Generation and analysis of novel Reln‐deleted mouse model corresponding to exonic Reln deletion in schizophrenia

Abstract

Aim: A Japanese individual with schizophrenia harboring a novel exonic deletion in RELN was recently identified by genome-wide copy-number variation analysis. Thus, the present study aimed to generate and analyze a model mouse to clarify whether Reln deficiency is associated with the pathogenesis of schizophrenia.Methods: A mouse line with a novel RELN exonic deletion (Reln-del) was established using the CRISPR/Cas9 method to elucidate the underlying molecular mechanism. Subsequently, general behavioral tests and histopathological examinations of the model mice were conducted and phenotypic analysis of the cerebellar granule cell migration was performed.Results: The phenotype of homozygous Reln-del mice was similar to that of reeler mice with cerebellar atrophy, dysplasia of the cerebral layers, and abrogated protein levels of cerebral reelin. The expression of reelin in heterozygous Reln-del mice was approximately half of that in wild-type mice. Conversely, behavioral analyses in heterozygous Relndel mice without cerebellar atrophy or dysplasia showed abnormal social novelty in the three-chamber social interaction test. In vitro reaggregation formation and neuronal migration were severely altered in the cerebellar cultures of homozygous Reln-del mice. Conclusion:The present results in novel Reln-del mice modeled after our patient with a novel exonic deletion in RELN are expected to contribute to the development of reelin-based therapies for schizophrenia.Reelin is a large extracellular matrix protein expressed in many brain regions. 1 During developmental stages, reelin is secreted primarily by Cajal-Retzius cells and plays a crucial role in neuronal migration and layer formation in the cerebral cortex 2,3 ; it is also required in cerebellar development. 4 In the adult brain, reelin is produced by GABAergic interneurons and contributes to synaptic plasticity, dendritic morphology, and cognitive function. [5][6][7] Previous studies reported lissencephaly and cerebellar hypoplasia in patients carrying RELN mutations; this phenotype is similar to that observed in reeler mice. 8,9 The full-length reelin protein is approximately 400 kDa in size, with eight repeated domains known as reelin repeats and is cleaved by proteases, such as disintegrin and metalloproteinase, with thrombospondin motifs 3 at two specific sites 10 : one site between reelin repeats 2 and 3 (N-t site) and another site between reelin repeats 6 and 7 (C-t site). In previous studies, two Reln-mutant mice were used to evaluate reelin function. Jackson Reln homozygous mice (Relnrl-J) have a 150-kB genomic deletion, whereas Orleans Reln homozygous mice (Relnrl-Orl) produce a transcript with a 220-bp deletion. 11,12 Reelin protein is not produced in Relnrl-J mice, 5 whereas Relnrl-Orl mice produce a non-secreting protein partially cleaved at the C-terminal. [13][14][15] Little reelin signaling induced reversed cortical layering and cerebellar atrophy in both Relnrl-J and Relnrl-Orl mice. Furthermore, heterozygous Relnrl-J (Relnrl-J/+) mice showed memory...

The Pathophysiological Link Between Reelin and Autism: Overview and New Insights

“…Some of these abnormalities are recapitulated in Reln mutant mice, supporting the association with human ASD. Increased locomotor activity in an open field test, typically reflecting increased anxiety in mouse models, was reported in Orleans hetero (BALB/C), Orleans homo (BALB/C), and ⊿C-KI (C57BL/6) mice ( Lalonde et al, 2004 ; Sakai et al, 2016 ; Sobue et al, 2018 ; Sawahata et al, 2020 ). Similarly, abnormal responses in the elevated plus maze test, evaluating innate anxiety in the rodents, were described in the Orleans homo (BALB/C), and ⊿C-KI (C57BL/6) models ( Lalonde et al, 2004 ; Sakai et al, 2016 ).…”

“…Additional mouse models harboring heterozygous or homozygous alterations in the Reln gene have been developed to investigate the potential link between Reelin and ASD ( Sawahata et al, 2020 ). The endophenotype of Reln mutant mice is complex and include behavioral abnormalities that can be related to core clinical features observed in human patients ( Sawahata et al, 2020 ). In general, rodent models of ASD have been reported to show excessive anxiety, aggressive behavior, and increased seizures susceptibility ( Argyropoulos et al, 2013 ).…”

“…Similarly, abnormal responses in the elevated plus maze test, evaluating innate anxiety in the rodents, were described in the Orleans homo (BALB/C), and ⊿C-KI (C57BL/6) models ( Lalonde et al, 2004 ; Sakai et al, 2016 ). Impaired social interaction was noticed in Orleans hetero (BALB/C), ⊿C-KI (C57BL/6), and in the recently developed Reln-del (C57BL/6) model ( Sakai et al, 2016 ; Sobue et al, 2018 ; Sawahata et al, 2020 ). Of note, the Jackson hetero (B6C3Fe) mice exhibited instead novel object recognition deficiency, decreased fear conditioning, and reduced prepulse inhibition ( Qiu et al, 2006 ).…”

Trends in big data analyses by multicenter collaborative translational research in psychiatry

“…synapse/neuron projection, oxidative stress response, small GTPase signaling) are common to the two disorders. 141 Furthermore, in‐depth functional analysis of pathogenic CNVs using patient‐derived iPSCs, mouse models, and postmortem brains has provided important clues to the pathophysiology and led to the identification of drug targets 143 , 144 , 145 , 146 , 147 {Torii, 2020 #86}.…”

Toward recovery in schizophrenia: Current concepts, findings, and future research directions

“…44 Knockout mice specifically lacking GAD67 in PV neurons exhibited abnormal social behavior and impaired prepulse inhibition. 45 Knockout mouse models deficient in other disease-related genes identified to date have been created as well 46 ; in particular, disease-related molecular networks that regulate various synaptic functions and maturation have been targeted in genetically modified mice, and these studies have significantly advanced efforts to decipher the molecular pathophysiology of schizophrenia. [47][48][49] To further understand the molecular pathophysiology underlying schizophrenia, it will also be important to systematically analyze the phenotypes of individual mutations associated with large effect sizes, which should directly correlate with pathophysiology, along with common mutations that have been observed across many patients.…”