Type XVII collagen (BP 180) in the developing avian cornea

Area of Science:

• Cell Biology
• Developmental Biology
• Molecular Biology

Background:

• Hemidesmosomes are crucial for epithelial cell adhesion.
• BP 180/collagen XVII is a key transmembrane component of hemidesmosomes.
• Previous studies noted species-specific differences in BP 180/collagen XVII.

Purpose of the Study:

• To determine if the same BP 180/collagen XVII mRNA exists in cornea and skin within the same species.
• To investigate the developmental expression of BP 180/collagen XVII.
• To compare the developmental timing of BP 180/collagen XVII and alpha 6 beta 4 integrin expression and hemidesmosome formation.

Main Methods:

• Cloning and sequencing of BP 180/collagen XVII cDNAs from cornea and skin using RT-PCR.
• Quantitative RT-PCR, immunoblotting, and immunofluorescence microscopy for developmental expression analysis.
• Immunofluorescence microscopy for alpha 6 beta 4 integrin and electron microscopy for hemidesmosome formation.

Main Results:

• The identical alpha 1 (XVII) collagen/BP 180 mRNA is present in both cornea and skin.
• Expression of alpha 1 (XVII) collagen mRNA and protein follows similar temporal patterns, with mRNA appearing approximately 2 days before protein.
• Mature hemidesmosome formation occurs later, and the developmental appearance of alpha 1 (XVII) collagen and alpha 6 beta 4 integrin is tightly coordinated.

Conclusions:

• Differences in human and chicken BP 180/collagen XVII are due to species divergence.
• Alpha 1 (XVII) collagen expression is tightly regulated, with protein expression lagging behind mRNA.
• While alpha 1 (XVII) collagen and alpha 6 beta 4 integrin appear coordinately, the initial trigger for hemidesmosome assembly is yet to be identified.