The importance of the domestication of horses to human civilisations is undisputed. But there are conflicting hypotheses about the origins of tamed horses; the 'restricted origin' hypothesis postulates selective breeding of a few founding lineages followed by distribution, while the 'multiple origins hypothesis' suggests independent recruitment of a large number of founders over an extended time period and geographical location. In the January 19 Science, Vila et al. describe genetic analysis t

Inbreeding is thought to cause reduced genetic variation and diminished viability. In the January 18 Nature, Visscher et al. studied the genome of a viable herd of cows, Chillingham cattle (Bos taurus), that have lived as an isolated inbred herd for over 300 years in the north of England (Nature 2001, 409:303). Visscher et al. analyzed 13 of the Chillingham animals (the breed totals just 49 animals) and scored for 25 polymorphic microsatellite markers. They report that the herd is remarkably ho

Members of the PU.1/Spi family of Ets-type transcription factors play key roles in mammalian hematopoiesis and lymphoid development. Lymphocytes are found in jawed vertebrates, including cartilaginous fish, but not in jawless vertebrates or invertebrates. In the January 16 Proceedings of the National Academy of Science Anderson et al. identified three PU.1 members in the cartilaginous fish Raja eglanteria (skate)(Proc Natl Acad Sci USA 2001, 98:553-558). Phylogenetic analysis established that

Mammalian Toll-like receptors (TLRs) bind to bacterial lipopolysaccharides (LPS) leading to the induction of several cytokine genes that are essential for the inflammatory response. Activation of the Rel proteins is thought to be critical for TLR-induced transcriptional induction. As described in the January Nature Immunology, Weinmann et al. have used TLR4 mutant mice to show that TLR signaling is required for nucleosome remodeling at the interleukin 12 p40 promoter upon induction with LPS (N

Loss of imprinting (LOI) has been implicated in the predisposition to certain colorectal cancers. Insulin-like growth factor II (IGF2) is an imprinted gene in which the maternal allele is normally silenced. In the January 16 Proceedings of the National Academy of Science, Nakagawa et al. describe the development of a fluorescence-based primer extension assay (SnuPE) to examine whether LOI is associated with allele-specific methylation in colorectal cancer samples (Proc Natl Acad Sci USA 2001,

The interactions of cells with the extracellular matrix (ECM) are critical for orchestrating immune and inflammatory responses. In the December Immunity, de Fougerolles et al. report a comprehensive analysis of gene expression profiles affected by the attachment of monocytes to fibronectin and other ECM components (Immunity 2000, 13:749-758). They used a quantitative, restriction enzyme-based profiling method, named GeneCalling, to examine the integrin-mediated induction of genes in the monocy

Only 8% of the 18,967 genes in the Caenorhabditis elegans genome have been extensively studied using biochemistry or genetics. In the January 2 Proceedings of the National Academy of Sciences, Jiang et al. constructed microarrays with nearly every C. elegans gene to profile expression throughout development (Proc Natl Acad Sci USA 2001, 98:218-223). They compared gene expression in six developmental stages from eggs to adult worms. Around two thirds of genes were found to vary during developm

Histone modifications are required to gain access to DNA sequences within the tightly compacted genome and enable gene transcription. It has been proposed that acetylation of the amino-terminal tails of the core histones within the nucleosome particle is critical for activating transcription. In the December Genes and Development, Nowak and Corces suggest that histone phosphorylation may play a greater role than acetylation in gene induction (Genes Dev 2000, 14:3003-3013). They studied the he

Introducing methylated DNA at specific genomic loci affects local histone acetylation.

The SNF5 protein (also called INI1) is a subunit common to two closely related mammalian SWI/SNF complexes that function as chromatin-remodeling machines. The human gene, hSNF5, is mutated in early childhood malignant rhabdoid tumors (MRT). In the December EMBO Reports, Klochendler-Yeivin et al. describe a mouse model for SNF5 deficiency (EMBO Reports 2000, 1:500-506). Knockout mice embryos lacking a functional SNF5 gene die shortly after implantation. Experiments with blastocytes in culture sho

Telomeres are specialized structures at the ends of chromosomes that prevent fusion events and promote chromosomal end replication. Telomeres are maintained by the regulation of telomerase activity and their capping by telomeric proteins. In the November Genes and Development, Hsu et al. show that the DNA repair protein Ku plays a role in telomere capping (Gene Dev 2000, 14:2807-2812). Hsu et al. used surface plasma resonance and co-immunoprecipitation to demonstrate that Ku forms a high-affini

DNA lesions are repaired by a cut-and-remove process called nucleotide excision repair. An in vitro biochemically defined system has been developed in which six repair factors are sufficient to excise damage from naked DNA. In the December Molecular and Cellular Biology, Hara et al. use this system to examine the effect of DNA organization into nucleosome structures on the DNA repair process (Mol Cell Biol 2000, 20:9173-9181). A nucleosome structure was assembled by mixing human histone protein