Src-family tyrosine kinase activities are essential for differentiation of human embryonic stem cells

Abstract

Embryonic stem (ES) cells are characterized by pluripotency, defined as the developmental potential to generate cell lineages derived from all three primary germ layers. In the past decade, great progress has been made on the cell culture conditions, transcription factor programs and intracellular signaling pathways that control both murine and human ES cell fates. ES cells of mouse vs. human origin have distinct culture conditions, responding to some tyrosine kinase signaling pathways in opposite ways. Previous work has implicated the Src family of non-receptor protein-tyrosine kinases in mouse ES cell self-renewal and differentiation. Seven members of the Src kinase family are expressed in mouse ES cells, and individual family members appear to play distinct roles in regulating their developmental fate. Both Hck and c-Yes are important in self-renewal, while c-Src activity alone is sufficient to induce differentiation. While these findings implicate Src-family kinase signaling in mouse ES cell renewal and differentiation, the role of this kinase family in human ES cells is largely unknown. Here, we explored Src-family kinase expression patterns and signaling in human ES cells during self-renewal and differentiation. Of the eleven Src-related kinases in the human genome, Fyn, c-Yes, c-Src, Lyn, Lck and Hck were expressed in H1, H7 and H9 hES cells, while Fgr, Blk, Srm, Brk, and Frk transcripts were not detected. Of these, c-Yes, Lyn, and Hck transcript levels remained constant in self-renewing human ES cells vs. differentiated EBs, while c-Src and Fyn showed a modest increase in expression as a function of differentiation. In contrast, Lck expression levels dropped dramatically as a function of EB differentiation. To assess the role of overall Src-family kinase activity in human ES cell differentiation, cultures were treated with inhibitors specific for the Src kinase family. Remarkably, human ES cells maintained in the presence of the potent Src-family kinase inhibitor A-419259 retained the morphology of domed, pluripotent colonies and continued to express the self-renewal marker TRA-1-60 despite culture under differentiation conditions. Taken together, these observations support a role for Src-family kinase signaling in the regulation of human ES cell fate, and suggest that the activities of individual Src-family members are required for initiation of the differentiation program.

Novel small molecule inhibiting CDCP1‐PKCδ pathway reduces tumor metastasis and proliferation

“…Accordingly, SFK inhibitors have been developed and tested in clinical trials . However, SFK is also ubiquitously expressed in normal tissues and involved in normal tissue development and cell differentiation through the conditional activation and phosphorylation of various physiological substrates . Therefore, compounds inhibiting the catalytic activity of SFK might naturally show significant side‐effects .…”

“…(25,26) However, SFK is also ubiquitously expressed in normal tissues and involved in normal tissue development and cell differentiation through the conditional activation and phosphorylation of various physiological substrates. (27)(28)(29) Therefore, compounds inhibiting the catalytic activity of SFK might naturally show significant sideeffects. (30) Conversely, CDCP1, a substrate of SFK, is predominantly expressed in various cancer cells whereas it exhibits limited expression in normal tissues including hematopoietic and neural stem/progenitor cells (31,32) although its functional roles in these tissues have not yet been elucidated.…”

A Role of MicroRNAs in Cell Differentiation During Gonad Development

“…We recently found that miR-125a-3p post-transcriptionally regulates the expression of Fyn, a Src-family kinase (SFK), in granulosa cells (Grossman et al 2015). SFKs can either synergize or operate apart and can also compensate one another (Bock and Herz 2003;Zhang et al 2014b). Of the SFKs, Src is essential for activation of primordial follicle by regulating the PI3K-PKC-ERK1/2 pathway (Du et al 2012).…”

A Fyn - specific biosensor reveals localized, pulsatile kinase activity and spatially regulated signaling crosstalk

“…Src family kinases (SFKs) are such key signaling nodes; activated by cell adhesion receptors, integrins, receptor tyrosine kinases (RTKs, including growth factor receptors) and G-coupled protein receptors (GPCR) among others 7–11 . Src-kinases critically influence cell fate; regulating cell shape, migration and adhesion, survival and growth, stemness and differentiation making them important therapeutic targets in multiple diseases 12–20 . Despite their importance, intracellular activity patterns of individual Src family kinases with spatial and temporal precision are still unclear.…”

“…Study of SFK activity is especially complicated by the presence of multiple closely related Src family members, including three ubiquitously expressed kinases c-Src, c-Yes and Fyn. While there is some functional redundancy, individual SFKs also perform critical, exclusive roles in the cell 20,27–32 . Therefore, despite decades of study, it is not always clear which kinase(s) is activated in a given cellular context?…”