Chromosome localization of the loci for PEPA, PEPB, PEPS, IDH1, GSR, MPI, PGM1, NP, SOD1, and ME1 in the common shrew (Sorex araneus)

Comparative FISH mapping of human cDNA clones to chromosomes of the musk shrew (Suncus murinus, Insectivora)

Forty-one cDNA clones of human functional genes were newly mapped to chromosomes of the musk shrew (Suncus murinus, Insectivora) by fluorescence in situ hybridization, and a comparative cytogenetic map of 51 genes, including 10 genes reported in our previous study, was constructed between human (HSA) and musk shrew (SMU) chromosomes. In this comparative map, the 51 genes localized to human autosomes, except HSA 8, 16, and 20, were mapped to 15 shrew autosomes, except SMU 4, 16, 17 and 18. Twelve conserved segments were identified between human and shrew chromosomes, and six segments among the musk shrew, human, and mouse. Our results defined the presence of at least one inversion and several interchromosomal rearrangements that occurred during evolution after the two species diverged from a common ancestor. Localization of three major histocompatibility complex (MHC) genes to shrew chromosome 3 suggested that the MHC genes of the musk shrew are located in a cluster on chromosome 3. The cytogenetic map constructed in this study is the first cytogenetic map with many functional genes in insectivore species. This approach provides clues for clarifying the chromosomal evolution in this order.

ZOO-FISH analysis in insectivores: "Evolution extols the virtue of the status quo"

In evolutionary terms, insectivores are thought to be close to primates. Through ZOO-FISH analysis using human chromosome-specific painting probes, the syntenic relationship between the human and common shrew, Sorex araneus, karyotypes was studied. The human karyotype was found to be conserved in the shrew, with 32 autosomal segments of common synteny. Special arrangements, already known from similar studies on other species, were noted: fusions of HSA 16 and 19, HSA 3 and 21, and HSA 14 and 15. Only 10 breaks are necessary to transform the human karyotype into the karyotype of the common shrew. Together with known ZOO-FISH data from species belonging to other orders, this puts the human karyotype arrangement near the basis of all mammalian karyotypes. Human chromosome 2 was found to be conserved in its entirety as a single chromosome arm in the shrew. Evidence is presented that the same fusion of two original chromosomal segments formed the shrew chromosome ortholog of HSA 2 as the fusion that occurred during primate evolution to form human chromosome 2. This is a remarkable example of chromosomal coevolution.