Cbsoverdosage is necessary and sufficient to induce cognitive phenotypes in mouse models of Down syndrome and interacts genetically withDyrk1a

Abstract

26Identifying dosage sensitive genes is a key to understand the mechanisms 27 underlying intellectual disability in Down syndrome (DS). The Dp(17Abcg1-Cbs)1Yah 28 DS mouse model (Dp1Yah) show cognitive phenotype and needs to be investigated 29 to identify the main genetic driver. Here, we report that, in the Dp1Yah mice, 3 copies 30 of the Cystathionine-beta-synthase gene (Cbs) are necessary to observe a deficit in 31 the novel object recognition (NOR) paradigm. Moreover, the overexpression of Cbs 32 alone is sufficient to induce NOR deficit. Accordingly targeting the overexpression of 33 human CBS, specifically in Camk2a-expressing neurons, leads to impaired objects 34 discrimination. Altogether this shows that Cbs overdosage is involved in DS learning 35 and memory phenotypes. In order to go further, we identified compounds that interfere 36 with the phenotypical consequence of CBS overdosage in yeast. Pharmacological 37 intervention in the Tg(CBS) with one selected compound restored memory in the novel 38 object recognition. In addition, using a genetic approach, we demonstrated an epistatic 39 interaction between Cbs and Dyrk1a, another human chromosome 21 gene encoding 40 the dual-specificity tyrosine phosphorylation-regulated kinase 1a and an already 41 ND 4.0 International license It is made available under a (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint . http:/ SIGNIFICANT STATEMENT 50Here, we investigated a region homologous to Hsa21 and located on mouse 51 chromosome 17. We demonstrated using three independent genetic approaches that 52 the overdosage of the Cystathionine-beta-synthase gene (Cbs) gene, encoded in the 53 segment, is necessary and sufficient to induce deficit in novel object recognition (NR). 54In addition, we identified compounds that interfere with the phenotypical 55 consequence of CBS overdosage in yeast and in mouse transgenic lines. Then we 56 analyzed the relation between Cbs overdosage and the consequence of DYRK1a 57 overexpression, a main driver of another region homologous to Hsa21 and we 58 demonstrated that an epistatic interaction exist between Cbs and Dyrk1a affecting 59 different pathways, including synaptic transmission, cell projection morphogenesis, 60 and actin cytoskeleton.

Modeling Down syndrome in animals from the early stage to the 4.0 models and next

“…Undeniably we should work with the whole set of genes homologous to Hsa21, either bringing together all the trisomies/duplication of regions homologous to Hsa21 in mouse and rats or use transchromosomic mice. This is supported by recent data showing an epistatic interaction between Dyrk1a and Cbs, located respectively on the Mmu16 and the Mmu17 homologous regions (Marechal et al, 2019b). Thus, it is really a challenge to get together DS models for the 3 chromosomal regions.…”

“…They further showed that, when adding trisomy of the Mmu17 region to the Dp(16)1Yey model, the rescue of the deficit observed in the Dp(16)1Yey model by crossing with Ms1Rhr mice was no longer observed, suggesting epistatic interactions between trisomic genes on Mmu17 and trisomic Mmu16 genes (Zhang et al, 2014). Our laboratory went further in deciphering the genes behind such epistatic interaction with Cbs found on Mmu17 and Dyrk1a on Mmu16 for their impact on DS-related memory deficits (Marechal et al, 2019b).…”

“…Behavioral analysis of mouse models trisomic for the Hsa21 homologous region on Mmu17 clearly indicated the presence in this region of one or more genes implicated in cognitive deficits (Lopes Pereira et al, 2009, Yu et al, 2010b. Further rescue experiment pointed at the gene CBS as being responsible for the cognitive phenotype observed in mice trisomic for this region (Marechal et al, 2019a). CBS codes for the Cystathionine-beta-synthase enzyme involved in homocysteine metabolism, with CBS loss-of-function leading to homocystinuria, a metabolic condition linked to intellectual disability (OMIM236200).…”

“…This decreased LTP was further associated to reduced glutamatergic NMDA receptors activation due to an increase in inhibitory gammaaminobutyric (GABA) neurotransmitter (Kleschevnikov et al, 2004, Costa and Grybko, 2005, Kurt et al, 2000. Further analyses of mouse models carrying a duplication of either the Mmu16, Mmu10 or Mmu17 syntenic region pointed at the importance of the Mmu16 region for most of the DS cognitive deficits (Yu et al, 2010c, Zhang et al, 2014, whereas Dp(17)1Yey and Dp1Yah mice having triplicated regions of the Mmu17 had only some learning impairment (Yu et al, 2010c, Marechal et al, 2019b, Lopes Pereira et al, 2009) and the Dp(10)1Yey showed no learning or memory deficit (Yu et al, 2010c). The Mmu10 syntenic region was further excluded as a DS-ID-relevant region by a subtractive approach crossing the Tc1 model with a mouse model monosomic for the Cstb-Prmt2 region on Mmu10 which showed no rescue of the cognitive deficits observed in the Tc1 model (Duchon et al, 2011a).…”

“…An alternative is to consider studying the phenotype outcomes in an outbred genetic background such as in the rat DS models (Birling et al, 2017b). Then, most of the current studies are done on one model for DS, the Ts65Dn mouse model, that is trisomic for a small subset of genes homologous to Hsa21, leaving aside some key genetic interactions between Hsa21 genes (Marechal et al, 2019b). Finally, more specific to DS, some phenotype will never be recapitulated in the mouse brain.…”