The scaffold protein Tks4 is required for the differentiation of mesenchymal stromal cells (MSCs) into adipogenic and osteogenic lineages.

Metta Dülk,László Radnai,Virag Vas,Ferenc Uher,Tamás Kovács,Anna Fekete,Dalma E. Csécsy,Judit E. Pongrácz,Árpád Lányi,Krisztián Kvell,Miklós Geiszt,Gyöngyi Kudlik,Bálint Szeder,Balázs L. Merő,Dávid Ernszt,László Buday

doi:10.1038/srep34280

Abstract

The commitment steps of mesenchymal stromal cells (MSCs) to adipogenic and other lineages have been widely studied but not fully understood. Therefore, it is critical to understand which molecules contribute to the conversion of stem cells into differentiated cells. The scaffold protein Tks4 plays a role in podosome formation, EGFR signaling and ROS production. Dysfunction of Tks4 causes a hereditary disease called Frank-ter Haar syndrome with a variety of defects concerning certain mesenchymal tissues (bone, fat and cartilage) throughout embryogenic and postnatal development. In this study, we aimed to analyze how the mutation of Tks4 affects the differentiation potential of multipotent bone marrow MSCs (BM-MSCs). We generated a Tks4 knock-out mouse strain on C57Bl/6 background, and characterized BM-MSCs isolated from wild type and Tks4−/− mice to evaluate their differentiation. Tks4−/− BM-MSCs had reduced ability to differentiate into osteogenic and adipogenic lineages compared to wild type. Studying the expression profile of a panel of lipid-regulated genes during adipogenic induction revealed that the expression of adipogenic transcription factors, genes responsible for lipid droplet formation, sterol and fatty acid metabolism was delayed or reduced in Tks4−/− BM-MSCs. Taken together, these results establish a novel function for Tks4 in the regulation of MSC differentiation.

Highlights

Frank-ter Haar syndrome (FTHS, OMIM:249420), is a rare genetic disorder associated with skeletal defects, craniofacial anomalies, cardiovascular abnormalities and, in some cases, reduced lipoid tissue[1,2]
The major observed phenotypic consequences of the genetic deletion of Tks[4] scaffold protein were smaller size compared to the wild type (Fig. 1d), craniofacial abnormalities with wide anterior fontanel and prominent eyes, (Fig. 1e,f) skeletal malformations as shortened long bones and kyphosis (Fig. 1g and Supplementary Table S1)
To characterize the differentiation defect of Tks[4] KO BM-Mesenchymal stromal cells (MSCs), we examined the expression of the main osteogenic transcription factors, RunX2 (66 kDa) and Osterix (54 kDa) by western blot

Summary

Introduction

Frank-ter Haar syndrome (FTHS, OMIM:249420), is a rare genetic disorder associated with skeletal defects, craniofacial anomalies, cardiovascular abnormalities and, in some cases, reduced lipoid tissue[1,2]. Two new homozygous loss-of-function mutations were identified in the SH3PXD2B gene in patients with Borrone dermato-cardio-skeletal syndrome (BDSC syndrome) which is a FTHS related genetic disease[5]. It has been described that Tks[4] is involved in ROS production and ROS modulates several signaling pathways regulating MSC differentiation[15]. We hypothesized that Tks[4] may play a role in the process necessary for MSC differentiation and one of the underlying mechanisms causing the FTHS phenotype could be the impaired stem cell functions of Tks[4] deficient MSCs. Here we present a novel Tks4−/− mouse strain on C57Bl/6 background with the complete loss of Tks[4] protein. Our data demonstrate that in the absence of Tks[4], adipogenic and osteogenic differentiation of BM-MSCs is impaired; we concluded that Tks[4] is necessary for the adipogenic and osteogenic mesenchymal differentiation pathways

Objectives

Methods

Results

Conclusion