KRT14 Human

What is KRT14 and where is it expressed in human tissues?

KRT14 (Cytokeratin 14) is a type I keratin protein expressed predominantly in the basal layer of stratified epithelia. In human epidermis, KRT14 represents one of the most abundantly expressed genes in undifferentiated keratinocytes, particularly in the "Basal1-6" clusters. KRT14 mRNA is markedly higher in expression compared to KRT5, which is the sole type II keratin gene expressed in undifferentiated keratinocytes of interfollicular epidermis . It forms heterodimers with type II keratins, predominantly KRT5, to create intermediate filaments that provide structural support to epithelial cells.

KRT14 is also expressed in other stratified epithelia, including the airway surface in certain pathological conditions. While KRT14 expression is infrequent on the normal airway surface, it dramatically expands its expression domain during injury and in chronic disease states .

How does KRT14 expression change during epithelial differentiation?

In human epidermis, single-cell RNA sequencing reveals distinct keratinocyte subpopulations based on KRT14 and KRT10 expression profiles. Analysis of 24,979 single epidermal keratinocytes shows that approximately 53% of cells exhibit a KRT14high/KRT10low profile (consistent with progenitor characteristics), while about 37% show a KRT14low/KRT10high profile (consistent with differentiating characteristics) . Interestingly, a significant subset of cells (9.5%) displays a hybrid KRT14high/KRT10high phenotype, suggesting a transitional state during differentiation .

The dynamic regulation of KRT14 is also evident in injury models. In ferret tracheal explant models, KRT14 is upregulated at the edges of regenerating wounds, with expression peaking around day 5 post-injury and diminishing by day 15 as tissue repairs .

What is the relationship between KRT14 and KRT15 in epithelial cells?

KRT14 and KRT15 show distinct but sometimes overlapping expression patterns in epithelia. In normal human trunk skin, KRT15 expression is more restricted compared to KRT14 and occurs at lower levels . In the airway epithelium, KRT15 is the predominant type I keratin in ferret airway surface basal cells under homeostatic conditions, whereas KRT14 expression is infrequent .

During injury and disease states, the balance between these two keratins shifts significantly. In chronic lung injuries such as restrictive allograft syndrome (RAS) and bronchiolitis obliterans (BO), KRT15 expression largely disappears while KRT14 persists in basal cells of large airways . Similar trends are observed in human obliterative bronchiolitis after lung transplantation, where KRT14-expressing basal cells become more abundant and KRT15-expressing cells decline in chronically injured airways .

What techniques are available for detecting KRT14 expression?

Several validated techniques are routinely used to detect KRT14 expression:

• Immunocytochemistry/Immunofluorescence: Using specific antibodies such as Alexa Fluor® 488 Anti-Cytokeratin 14 antibody [EP1612Y] allows visualization of KRT14 protein in fixed cells or tissue sections . This technique enables co-localization studies with other markers.

• Western Blot: Antibodies such as Anti-Cytokeratin 14 antibody [EPR17336] can detect KRT14 protein expression levels in cell or tissue lysates .

• Single-cell RNA Sequencing (scRNA-seq): This technique allows quantification of KRT14 mRNA at the single-cell level, enabling identification of distinct cell populations based on KRT14 expression .

• Next-Generation Sequencing: Used to validate genetic modifications in KRT14 knockout cell lines and to study broader transcriptional changes .

How is KRT14 regulated at the epigenetic level?

KRT14 expression is subject to epigenetic regulation, particularly through histone modifications. Research shows that H3K27me3 (histone H3 lysine 27 trimethylation) plays a crucial role in regulating KRT14 expression in triple-negative breast cancer (TNBC). Selective hyperactivation of H3K27me3 over non-canonical EZH2 (NC-EZH2) promotes upregulation of KRT14 gene expression by altering the recruitment pattern of its transcription factor Sp1 .

This epigenetic mechanism not only promotes TNBC metastasis but also alters the metastatic landscape of TNBC. When EZH2 function is lost, either through knockdown or treatment with the H3K27me3 selective inhibitor EPZ6438, there is a significant reduction in TNBC migration, invasion in vitro, and peritoneal metastasis in vivo .

What functional roles does KRT14 play in tissue regeneration and repair?

KRT14 plays critical roles in epithelial regeneration and repair processes:

• Wound Healing: In ferret tracheal explant models, KRT14 is dramatically upregulated at the edges of regenerating wounds as early as 2 days post-injury, with expression peaking around day 5 and subsequently diminishing by day 15 as wound healing progresses .

• Progenitor Cell Function: KRT14 functionally regulates basal cell behavior, affecting their proliferation, maintenance, and differentiation capabilities. This functional impact becomes particularly relevant in chronic disease states like bronchiolitis obliterans .

• Differentiation Program: KRT14 knockout affects epithelial differentiation programs. In airway epithelial cultures, KRT14-KO cells exhibit altered nuclear morphology (enlarged and elongated nuclei) and impaired specification of club and ciliated cells .

What are the consequences of KRT14 dysfunction in disease models?

KRT14 dysfunction has significant consequences in various disease models:

• Airway Pathologies: KRT14-knockout mice display reduced glandular size, decreased Scgb1a1 gland secretions, and reduced abundance of club cells in the airway epithelium . These changes may contribute to respiratory pathologies.

• Cancer Metastasis: In TNBC models, KRT14 functions as a critical regulator of splenic metastasis. Loss of KRT14, even in H3K27me3 hyper-activated backgrounds, severely compromises TNBC peritoneal metastasis .

• Epithelial Differentiation: KRT14-knockout cells grown in air-liquid interface (ALI) cultures show distinct morphological changes, including enlarged and elongated nuclei, and impaired specification of secretory (club) and ciliated cells .

• Epidermolysis Bullosa Simplex: While not directly covered in the search results, KRT14 mutations are known to cause epidermolysis bullosa simplex, a skin fragility disorder characterized by blister formation .

How do KRT14 and KRT15 differentially regulate epithelial stem cell properties?

KRT14 and KRT15 have distinct functional impacts on epithelial stem cell behavior:

• Expression Dynamics: During homeostasis, KRT15 is the predominant type I keratin in ferret airway surface basal cells, while KRT14 expression is infrequent. After injury (e.g., polidocanol exposure), KRT14 dramatically expands its expression domain, while KRT15 expression continues .

• Chronic Injury Response: In chronic injuries such as RAS and BO, KRT15 expression largely disappears while KRT14 persists in basal cells of large airways .

• Cellular Properties: The shift in keratin expression (KRT14 vs. KRT15) has functional implications for basal stem cell properties, particularly affecting their proliferation, maintenance, and differentiation capabilities .

• Compensatory Mechanisms: In KRT14-knockout models, there may be compensatory upregulation of KRT15 in the surface airway epithelium, suggesting overlapping but distinct functions .

What approaches are effective for generating KRT14 knockout models?

CRISPR/Cas9 technology has proven effective for generating KRT14 knockout models:

• Cell Line Generation: CRISPR/Cas9-mediated knockout of KRT14 in A-431 cells has been successfully achieved, resulting in a 13 bp deletion that causes a frameshift with 99.9% efficiency .

• Validation Methods: Multiple validation approaches should be employed, including:

  • Immunocytochemistry to confirm absence of KRT14 protein

  • Next-Generation Sequencing to verify the genetic modification

  • Western blot to confirm the absence of protein expression

• Mouse Models: KRT14-knockout mice have been established and can be used to study the consequences of KRT14 loss in vivo. These models show alterations in submucosal gland size, club cell abundance, and epithelial differentiation .

• In Vitro Models: ROSA-TG:H11-Cas9 cells transfected with Krt14 gRNAs and sorted for appropriate markers can be grown in air-liquid interface cultures to study the effects of KRT14 knockout on epithelial differentiation .

What experimental systems are suitable for studying KRT14 function?

Several experimental systems have proven valuable for studying KRT14 function:

How should researchers interpret KRT14/KRT10 co-expression patterns?

Interpreting KRT14/KRT10 co-expression patterns requires consideration of the following principles:

• Population Analysis: Scatter plot analysis relating KRT14 to KRT10 expression reveals distinct subpopulations: KRT14high/KRT10low (53%, progenitor-like), KRT14low/KRT10high (37%, differentiating), and KRT14high/KRT10high (9.5%, hybrid) .

• Transitional States: Cells co-expressing high levels of both KRT14 and KRT10 likely represent transitional states during differentiation, rather than technical artifacts or anomalies .

• Spatial Context: The location of cells within the tissue architecture provides important context for interpreting expression patterns. Basal layer cells typically express KRT14, while suprabasal cells express KRT10 .

• Single-Cell Methods: Single-cell approaches are preferable to bulk analysis for accurately capturing the heterogeneity and transitional states in keratin expression .

• Quantitative Assessment: Researchers should establish clear thresholds for "high" versus "low" expression based on the distribution of expression values in their dataset .

What are emerging areas in KRT14 research?

Several promising research directions emerge from current KRT14 studies:

• Epigenetic Regulation: Further investigation into how histone modifications like H3K27me3 regulate KRT14 expression could yield insights into disease processes and potential therapeutic targets .

• Keratin Switching: The mechanisms driving the switch between KRT14 and KRT15 expression in response to injury and chronic disease warrant deeper investigation .

• Single-Cell Heterogeneity: Exploring the functional significance of keratinocyte subpopulations with distinct keratin expression profiles could reveal new insights into epithelial homeostasis and pathology .

• Therapeutic Targeting: Investigating whether modulating KRT14 expression or function could impact disease progression, particularly in cancers where KRT14 contributes to metastasis .

• Coordinate Regulation: Unraveling the mechanisms behind the coordinate regulation of type I and type II keratin genes, which are located on separate chromosomes yet show remarkable co-regulation .

What technical challenges persist in KRT14 research?

Researchers face several challenges when studying KRT14:

• Tissue Heterogeneity: The heterogeneous expression of KRT14 across different cell types and states necessitates single-cell approaches, which bring their own technical challenges .

• Model Systems: Differences between human and mouse keratin expression patterns may limit the translational relevance of findings from mouse models .

• Dynamic Regulation: Capturing the dynamic changes in KRT14 expression during processes like wound healing requires sophisticated time-course experiments and imaging techniques .

• Functional Redundancy: Potential compensatory mechanisms involving other keratins may mask the effects of KRT14 manipulation in experimental models .

• Integration of Multi-Omics Data: Combining transcriptomic, epigenomic, and proteomic data to build comprehensive models of KRT14 regulation remains technically challenging.