Stem cells are widely publicized for their potential therapeutic benefits, but current culture methodologies restrict the progression of both research and clinical applications of stem cell technology. There is an increasing movement toward countering these problems by replacing exogenous growth factors and animal components with small molecules to create chemically-defined conditions for stem cell growth. The small molecule ID-8 was found to aid stem cell self renewal, via inhibition of DYRK kinases. The DYRK kinases are a family of protein kinases that play a role in a wide variety of cellular processes such as differentiation, self-renewal and neurogenesis, but their biological mechanism of action is not known. There is no singular role for this family of kinases, with evidence that different isoforms have divergent roles in cell development. DYRK1A is best characterised as a modulator of neuronal development, playing a role in the pathology of Down’s syndrome, whereas DYRK2, typically involved in apoptosis, has been suggested as aiding stem cell self-renewal.
Through kinase inhibition profiling we provide direct evidence that ID-8 is a potent and selective DYRK1A inhibitor. In support of the DYRK-inhibitory effects of ID-8 on stem cell self-renewal, we show that other validated DYRK inhibitors can aid pluripotent stem cell self-renewal through single-cell replating assays with human embryonic stem (hES) cells. Neural stem cell precursors cultured for two weeks in the presence of ID-8 exhibit retardation of differentiation and growth. Incubation of these neural precursors with validated DYRK1A inhibitors yields a similar morphological phenotype of retarded growth and differentiation. These results support the proposed function of DYRK1A as a promoter of neuronal development in stem cell populations.