Intracellular thermometry at the microscopic level is currently a hot topic. Herein we describe a small molecule fluorescent thermometer targeting mitochondria (Mito thermo yellow). Mito thermo yellow successfully demonstrates the ability to monitor the intracellular temperature gradient, generated by exogenous heating, in various cells.

A major barrier to regeneration of CNS axons is the presence of growth-inhibitory proteins associated with myelin and the glial scar. To identify chemical compounds with the ability to overcome the inhibition of regeneration, we screened a novel triazine library, based on the ability of compounds to increase neurite outgrowth from cerebellar neurons on inhibitory myelin substrates. The screen produced four "hit compounds," which act with nanomolar potency on several different neuronal types and on several distinct substrates relevant to glial inhibition. Moreover, the compounds selectively overcome inhibition rather than promote growth in general. The compounds do not affect neuronal cAMP levels, PKC activity, or EGFR (epidermal growth factor receptor) activation. Interestingly, one of the compounds alters microtubule dynamics and increases microtubule density in both fibroblasts and neurons. This same compound promotes regeneration of dorsal column axons after acute lesions and potentiates regeneration of optic nerve axons after nerve crush in vivo. These compounds should provide insight into the mechanisms through which glial-derived inhibitors of regeneration act, and could lead to the development of novel therapies for CNS injury.

During muscle differentiation, mitochondria undergo dramatic changes in their morphology and distribution to prepare for the higher rate of energy consumption. By applying a mitochondria-targeted rosamine library in C2C12 myogenesis, we discovered one compound that controls muscle differentiation. When treated to undifferentiated myoblasts, our selected compound, B25, inhibited myotube formation, and when treated to fully differentiated myotubes, it induced fission of multinucleated myotubes into mononucleated fragments. Compared to myoseverin, which is known for inducing myotube fission by destabilizing microtubules, B25 affects neither microtubule stability nor cell cycle. Further investigation identified that B25 induces myotube fission through the activation of NF-kappaB, which is one of the important signaling pathways linked to skeletal muscle differentiation. So far, the use of small-molecule fluorophores is limited in the discovery of labeling agents or sensors. In addition to their potential as a sensor, here we show the application of fluorescent small molecules in the discovery of a bioactive probe that induces a specific cellular response.

The cell‐by date: The fluorescent compound CDy1 selectively stains embryonic stem cells (see scheme). CDy1 was used to identify fibroblasts undergoing reprogramming to induced pluripotent stem cells prior to the expression of green fluorescent protein under the control of the Oct4 promoter.

Lighten up! To investigate intracellular binders of myotube‐specific probes, a thiol‐reactive derivative, CDy2, was prepared. In live cells, the derivative selectively localizes in mitochondria and covalently labels its binding partners.