Eda, short for Ectodysplasin A, is a gene encoding a skin-specific TNF ligand. It plays a crucial role in the morphogenic signaling that regulates the formation of skin appendages such as teeth, hair follicles, and exocrine glands in mammals [1,2,3,4,5]. The Eda-EDAR signaling pathway is essential for these processes, and mutations in Eda can lead to hypohidrotic ectodermal dysplasia (HED), a congenital disease characterized by malformation of skin appendages [1,4]. Gene knockout mouse models have been valuable in studying Eda's function.

In Eda -/- mice, incisors are hypoplastic and hypomineralized, and there are changes in tooth number in the molar region. Lack of functional Eda protein during early incisor tooth germ development minimally impacts early Shh expression, but later affects Shh expression in the primary enamel knot of the functional tooth, leading to a smaller enamel knot and abnormal enamel organ formation [3]. Functional studies on Eda gene variants found in Chinese patients with tooth agenesis showed that these variants can greatly affect protein stability or impair the Eda-EDAR interaction, significantly affecting downstream NF-κB transcriptional activity [2]. In two X-linked oligodontia families, missense mutations in Eda were identified, with one affecting the cleavage of Eda and the other interfering with receptor binding, leading to different phenotypes of oligodontia and ectodermal dysplasia [5].

In conclusion, Eda is essential for the development of skin appendages, especially teeth. Studies using gene-knockout mouse models and human genetic analysis have revealed its role in regulating the development of tooth germs and the downstream signaling pathways. Understanding Eda's function provides insights into the pathogenesis of diseases like HED and tooth agenesis, potentially guiding future genetic counseling and treatment strategies.

References:

1. Yang, Ruihan, Mei, Yilan, Jiang, Yuhan, Sima, Jian, Yao, Yuyuan. 2022. Ectodysplasin A (EDA) Signaling: From Skin Appendage to Multiple Diseases. In International journal of molecular sciences, 23, . doi:10.3390/ijms23168911. https://pubmed.ncbi.nlm.nih.gov/36012178/

2. Yu, Kang, Sheng, Yihan, Wang, Feng, Lei, Ming, Wu, Yiqun. 2024. Eight EDA mutations in Chinese patients with tooth agenesis and genotype-phenotype analysis. In Oral diseases, 30, 4598-4607. doi:10.1111/odi.14878. https://pubmed.ncbi.nlm.nih.gov/38287639/

3. Horakova, Lucie, Dalecka, Linda, Zahradnicek, Oldrich, Tucker, Abigail S, Hovorakova, Maria. 2023. Eda controls the size of the enamel knot during incisor development. In Frontiers in physiology, 13, 1033130. doi:10.3389/fphys.2022.1033130. https://pubmed.ncbi.nlm.nih.gov/36699680/

4. Yao, Yuyuan, Yang, Ruihan, Zhu, Jian, Schlessinger, David, Sima, Jian. 2023. EDA ligand triggers plasma membrane trafficking of its receptor EDAR via PKA activation and SNAP23-containing complexes. In Cell & bioscience, 13, 128. doi:10.1186/s13578-023-01082-8. https://pubmed.ncbi.nlm.nih.gov/37430358/

5. Lee, Ye Ji, Kim, Youn Jung, Chae, Wonseon, Kim, Seon Hee, Kim, Jung-Wook. 2024. EDA Mutations Causing X-Linked Recessive Oligodontia with Variable Expression. In Genes, 16, . doi:10.3390/genes16010012. https://pubmed.ncbi.nlm.nih.gov/39858559/