RESUMO
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) shows cognitive phenotypes that need to be investigated to identify the main genetic driver. Here, we report that three copies of the cystathionine-beta-synthase gene (Cbs) in the Dp1Yah mice are necessary to observe a deficit in the novel object recognition (NOR) paradigm. Moreover, the overexpression of Cbs alone is sufficient to induce deficits in the NOR test. Accordingly, overexpressing 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. To go further, we identified compounds that interfere with the phenotypical consequence of CBS overdosage in yeast. Pharmacological intervention in Tg(CBS) mice with one selected compound restored memory in the NOR test. In addition, using a genetic approach, we demonstrated an epistatic interaction between Cbs and Dyrk1a, another human chromosome 21-located gene (which encodes the dual-specificity tyrosine phosphorylation-regulated kinase 1a) and an already known target for DS therapeutic intervention. Further analysis using proteomic approaches highlighted several molecular 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.
Assuntos
Cistationina beta-Sintase/genética , Síndrome de Down/diagnóstico , Síndrome de Down/genética , Epistasia Genética , Dosagem de Genes , Fenótipo , Proteínas Serina-Treonina Quinases/genética , Proteínas Tirosina Quinases/genética , Animais , Comportamento Animal , Cognição , Modelos Animais de Doenças , Humanos , Locomoção , Memória , Camundongos , Camundongos Transgênicos , Neurônios/metabolismo , Proteoma , Proteômica/métodos , Quinases DyrkRESUMO
PCP4/PEP19 is a modulator of Ca(2+)-CaM signaling. In the brain, it is expressed in a very specific pattern in postmitotic neurons. In particular, Pcp4 is highly expressed in the Purkinje cell, the sole output neuron of the cerebellum. PCP4, located on human chromosome 21, is present in three copies in individuals with Down syndrome (DS). In a previous study using a transgenic mouse model (TgPCP4) to evaluate the consequences of 3 copies of this gene, we found that PCP4 overexpression induces precocious neuronal differentiation during mouse embryogenesis. Here, we report combined analyses of the cerebellum at postnatal stages (P14 and adult) in which we identified age-related molecular, electrophysiological, and behavioral alterations in the TgPCP4 mouse. While Pcp4 overexpression at P14 induces an earlier neuronal maturation, at adult stage it induces increase in cerebellar CaMK2alpha and in cerebellar LTD, as well as learning impairments. We therefore propose that PCP4 contributes significantly to the development of Down syndrome phenotypes through molecular and functional changes.
Assuntos
Cerebelo/crescimento & desenvolvimento , Cerebelo/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Proteínas do Tecido Nervoso/metabolismo , Animais , Animais Recém-Nascidos , Cerebelo/citologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Regulação da Expressão Gênica no Desenvolvimento/genética , Humanos , Técnicas In Vitro , Depressão Sináptica de Longo Prazo/efeitos dos fármacos , Depressão Sináptica de Longo Prazo/genética , Aprendizagem em Labirinto/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , Atividade Motora/genética , Proteínas do Tecido Nervoso/genética , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Desempenho Psicomotor/efeitos dos fármacos , Desempenho Psicomotor/fisiologia , Quinoxalinas/farmacologia , Tempo de Reação/efeitos dos fármacos , Tempo de Reação/genética , Reconhecimento Psicológico/efeitos dos fármacos , Reconhecimento Psicológico/fisiologia , Bloqueadores dos Canais de Sódio/farmacologia , Tetrodotoxina/farmacologia , Valina/análogos & derivados , Valina/farmacologiaRESUMO
Down syndrome (DS) results from one extra copy of human chromosome 21 and leads to several alterations including intellectual disabilities and locomotor defects. The transchromosomic Tc1 mouse model carrying an extra freely-segregating copy of human chromosome 21 was developed to better characterize the relation between genotype and phenotype in DS. The Tc1 mouse exhibits several locomotor and cognitive deficits related to DS. In this report we analyzed the contribution of the genetic dosage of 13 conserved mouse genes located between Abcg1 and U2af1, in the telomeric part of Hsa21. We used the Ms2Yah model carrying a deletion of the corresponding interval in the mouse genome to rescue gene dosage in the Tc1/Ms2Yah compound mice to determine how the different behavioral phenotypes are affected. We detected subtle changes with the Tc1/Ms2Yah mice performing better than the Tc1 individuals in the reversal paradigm of the Morris water maze. We also found that Tc1/Ms2Yah compound mutants performed better in the rotarod than the Tc1 mice. This data support the impact of genes from the Abcg1-U2af1 region as modifiers of Tc1-dependent memory and locomotor phenotypes. Our results emphasize the complex interactions between triplicated genes inducing DS features.