Functional transcriptome analysis of the postnatal brain of the Ts1Cje mouse model for Down syndrome reveals global disruption of interferon-related molecular networks

Abstract

Background: The Ts1Cje mouse model of Down syndrome (DS) has partial triplication of mouse chromosome 16 (MMU16), which is partially homologous to human chromosome 21. These mice develop various neuropathological features identified in DS individuals. We analysed the effect of partial triplication of the MMU16 segment on global gene expression in the cerebral cortex, cerebellum and hippocampus of Ts1Cje mice at 4 time-points: postnatal day (P)1, P15, P30 and P84.

Results: Gene expression profiling identified a total of 317 differentially expressed genes (DEGs), selected from various spatiotemporal comparisons, between Ts1Cje and disomic mice. A total of 201 DEGs were identified from the cerebellum, 129 from the hippocampus and 40 from the cerebral cortex. Of these, only 18 DEGs were identified as common to all three brain regions and 15 were located in the triplicated segment. We validated 8 selected DEGs from the cerebral cortex (Brwd1, Donson, Erdr1, Ifnar1, Itgb8, Itsn1, Mrps6 and Tmem50b), 18 DEGs from the cerebellum (Atp5o, Brwd1, Donson, Dopey2, Erdr1, Hmgn1, Ifnar1, Ifnar2, Ifngr2, Itgb8, Itsn1, Mrps6, Paxbp1, Son, Stat1, Tbata, Tmem50b and Wrb) and 11 DEGs from the hippocampus (Atp5o, Brwd1, Cbr1, Donson, Erdr1, Itgb8, Itsn1, Morc3, Son, Tmem50b and Wrb). Functional clustering analysis of the 317 DEGs identified interferon-related signal transduction as the most significantly dysregulated pathway in Ts1Cje postnatal brain development. RT-qPCR and western blotting analysis showed both Ifnar1 and Stat1 were over-expressed in P84 Ts1Cje cerebral cortex and cerebellum as compared to wild type littermates.

Conclusions: These findings suggest over-expression of interferon receptor may lead to over-stimulation of Jak-Stat signaling pathway which may contribute to the neuropathology in Ts1Cje or DS brain. The role of interferon mediated activation or inhibition of signal transduction including Jak-Stat signaling pathway has been well characterized in various biological processes and disease models including DS but information pertaining to the role of this pathway in the development and function of the Ts1Cje or DS brain remains scarce and warrants further investigation.

Figure 1

MA plots of trisomic and disomic microarray probe-sets from 3 different brain regions (cerebral cortex, cerebellum and hippocampus) at 4 postnatal (P) time points (P1, P15, P30 and P84). The Y-axis represents the M value, which is the ratio (log₂(T/D)) whereas the X-axis represents the A value, which is the mean ratio (1/2xlog₂(TxD)). T and D represent the intensities of microarray probe-sets for Ts1Cje and disomic samples, respectively. Each blue dot represents a single probe. Red dotted lines denote the cutoff at M values of 0.58, signifying 1.5-fold upregulation of microarray probe-sets.

Figure 2

Venn diagrams depicting the spatiotemporal distribution of DEGs for comparison of Ts1Cje vs. disomic mice at 4 postnatal (P) time points (P1, P15, P30 and P84). The combined Venn diagram consists of non-redundant DEGs from each brain region at all time points. CC = Cerebral cortex; CB = Cerebellum; HIPP = Hippocampus.

Figure 3

Summary of functional clustering analysis of 317 DEGs using DAVID tools. Gene names in yellow denote trisomic genes. Thick dotted lines connect the DEG cluster with their associated functional ontologies whereas the thin solid lines connect DEGs to various brain regions. The colour of the thin solid lines corresponds to the brain regions to which they are connected. CC = Cerebral cortex; CB = Cerebellum; HIPP = Hippocampus.

Figure 4

RT-qPCR validation of selected DEGs in the cerebral cortex. Red lines or asterisks denote RT-qPCR data whereas black lines or asterisks denote microarray data. *p < 0.05, **p < 0.01 and ***p < 0.001 based on Empirical Bayes t-statistic test.

Figure 5

RT-qPCR validation of selected DEGs in the cerebellum. Red lines or asterisks denote RT-qPCR data whereas black lines or asterisks denote microarray data. *p < 0.05, **p < 0.01 and ***p < 0.001 based on Empirical Bayes t-statistic test

Figure 6

RT-qPCR validation of selected DEGs in the hippocampus. Red lines or asterisks denote RT-qPCR data whereas black lines or asterisks denote microarray data. *p < 0.05, **p < 0.01 and ***p < 0.001 based on Empirical Bayes t-statistic test.

Figure 7

Western blotting analysis of Ifnar1 (66 kDa), Ifnar2 (55 kDa) and Stat1 (91 kDa) in the cerebral cortex and cerebellum of adult (P84) Ts1Cje and wild type littermates. Each band represents each Ts1Cje or wild type mouse in the respective brain region.