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Divergent expression patterns of Sox9 duplicates in teleosts indicate a lineage specific subfunctionalization
Nils Klüver1, Mariko Kondo, Amaury Herpin
1Department of Physiological Chemistry I, University of Würzburg, 97074 Würzburg, Germany.
Development Genes and Evolution
|April 9, 2005
Summary
Researchers identified a second Sox9 gene in medaka, revealing distinct but overlapping roles for Sox9a and Sox9b in craniofacial development. These findings suggest lineage-specific evolution of Sox9 functions in teleosts.
Area of Science:
- Developmental Biology
- Genetics
- Comparative Genomics
Background:
- Sry-related HMG-box (Sox) genes regulate critical developmental processes.
- Sox9 is essential for mammalian cartilage formation and testis determination.
- Teleosts like zebrafish and stickleback possess two Sox9 co-orthologs, unlike the previously assumed single Sox9 in medaka.
Purpose of the Study:
- To isolate and characterize the second Sox9 gene in medaka (Oryzias latipes).
- To investigate the evolutionary relationship and expression patterns of medaka Sox9a and Sox9b.
- To compare medaka Sox9 expression with zebrafish Sox9 orthologs to understand functional divergence.
Main Methods:
- Gene isolation and sequencing.
- Phylogenetic analysis to confirm co-orthology.
- Linkage mapping to determine gene location.
- Whole-mount in situ hybridization to analyze expression patterns during embryogenesis.
Main Results:
- The second medaka Sox9 gene, Sox9b, was successfully isolated.
- Sequence, phylogenetic, and mapping data confirm Sox9a and Sox9b as medaka co-orthologs.
- Medaka Sox9a and Sox9b exhibit distinct yet overlapping expression patterns, particularly in craniofacial cartilage.
- Comparison with zebrafish revealed both conserved and divergent expression domains for Sox9 orthologs.
Conclusions:
- Medaka possesses two Sox9 co-orthologs, Sox9a and Sox9b.
- Sox9a and Sox9b have partially diverged functions in medaka embryogenesis, especially in craniofacial development.
- Regulatory subfunctions of Sox9 were not fully partitioned before teleost divergence and have evolved lineage-specific expression patterns.