KRTs

KRTs, short for keratins, are a large family of intermediate filament proteins that form the cytoskeleton of epithelial cells. They provide mechanical strength, help maintain cell and tissue integrity, and participate in signaling and organelle positioning. Keratins assemble as obligate heterodimers of type I (acidic) and type II (basic to neutral) keratins, which then co-assemble into 10-nanometer intermediate filaments that span the cytoplasm.

In humans, there are more than 50 functional keratin genes, divided into two broad classes: type I (acidic) and type II (basic to neutral). Each epithelial cell type expresses a characteristic set of keratins: basal keratinocytes typically express KRT5 and KRT14; suprabasal layers express KRT1 and KRT10; simple epithelia express keratins such as KRT8 and KRT18. The keratin genes are organized in distinct clusters in the genome.

Keratins collaborate with desmosomal and hemidesmosomal components to form a resilient cytoskeleton and influence processes such as cell migration, wound healing, and stress responses. They can be post-translationally modified by phosphorylation and cross-linking, which affects filament assembly and turnover.

Clinical relevance: Mutations in KRT genes cause keratinopathies, notably epidermolysis bullosa simplex resulting from KRT5 or KRT14 mutations, and pachyonychia congenita associated with KRT6A, KRT16, or KRT17 mutations. Keratin expression patterns are widely used in pathology as tissue- and tumor-origin markers (for example in immunohistochemistry panels) and as epithelial indicators in research.