Biology subjects

Dudakovic, A.

Publications and source records attributed to Dudakovic, A..

3 recordsLinked to original sources

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

Lamin A/C functions independently from mechanical signaling during adipogenesis

Mesenchymal stem cells (MSC) maintain the musculoskeletal system by differentiating into multiple cell types including osteocytes and adipocytes. Mechanical signals, including strain and low intensity vibration (LIV), are important regulators of MSC differentiation. Lamin A/C is a vital protein for nuclear architecture that supports chromatin organization, as well as mechanical integrity and mechano-sensitivity of the nucleus in MSCs. Here, we investigated whether Lamin A/C and mechano-responsiveness are functionally coupled during adipogenesis. Lamin depletion in MSCs using siRNA increased nuclear area, height and volume and decreased circularity and stiffness, while phosphorylation of focal adhesions and dynamic substrate strain in response to LIV remained intact. Lamin A/C depletion decelerates adipogenesis as reflected by delayed appearance of key biomarkers (e.g., adiponectin/ADIPOQ). Based on RNA-seq data, reduced Lamin A/C levels decrease the activation of the adipocyte transcriptome that is normally observed in response to adipogenic cues mediating differentiation of MSCs. Mechanical stimulation via daily LIV application reduced the expression levels of ADIPOQ in both control and Lamin A/C depleted cells. Yet, treatment with LIV did not induce major transcriptome changes in either control or Lamin A/C depleted MSCs, suggesting that the biological effects of LIV on adipogenesis may not occur at the transcriptional level. We conclude that while Lamin A/C activation is essential for normal adipogenesis, it is dispensible for activation of focal adhesions by dynamic vibration induced mechanical signals.

bioengineering↗

bioRxiv2020

Modifiers and Mediators of Craniosynostosis Severity Revealed by Differential Gene Expression

Severity of craniosynostosis in humans varies widely even in patients with identical genetic mutations. In this study we compared RNA sequencing data from cranial tissues of a severe form of Crouzon craniosynostosis syndrome (C57BL/6 FGFR2C342Y/+ mice) with those of a less severe form of Crouzon craniosynostosis (BALB/c FGFR2C342Y/+ mice) to identify genetic modifiers that influence craniosynostosis phenotype severity. Comparison of the mice revealed neonatal onset of coronal suture fusion in the form of suture obliteration in C57BL/6 mice (88% incidence, p<.001 between genotypes). Coronal suture fusion in the form of point fusions across the suture occurred at approximately 4 weeks after birth, with less severe skull shape abnormalities, in BALB/c mice. Substantially fewer genes were differentially expressed in BALB/c FGFR2+/+ vs. FGFR2C342Y/+ mice (87 out of 15,893 expressed genes) than C57BL/6 FGFR2C+/+ vs. FGFR2C342Y/+ mice (2,043 out of 19,097 expressed genes). Further investigation revealed differential expression of coronal suture fusion associated genes, eph/ephrin boundary genes, cell proliferation genes, osteoblast differentiation genes and epigenetic regulators, among others. The most striking pattern in the data was the minimal change in gene expression seen for most genes in BALB/c FGFR2+/+ vs. FGFR2C342Y/+ mice. Analysis of protein processing and lysosomal components support the hypothesis that the craniosynostosis phenotype is less severe in BALB/c mice because the mutant FGFR2C342Y protein is not expressed to the same extent as that seen in C57BL/6 mice. Together, these results suggest that a strategy aimed at increasing degradation of the mutant receptor or downstream signaling inhibition could lead to diminished phenotype severity.

developmental biology↗