Measuring inputs to a common function: The case of Dlx5 and Dlx6

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Dlx5 and Dlx6 are physically linked paralogs co-expressed in vertebrates.
• Studies in mice reveal functional redundancy and similar quantitative contributions to craniofacial development.
• These genes are largely interchangeable for many head-related functions.

Purpose of the Study:

• To assess the relative quantitative contribution of each paralog to bigene function.
• To compare Dlx5 and Dlx6 expression in chick embryos.
• To quantify the transcriptional properties of Dlx5 and Dlx6 proteins in various contexts.

Main Methods:

• Comparative expression analysis of Dlx5 and Dlx6 in chick embryos.
• Quantification of transcriptional properties of Dlx5 and Dlx6 proteins.
• In vitro assays using isolated domains and fused proteins in different cellular contexts.

Main Results:

• Transcriptional activities of Dlx5 and Dlx6 are highly context-dependent.
• Isolated domains show little intrinsic activity; domains contiguous with their homeodomain are more active.
• Dlx5 and Dlx6 are quantitatively indistinguishable on heterologous cis-regulatory sequences but show differential outputs in native cells, suggesting co-activator interactions.

Conclusions:

• Dlx5 and Dlx6 exhibit context-dependent transcriptional regulation.
• Differential interactions with co-activators in native cells explain quantitative differences in transcriptional output.
• These findings highlight the nuanced roles of paralogs in developmental gene regulation.