Developmental expression of the mouse Evx-2 gene: relationship with the evolution of the HOM/Hox complex

Denis Duboule
1994
Article

The mouse Evx-2 gene is located in the immediate vicinity of the Hoxd-13 gene, the most posteriorly expressed gene of the HOXD complex. While the Evx-1 gene is also physically linked to the HOXA complex, it is more distantly located from the corresponding Hoxa-13 gene. We have analysed the expression of Evx-2 during development and compared it to that of Evx-1 and Hoxd-13. We show that, even though Evx-2 is expressed in the developing CNS in a pattern resembling that of other Evx-related genes, the overall expression profile is similar to that of the neighbouring limbs and genitalia. We propose that the acquisition of expression features typical of Hox genes, together with the disappearance of some expression traits common to Evx genes, is due to the close physical linkage of Evx-2 to the HOXD complex, which results in Evx-2 expression being partly controlled by mechanisms acting in the HOX complex. This transposition of the Evx-2 gene next to the Hoxd-13 gene may have occurred soon after the large scale duplications of the HOX complexes. A scheme is proposed to account for the functional evolution of eve-related genes in the context of their linkage to the HOM/Hox complexes.

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Denis Duboule
1994
Article

Résumé

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https://infoscience.epfl.ch/record/117667?ln=fr

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Concepts associés (9)

Concepts associés

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Publications associées (8)

Publications associées

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Cooperation of regulatory elements involved in the activation of the Hoxd-11 gene

Denis Duboule, Jozsef Zakany

We have used lacZ reporter gene constructs to study the cis regulation of the murine Hoxd-11 gene (previously Hox-4.6) in transgenic mice. We identified a genomic region, which was able to simulate important aspects of the developmental regulation of the gene. A short regulatory region, located 3' to the Hoxd-11 transcription unit, was required to mimic initial activation. This regulatory region contains two stretches of DNA, that are highly conserved in the chicken Hoxd-11 3' flanking region. A chimeric construct containing these short homologous regions from the chicken gene could replace the complete murine fragment thus demonstrating that the conserved domains carry the main regulatory elements involved in this activation. The first half of this bipartite regulatory region has positive regulatory activity, while the second half is required to restrict gene expression to the proper posterior domain in the somitic mesoderm. Our results suggest that the control of the Hoxd-11 promoter involves tissue-specific cooperations between regulatory elements.

1993

Chargement

In tetrapods, Hox genes are essential for the proper organization and development of axial structures. Experiments involving Hox gene inactivations have revealed their particularly important functions in the establishment of morphological transitions within metameric series such as the vertebral column. Teleost fish show a much simpler range of axial (trunk or appendicular) morphologies, which prompted us to investigate the nature of the Hox system in these lower vertebrates. Here, we show that fish have a family of Hox genes, very similar in both number and general organization, to that of tetrapods. Expression studies, carried out with HoxD and HoxA genes, showed that all vertebrates use the same general scheme, involving the colinear activation of gene expression in both space and time. Comparisons between tetrapods and fish allowed us to propose a model which accounts for the primary function of this gene family. In this model, a few ancestral Hox genes were involved in the determination of polarity in the digestive tract and were further recruited in more elaborate axial structures.

1996

Chargement

Atypical relaxation of structural constraints in Hox gene clusters of the green anole lizard

Denis Duboule

Hox genes control many aspects of embryonic development in metazoans. Previous analyses of this gene family revealed a surprising diversity in terms of gene number and organization between various animal species. In vertebrates, Hox genes are grouped into tightly organized clusters, claimed to be devoid of repetitive sequences. Here, we report the genomic organization of the four Hox loci present in the green anole lizard and show that they have massively accumulated retrotransposons, leading to gene clusters larger in size when compared to other vertebrates. In addition, similar repeats are present in many other development-related gene-containing regions, also thought to be refractory to such repetitive elements. Transposable elements are major sources of genetic variations, including alterations of gene expression, and hence this situation, so far unique among vertebrates, may have been associated with the evolution of the spectacular realm of morphological variations in the body plans of Squamata. Finally, sequence alignments highlight some divergent evolution in highly conserved DNA regions between vertebrate Hox clusters, which may coincide with the emergence of mammalian-specific features.

2009

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