Type II keratin cDNAs from the rainbow trout: implications for keratin evolution

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Biochemistry

Background:

• Keratins are intermediate filament proteins crucial for cellular structure.
• Type II keratins, along with type I keratins, form heterodimers essential for keratin filament assembly.
• Understanding keratin diversity and evolution provides insights into vertebrate tissue development and adaptation.

Purpose of the Study:

• To clone and characterize type II keratins from the rainbow trout (Oncorhynchus mykiss).
• To investigate the evolutionary relationships of teleost type II keratins with those from other vertebrates.
• To identify epidermal (IIe) and simple epithelial/mesenchymal (IIs) keratin subtypes in trout.

Main Methods:

• Cloning and sequencing of complementary DNAs (cDNAs) encoding type II keratins.
• Separation of protein spots using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE).
• Identification of protein spots via peptide mass mapping using MALDI mass spectrometry.
• Phylogenetic analysis of keratin rod domains from various vertebrate species.

Main Results:

• Five type II keratin cDNAs were cloned and sequenced from rainbow trout.
• Three keratins were identified as subtype IIe (epidermal) and two as subtype IIs (simple epithelia/mesenchymal).
• The IIs keratins are orthologs of human K8.
• Phylogenetic analysis indicated independent diversification of teleost IIe keratins from mammalian IIe keratins.
• K8-like keratins are conserved across investigated species, suggesting common ancestry for IIe branches.

Conclusions:

• Rainbow trout possess a distinct set of type II keratins, with IIe subtypes evolving independently of mammalian IIe keratins.
• The conserved presence of K8-like keratins highlights their fundamental role across vertebrate evolution.
• This study contributes to the comprehensive cataloging of keratin diversity and evolutionary patterns in teleost fish.