Homeobox

Homeoboxes code for homeodomains, sequences of 60 amino acids that function as the DNA-binding regions of transcription factors. Each homeo-box gene in Drosophila is expressed only in its own characteristic subset of embryonic cells, and almost every embryonic cell contains a unique combination of homeodomain proteins. 

Hashimoto, T., Nakano, Y., Morinaga, T., and Tamaoki, T. (1992). A new family of homeobox genes encoding multiple homeodomain and zinc finger motifs. Mech. Dev. 39 125-126. 

McGinnis, W., and Krumlauf, R. (1992). Homeobox genes and axial patterning. Cell 68 283-302. 

Wright, C. V. E. (1991). Vertebrate homeobox genes. Curr. Opin. Cell Biol. 3 976-982. 

TRANSCRIPTION FACTORS IN MAMMALIAN DEVELOPMENT MURINE HOMEOBOX GENES... 

VIII. Mammalian-D/wop/iifa Homeobox Gene Exchanges.105... 

IX. Homeobox Gene Circuitry Upstream and Downstream Genes.109... 

The amino acid sequence encoded by the homeobox includes a helix-tum-helix motif that has now been shown by X-ray crystallography to be structurally virtually identical to that found in various prokaryotic... 

Many mouse homeobox genes are found in four clusters (a-d) on chromosomes 2,6,11, and 15 (Fig. 2). Each Hox cluster carries about 10 genes and displays a number of interesting features. First, genes within... 

These dispersed homeobox genes often show rather unique expression patterns. Both the Dlx and Dbx genes, for example, are expressed in the developing embryonic forebrain, where no expression is detected for the Hox complex genes. And the S-8 and K-2 (MHox) genes are expressed... 

The genes with paired boxes often, but not always, have homeoboxes as well. The homeoboxes that are associated with paired boxes have distinctive sequence characteristics that set them apart as a separate homeobox subfamily. Interestingly, these paired-type homeoboxes in mouse can sometimes reside on genes such as the K-2 (MHox) and S-8 paired-type homeobox genes, which have not been found to carry paired boxes. 

It seems reasonable to hope that misexpression analysis of murine homeobox genes might also provide clues to their function. The first such... 

Lufkin et al. (1992) also used a homeobox gene promoter exchange to drive misexpression of the Hox-4.2 gene. The Hox-1.6 promoter was observed to extend the anterior transcription boundary, and this region of ectopic expression gave a number of abnormalities, including absence... 

Other homeobox gene targeting experiments have resulted in more dramatic developmental defects. Homozygous //ox-1.5 null mutants showed a number of alterations (Chisaka and Capecchi, 1991). The mice died at or shortly after birth, apparently from circulation and/or pulmonary problems. These animals showed hypertrophy of the atria and... 

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