Complexin2 null mutation requires a 'second hit' for induction of phenotypic changes relevant to schizophrenia

Area of Science:

• Neuroscience
• Psychiatry
• Genetics

Background:

• Schizophrenia affects 1% of the population, with unknown neurobiological causes.
• Genetic predisposition and environmental factors likely interact to trigger schizophrenia.
• Existing animal models often lack construct validity due to incomplete etiological representation.

Purpose of the Study:

• To develop a valid mouse model for schizophrenia based on the "second hit" hypothesis.
• To investigate the combined effects of a genetic risk factor (Cplx2 null mutation) and an environmental insult (parietal neurotrauma).
• To explore the role of synaptic transmission dysfunction in schizophrenia pathogenesis.

Main Methods:

• Created Cplx2 null mutant mice as a genetic model.
• Administered mild parietal neurotrauma during puberty as an environmental "second hit".
• Assessed behavioral phenotypes (pre-pulse inhibition, spatial learning, MK-801 response, motor function) and hippocampal volume via MRI.

Main Results:

• Cplx2 null mutants with neurotrauma exhibited reduced pre-pulse inhibition and spatial learning deficits.
• Lesioned Cplx2 null mutants showed impaired response to MK-801 challenge and accentuated motor deficits.
• MRI revealed hippocampal volume reduction exclusively in lesioned Cplx2 null mutants.
• These abnormalities were absent in lesioned wild-type mice and non-lesioned mutants.

Conclusions:

• Findings support the "second hit" hypothesis of schizophrenia, highlighting gene-environment interactions.
• The developed mouse model demonstrates construct validity for studying schizophrenia.
• This model may facilitate the development of novel therapeutic strategies for schizophrenia.