Authors:

Min-Song Kim

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About Paper:

Rett syndrome (RTT) is a progressive neurodevelopmental disorder primarily affecting females caused by mutations in the X-linked MECP2 gene, a protein responsible for transcriptional regulation, resulting in impaired synaptic plasticity, motor dysfunction, seizures, and cognitive deficits [1]. Importantly, RTT reflects functional dysregulation of neuronal signaling rather than widespread neurodegeneration, suggesting that its symptoms may be partially reversible with targeted interventions. Trofinetide is currently the only FDA approved therapeutic for RTT; however, its modest efficacy and frequent gastrointestinal side effects underscore the need for more potent and better tolerated treatments. We hypothesized that NQ-13, an IGFBP2 derived peptide with high affinity for insulin-like growth factor 2 receptor (IGF2R), would restore behavioral and molecular deficits in RTT models through IGF2R-dependent signaling. Adult Mecp2 heterozygous mice were treated with NQ-13 and evaluated using assays measuring seizure threshold, motor coordination, respiratory function, circadian activity, and working memory. NQ-13 significantly increased seizure threshold, reduced paw dragging and paw slips, restored circadian amplitude, decreased abnormal breathing patterns, and improved Y maze working memory performance compared to vehicle treated RTT mice. To further contextualize the behavioral findings, molecular assays were performed to compare NQ-13 and Trofinetide at the level of I|GF2R engagement and pathway activation. Notably, NQ-13 demonstrated greater efficacy at lower doses than Trofinetide. In vitro competition assays revealed that NQ-13 binds IGF2R with ~100-fold greater potency than Trofinetide. Pharmacological inhibition of sphingosine kinase attenuated NQ-13-mediated IGF2R signaling, suggesting a lipid-dependent pathway. Additionally, molecular analysis of medial prefrontal cortex tissue revealed increased MeCP2 protein replication in NQ-13 treated mice. Together, these findings demonstrate that NQ-13 reverses core molecular deficits in RTT models and engages IGF2R-dependent pathways that may restore activity-dependent plasticity. Further investigation will define MEK/ERK and CREB-dependent signaling pathways to clarify the molecular basis of NQ-13 mediated therapeutic rescue in RTT.

Source:

Northwestern University

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Co-authors:

Min-Song Kim