Comparative mapping of mouse and rat chromosomes by fluorescence in situ hybridization

Comparative fluorescence in situ hybridization mapping using DNA libraries from flow-sorted mouse chromosomes and region-specific mouse BAC clones on rat chromosomes reveals chromosomal homologies between mouse (Mus musculus, MMU) and rat (Rattus norvegicus, RNO). Each of the MMU 2, 3, 4, 6, 7, 9, 1 2, 14, 15, 16, 18, 19, and X chromosomes paints only a single rat chromosom e or chromosome segment and, thus, the chromosomes are largely conserved be tween the two species. In contrast, the painting probes for MMU chromosomes 1, 5, 8, 10, 11, 13, and 17 produce split hybridization signals in the rat , disclosing evolutionary chromosome rearrangements. Comparative mapping da ta delineate several large linkage groups on RNO 1, 2, 4, 7, and 14 that ar e conserved in human but diverged in the mouse. On the other hand, there ar e linkage groups in the mouse, i.e., on MMU 1, 8, 10, and 11, that are disr upted in both rat and human. In addition, we have hybridized probes for Nap 2, p57, Igf2, H19, and Sh3d2c from MMU 7 to RNO Iq and found the orientatio n of the imprinting gene cluster and Sh3d2c to be the same in mouse and rat . Hybridization of rat genomic DNA shows blocks of (rat-specific) repetitiv e sequences in the pericentromeric region of RNO chromosomes 3-5, 7-13, and 20; on the short arms of RNO chromosomes 3, 12, and 13; and on the entire Y chromosome, (C) 1999 Academic Press.