Sequences and expression of pathway-specific complement components in developing red-tailed phascogale (Phascogale...

Area of Science:

• Immunology
• Developmental Biology
• Comparative Genomics

Background:

• Marsupials are born with underdeveloped immune systems, relying heavily on maternal milk for protection.
• While immunoglobulins and some complement proteins are known in marsupial milk, specific complement protein expression is poorly understood.

Purpose of the Study:

• To identify and characterize complement-activating proteins (C3, C1r, CFP, MASP2) in the red-tailed phascogale (Phascogale calura).
• To investigate the gene expression patterns of these complement proteins during marsupial development.

Main Methods:

• Partial cDNA sequencing of complement proteins C3, C1r, CFP, and MASP2 in phascogale liver tissue.
• Analysis of conserved functional motifs in translated protein sequences.
• Quantitative gene expression analysis in whole-body and liver tissues across different developmental stages.

Main Results:

• Partial cDNA sequences for C3, C1r, CFP, and MASP2 were obtained, showing conserved motifs compared to eutherian mammals.
• Complement gene expression increased significantly in juveniles compared to pouch young, indicating developing immune systems.
• Complement component Factor Properdin (CFP) expression was higher in pouch young than juveniles in liver tissue, while other complement genes showed similar trends across tissues.

Conclusions:

• The identified complement proteins are conserved in marsupials, suggesting a functional role in early immunity.
• Complement gene expression undergoes significant developmental changes, increasing with maturation and decreasing in adulthood.
• These findings provide insights into the ontogeny of the marsupial immune system and the role of complement in neonatal protection.