Lack of phosphomannomutase 2 affects Xenopus laevis morphogenesis and the non-canonical Wnt5a/Ror2 signalling
Nastassja Himmelreich1, Lilian T Kaufmann2, Herbert Steinbeisser2
1Center for Child- and Adolescent Medicine and Center for Metabolic Diseases Heidelberg, Department I, Im Neuenheimer Feld 669, 69120, Heidelberg, Germany.
Abstract:
Reduced phosphomannomutase 2 activity in man leads to hypoglycosylation of glycoconjugates causing PMM2-CDG, the most common type of congenital disorders of glycosylation. Here we show that an antisense morpholino-mediated knockdown of the Xenopus laevis phosphomannomutase 2 gene provoked a general underglycosylation in frog embryos, which led to an altered phenotype and reduced glycosylation of Wnt5a as member of the non-canonical Wnt signalling. Loss of function experiments in hemi-sectioned embryos proved that due to the phosphomannomutase 2 knockdown expression of the Wnt5a/Ror2 target gene paraxial protocadherin was significantly decreased. Regarding the expression of paraxial protocadherin, a gain of function could only be achieved by injections of wnt5a and ror2 in dorsal neighbouring blastomeres, while a parallel injection of phosphomannomutase 2 morpholino led to a significant reduced level of expression. Our data show for the first time that a knockdown of phosphomannomutase 2 influences in vivo the non-canonical Wnt signalling during early embryogenesis.
Insights
Reduced phosphomannomutase 2 (PMM2) activity causes PMM2-congenital disorder of glycosylation. This study shows PMM2 knockdown in frog embryos disrupts Wnt signaling and reduces paraxial protocadherin expression, impacting early development.
Area of Science:
- Developmental Biology
- Molecular Genetics
- Biochemistry
Background:
- Phosphomannomutase 2 (PMM2) deficiency causes PMM2-congenital disorder of glycosylation (CDG), the most common CDG type.
- Glycosylation is crucial for proper protein function and cellular processes.
Purpose of the Study:
- To investigate the role of PMM2 in early embryogenesis using a Xenopus laevis model.
- To determine the impact of PMM2 knockdown on non-canonical Wnt signaling pathways.
Main Methods:
- Antisense morpholino-mediated knockdown of the Xenopus laevis PMM2 gene.
- Analysis of embryonic phenotype and Wnt5a glycosylation.
- Loss-of-function experiments in hemi-sectioned embryos.
- Gain-of-function studies involving wnt5a and ror2 injections.
Main Results:
- PMM2 knockdown led to general underglycosylation in frog embryos, causing developmental abnormalities.
- Reduced glycosylation of Wnt5a was observed.
- Knockdown significantly decreased the expression of the Wnt5a/Ror2 target gene, paraxial protocadherin.
- Wnt5a and Ror2 overexpression could not rescue the reduced paraxial protocadherin levels caused by PMM2 knockdown.
Conclusions:
- PMM2 plays a critical role in regulating non-canonical Wnt signaling during early Xenopus embryogenesis.
- PMM2 deficiency impacts Wnt signaling through Wnt5a and affects downstream targets like paraxial protocadherin.
- This study provides novel insights into the in vivo function of PMM2 in developmental processes.
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