PTEN In Vivo Imaging Opens A New Era in Neuroscience

In the microscopic cellular universe, a protein called PTEN (Phosphatase and tensin homolog) is like a precise molecular brake, constantly regulating cell proliferation and survival. This "life guardian" with only 403 amino acids plays a key role in embryonic development, synaptic plasticity and even tumor suppression by antagonizing the PI3K/AKT/mTOR signaling pathway. However, surprisingly, although 30% of cancers and various neurodevelopmental diseases (such as autism and epilepsy) are closely related to PTEN dysfunction, researchers have long lacked tools to directly observe its dynamics in living tissues-until the emergence of this breakthrough study in Nature Methods ("Genetically encoded biosensor for fluorescence lifetime imaging of PTEN dynamics in the intact brain").

The researchers cleverly used the principle of fluorescence resonance energy transfer (FRET) to transform the PTEN protein into a conformation-sensitive "molecular probe". By labeling green fluorescent protein (mEGFP) and quenching protein (sREACh) at its N-terminus and C-terminus respectively, the team successfully captured the conformational transition of PTEN from the closed state to the open state. This fluorescence lifetime change of only 0.3 nanoseconds (from 2.20 ns to 2.53 ns) was clearly discernible using two-photon fluorescence lifetime imaging microscopy (2pFLIM) technology.

Even more amazing is that the R14G mutant screened by the research team through directed evolution, while retaining 95% conformational sensitivity, reduced the catalytic activity to 5% of the wild type. This "invisible" design not only did not change the density of dendritic spines in the somatosensory cortical neurons of mice, but also achieved the dynamic tracking of PTEN subcellular localization in the living brain for the first time: the PTEN activity in the neuronal cell body (2.20±0.004 ns) was significantly higher than that in the dendritic region (2.11±0.009 ns). These studies reveal the exquisite division of labor of this molecular brake in spatial regulation.

Figure 1. Dual imaging of PTEN activity using a red-shifted PTEN sensor. (Kagan T, et al., 2025)

When this technology is applied to cross-species research, more surprises follow. In the nematode model, researchers found that PTEN activity gradually increased with the developmental stage, from 2.51 ns in L1 larvae to 2.64 ns in adults. In the in vivo mouse experiment, the dual-color probe system (red light R-PTEN and green GCaMP) captured the neuronal specific response caused by sensory deprivation for the first time. While the activity of excitatory neuron PTEN decreases by 0.04 ns, the activity of inhibitory neurons increases by 0.15 ns. This "molecular seesaw" phenomenon provides a new perspective for analyzing the imbalance of neural networks in autism.

This technological breakthrough not only fills the century-old gap in PTEN dynamic monitoring, but also opens a new era of in vivo molecular imaging. When researchers can observe the working status of the "life brake" in real time, we are one step closer to the goal of cracking the mysteries of the brain and treating major diseases.