epidermal cell differentiation

Definition

Target type: biologicalprocess

The process in which a relatively unspecialized cell acquires specialized features of an epidermal cell, any of the cells making up the epidermis. [GOC:dph, GOC:go_curators, GOC:mtg_sensu, GOC:sdb_2009, GOC:tb]

Epidermal cell differentiation is a complex and tightly regulated process that results in the formation of a stratified, multi-layered epidermis, the outermost layer of skin. This process involves a series of sequential stages, each characterized by specific morphological and molecular changes, ultimately giving rise to specialized cell types with distinct functions.

The journey begins with basal cells, located in the stratum basale, the innermost layer of the epidermis. These cells are mitotically active, constantly dividing and replenishing the epidermal layers. They are also pluripotent, possessing the potential to differentiate into various cell types, such as keratinocytes, melanocytes, Langerhans cells, and Merkel cells.

As basal cells migrate upward, they enter the stratum spinosum. Here, they undergo a process called keratinization, characterized by the synthesis and accumulation of keratin, a tough fibrous protein. Keratin filaments, along with desmosomes, cell-to-cell junctions, give the cells their characteristic spiny appearance. This layer also sees the formation of lamellar granules, which release lipids that contribute to the skin's barrier function.

In the stratum granulosum, keratinization intensifies as the cells flatten and produce keratohyalin granules. These granules contain proteins that further bind and organize keratin filaments, solidifying the cells. The cells also begin to lose their nuclei and organelles, further contributing to the formation of a protective barrier.

The stratum lucidum, a thin, clear layer present only in thick skin (e.g., palms and soles), consists of flattened, dead cells that have completely lost their organelles. These cells are densely packed with keratin, forming a transparent layer that helps protect the deeper layers from injury.

Finally, the stratum corneum, the outermost layer of the epidermis, is composed of flattened, dead cells, known as corneocytes, completely filled with keratin. These cells are tightly interconnected by lipids, forming a tough, waterproof barrier that protects the body from environmental damage.

The differentiation process is driven by a complex interplay of transcription factors, signaling pathways, and extracellular matrix components. Key transcription factors involved include keratinocyte differentiation factors (KDFs), such as KLF4 and AP-1, which regulate the expression of genes involved in keratinization and cell adhesion. Growth factors, such as epidermal growth factor (EGF) and transforming growth factor-α (TGF-α), also play crucial roles in promoting cell proliferation and differentiation.

The process of epidermal cell differentiation is crucial for maintaining skin integrity and protecting the body from external threats. It ensures the continuous replenishment of the epidermis, contributing to the skin's ability to repair itself and adapt to changing environmental conditions. Dysregulation of this process can lead to various skin disorders, including psoriasis, atopic dermatitis, and skin cancer.'
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Proteins (3)

Compounds (119)