Research articleCalcium-dependent activator protein for secretion 2 (CADPS2) deficiency causes abnormal synapse development in hippocampal mossy fiber terminals
Introduction
Hippocampal mossy fiber (MF) project from hippocampal dentate gyrus granule cells onto the hippocampal CA2 and CA3 region, and participate in hippocampal-dependent learning and memory [6,12,15,16]. Therefore, the normal development and functional organization of MF terminals are critical for hippocampal function; however, the cell and molecular mechanisms of MF development are unclear.
We recently reported that calcium-dependent activator protein for secretion 2 (CADPS2) regulates dense-core vesicle (DCV) secretion [2,8,39,41], which is strongly enriched in MF terminals [28]. CADPS2 is also known as an autism spectrum disorder-related gene [4,7,21,27,33,37,42], and MF synapses are altered in some autism model mice [19,35]. Therefore, we hypothesized that CADPS2 is involved in MF synaptic development and functional organization. In the present study, we compared hippocampal synaptic microstructures in the stratum lucidum in wild-type (WT) and Cadps2 KO mice using electron microscopy (EM). Our data strongly suggest that synaptic development of hippocampal MF terminals is regulated by CADPS2.
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Animals
All experimental protocols were evaluated and approved by the Regulation for Animal Research at RIKEN and Tokyo University of Science, and were performed in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki) for experiments involving humans. The generation of Cadps2 KO mice was described previously [33]. Male mice were housed in home cages, at most four per cage, and maintained under a 12:12-h light–dark cycle, with ad libitum access to water and food.
The number and distribution of SVs are affected by Cadps2 deficiency, especially in the adult
To assess MF synaptic development, we performed EM in the hippocampal CA3 stratum lucidum to analyze presynaptic bouton area, SV number, SV distribution and SV density in WT and Cadps2 KO mice at the juvenile (P15) and adult (P56) stages (Fig. 1). Presynaptic boutons were defined as structures containing SVs and completely surrounded by the lipid bilayer in apposition with a single or a few PSDs. In the juvenile (P15) animal, the area of the presynaptic bouton was significantly smaller in the
Discussion
In the present study, we show, using EM, that there are major differences in the morphology of hippocampal MF terminals between WT and Cadps2 KO mice (Schematic model is depicted in Fig. 5). CADPS2 deficiency resulted in several synaptic structural abnormalities, including the accumulation of SVs and DCVs in MF terminals in both young and adult animals, and a decrease in the number of PSDs in young mice, but an increase in adults. Furthermore, the greater number of PSDs was caused by an
Conflicts of interest
No conflicts of interest, financial or otherwise, are declared by any of the authors.
Author contributions
Y.Sh., T.S. and T.F. designed the research; Y.Sh., T.S., T.A., Y.Sak. and H.Y performed the research; Y.Sh. analyzed the data; Y.Sh. Y.San. and T.F. wrote the paper.
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific Research on Innovative Areas (Comprehensive Brain Science Network) and KAKENHI from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT; grant number, 21790219). Grants-in-Aid for Scientific Research from Takeda Science Foundation, Life Science Foundation of Japan, Kawano Masanori Memorial Public Interest Incorporated Foundation for Promotion of Pediatrics. We thank Barry Patel, PhD, from Edanz Group (//www.edanzediting.com/ac
References (45)
- et al.
Regulation of dense core vesicle release from PC12 cells by interaction between the D2 dopamine receptor and calcium-dependent activator protein for secretion (CAPS)
Biochem. Pharmacol.
(2005) - et al.
CAPS acts at a prefusion step in dense-core vesicle exocytosis as a PIP2 binding protein
Neuron
(2004) - et al.
Brain-derived neurotrophic factor-estrogen interactions in the hippocampal mossy fiber pathway: implications for normal brain function and disease
Neuroscience
(2013) - et al.
The multifarious hippocampal mossy fiber pathway: a review
Neuroscience
(2000) - et al.
Expansion of the dentate mossy fiber-CA3 projection in the brain-derived neurotrophic factor-enriched mouse hippocampus
Neuroscience
(2015) Hippocampal mossy fiber synaptic transmission and its modulation
Vitam. Horm.
(2010)- et al.
Mossy fiber-CA3 synapses mediate homeostatic plasticity in mature hippocampal neurons
Neuron
(2013) - et al.
Roles of afadin in the formation of the cellular architecture of the mouse hippocampus and dentate gyrus
Mol. Cell. Neurosci.
(2017) - et al.
Recombinant BDNF rescues deficits in basal synaptic transmission and hippocampal LTP in BDNF knockout mice
Neuron
(1996) - et al.
The neural cell adhesion molecule (NCAM) in development and plasticity of the nervous system
Exp. Gerontol.
(1998)