High impact information on Mix.1

• The homeobox gene goosecoid controls cell migration in Xenopus embryos [1].
• Goosecoid (gsc), a homeobox gene expressed specifically in the dorsal blastopore lip of the Xenopus gastrula, is considered to play an important role in Spemann's organizer phenomenon [1].
• The results suggest a function for gsc in the control of gastrulation movements in groups of cells, but not in dissociated cells, and demonstrate that a vertebrate homeobox gene can regulate region-specific cell migration [1].
• Unexpectedly, Mix.1 is expressed mostly in the future endoderm, suggesting that endoderm may be formed by induction in a similar way as mesoderm [2].
• Mix.1 behaves as an immediate early response to induction, and its kinetics of expression suggest a major role for MBT in the control of inducible gene expression [2].

Biological context of Mix.1

• We report the cloning, sequence analysis, and developmental expression pattern of lim1, a member of the LIM class homeobox gene family in the mouse. lim1 cDNA encodes a predicted 406 amino acid protein that is 93% identical with the product of the Xenopus LIM class homeobox gene Xlim1 [3].
• Like the chromosomal Mix.1 gene, microinjected Mix.2 gene plasmids respond to activin in the presence of cycloheximide in animal cap assays and also respond to the embryonic inductive signal in Nieuwkoop recombinants [4].
• We have determined the DNA sequence of a Xhox-1 cDNA and this allows us to predict the complete sequence of a vertebrate homeobox protein [5].
• The sequence homology, expression pattern and gain-of-function phenotype of Xtwn is most similar to the previously isolated Xenopus homeobox gene siamois (Xsia) suggesting that Xtwn and Xsia comprise a new subclass of homeobox genes important in dorsal axis specification [6].
• In Xenopus, this territory is initially included within the expression domain of the bicoid-class homeobox gene Xotx2 but very soon, at the beginning of neurulation, it becomes devoid of Xotx2 transcripts in spatiotemporal concomitance with the transcriptional activation of the paired-like homeobox gene Xrx1 [7].

Anatomical context of Mix.1

• Next, injection of dsRNA for Xlim-1, a homeobox gene suggested to be involved in Spemann organizer functions, reduced the endogenous level of Xlim-1 mRNA and produced embryos with reduced eyes or anterior truncation at high efficiency [8].
• This activity is necessary for normal expression of Mix.1, a mesoendodermal marker, in the endoderm as well as in the mesoderm, indicating that MAP kinase plays a functional role in patterning of both of these germ layers [9].
• We generated domain swap mutants between Mix.3/Mixer and Mix.1 and tested their ability to induce endoderm in explanted ectoderm [10].
• Expression of Xenopus Mix.3/Mixer in explanted ectoderm results in endoderm differentiation, whereas Mix.1 expression does not [10].
• Interference with function of a homeobox gene in Xenopus embryos produces malformations of the anterior spinal cord [11].

Associations of Mix.1 with chemical compounds

• The regional expression of two cell-specific markers, the homeobox protein Xhox3 and the neurotransmitter serotonin was also examined in embryos exposed to RA [12].
• Under these conditions, expression of the anterior neural-specific homeobox gene engrailed is not detected, while the notochord-specific epitope recognized by the Tor-70 antibody is expressed in the presence of H2DIDS [13].

Other interactions of Mix.1

• Xlim-1, a LIM class homeobox gene expressed in Xenopus laevis, is one of the earliest known marker genes of pronephros development and is expressed in pronephros rudiment [14].
• This mutual repression is important for the specification of the embryonic body plan as ectopic expression of Mix.1 in the Xbra domain suppresses mesoderm differentiation [15].
• We show that p53 functionally and physically interacts with the activin and bone morphogenetic protein pathways to directly induce the expression of the homeobox genes Xhox3 and Mix.1/2 [16].
• However, activin-type signaling is present in vegetal cells, since the vegetal expression of Mix.1 and goosecoid is inhibited by the truncated activin receptor [17].
• Expression of LIM class homeobox gene Xlim-3 in Xenopus development is limited to neural and neuroendocrine tissues [18].

Analytical, diagnostic and therapeutic context of Mix.1

• Electrophoretic mobility shift assays revealed that Xlim-1, Siamois, and Mix.1 are likely to bind as a complex, in a LIM domain-dependent manner, to the region containing the 3xTAAT element [19].
• Microinjection of synthetic Xhox-1A homeobox mRNA disrupts somite formation in developing Xenopus embryos [20].

References