Biology subjects

Tufa, S. F.

Publications and source records attributed to Tufa, S. F..

4 recordsLinked to original sources

bioRxiv2020

Cell autonomous TGF-beta signaling is essential for cell recruitment into degenerating tendons

Understanding the role of cell recruitment in tendon disorders is critical for improvements in regenerative therapy. We recently reported that targeted disruption of TGF{beta} type II receptor in the tendon cell lineage (Tgfbr2ScxCre) resulted in tenocyte dedifferentiation and tendon degradation in post-natal stages. Here we extend the analysis and identify direct recruitment of stem/progenitor cells into the degenerative mutant tendons. Cre-lineage tracing indicates that these cells are not derived from tendon ensheathing tissues or from a Scleraxis-lineage, and they turned on tendon markers only upon entering the mutant tendons. Through immunohistochemistry and inducible gene deletion, we further find that the recruited cells originated from a Sox9-expressing lineage and their recruitment was dependent on cell-autonomous TGF{beta} signaling. These results thus differ from previous reports of cell recruitment into injured tendons, and suggest a critical role for TGF{beta} signaling and cell recruitment in the etiology and treatment of tendon degeneration.

cell biology↗

bioRxiv2020

Enhancer of Zeste Homolog 2 (Ezh2) is essential for patterning of multiple musculoskeletal tissues but dispensable for tendon differentiation

An efficient musculoskeletal system depends on the precise assembly and coordinated growth and function of muscles, skeleton and tendons. However, the mechanisms that drive integrated musculoskeletal development and coordinated growth and differentiation of each of these tissues are still being uncovered. Epigenetic modifiers have emerged as critical regulators of cell fate differentiation, but so far almost nothing is known about their roles in tendon biology. Previous studies have shown that epigenetic modifications driven by Enhancer of zeste homolog 2 (EZH2), a major histone methyltransferase, have significant roles in vertebrate development including skeletal patterning and bone formation. We now find that targeting Ezh2 through the limb mesenchyme also has significant effects on tendon and muscle patterning, likely reflecting the essential roles of early mesenchymal cues mediated by Ezh2 for coordinated patterning and development of all tissues of the musculoskeletal system. Conversely, loss of Ezh2 in the tendon cells did not disrupt the tendon cell fate suggesting that tenocyte differentiation and tendon maturation are independent of Ezh2 signaling.

developmental biology↗

bioRxiv2020

Tendon and Motor Phenotypes in the Crtap-/- Mouse Model of Recessive Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is characterized by short stature, skeletal deformities, low bone mass with bone fragility, and motor deficits. A subset of OI patients also present with joint hypermobility; however, the role of tendon/ligament dysfunction in OI pathogenesis is largely unknown. Using the Crtap-/- mouse model of severe, recessive OI, we found that mutant Achilles tendons and patellar ligaments were thinner with increased collagen cross-links and reduced collagen fibril size at 1- and 4-months compared to wildtype. Patellar ligaments from Crtap-/- mice also had fewer progenitors with a concomitant increase in immature cells. RNA-seq analysis of Achilles tendons and patellar ligaments from 1-month Crtap-/- mice revealed dysregulation in matrix gene expression concomitant with predicted alterations in TGF-{beta}, inflammatory, and metabolic signaling. Finally, a series of behavioral tests revealed severe motor impairments and reduced grip strength in 4-month Crtap-/- mice - a phenotype that correlates with the tendon/ligament pathology.

genetics↗

bioRxiv2019

TGF-β signaling is critical for maintenance of the tendon cell fate

Studies of cell fate focus on specification, but little is known about maintenance of the differentiated state. We find that TGF{beta} signaling plays an essential role in maintenance of the tendon cell fate. To examine the role TGF{beta} signaling in tenocytes TGF{beta} type II receptor was targeted in the Scleraxis cell lineage. Tendon development was not disrupted in mutant embryos, but shortly after birth tenocytes lost differentiation markers and reverted to a more stem/progenitor state. Targeting of Tgfbr2 using other Cre drivers did not cause tenocyte dedifferentiation suggesting a critical significance for the spatio-temporal activity of ScxCre. Viral reintroduction of Tgfbr2 to mutants was sufficient to prevent and even rescue mutant tenocytes suggesting a continuous and cell-autonomous role for TGF{beta} signaling in cell fate maintenance. These results uncover the critical importance of molecular pathways that maintain the differentiated cell fate and a key role for TGF{beta} signaling in these processes.

cell biology↗