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Updated: Sep 1, 2025
Immunohistochemical Visualization of Hippocampal Neuron Activity After Spatial Learning in a Mouse Model of Neurodevelopmental Disorders
Published on: May 12, 2015
Neuronal density in the brain cortex and hippocampus in Clsnt2-KO mouse strain modeling autistic spectrum disorder
I N Rozhkova1, S V Okotrub2, E Yu Brusentsev1
1Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.
Insights
Calsyntenin-2 deficiency in mice models of autism spectrum disorder (ASD) leads to reduced neuronal density in specific hippocampal regions, particularly CA1. This suggests CA1 neurons could be a target for early ASD therapies.
Area of Science:
- Neuroscience
- Genetics
- Developmental Disorders
Background:
- Autistic spectrum disorders (ASD) are complex developmental conditions characterized by social and communication deficits, and repetitive behaviors.
- The underlying mechanisms and origins of ASD remain largely unknown, hindering the development of effective preventive strategies.
- Genetic factors are implicated in ASD, but specific gene functions related to neurodevelopmental alterations are still under investigation.
Purpose of the Study:
- To investigate the role of calsyntenin-2 (Clstn2) in neuronal density and neurogenesis within the brain.
- To assess neuronal density in the prefrontal cortex and hippocampal subfields (CA1, CA2, CA3, DG) of Clstn2-knockout (KO) mice, a genetic model for ASD.
- To evaluate neurogenesis in the dentate gyrus (DG) of the hippocampus in Clstn2-KO mice compared to wild-type controls.
Main Methods:
- Generation of Clstn2-KO mice by gene knockout in a C57BL/6J background, with wild-type mice serving as controls.
- Preparation of serial brain sections for immunohistochemical labeling using neuronal marker anti-NeuN to quantify neuronal density.
- Assessment of neurogenesis using the anti-doublecortin (anti-DCX) antibody in the hippocampal DG region.
Main Results:
- Clstn2-KO mice exhibited significantly lower neuronal density in the CA1 hippocampal subfield compared to control mice, irrespective of sex.
- In both Clstn2-KO and control mice, males showed lower neuronal density in the CA1 region than females.
- Sex-specific differences in neuronal density were also observed in the CA2 and CA3 hippocampal subfields, with males generally having lower density.
Conclusions:
- Calsyntenin-2 plays a critical role in regulating neuronal density in a subfield-specific manner within the hippocampus.
- The CA1 hippocampal subpopulation of neurons is particularly affected by the absence of calsyntenin-2.
- These findings suggest that the CA1 neuronal subpopulation may represent a potential cellular target for early-life preventive therapies for ASD.
Abstract:
Autistic spectrum disorders (ASD) represent conditions starting in childhood, which are characterized by diff iculties with social interaction and communication, as well as non-typical and stereotyping models of behavior. The mechanisms and the origin of these disorders are not yet understood and thus far there is a lack of prophylactic measures for these disorders. The current study aims to estimate neuronal density in the prefrontal cortex and four hippocampal subf ields, i. e. СA1, СA2, СA3, and DG in Clstn2-KO mice as a genetic model of ASD. In addition, the level of neurogenesis was measured in the DG area of the hippocampus. This mouse strain was obtained by a knockout of the calsinthenin-2 gene (Clsnt2) in C57BL/6J mice; the latter (wild type) was used as controls. To estimate neuronal density, serial sections were prepared on a cryotome for the above-mentioned brain structures with the subsequent immunohistochemical labeling and confocal microscopy; the neuronal marker (anti-NeuN) was used as the primary antibody. In addition, neurogenesis was estimated in the DG region of the hippocampus; for this purpose, a primary antibody against doublecortin (anti-DCX) was used. In all cases Goat anti-rabbit IgG was used as the secondary antibody. The density of neurons in the CA1 region of the hippocampus was lower in Clstn2-KO mice of both sexes as compared with controls. Moreover, in males of both strains, neuronal density in this region was lower as compared to females. Besides, the differences between males and females were revealed in two other hippocampal regions. In the CA2 region, a lower density of neurons was observed in males of both strains, and in the CA3 region, a lower density of neurons was also observed in males as compared to females but only in C57BL/6J mice. No difference between the studied groups was revealed in neurogenesis, nor was it in neuronal density in the prefrontal cortex or DG hippocampal region. Our new f indings indicate that calsyntenin-2 regulates neuronal hippocampal density in subf ield-specif ic manner, suggesting that the CA1 neuronal subpopulation may represent a cellular target for early-life preventive therapy of ASD.
