Canonical Wnt signalling regulates nuclear export of Setdb1 during skeletal muscle terminal differentiation

Abstract

The histone 3 lysine 9 methyltransferase Setdb1 is essential for both stem cell pluripotency and terminal differentiation of different cell types. To shed light on the roles of Setdb1 in these mutually exclusive processes, we used mouse skeletal myoblasts as a model of terminal differentiation. Ex vivo studies on isolated single myofibres showed that Setdb1 is required for adult muscle stem cells expansion following activation. In vitro studies in skeletal myoblasts confirmed that Setdb1 suppresses terminal differentiation. Genomic binding analyses showed a release of Setdb1 from selected target genes upon myoblast terminal differentiation, concomitant to a nuclear export of Setdb1 to the cytoplasm. Both genomic release and cytoplasmic Setdb1 relocalisation during differentiation were dependent on canonical Wnt signalling. Transcriptomic assays in myoblasts unravelled a significant overlap between Setdb1 and Wnt3a regulated genetic programmes. Together, our findings revealed Wnt-dependent subcellular relocalisation of Setdb1 as a novel mechanism regulating Setdb1 functions and myogenesis.

A drive in SUVs: From development to disease

“…This indicates that, similar to G9a, SETDB1 could also be involved in mediating gene activation. 33 In contrast to these observations, in P19 cells, SETDB1 represses the E2F1 promoter upon thyroid hormone treatment. Depletion of SETDB1 led to increased colony formation and cells in the S phase.…”

“…Among these, canonical Wnt signaling is involved in SETDB1 export during muscle differentiation and concomitantly release its occupancy on target genes such as Ankyrin repeat domain 1 (Ankrd1), whose expression is crucial for myogenic differentiation. 33 During the S phase, SETDB1 is localized to pericentric heterochromatin suggesting its function in heterochromatic H3K9me3 during replication. 34 …”

“…Consistently, similar to G9a, knockdown of SETDB1 at the onset of differentiation led to enhanced differentiation. 33 SETDB1 is also involved in inhibition of adipogenic differentiation. SETDB1 mediates H3K9 methylation on CEBPa promoter, and its knockdown led to a decrease in H3K9 methylation and enhanced adipogenic differentiation.…”

“…110 Overexpressed in prostrate and liver cancer [100][101][102] Promotes expansion of muscle progenitor cells. 33 Inhibits adipogenesis by repressing CEBPa. 79 Knockdown slows growth in myoblasts.…”

The impact of cell geometry and the cytoskeleton on the nucleo-cytoplasmic localisation of the SMYD3 methyltransferase suggests that the epigenetic machinery is mechanosensitive

“…We used our experimental set- up to investigate nuclear:cytoplasmic ratios for C2C12 cells spread on square or rectangular fibronectin over a range of pattern areas (500-1800 µm 2 ) [ Figure 5 and Figure S4]. We tested localization of another methyltransferase, SETDB1, which was also recently reported to be cytoplasmic [ 25 ]. We tested G-actin, which is known to play a role in gene transcription [ 47 ].…”