Inhibition of Cxcr4 chemokine receptor signaling improves habituation learning and increases cAMP-PKA signaling in a zebrafish model of Neurofibromatosis type 1

bioRxiv (Cold Spring Harbor Laboratory) · 2025-06-02

Abstract 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 identify Cxcr4 chemokine receptor signaling as 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 in nf1 mutants. We further demonstrate that Plerixafor treatment 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 provide evidence that Cxcr4 signaling also regulates neurofibromin-dependent cognitive function.

Mechanistic insights from animal models of neurofibromatosis type 1 cognitive impairment

Disease Models & Mechanisms · 2022 · 25 citations

• Biology
• Computational biology
• Evolutionary biology

Neurofibromatosis type 1 (NF1) is an autosomal-dominant neurogenetic disorder caused by mutations in the gene neurofibromin 1 (NF1). NF1 predisposes individuals to a variety of symptoms, including peripheral nerve tumors, brain tumors and cognitive dysfunction. Cognitive deficits can negatively impact patient quality of life, especially the social and academic development of children. The neurofibromin protein influences neural circuits via diverse cellular signaling pathways, including through RAS, cAMP and dopamine signaling. Although animal models have been useful in identifying cellular and molecular mechanisms that regulate NF1-dependent behaviors, translating these discoveries into effective treatments has proven difficult. Clinical trials measuring cognitive outcomes in patients with NF1 have mainly targeted RAS signaling but, unfortunately, resulted in limited success. In this Review, we provide an overview of the structure and function of neurofibromin, and evaluate several cellular and molecular mechanisms underlying neurofibromin-dependent cognitive function, which have recently been delineated in animal models. A better understanding of neurofibromin roles in the development and function of the nervous system will be crucial for identifying new therapeutic targets for the various cognitive domains affected by NF1.

Author response: KLC4 shapes axon arbors during development and mediates adult behavior

2022-09-11

Voltage-gated sodium channel<i>scn8a</i>is required for innervation and regeneration of amputated adult zebrafish fins

Proceedings of the National Academy of Sciences · 2022 · 9 citations

• Neuroscience
• Anatomy
• Materials science

mutations reduced neural activity as expected, they also disrupted axon regrowth and patterning in fin regenerates, resulting in hypoinnervation. Our findings indicate that the activity of VGSCs plays a proregenerative role by promoting innervation of appendage stumps.

KLC4 shapes axon arbors during development and mediates adult behavior

eLife · 2022 · 16 citations

• Biology
• Neuroscience
• Cell biology

Development of elaborate and polarized neuronal morphology requires precisely regulated transport of cellular cargos by motor proteins such as kinesin-1. Kinesin-1 has numerous cellular cargos which must be delivered to unique neuronal compartments. The process by which this motor selectively transports and delivers cargo to regulate neuronal morphogenesis is poorly understood, although the cargo-binding kinesin light chain (KLC) subunits contribute to specificity. Our work implicates one such subunit, KLC4, as an essential regulator of axon branching and arborization pattern of sensory neurons during development. Using live imaging approaches in klc4 mutant zebrafish, we show that KLC4 is required for stabilization of nascent axon branches, proper microtubule (MT) dynamics, and endosomal transport. Furthermore, KLC4 is required for proper tiling of peripheral axon arbors: in klc4 mutants, peripheral axons showed abnormal fasciculation, a behavior characteristic of central axons. This result suggests that KLC4 patterns axonal compartments and helps establish molecular differences between central and peripheral axons. Finally, we find that klc4 mutant larva are hypersensitive to touch and adults show anxiety-like behavior in a novel tank test, implicating klc4 as a new gene involved in stress response circuits.

Pregnancy-associated plasma protein-aa regulates endoplasmic reticulum–mitochondria associations

eLife · 2021-03-24 · 7 citations

Endoplasmic reticulum (ER) and mitochondria form close physical associations to facilitate calcium transfer, thereby regulating mitochondrial function. Neurons with high metabolic demands, such as sensory hair cells, are especially dependent on precisely regulated ER–mitochondria associations. We previously showed that the secreted metalloprotease pregnancy-associated plasma protein-aa (Pappaa) regulates mitochondrial function in zebrafish lateral line hair cells (Alassaf et al., 2019). Here, we show that pappaa mutant hair cells exhibit excessive and abnormally close ER–mitochondria associations, suggesting increased ER–mitochondria calcium transfer. pappaa mutant hair cells are more vulnerable to pharmacological induction of ER–calcium transfer. Additionally, pappaa mutant hair cells display ER stress and dysfunctional downstream processes of the ER–mitochondria axis including altered mitochondrial morphology and reduced autophagy. We further show that Pappaa influences ER–calcium transfer and autophagy via its ability to stimulate insulin-like growth factor-1 bioavailability. Together our results identify Pappaa as a novel regulator of the ER–mitochondria axis.

KLC4 shapes axon arbors during development and mediates adult behavior

bioRxiv (Cold Spring Harbor Laboratory) · 2021-09-26 · 2 citations

Abstract Development of elaborate and polarized neuronal morphology requires precisely regulated transport of cellular cargos by motor proteins such as kinesin-1. Kinesin-1 has numerous cellular cargos which must be delivered to unique neuronal compartments. The process by which this motor selectively transports and delivers cargo to regulate neuronal morphogenesis is poorly understood, although the cargo-binding kinesin light chain (KLC) subunits contribute to specificity. Our work implicates one such subunit, KLC4, as an essential regulator of axon branching and arborization pattern of sensory neurons during development. Using live imaging approaches in klc4 mutant zebrafish, we show that KLC4 is required for stabilization of nascent axon branches, proper microtubule (MT) dynamics, and endosomal transport. Furthermore, KLC4 is required for proper tiling of peripheral axon arbors: in klc4 mutants, peripheral axons showed abnormal fasciculation, a behavior characteristic of central axons. This result suggests that KLC4 patterns axonal compartments and helps establish molecular differences between central and peripheral axons. Finally, we find that klc4 mutant larva are hypersensitive to touch and adults show anxiety-like behavior in a novel tank test, implicating klc4 as a new gene involved in stress response circuits.

Author response: Pregnancy-associated plasma protein-aa regulates endoplasmic reticulum–mitochondria associations

2020-11-23

Pregnancy associated plasma protein-aa regulates endoplasmic reticulum-mitochondria associations

bioRxiv (Cold Spring Harbor Laboratory) · 2020-06-11 · 1 citations

Abstract The endoplasmic reticulum (ER) and mitochondria form close physical associations to facilitate calcium transfer, thereby regulating mitochondrial function and dynamics. For neurons with high metabolic demands, such as sensory hair cells, precise regulation of ER-mitochondria associations is especially critical for cell survival. We previously identified the secreted metalloprotease Pregnancy associated plasma protein-aa (Pappaa) as a novel regulator of mitochondrial function in zebrafish lateral line hair cells (Alassaf et al., 2019). Here, we show that pappaa mutant hair cells exhibit excessive and abnormally close ER-mitochondria associations, suggesting increased ER-mitochondria calcium transfer. Indeed, we find that pappaa mutant hair cells are more vulnerable to pharmacological induction of ER-calcium release. Additionally, pappaa mutant hair cells display ER stress and dysfunctional downstream processes of the ER-mitochondria axis including mitochondrial fragmentation and autophagy. Together our results support a model in which Pappaa regulates mitochondrial function, at least in part, by regulating ER-mitochondria associations.