Scientists use zebrafish to study how Merkel cells develop

July 29, 2025

Journal

Development

Publication Date

July 29, 2025

Authors

Craig E, Black E, Fernandes S, et al, Rasmussen J

Merkelcell.org Summary

Sensory cells help our bodies notice things like touch, and these cells often have certain shapes that help them do their job. Merkel cells are a type of sensory cell in the skin that help us feel gentle touches. They have a special shape with tiny, finger-like parts sticking out.

It was previously unknown how Merkel cells get their special shape. In this study, researchers looked at developing skin in zebrafish and found that a kind of cell called a dendritic Merkel cell (dMC) helps form mature Merkel cells. These dMCs appear in waves as the skin grows or heals, and they can move around and divide like other skin cells.

The dMCs then change into full Merkel cells by changing their shape and the way their inner skeleton is built. The study also found that when a protein signal called Ectodysplasin A is missing, the shape of Merkel cells changes in certain parts of the skin. dMCs have also been found while studying human development, and future studies will compare how zebrafish and human dMCs are similar.

In short, this study discovered an in-between cell that helps make mature Merkel cells and found an important signal that controls how Merkel cells get their final shape. Future studies like this may help us understand how Merkel cell carcinoma spreads and how to stop it.

Abstract

Sensory cells often adopt specific morphologies that aid in the detection of external stimuli. Merkel cells encode gentle touch stimuli in vertebrate skin and adopt a reproducible shape characterized by spiky actin-rich microvilli that emanate from the cell surface. The mechanisms by which Merkel cells acquire this stereotyped morphology from keratinocyte progenitors are unknown. Here, we establish that dendritic Merkel cells (dMCs) express atonal homolog 1a (atoh1a), extend dynamic filopodial processes, and arise in transient waves during zebrafish skin development and regeneration. We find that dMCs share molecular similarities with both basal keratinocytes and Merkel cells, yet display mesenchymal-like behaviors, including local cell motility and proliferation within the epidermis. Furthermore, dMCs can directly adopt the mature, microvilliated Merkel cell morphology through substantial remodeling of the actin cytoskeleton. Loss of Ectodysplasin A signaling alters the morphology of dMCs and Merkel cells within specific skin regions. Our results show that dMCs represent an intermediate state in the Merkel cell maturation program and identify Ectodysplasin A signaling as a key regulator of Merkel cell morphology.
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