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Ubiquitin-mediated proteasome degradation regulates optic fissure fusion
Warlen Pereira Piedade1, Sydney Veith1, Jakub Konrad Famulski2
1University of Kentucky, Department of Biology, 40506, Lexington, KY, USA.
Abstract:
Optic fissure fusion is a critical event during retinal development. Failure of fusion leads to coloboma, a potentially blinding congenital disorder. Pax2a is an essential regulator of optic fissure fusion and the target of numerous morphogenetic pathways. In our current study, we examined the negative regulator of pax2a expression, Nz2, and the mechanism modulating Nlz2 activity during optic fissure fusion. Upregulation of Nlz2 in zebrafish embryos resulted in downregulation of pax2a expression and fissure fusion failure. Conversely, upregulation of pax2a expression also led to fissure fusion failure suggesting Pax2 levels require modulation to ensure proper fusion. Interestingly, we discovered Nlz2 is a target of the E3 ubiquitin ligase Siah. We show that zebrafish siah1 expression is regulated by Hedgehog signaling and that Siah1 can directly target Nlz2 for proteasomal degradation, in turn regulating the levels of pax2a mRNA. Finally, we show that both activation and inhibition of Siah activity leads to failure of optic fissure fusion dependent on ubiquitin-mediated proteasomal degradation of Nlz2. In conclusion, we outline a novel, proteasome-mediated degradation regulatory pathway involved in optic fissure fusion.
Insights
Proper optic fissure fusion requires precise regulation of Pax2a levels. This study reveals Nlz2, a negative regulator of Pax2a, is degraded by Siah1, a ubiquitin ligase, ensuring correct eye development.
Area of Science:
- Developmental biology
- Ophthalmology
- Molecular genetics
Background:
- Optic fissure fusion is crucial for normal retinal development.
- Coloboma, a congenital disorder, results from failed optic fissure fusion.
- Pax2a is a key regulator of optic fissure fusion.
Purpose of the Study:
- To investigate the role of Nlz2, a negative regulator of Pax2a, in optic fissure fusion.
- To elucidate the mechanism controlling Nlz2 activity during this process.
Main Methods:
- Zebrafish embryos were used to study gene expression and protein degradation.
- Manipulation of Nlz2 and Siah1 levels to observe effects on optic fissure fusion.
- Analysis of the interaction between Nlz2, Siah1, and the proteasomal degradation pathway.
Main Results:
- Nlz2 upregulation downregulated Pax2a expression, leading to fusion failure.
- Nlz2 is a target of the E3 ubiquitin ligase Siah1, which is regulated by Hedgehog signaling.
- Siah1-mediated proteasomal degradation of Nlz2 is essential for regulating Pax2a levels and enabling optic fissure fusion.
Conclusions:
- A novel regulatory pathway involving proteasome-mediated degradation of Nlz2 by Siah1 is critical for optic fissure fusion.
- Precise modulation of Pax2a levels, through Nlz2 degradation, is necessary for proper eye development and preventing coloboma.
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