Keratineisoformen

Keratineisoformen, in English keratin isoforms, are distinct protein products of the keratin gene family that populate epithelial cells. Keratins are intermediate filament proteins that provide mechanical support and resilience to epithelia. In humans they are organized into two major types: type I (acidic) and type II (basic to neutral). Functional keratin filaments form when one type I and one type II keratin pair as a heterodimer, which then assemble into 10-nanometer intermediate filaments that extend through the cytoplasm.

Keratineisoformen are expressed in tissue- and differentiation-specific patterns. Basal keratinocytes predominantly express KRT5 and KRT14, while suprabasal layers express keratins such as KRT1 and KRT10. Hair and nail structures express specialized keratins (including hair keratins such as KRT31–KRT40). The keratin gene family (KRT genes) comprises many isoforms produced by different genes, with regulation at transcriptional and post-transcriptional levels yielding diverse isoform repertoires across tissues and developmental stages.

Mutations or dysregulation of keratineisoformen can lead to skin and nail disorders. For example, mutations in KRT5 or KRT14 cause epidermolysis bullosa simplex, while mutations in KRT6A, KRT16, or KRT17 are linked to pachyonychia congenita. In pathology, keratin isoforms are widely used as immunohistochemical markers to determine tissue origin and differentiation state in tumors, with panels such as KRT5/6, KRT14, and KRT8/18 guiding diagnosis.

Properties of keratineisoformen include differences in molecular weight and isoelectric point among isoforms, as well as regulation by post-translational modifications such as phosphorylation, which influence filament assembly and dynamics.