Musashi2 Is Required for the Self-Renewal and Pluripotency of Embryonic Stem Cells

Abstract

Recent studies have shown that the RNA binding protein Musashi 2 (Msi2) plays important roles during development. Msi2 has also been shown to be elevated in several leukemias and its elevated expression has been linked with poorer prognosis in these cancers. Additionally, in embryonic stem cells (ESC) undergoing the early stages of differentiation, Msi2 has been shown to associate with the transcription factor Sox2, which is required for the self-renewal of ESC. These findings led us to examine the effects of Msi2 on the behavior of ESC. We determined that ESC express two isoforms of Msi2, the larger canonical isoform (isoform 1) and a shorter, splice-variant isoform (isoform 2). Using multiple shRNA lentiviral vectors, we determined that knockdown of Msi2 disrupts the self-renewal of ESC and promotes their differentiation into cells that express markers associated with mesoderm, ectoderm, and trophectoderm. Moreover, our studies indicate that the extent of differentiation and the loss of self-renewal capacity correlate with the levels to which Msi2 levels were decreased. We extended these findings by engineering ESC to inducibly express either Msi2 isoform1 or isoform 2. We determined that ectopic expression of Msi2 isoform 1, but not isoform 2, enhances the cloning efficiency of ESC. In addition, we examined how Msi2 isoform 1 and isoform 2 affect the differentiation of ESC. Interestingly, ectopic expression of either Msi2 isoform 1 or isoform 2 does not affect the pattern of differentiation induced by retinoic acid. Finally, we show that ectopic expression of either isoform 1 or isoform 2 is not sufficient to block the differentiation that results from the knockdown of both isoforms of Msi2. Thus, it appears that both isoforms of Msi2 are required for the self-renewal of ESC.

The SOX2-Interactome in Brain Cancer Cells Identifies the Requirement of MSI2 and USP9X for the Growth of Brain Tumor Cells

“…S4, supplemental Table S6). Recently, we have shown that Msi2 is required for the self-renewal and pluripotency of mouse ESC [14] and, more recently, we have determined that knockdown of Usp9x in mouse ESC substantially increases the differentiation of ESC (unpublished results). Furthermore, MSI2 and USP9X have been implicated in other cancers [16]–[21], but their roles in brain tumors have not been examined.…”

Musashi-2 promotes migration and invasion in bladder cancer via activation of the JAK2/STAT3 pathway

“…In addition, Msi2 isoform 2 appears to be the major isoform expressed in bladder cancer cell lines and tissues, which was consistent with the expression pattern of Msi2 in glioblastoma cells and embryonic stem cells. 18,19 Clinical analysis also indicated that high expression of Msi2 was correlated with poor overall and Msi2 promotes bladder cancer metastasis via JAK2/STAT3 pathway C Yang et al recurrence-free survival in patients with bladder cancer. Moreover, in vitro assays indicated that overexpression of Msi2 promoted, while silencing of Msi2 inhibited, the migration and invasiveness of bladder cancer cell through activating JAK2/STAT3 pathway.…”

SOX2 functions as a molecular rheostat to control the growth, tumorigenicity and drug responses of pancreatic ductal adenocarcinoma cells

“…Separate lentiviral vectors were generated with pLVX-tetO-(fs)SOX2 and with a vector expressing the reverse tet transactivator, pLVX-Tet-On® Advanced (modified to use a PGK rather than a CMV promoter) [66]. Cells which successfully integrated these viral vectors were selected for in medium containing 5 μg/ml puromycin (P8833, Sigma-Aldrich, St. Louis, MO) for 48 hours and 300 μg/mL G418 sulfate (#631308, Clontech, Mountain View, CA) for 9-12 days, respectively.…”