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Models and Advances in Genetics of Down Syndrome
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Models and Advances in Genetics of Down Syndrome

A special issue of Genes (ISSN 2073-4425). This special issue belongs to the section "Human Genomics and Genetic Diseases".

Deadline for manuscript submissions: closed (1 September 2021) | Viewed by 21725

Special Issue Editor

Dr. Yann Herault

E-Mail Website
Guest Editor
University of Strasbourg, CNRS, INSERM, ICS, Institute of Genetics and Molecular and Cellular Biology, 67404 Illkirch, France
Interests: aneuploidy; mouse genetics; functional genomics, mouse models for fundamental, biomedical and pharmaceutical research; mouse phenotyping and expression analysis; intellectual disability; autism spectrum disorders

Special Issue Information

Dear Colleagues,

Down syndrome (DS) is the most common form of intellectual disability (ID) in the world, with an incidence of 1 in 1000 births, affecting more than 5 million people worldwide. This disorder is caused by an extra copy of chromosome 21 (Hsa21), which leads to early neurodevelopmental features and late neurodegenerative alterations. As such, DS is a paradigmatic case of ID, aneuploidy, gene dosage effect, comorbidity, and multi-morbidity. Many features appear during the lifetime, some with a higher risk during the early phase in persons with DS compared with the normal population, suggesting that specific genetic and/or epigenetic mechanisms associated with trisomy 21 predispose some disorders, although the phenotype varies.

Down syndrome (DS) research has been very successful in the last years, with plenty of progresses being made to increase our knowledge on the condition. In the last few years, a series of new studies, at both cellular and organismal levels, have increased the understanding about the genetics of DS, the identification of pathways and driver genes, and the validation of several therapeutic avenues at the preclinical level. They have also highlighted the alteration of several biological processes during development or in adults. They have also unravelled new unexplored dimensions, such as neurodevelopmental alterations, the origin of DS comorbidities, the evolution of the condition over the entire lifespan, the onset of Alzheimer’s disease, and prenatal and life-time treatment.

In this Special Issue, we would like to gather reviews or original manuscripts that focus on these topics in order to better understand the genetics of DS and to propose alternative measures for reducing its impact in humans.

Dr. Yann Herault
Guest Editor

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Keywords

  • trisomy 21
  • models of disease
  • neurodevelopment
  • neurodegeneration
  • phenotype–genotype relationship
  • gene dosage
  • driver genes
  • therapeutic pathways
  • genetic interaction

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Published Papers (7 papers)

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Research

Jump to: Review

14 pages, 2645 KiB  
Article
DYRK1A Overexpression in Mice Downregulates the Gonadotropic Axis and Disturbs Early Stages of Spermatogenesis
by Rodolphe Dard, Manon Moreau, Estelle Parizot, Farah Ghieh, Leslie Brehier, Nadim Kassis, Valérie Serazin, Antonin Lamaziere, Chrystèle Racine, Nathalie di Clemente, François Vialard and Nathalie Janel
Genes 2021, 12(11), 1800; https://doi.org/10.3390/genes12111800 - 16 Nov 2021
Cited by 2 | Viewed by 2505
Abstract
Down syndrome (DS) is the most common chromosomal disorder. It is responsible for intellectual disability (ID) and several medical conditions. Although men with DS are thought to be infertile, some spontaneous paternities have been reported. The few studies of the mechanism of infertility [...] Read more.
Down syndrome (DS) is the most common chromosomal disorder. It is responsible for intellectual disability (ID) and several medical conditions. Although men with DS are thought to be infertile, some spontaneous paternities have been reported. The few studies of the mechanism of infertility in men with DS are now dated. Recent research in zebrafish has indicated that overexpression of DYRK1A (the protein primarily responsible for ID in DS) impairs gonadogenesis at the embryonic stage. To better ascertain DYRK1A’s role in infertility in DS, we investigated the effect of DYRK1A overexpression in a transgenic mouse model. We found that overexpression of DYRK1A impairs fertility in transgenic male mice. Interestingly, the mechanism in mice differs slightly from that observed in zebrafish but, with disruption of the early stages of spermatogenesis, is similar to that seen in humans. Unexpectedly, we observed hypogonadotropic hypogonadism in the transgenic mice. Full article
(This article belongs to the Special Issue Models and Advances in Genetics of Down Syndrome)
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18 pages, 2842 KiB  
Article
Skeletal Deficits in Male and Female down Syndrome Model Mice Arise Independent of Normalized Dyrk1a Expression in Osteoblasts
by Jared R. Thomas, Kourtney Sloan, Kelsey Cave, Joseph M. Wallace and Randall J. Roper
Genes 2021, 12(11), 1729; https://doi.org/10.3390/genes12111729 - 28 Oct 2021
Cited by 11 | Viewed by 2480
Abstract
Trisomy 21 (Ts21) causes alterations in skeletal development resulting in decreased bone mass, shortened stature and weaker bones in individuals with Down syndrome (DS). There is a sexual dimorphism in bone mineral density (BMD) deficits associated with DS with males displaying earlier deficits [...] Read more.
Trisomy 21 (Ts21) causes alterations in skeletal development resulting in decreased bone mass, shortened stature and weaker bones in individuals with Down syndrome (DS). There is a sexual dimorphism in bone mineral density (BMD) deficits associated with DS with males displaying earlier deficits than females. The relationships between causative trisomic genes, cellular mechanisms, and influence of sex in DS skeletal abnormalities remain unknown. One hypothesis is that the low bone turnover phenotype observed in DS results from attenuated osteoblast function, contributing to impaired trabecular architecture, altered cortical geometry, and decreased mineralization. DYRK1A, found in three copies in humans with DS, Ts65Dn, and Dp1Tyb DS model mice, has been implicated in the development of postnatal skeletal phenotypes associated with DS. Reduced copy number of Dyrk1a to euploid levels from conception in an otherwise trisomic Ts65Dn mice resulted in a rescue of appendicular bone deficits, suggesting DYRK1A contributes to skeletal development and homeostasis. We hypothesized that reduction of Dyrk1a copy number in trisomic osteoblasts would improve cellular function and resultant skeletal structural anomalies in trisomic mice. Female mice with a floxed Dyrk1a gene (Ts65Dn,Dyrk1afl/wt) were mated with male Osx-Cre+ (expressed in osteoblasts beginning around E13.5) mice, resulting in reduced Dyrk1a copy number in mature osteoblasts in Ts65Dn,Dyrk1a+/+/Osx-Cre P42 male and female trisomic and euploid mice, compared with littermate controls. Male and female Ts65Dn,Dyrk1a+/+/+ (3 copies of DYRK1A in osteoblasts) and Ts65Dn,Dyrk1a+/+/Osx-Cre (2 copies of Dyrk1a in osteoblasts) displayed similar defects in both trabecular architecture and cortical geometry, with no improvements with reduced Dyrk1a in osteoblasts. This suggests that trisomic DYRK1A does not affect osteoblast function in a cell-autonomous manner at or before P42. Although male Dp1Tyb and Ts65Dn mice exhibit similar skeletal deficits at P42 in both trabecular and cortical bone compartments between euploid and trisomic mice, female Ts65Dn mice exhibit significant cortical and trabecular deficits at P42, in contrast to an absence of genotype effect in female Dp1Tyb mice in trabecular bone. Taken together, these data suggest skeletal deficits in DS mouse models and are sex and age dependent, and influenced by strain effects, but are not solely caused by the overexpression of Dyrk1a in osteoblasts. Identifying molecular and cellular mechanisms, disrupted by gene dosage imbalance, that are involved in the development of skeletal phenotypes associated with DS could help to design therapies to rescue skeletal deficiencies seen in DS. Full article
(This article belongs to the Special Issue Models and Advances in Genetics of Down Syndrome)
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18 pages, 2761 KiB  
Article
Trisomy of Human Chromosome 21 Orthologs Mapping to Mouse Chromosome 10 Cause Age and Sex-Specific Learning Differences: Relevance to Down Syndrome
by Ross Minter and Katheleen J. Gardiner
Genes 2021, 12(11), 1697; https://doi.org/10.3390/genes12111697 - 26 Oct 2021
Cited by 2 | Viewed by 2310
Abstract
Down syndrome (DS), trisomy of human chromosome 21 (Hsa21), is the most common genetic cause of intellectual disability. The Dp10(1)Yey (Dp10) is a mouse model of DS that is trisomic for orthologs of 25% of the Hsa21 protein-coding genes, the entirety of the [...] Read more.
Down syndrome (DS), trisomy of human chromosome 21 (Hsa21), is the most common genetic cause of intellectual disability. The Dp10(1)Yey (Dp10) is a mouse model of DS that is trisomic for orthologs of 25% of the Hsa21 protein-coding genes, the entirety of the Hsa21 syntenic region on mouse chromosome 10. Trisomic genes include several involved in brain development and function, two that modify and regulate the activities of sex hormones, and two that produce sex-specific phenotypes as null mutants. These last four are the only Hsa21 genes with known sexually dimorphic properties. Relatively little is known about the potential contributions to the DS phenotype of segmental trisomy of Mmu10 orthologs. Here, we have tested separate cohorts of female and male Dp10 mice, at 3 and 9 months of age, in an open field elevated zero maze, rotarod, and balance beam, plus the learning and memory tasks, spontaneous alternation, puzzle box, double-H maze, context fear conditioning, and acoustic startle/prepulse inhibition, that depend upon the function of the prefrontal cortex, striatum, hippocampus, and cerebellum. We show that there are age and sex-specific differences in strengths and weaknesses, suggesting that genes within the telomere proximal region of Hsa21 influence the DS phenotype. Full article
(This article belongs to the Special Issue Models and Advances in Genetics of Down Syndrome)
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14 pages, 690 KiB  
Article
Context Fear Conditioning in Down Syndrome Mouse Models: Effects of Trisomic Gene Content, Age, Sex and Genetic Background
by Md. Mahiuddin Ahmed, Aaron Block, Nicolas Busquet and Katheleen J. Gardiner
Genes 2021, 12(10), 1528; https://doi.org/10.3390/genes12101528 - 28 Sep 2021
Cited by 4 | Viewed by 2519
Abstract
Down syndrome (DS), trisomy of the long arm of human chromosome 21 (Hsa21), is the most common genetic cause of intellectual disability (ID). Currently, there are no effective pharmacotherapies. The success of clinical trials to improve cognition depends in part on the design [...] Read more.
Down syndrome (DS), trisomy of the long arm of human chromosome 21 (Hsa21), is the most common genetic cause of intellectual disability (ID). Currently, there are no effective pharmacotherapies. The success of clinical trials to improve cognition depends in part on the design of preclinical evaluations in mouse models. To broaden understanding of the common limitations of experiments in learning and memory, we report performance in context fear conditioning (CFC) in three mouse models of DS, the Dp(16)1Yey, Dp(17)1Yey and Dp(10)1Yey (abbreviated Dp16, Dp17 and Dp10), separately trisomic for the human Hsa21 orthologs mapping to mouse chromosomes 16, 17 and 10, respectively. We examined female and male mice of the three lines on the standard C57BL/6J background at 3 months of age and Dp17 and Dp10 at 18 months of age. We also examined female and male mice of Dp17 and Dp10 at 3 months of age as F1 hybrids obtained from a cross with the DBA/2J background. Results indicate that genotype, sex, age and genetic background affect CFC performance. These data support the need to use both female and male mice, trisomy of sets of all Hsa21 orthologs, and additional ages and genetic backgrounds to improve the reliability of preclinical evaluations of drugs for ID in DS. Full article
(This article belongs to the Special Issue Models and Advances in Genetics of Down Syndrome)
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14 pages, 3505 KiB  
Communication
Coat Color-Facilitated Efficient Generation and Analysis of a Mouse Model of Down Syndrome Triplicated for All Human Chromosome 21 Orthologous Regions
by Yichen Li, Zhuo Xing, Tao Yu, Annie Pao, Marcel Daadi and Y. Eugene Yu
Genes 2021, 12(8), 1215; https://doi.org/10.3390/genes12081215 - 6 Aug 2021
Viewed by 2652
Abstract
Down syndrome (DS) is one of the most complex genetic disorders in humans and a leading genetic cause of developmental delays and intellectual disabilities. The mouse remains an essential model organism in DS research because human chromosome 21 (Hsa21) is orthologously conserved with [...] Read more.
Down syndrome (DS) is one of the most complex genetic disorders in humans and a leading genetic cause of developmental delays and intellectual disabilities. The mouse remains an essential model organism in DS research because human chromosome 21 (Hsa21) is orthologously conserved with three regions in the mouse genome. Recent studies have revealed complex interactions among different triplicated genomic regions and Hsa21 gene orthologs that underlie major DS phenotypes. Because we do not know conclusively which triplicated genes are indispensable in such interactions for a specific phenotype, it is desirable that all evolutionarily conserved Hsa21 gene orthologs are triplicated in a complete model. For this reason, the Dp(10)1Yey/+;Dp(16)1Yey/+;Dp(17)1Yey/+ mouse is the most complete model of DS to reflect gene dosage effects because it is the only mutant triplicated for all Hsa21 orthologous regions. Recently, several groups have expressed concerns that efforts needed to generate the triple compound model would be so overwhelming that it may be impractical to take advantage of its unique strength. To alleviate these concerns, we developed a strategy to drastically improve the efficiency of generating the triple compound model with the aid of a targeted coat color, and the results confirmed that the mutant mice generated via this approach exhibited cognitive deficits. Full article
(This article belongs to the Special Issue Models and Advances in Genetics of Down Syndrome)
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Review

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29 pages, 1031 KiB  
Review
Dyrk1a from Gene Function in Development and Physiology to Dosage Correction across Life Span in Down Syndrome
by Helin Atas-Ozcan, Véronique Brault, Arnaud Duchon and Yann Herault
Genes 2021, 12(11), 1833; https://doi.org/10.3390/genes12111833 - 20 Nov 2021
Cited by 27 | Viewed by 5343
Abstract
Down syndrome is the main cause of intellectual disabilities with a large set of comorbidities from developmental origins but also that appeared across life span. Investigation of the genetic overdosage found in Down syndrome, due to the trisomy of human chromosome 21, has [...] Read more.
Down syndrome is the main cause of intellectual disabilities with a large set of comorbidities from developmental origins but also that appeared across life span. Investigation of the genetic overdosage found in Down syndrome, due to the trisomy of human chromosome 21, has pointed to one main driver gene, the Dual-specificity tyrosine-regulated kinase 1A (Dyrk1a). Dyrk1a is a murine homolog of the drosophila minibrain gene. It has been found to be involved in many biological processes during development and in adulthood. Further analysis showed its haploinsufficiency in mental retardation disease 7 and its involvement in Alzheimer’s disease. DYRK1A plays a role in major developmental steps of brain development, controlling the proliferation of neural progenitors, the migration of neurons, their dendritogenesis and the function of the synapse. Several strategies targeting the overdosage of DYRK1A in DS with specific kinase inhibitors have showed promising evidence that DS cognitive conditions can be alleviated. Nevertheless, providing conditions for proper temporal treatment and to tackle the neurodevelopmental and the neurodegenerative aspects of DS across life span is still an open question. Full article
(This article belongs to the Special Issue Models and Advances in Genetics of Down Syndrome)
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10 pages, 879 KiB  
Review
Genes Associated with Disturbed Cerebral Neurogenesis in the Embryonic Brain of Mouse Models of Down Syndrome
by Keiichi Ishihara
Genes 2021, 12(10), 1598; https://doi.org/10.3390/genes12101598 - 11 Oct 2021
Cited by 5 | Viewed by 2757
Abstract
Down syndrome (DS), also known as trisomy 21, is the most frequent genetic cause of intellectual disability. Although the mechanism remains unknown, delayed brain development is assumed to be involved in DS intellectual disability. Analyses with human with DS and mouse models have [...] Read more.
Down syndrome (DS), also known as trisomy 21, is the most frequent genetic cause of intellectual disability. Although the mechanism remains unknown, delayed brain development is assumed to be involved in DS intellectual disability. Analyses with human with DS and mouse models have shown that defects in embryonic cortical neurogenesis may lead to delayed brain development. Cre-loxP-mediated chromosomal engineering has allowed the generation of a variety of mouse models carrying various partial Mmu16 segments. These mouse models are useful for determining genotype–phenotype correlations and identifying dosage-sensitive genes involved in the impaired neurogenesis. In this review, we summarize several candidate genes and pathways that have been linked to defective cortical neurogenesis in DS. Full article
(This article belongs to the Special Issue Models and Advances in Genetics of Down Syndrome)
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