Sdk1, short for Sidekick cell adhesion molecule 1, belongs to the immunoglobulin superfamily (IgSF). It plays a role in cell communication and is involved in the formation and maintenance of neural circuits, especially in the retina. It is also reported to be associated with disease resistance in cattle and may influence various neurodevelopmental and psychiatric disorders [4,3]. Sdk1 first evolved from the Sdk gene in multicellular animals during the Precambrian age through gene duplication [4].

In a lung adenocarcinoma patient, a rare SDK1-ALK fusion was discovered, and the patient had an excellent response to ALK inhibitor treatment, suggesting potential implications for ALK-TKI applications in NSCLC patients with ALK fusion [1]. In the retina, genetic and physiological studies in mice revealed that Sdk1 loss selectively disrupts the visual responses of a novel retinal ganglion cell (RGC) type (S1-RGC) due to loss of excitatory and inhibitory inputs and dendritic deficits, indicating that Sdk1 shapes dendrite growth and wiring to help S1-RGCs become feature-selective [2].

In conclusion, Sdk1 is crucial for the assembly of neural circuits, especially in the retina, and its genetic alterations can have implications in cancer, like the SDK1-ALK fusion in lung adenocarcinoma. The study of Sdk1 through genetic models such as gene knockout in mice has provided insights into its role in specific biological processes and disease conditions, highlighting its importance in both normal biological functions and disease development.

References:

1. Ma, Lin, Xiao, Junjuan, Guan, Yaping, Gu, Tiantian, Wang, Jun. 2022. SDK1-ALK Fusion in a Lung Adenocarcinoma Patient With Excellent Response to ALK Inhibitor Treatment: A Case Report. In Frontiers in oncology, 12, 860060. doi:10.3389/fonc.2022.860060. https://pubmed.ncbi.nlm.nih.gov/35311071/

2. Rochon, Pierre-Luc, Theriault, Catherine, Rangel Olguin, Aline Giselle, Krishnaswamy, Arjun. 2021. The cell adhesion molecule Sdk1 shapes assembly of a retinal circuit that detects localized edges. In eLife, 10, . doi:10.7554/eLife.70870. https://pubmed.ncbi.nlm.nih.gov/34545809/

3. Wan, Peng, Yang, Xueyao, Li, Yulian, Huang, Bizhi, Cai, Cuicui. 2021. The distribution of a missense mutation in SDK1 gene across native Chinese breeds. In Animal biotechnology, 34, 734-737. doi:10.1080/10495398.2021.1974467. https://pubmed.ncbi.nlm.nih.gov/34550863/

4. Yamagata, Masahito. 2020. Structure and Functions of Sidekicks. In Frontiers in molecular neuroscience, 13, 139. doi:10.3389/fnmol.2020.00139. https://pubmed.ncbi.nlm.nih.gov/32982686/