Significance of the Tks4 scaffold protein in bone tissue homeostasis

Sci Rep. 2019 Apr 8;9(1):5781. doi: 10.1038/s41598-019-42250-6.

Abstract

The main driver of osteoporosis is an imbalance between bone resorption and formation. The pathogenesis of osteoporosis has also been connected to genetic alterations in key osteogenic factors and dysfunction of bone marrow mesenchymal stem/stromal cells (BM-MSCs). Tks4 (encoded by the Sh3pxd2b gene) is a scaffold protein involved in podosome organization. Homozygous mutational inactivation of Sh3pxd2b causes Frank-ter Haar syndrome (FTHS), a genetic disease that affects bone tissue as well as eye, ear, and heart functions. To date, the role of Tks4 in adult bone homeostasis has not been investigated. Therefore, the aim of this study was to analyze the facial and femoral bone phenotypes of Sh3pxd2b knock-out (KO) mice using micro-CT methods. In addition to the analysis of the Sh3pxd2b-KO mice, the bone microstructure of an FTHS patient was also examined. Macro-examination of skulls from Tks4-deficient mice revealed craniofacial malformations that were very similar to symptoms of the FTHS patient. The femurs of the Sh3pxd2b-KO mice had alterations in the trabecular system and showed signs of osteoporosis, and, similarly, the FTHS patient also showed increased trabecular separation/porosity. The expression levels of the Runx2 and osteocalcin bone formation markers were reduced in the bone and bone marrow of the Sh3pxd2b-KO femurs, respectively. Our recent study demonstrated that Sh3pxd2b-KO BM-MSCs have a reduced ability to differentiate into osteoblast lineage cells; therefore, we concluded that the Tks4 scaffold protein is important for osteoblast formation, and that it likely plays a role in bone cell homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Bone Marrow / metabolism
  • Cancellous Bone / diagnostic imaging
  • Cancellous Bone / metabolism
  • Cancellous Bone / pathology
  • Cells, Cultured
  • Core Binding Factor Alpha 1 Subunit / genetics
  • Core Binding Factor Alpha 1 Subunit / metabolism
  • Craniofacial Abnormalities / genetics*
  • Craniofacial Abnormalities / metabolism
  • Craniofacial Abnormalities / pathology
  • Developmental Disabilities / genetics
  • Developmental Disabilities / metabolism
  • Developmental Disabilities / pathology
  • Femur / diagnostic imaging
  • Femur / metabolism
  • Femur / pathology
  • Heart Defects, Congenital / genetics*
  • Heart Defects, Congenital / metabolism
  • Heart Defects, Congenital / pathology
  • Homeostasis*
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Osteocalcin / genetics
  • Osteocalcin / metabolism
  • Osteochondrodysplasias / congenital*
  • Osteochondrodysplasias / genetics
  • Osteochondrodysplasias / metabolism
  • Osteochondrodysplasias / pathology
  • Osteogenesis
  • Young Adult

Substances

  • Adaptor Proteins, Signal Transducing
  • Core Binding Factor Alpha 1 Subunit
  • RUNX2 protein, human
  • SH3PXD2B protein, human
  • Osteocalcin

Supplementary concepts

  • Ter Haar syndrome