RESUMO
The murine Hox-3.5 gene has been mapped and linked genomically to a position 18 kb 3' of its most 5' locus neighbour, Hox-3.4, on chromosome 15. The sequence of the Hox-3.5 cDNA, together with the position of the gene within the locus, show it to be a paralogue of Hox-2.6, Hox-1.4 and Hox-4.2. The patterns of embryonic expression for the Hox-3.5 gene are examined in terms of three rules, proposed to relate a Hox gene's expression pattern to its position within the locus. The anterior boundaries of Hox-3.5 expression in the hindbrain and prevertebral column lie anterior to those of Hox-3.4 and all other, more 5'-located Hox-3 genes. Within the hindbrain, the Hox-3.5 boundary is seen to lie posterior to that of its paralogue, Hox-2.6, by a distance equal to about the length of one rhombomere. Patterns of Hox-3.5 expression within the oesophagus and spinal cord, but not the testis, are similar to those of other Hox-3 genes, Hox-3.3 and Hox-3.4.
Assuntos
Desenvolvimento Embrionário e Fetal/genética , Expressão Gênica/genética , Genes Homeobox/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Mapeamento Cromossômico , Esôfago/embriologia , Hibridização in Situ Fluorescente , Camundongos , Dados de Sequência Molecular , Rombencéfalo/embriologia , Homologia de Sequência de Aminoácidos , Medula Espinal/embriologiaRESUMO
The Hox-C6 gene, in common with its Xenopus and human homologues, is organised as 3 exons with 2 distinct promoters (PRI and PRII) producing 2 different transcripts. The PRII promoter produces a 'typical' Hox transcript by splicing 2 exons separated by a 700 bp intron. The PRI promoter initiates transcription from a 3rd exon, 9 kbp 5' of PRII. This exon is spliced into the 1st exon of the PRII transcript at a point 3' of the translation start codon. This means that the predicted protein product of the PRI protein contains the Hox-C6 homeodomain but is truncated by 82 amino acids compared with the PRII product. In situ hybridisation using probes specific for PRI or PRII showed them to have essentially the same distribution in the developing nervous system and prevertebrae of 12.5 d embryos. However, the distribution of transcripts in the CNS was distinctly different from that reported previously for a probe containing the Hox-C6 homeobox.