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Hox9 genes and vertebrate limb specification
M J Cohn1, K Patel, R Krumlauf
1Department of Anatomy and Developmental Biology, University College London Medical School, UK. m.cohn@ucl.ac.uk
Nature
|May 1, 1997
Summary
Fibroblast growth factors (FGFs) can induce ectopic limbs in chick embryos. Limb type depends on Hox gene expression changes in flank cells, suggesting a key evolutionary role for this regulation.
Area of Science:
- Developmental biology
- Evolutionary developmental biology
- Genetics
Background:
- Paired appendages are characteristic of jawed vertebrates.
- Hox genes are implicated in determining limb position along the body axis.
- Fibroblast growth factors (FGFs) can induce limb development.
Purpose of the Study:
- To investigate if flank cells can form different limb types (wing or leg) based on induction.
- To determine if induced limb formation involves changes in Hox gene expression.
- To explore the role of Hox gene regulation in the evolution of paired appendages.
Main Methods:
- Local application of FGFs to anterior and posterior flank regions of chick embryos.
- Analysis of Hox gene expression patterns in lateral plate mesoderm and paraxial mesoderm.
- Observation and characterization of induced ectopic limb development.
Main Results:
- The same flank cells can be induced to form either a wing or a leg.
- Ectopic limb induction is associated with specific changes in three Hox genes within the lateral plate mesoderm.
- Hox gene expression patterns in the flank mirror those found at normal limb development sites.
- Hox gene expression reprogramming occurs in lateral plate mesoderm but not paraxial mesoderm.
Conclusions:
- Hox gene expression in lateral plate mesoderm is reprogrammable, influencing ectopic limb type.
- Independent regulation of Hox genes in lateral plate mesoderm may be crucial for paired appendage evolution.
- This study provides insights into the genetic mechanisms underlying limb development and vertebrate evolution.