The Notch pathway in Metazoa: a comparative analysis across cnidarians and beyond

Area of Science:

• Evolutionary developmental biology
• Comparative genomics
• Cell signalling

Background:

• The Notch signalling pathway regulates key cellular processes like differentiation and apoptosis in Metazoa.
• Its evolutionary history and functional diversification in early-branching lineages, including cnidarians and myxozoans, are poorly understood.

Purpose of the Study:

• To investigate the presence and structural diversity of Notch pathway components in early diverging metazoan lineages.
• To focus on Myxozoa, parasitic cnidarians with extreme genomic reduction.

Main Methods:

• Comparative analysis of Notch pathway components across 58 metazoan species.
• Phylogenetic analyses of Notch receptors and ligands (Delta, Jagged).
• Immunolocalization studies in Sphaerospora molnari.

Main Results:

• Core Notch components are broadly conserved, with notable losses in ctenophores, placozoans, poriferans, and cnidarians.
• Myxozoa possess only 14 of 28 canonical components, lacking key elements like MAML, Hes/Hey, and DVL.
• Phylogenetic analyses revealed structural divergence in Notch receptors and early diversification of Delta ligands.

Conclusions:

• The Notch pathway's evolution shows lineage-specific losses and structural variations in early metazoans.
• Despite reductions, Notch signalling components remain crucial for developmental regulation in these diverse lineages.