Cellular localization of tenomodulin isoforms

Abstract

Tenomodulin, as a major tendon biomarker, TNMD is highly expressed in tendons. However, the functions of TNMD in tendons are not clear although it was suggested to play a role in anti‐angiogenesis in eye and its single nucleotide polymorphisms are associated with obesity. To investigate the function of TNMD in tendons, we performed studies on TNMD isoforms. Data mining showed that three different transcripts exist in human tissues, with deduced molecular weights of 37.1, 20.3 and 25.4 kDa. To clone TNMD isoforms, the cDNAs of human TNMD isoforms were amplified from human total RNA isolated from human tendon specimen and cloned into pEGFP‐C1 vector. GFP‐fused TNMDs were expressed in human and porcine tenocytes. Knockdown of TNMD expression was performed with a RNA interference technique. In the present study, we showed the existence of multiple Tnmd isoforms in tendons with Real time PCR and western blot. Knockdown of all TNMD isoforms with siRNA reduced cell proliferation. Each TNMD isoform showed different localization in tenocytes. Prediction of each isoform in I‐TASSER gave different functions, TNMD I was predicted to be a cytosine‐specific methyltransferase, TNMD II was classified as a SUMO protease, SENP1, and TNMD III was similar to á‐syntrophin. These results suggest that each Tnmd isoform may play distinct roles in tendons.This study was supported by Flexcell International Corp.