps on MMU2C2. (B) BAC 412G6 (green) maps on MMU2H4; 412F19 (red) maps on MMU1C2.

Figure 2

Dual-color FISH mapping of BACs on high-resolution reverse-banded mouse chromosomes. Two differently labeled BACs (biotin and digoxigenin) were cohybridized and detected simultaneously on R-banded chromosomes. (A) BAC 412F6 (green) maps on MMU6F2-3; BAC 412E19 (red) maps on MMU2C2. (B) BAC 412G6 (green) maps on MMU2H4; 412F19 (red) maps on MMU1C2.

Figure 3

Composite mouse karyotype illustrating fluorescence signals from simultaneous hybridization of BACs linked to genetic markers defining the centromeric and telomeric ends of the genetic maps. Centromeric clones are shown in red; telomeric clones in green.

Figure 4

Ideogram of the integrated BAC resource for mouse cytogenetics. The locations of the 157 FISH-mapped BACs are shown relative to the fluorescent R-banded mouse chromosomes. Those clones containing centromeric and telomeric genetic markers are represented by blue boxes; clones mapped at random and clones containing markers from the chromosome arms are represented as red circles. Clones with two sites of hybridization are represented as target circles for the primary signal and open circles for the secondary signal.

Figure 5

Trisomy 16 detected in interphase cells by the chromosome 16 telomeric BAC. BAC 43D12 linked to D16Mit52 was used to define cells from the Ts16 mouse model of Down syndrome. Three sets of FITC signals are clearly seen on 90% of interphase cells in contrast to probes from other chromosomes that produce just two pairs of signals (data not shown).