Snorc, short for Small NOvel Rich in Cartilage, is a chondrocyte-specific gene. It encodes a small, 121-amino-acid-long type I single-pass transmembrane chondroitin sulfate proteoglycan [2]. Snorc is important in maintaining chondrocyte phenotype, and may be involved in pathways related to chondrocyte development and homeostasis. Genetic models, such as knockout mouse models, are valuable for studying its function [3].

In Snorc knockout mouse models, the secondary ossification centers (SOCs) in knee epiphyses were smaller, and growth plate (GP) maturation was disturbed. The central proliferative and hypertrophic zones were enlarged with higher extracellular matrix (ECM) volume and rounded chondrocyte morphology. Also, increased levels of Ihh and Col10a1, and reduced Mmp13 mRNA expression were observed, suggesting Snorc's role in regulating chondrocyte maturation and postnatal endochondral ossification [3]. Moreover, knocking down Snorc in interleukin (IL)-1β-induced chondrocytes alleviated inflammation, matrix degradation, autophagy defect and excessive apoptosis during osteoarthritis (OA) development by suppressing the phosphatidylinositol-3-kinase/serine threonine kinase (PI3K/AKT) and c-Jun N-terminal kinase (JNK)/c-Jun signaling pathway [1].

In conclusion, Snorc is crucial for chondrocyte maturation, postnatal endochondral ossification and maintaining normal chondrocyte function. The study of Snorc knockout mouse models has revealed its significant role in conditions like OA, providing insights into the mechanisms of cartilage-related diseases and potential therapeutic targets.

References:

1. Tang, Zhifang, Feng, Hanzhen, Chen, Xusheng, Shao, Shuiyan, Li, Chuan. 2023. SNORC knockdown alleviates inflammation, autophagy defect and matrix degradation of chondrocytes in osteoarthritis development. In Molecular and cellular biochemistry, 479, 2323-2335. doi:10.1007/s11010-023-04842-9. https://pubmed.ncbi.nlm.nih.gov/37659033/

2. Heinonen, J, Taipaleenmäki, H, Roering, P, Laitala-Leinonen, T, Säämänen, A-M. 2011. Snorc is a novel cartilage specific small membrane proteoglycan expressed in differentiating and articular chondrocytes. In Osteoarthritis and cartilage, 19, 1026-35. doi:10.1016/j.joca.2011.04.016. https://pubmed.ncbi.nlm.nih.gov/21624478/

3. Heinonen, J, Zhang, F-P, Surmann-Schmitt, C, Poutanen, M, Säämänen, A-M. 2017. Defects in chondrocyte maturation and secondary ossification in mouse knee joint epiphyses due to Snorc deficiency. In Osteoarthritis and cartilage, 25, 1132-1142. doi:10.1016/j.joca.2017.03.010. https://pubmed.ncbi.nlm.nih.gov/28323137/