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Forebrain Shh overexpression improves cognitive function and locomotor hyperactivity in an aneuploid mouse model of Down syndrome and its euploid littermates.

ABSTRACT: Down syndrome (DS) is the leading genetic cause of intellectual disability and causes early-onset dementia and cerebellar hypoplasia. The prevalence of attention deficit hyperactivity disorder is elevated in children with DS. The aneuploid DS mouse model "Ts65Dn" shows prominent brain phenotypes, including learning and memory deficits, cerebellar hypoplasia, and locomotor hyperactivity. Previous studies indicate that impaired Sonic hedgehog (Shh) signaling contributes to neurological phenotypes associated with DS and neurodegenerative diseases. However, because of a lack of working inducible Shh knock-in mice, brain region-specific Shh overexpression and its effects on cognitive function have not been studied in vivo. Here, with Gli1-LacZ reporter mice, we demonstrated that Ts65Dn had reduced levels of Gli1, a sensitive readout of Shh signaling, in both hippocampus and cerebellum at postnatal day 6. Through site-specific transgenesis, we generated an inducible human Shh knock-in mouse, TRE-bi-hShh-Zsgreen1 (TRE-hShh), simultaneously expressing dually-lipidated Shh-Np and Zsgreen1 marker in the presence of transactivator (tTA). Double transgenic mice "Camk2a-tTA;TRE-hShh" and "Pcp2-tTA;TRE-hShh" induced Shh overexpression and activated Shh signaling in a forebrain and cerebellum, respectively, specific manner from the perinatal period. Camk2a-tTA;TRE-hShh normalized locomotor hyperactivity and improved learning and memory in 3-month-old Ts65Dn, mitigated early-onset severe cognitive impairment in 7-month-old Ts65Dn, and enhanced spatial cognition in euploid mice. Camk2a-tTA;TRE-hShh cohort maintained until 600days old showed that chronic overexpression of Shh in forebrain from the perinatal period had no effect on longevity of euploid or Ts65Dn. Pcp2-tTA;TRE-hShh did not affect cognition but mitigated the phenotype of cerebellar hypoplasia in Ts65Dn. Our study provides the first in vivo evidence that Shh overexpression from the perinatal period protects DS brain integrity and enhances learning and memory in normal mice, indicating the broad therapeutic potential of Shh ligand for other neurological conditions. Moreover, the first inducible hShh site-specific knock-in mouse could be widely used for spatiotemporal Shh signaling regulation.

SUBMITTER: Gao FJ

PROVIDER: S-EPMC8365939 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Purpose:To dissect the mechanisms underlying altered gene expression in aneuploids, we measured transcript abundance in colonies of haploid yeast strain F45 and derived strains, including strains disomic for chromosomes XV and XVI, using RNA-seq. F45 colonies display complex “fluffy” morphologies, while the disomic colonies are smooth, resembling laboratory strains Methods: RNA-seq analysis was carried out on RNA isolated from fully developed S. cerevisiae colonies, grown on solid medium for four days, either in triplicate or quadruplicate. Stranded, paired-end sequencing was carried out in two batches. In the first batch 2x51 bp sequencing was carried out on an Illumina Hiseq2000 and in the second batch 2x75 bp sequencing was carried out on an Illumina NextSeq. Readpairs were aligned using Bowtie2 (version 2.1.0)with the parameters [-N 1 -I 50 -X 450 -p 6 --reorder -x -S] and allowing 1 mismatch per read. Differential transcription was detected and quantified using EdgeR (v. 3.6.8) Results: Our two disomes displayed similar transcriptional profiles, a phenomenon not driven by their shared smooth colony morphology nor specified purely by the karyotype. Surprisingly, the environmental stress response (ESR) was induced in euploid F45, relative to the two disomes, rather than vice-versa. We also identified genes whose expression reflected a non-linear interaction between the copy number of a transcriptional regulatory gene on chromosome XVI, DIG1, and the copy number of other chromosome XVI genes. DIG1 and the remaining chromosome XVI genes also demonstrated distinct contributions to the effect of the chromosome XVI disome on ESR gene expression. Conclusions: Expression changes in aneuploids reflect a mixture of effects shared between different aneuploidies, including stress responses, and effects unique to perturbing the copy number of particular chromosomes, including non-linear copy number interactions between genes. The balance between these two phenomena is likely to be genotype and environment specific.

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Forebrain Shh overexpression improves cognitive function and locomotor hyperactivity in an aneuploid mouse model of Down syndrome and its euploid littermates.

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