Differential roles of the fish chitinous membrane in gut barrier immunity and digestive compartments

Area of Science:

• * Comparative physiology
• * Vertebrate gut evolution
• * Invertebrate-vertebrate comparative biology

Background:

• * The chitin-based peritrophic matrix (PM) is crucial for invertebrate gut immunity and digestion.
• * A PM-like chitinous membrane (CM) has been identified in fish, challenging previous assumptions about its loss in vertebrates.
• * Understanding the CM's role in fish offers insights into vertebrate gut physiology and structural evolution.

Purpose of the Study:

• * To investigate the functional significance of the chitinous membrane (CM) in zebrafish.
• * To determine the CM's impact on gut homeostasis, epithelial renewal, digestion, growth, and longevity.
• * To explore the CM's role in gut immunity and its implications for vertebrate gut evolution.

Main Methods:

• * Utilized zebrafish as a model organism.
• * Compared wild-type and mutant zebrafish lacking the CM.
• * Assessed gut health, microbial balance, epithelial integrity, and physiological parameters.

Main Results:

• * Zebrafish lacking CM exhibit normal development but develop gut inflammation and atrophy with age.
• * The CM influences ingestion behavior, microbial homeostasis, epithelial renewal, digestion, growth, and longevity.
• * CM is not essential for antibacterial immunity in young zebrafish, unlike mammalian mucin layers.

Conclusions:

• * The chitinous membrane (CM) plays a critical role in maintaining zebrafish gut health and promoting longevity.
• * The CM's function in fish provides insights into its evolutionary loss in tetrapods.
• * Findings advance understanding of vertebrate gut physiology, fish health, and human intestinal diseases.