Cbs overdosage is necessary and sufficient to induce cognitive phenotypes in mouse models of Down syndrome and interacts genetically with Dyrk1a

ABSTRACT Identifying dosage sensitive genes is a key to understand the mechanisms underlying intellectual disability in Down syndrome (DS). The Dp(17Abcg1-Cbs)1Yah DS mouse model (Dp1Yah) show cognitive phenotype and needs to be investigated to identify the main genetic driver. Here, we report that, in the Dp1Yah mice, 3 copies of the Cystathionine-beta-synthase gene (Cbs) are necessary to observe a deficit in the novel object recognition (NOR) paradigm. Moreover, the overexpression of Cbs alone is sufficient to induce NOR deficit. Accordingly targeting the overexpression of human CBS, specifically in Camk2a-expressing neurons, leads to impaired objects discrimination. Altogether this shows that Cbs overdosage is involved in DS learning and memory phenotypes. In order to go further, we identified compounds that interfere with the phenotypical consequence of CBS overdosage in yeast. Pharmacological intervention in the Tg(CBS) with one selected compound restored memory in the novel object recognition. In addition, using a genetic approach, we demonstrated an epistatic interaction between Cbs and Dyrk1a, another human chromosome 21 gene encoding the dual-specificity tyrosine phosphorylation-regulated kinase 1a and an already known target for DS therapeutic intervention. Further analysis using proteomic approaches highlighted several pathways, including synaptic transmission, cell projection morphogenesis, and actin cytoskeleton, that are affected by DYRK1A and CBS overexpression. Overall we demonstrated that CBS overdosage underpins the DS-related recognition memory deficit and that both CBS and DYRK1A interact to control accurate memory processes in DS. In addition, our study establishes CBS as an intervention point for treating intellectual deficiencies linked to DS. SIGNIFICANT STATEMENTHere, we investigated a region homologous to Hsa21 and located on mouse chromosome 17. We demonstrated using three independent genetic approaches that the overdosage of the Cystathionine-beta-synthase gene (Cbs) gene, encoded in the segment, is necessary and sufficient to induce deficit in novel object recognition (NR).In addition, we identified compounds that interfere with the phenotypical consequence of CBS overdosage in yeast and in mouse transgenic lines. Then we analyzed the relation between Cbs overdosage and the consequence of DYRK1a overexpression, a main driver of another region homologous to Hsa21 and we demonstrated that an epistatic interaction exist between Cbs and Dyrk1a affecting different pathways, including synaptic transmission, cell projection morphogenesis, and actin cytoskeleton.