A murine even-skipped homologue, Evx 1, is expressed during early embryogenesis and neurogenesis in a biphasic manner

Using the Drosophila even-skipped (eve) homeobox as a probe, we have isolated two murine genes, Evx 1 and Evx 2, from a genomic library. Evx 1, Evx 2, eve and the Xenopus Xhox-3 constitute a family of related genes based on similar homeodomain sequences. In addition, Evx 1 and Evx 2 share extended amino acid conservation outside of the homeobox. The Evx 1 protein consists of 416 amino acids as deduced from the longest open reading frame of Evx 1 cDNAs. Evx 1 is located 3.7 cM from the Hox 5 locus on mouse chromosome 2. It is expressed in undifferentiated F9 stem cells but not in cells differentiated with retinoic acid and cAMP. During embryogenesis, Evx 1 shows a biphasic expression pattern. From days 7 to 9 p.c. Evx 1 expression emerges at the posterior end of the embryo within the primitive ectoderm, and later in the mesoderm and neuroectoderm. From days 10 to 12.5 p.c. Evx 1 transcripts are restricted to specific cells within the neural tube and hindbrain along their entire lengths and coincides temporally, as well as spatially, with maturation of early forming interneurons, possibly commissural interneurons. The early and late transcription pattern is compatible with a role of Evx 1 in specifying posterior positional information along the embryonic axis similar to the Xenopus Xhox-3 and in specifying neuronal cell fates within the differentiating neural tube in analogy to eve in the embryonic central nervous system of Drosophila, respectively

The homeobox in vertebrate development.

http://dx.doi.org

Murine developmental control genes.

Various strategies have been used to isolate genes that participate in the regulation of mouse development. Gene families that have been identified on the basis of their homology to motifs within Drosophila control genes or human transcription factor genes, namely homeobox (Hox), paired-box (Pax), and POU genes, can be compared with respect to gene organization, structure, and expression patterns. The functions of these genes can be analyzed molecularly in vitro and in vivo with the use of available mouse mutants or transgenic mice. In addition, it has been possible to generate gain- or loss-of-function mutations by random or targeted introduction of transgenes. Models derived from these studies can reveal the successive steps of developmental control on a genetic level

Anterior boundaries of Hox gene expression in mesoderm-derived structures correlate with the linear gene order along the chromosome.

The developmental expression patterns of four genes, Hox 1.1., Hox 1.2, Hox 1.3 and Hox 3.1, were examined by in situ hybridization to serial embryonic sections. The three genes of the Hox 1 cluster, used in this study, map to adjacent positions along chromosome 6, whereas the Hox 3.1 gene maps to the Hox 3 cluster on chromosome 15. The anterior expression limits in segmented mesoderm varied among the four genes examined. Interestingly, a linear correlation exists between the position of the gene along the chromosome and the extent of anterior expression. Genes that are expressed more posterior are also more restricted in their expression in other mesoderm-derived tissues. The order of expression anterior to posterior was determined as: Hox 1.3, Hox 1.2, Hox 1.1 and Hox 3.1. Similarly, genes of the Drosophila Antennapedia and Bithorax complex specifying segment identity also exhibit anterior expression boundaries that correlate with gene position. The data suggest that Hox genes may specify positional information along the anterior-posterior axis during the formation of the body plan