Variable Meis-dependence among paralog group-1 Hox proteins

Area of Science:

• Developmental biology
• Genetics
• Molecular biology

Background:

• Hox transcription factors are crucial for development.
• Meis and Pbx proteins are known cofactors for Hox proteins.
• The in vivo requirements for these cofactors in zebrafish are not fully understood.

Purpose of the Study:

• To investigate the in vivo Meis-cofactor dependence of two zebrafish paralog group-1 (PG1) Hox proteins, Hoxb1a and Hoxb1b.
• To determine if different Hox proteins exhibit distinct Meis requirements.
• To explore genetic interactions between Meis, Pbx, and PG1 Hox genes.

Main Methods:

• Misexpression of Hoxb1a and Hoxb1b in zebrafish embryos.
• Disruption of endogenous Meis function.
• Addition of Meis3 to observe phenotypic rescue.
• Construction of chimeric proteins to map functional domains.
• Analysis of genetic interactions between relevant genes.

Main Results:

• Both Hoxb1a and Hoxb1b exhibit reduced ectopic gene expression upon Meis disruption, confirming Meis-dependence.
• Hoxb1b requires higher Meis levels than Hoxb1a to achieve similar ectopic gene expression patterns.
• Chimeric protein analysis localized the difference in Meis requirement to the N-terminus, containing the transcription activation domain.
• Significant genetic interactions were observed between meis and PG1 hox genes, as well as between meis and pbx genes.

Conclusions:

• PG1 Hox genes in zebrafish function in vivo requiring Pbx and Meis cofactors.
• Different Hox proteins display distinct quantitative requirements for Meis cofactors.
• The N-terminus of Hox proteins plays a role in determining Meis cofactor specificity.