Inhibition of Cxcr4 chemokine receptor signaling improves habituation learning in a zebrafish model of neurofibromatosis.

Neurofibromatosis type 1 (NF1) is a neurogenetic disorder caused by loss-of-function mutations in the gene neurofibromin 1 (NF1). NF1 encodes neurofibromin, a multifunctional tumor-suppressing protein that regulates Ras, cAMP and dopamine signaling. NF1 predisposes patients to a wide range of symptoms, including peripheral nerve tumors, brain tumors and cognitive dysfunction. Despite considerable work using animal models to investigate the role of neurofibromin in behavior, translating research into treatment for NF1-associated cognitive dysfunction has not yet been successful. Here, we provide evidence that Cxcr4 chemokine receptor signaling is a regulator of habituation learning and modulator of cAMP-PKA signaling in nf1 mutant larval zebrafish. Combining a small-molecule drug screen and RNAseq analysis, we show that cxcr4b expression is increased in nf1 mutants and that pharmacological inhibition of Cxcr4 with AMD3100 (plerixafor) improves habituation learning. We further demonstrate that plerixafor activates cAMP-PKA pathway signaling but has limited effects on Ras-Raf-MEK-ERK pathway signaling in the nf1 mutant brain. CXCR4 has previously been identified as a potential therapeutic target for neurofibromin-deficient tumorigenesis. Our results suggest that Cxcr4 signaling also regulates neurofibromin-dependent cognitive function.