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 was previously identified as a potential therapeutic target for neurofibromin-deficient tumorigenesis. Our results suggest that Cxcr4 signaling also regulates neurofibromin-dependent cognitive function. Overall design: Bulk RNA-seq profiling of wild-type (Tüpfel long fin background) and putative nf1 double homozygous (nf1a-/-;nf1b-/-) mutant zebrafish. Samples were isolated from groups of 20 whole zebrafish larvae at 5 days post-fertilization, including 8 biological replicates from each group.