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Duplicate dmbx1 genes regulate progenitor cell cycle and differentiation during zebrafish midbrain and retinal
Loksum Wong1, Cameron J Weadick, Claire Kuo
1Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada.
BMC Developmental Biology
|September 24, 2010
Summary
Zebrafish dmbx1a and dmbx1b genes are essential for midbrain and retinal neurogenesis, regulating progenitor cell differentiation. These genes show partially diverged functions and evolved under positive selection after duplication in teleosts.
Area of Science:
- Developmental Biology
- Neuroscience
- Evolutionary Biology
Background:
- The Dmbx1 gene is crucial for midbrain-hindbrain development and feeding behaviors in mammals.
- Teleost fish possess at least two Dmbx1 paralogs (dmbx1a and dmbx1b), unlike terrestrial vertebrates with a single copy.
Purpose of the Study:
- To investigate the function of zebrafish dmbx1a and dmbx1b in neurogenesis.
- To understand the molecular mechanisms of Dmbx1 in regulating neurogenesis.
- To explore the reasons for the retention of duplicate Dmbx1 genes in zebrafish.
Main Methods:
- Gene knockdown experiments in zebrafish to assess loss-of-function phenotypes.
- Analysis of neurogenesis, cell cycle exit, and differentiation in morphants.
- Molecular evolutionary analyses to study Dmbx1 gene evolution.
- Cross-species gene overexpression experiments (zebrafish and mouse).
Main Results:
- Loss of dmbx1a and dmbx1b function in zebrafish leads to reduced midbrain and retinal growth.
- The observed phenotype is due to impaired progenitor cell cycle exit and differentiation, not patterning defects or cell death.
- Paralogous functions are partially diverged, with dmbx1a loss being more severe than dmbx1b loss.
- Evolutionary analysis suggests positive selection on teleost Dmbx1 genes post-duplication.
- Mouse Dmbx1 cannot fully rescue zebrafish dmbx1a knockdown, and zebrafish dmbx1b only partially compensates.
Conclusions:
- Both dmbx1a and dmbx1b are retained in zebrafish due to their roles in midbrain and retinal neurogenesis, exhibiting diverged functions.
- Dmbx1 regulates progenitor cell cycle exit and differentiation.
- Teleost Dmbx1 genes may have evolved distinct functions in neurogenesis regulation, indicated by positive selection and interspecies functional differences.
