The structure and expression of a gene encoding chick claw keratin

Area of Science:

• * Molecular biology
• * Developmental biology
• * Genomics

Background:

• * Keratins are structural proteins essential for epidermal development in vertebrates.
• * Avian keratins exhibit diverse sequences and expression patterns, reflecting specialized functions in feathers, scales, and claws.
• * Understanding keratin gene structure and expression is crucial for elucidating avian appendage formation.

Purpose of the Study:

• * To isolate and characterize claw keratin (cKer) encoding genes from embryonic chick mRNA.
• * To investigate the genomic structure and differential expression of cKer genes.
• * To compare cKer sequences with feather (fKer) and scale (sKer) keratins.

Main Methods:

• * Construction of a complementary DNA (cDNA) library from embryonic chick claw mRNA.
• * Isolation and sequencing of claw keratin (cKer)-encoding cDNA and genomic clones.
• * DNA sequencing and comparative sequence analysis of cKer, fKer, and sKer.
• * Genomic Southern analysis to assess gene family size.

Main Results:

• * A cKer-encoding clone was isolated and sequenced, revealing a gene containing four cKer-encoding genes.
• * The cKer1 gene showed abundant expression in embryonic chick claws and low expression in feather tissues.
• * Sequence analysis indicated conserved regions with fKer and sKer, and a shortened glycine-rich repeat region characteristic of sKer.
• * Genomic Southern analysis suggested the presence of multiple related cKer genes in the chick genome.

Conclusions:

• * The cKer1 gene is differentially expressed in avian keratinizing tissues, with a predilection for claw development.
• * cKer genes share conserved structural and sequence features with other avian keratins, but possess unique characteristics.
• * The presence of multiple cKer genes implies a complex role in claw formation and differentiation.