Molecular cloning, chromosomal assignment, and nucleotide sequence of the feline homeobox HOX3A

Human colorectal carcinogenesis is associated with deregulation of homeobox gene expression

In the present study, the possible involvement of homeobox-containing genes in colorectal cancer (CRC) development was investigated. Using a stepwise screening approach and RT-PCR, we have demonstrated that the human HOXB6, B8, C8 and C9 are overexpressed at various stages of CRC. In contrast, all CRC cases exhibited a marked decrease in the homeodomain-containing Cdx1 gene expression. Recent data which suggest a regulatory link between HOXB8 and several tumor suppressor genes, such as DCC, APC, and TGF beta, sustain a possible implication of homeobox genes in colon carcinogenesis. Moreover, our data showing a decrease in Cdx1 expression are consistent with the notion that genes functioning in the establishment and maintenance of the intestinal epithelium might, upon deregulation, disturb the normal control of cellular proliferation, differentiation, and death, thus leading to cancer development.

Numt, a recent transfer and tandem amplification of mitochondrial DNA to the nuclear genome of the domestic cat

The mitochondrial DNA of plant and animal cells is a transcriptionally active genome that traces its origins to a symbiotic infection of eucaryotic cells by bacterial progenitors. As prescribed by the Serial Endosymbiosis Theory, symbiotic organelles have gradually transferred their genes to the eucaryotic genome, producing a functional interaction of nuclear and mitochondrial genes in organelle function. We report here a recent remarkable transposition of 7.9 kb of a typically 17.0-kb mitochondrial genome to a specific nuclear chromosomal position in the domestic cat. The intergrated segment has subsequently become amplified 38-76 times and now occurs as a tandem repeat macrosatellite with multiple-length alleles resolved by pulse-field gel electrophoresis (PFGE) segregating in cat populations. Sequence determination of the nuclear mitochondrial DNA segment, Numt, revealed a d(CA)-rich 8-bp motif [ACACACGT] repeated imperfectly five times at the deletion junction that is a likely target for recombination. The extent and pattern of sequence divergence of Numt genes from the cytoplasmic mtDNA homologues plus the occurrence of Numt in other species of the family Felidae allowed an estimate for the origins of Numt at 1.8-2.0 million years ago in an ancestor of four modern species in the genus Felis. Numt genes do not function in cats; rather, the locus combines properties of nuclear minisatellites and pseudogenes. These observations provide an empirical glimpse of historic genomic events that may parallel the accommodation of organelles in eucaryotes.

Anchored reference loci for comparative genome mapping in mammals

Recent advances in gene mapping technologies have led to increased emphasis in developing representative genetic maps for several species, particularly domestic plants and animals. These maps are being compiled with two distinct goals: to provide a resource for genetic analysis, and to help dissect the evolution of genome organization by comparing linkage relationships of homologous genes. We propose here a list of 321 reference anchor loci suitable for comparative gene mapping in mammals and other vertebrate classes. We selected cloned mouse and human functional genes spaced an average of 5-10 centiMorgans throughout their respective genomes. We also attempted to include loci that are evolutionarily conserved and represented in comparative gene maps in other mammalian orders, particularly cattle and the domestic cat. We believe that the map may provide the basis for a unified approach to comparative analysis of mammalian species genomes.