RESUMEN
Background: Trisomy of human chromosome 21 (Hsa21) results in a constellation of features known as Down syndrome (DS), the most common genetic form of intellectual disability. Hsa21 is orthologous to three regions in the mouse genome on mouse chromosome 16 (Mmu16), Mmu17 and Mmu10. We investigated genotype-phenotype relationships by assessing the contribution of these three regions to memory function and age-dependent cognitive decline, using three mouse models of DS, Dp1Tyb, Dp(17)3Yey, Dp(10)2Yey, that carry an extra copy of the Hsa21-orthologues on Mmu16, Mmu17 and Mmu10, respectively. Hypothesis: Prior research on cognitive function in DS mouse models has largely focused on models with an extra copy of the Mmu16 region and relatively little is known about the effects of increased copy number on Mmu17 and Mmu10 on cognition and how this interacts with the effects of aging. As aging is is a critical contributor to cognitive and psychiatric changes in DS, we hypothesised that ageing would differentially impact memory function in Dp1Tyb, Dp(17)3Yey, and Dp(10)2Yey, models of DS. Methods: Young (12-13 months and old (18-20 months mice Dp1Tyb, Dp(17)3Yey and Dp(10)2Yey mice were tested on a battery of object recognition memory test that assessed object novelty detection, novel location detection and associative object-in place memory. Following behavioral testing, hippocampal and frontal cortical tissue was analysed for expression of glutamatergic receptor proteins using standard immunoblot techniques. Results: Young (12-13 months and old (18-20 months mice Dp1Tyb, Dp(17)3Yey and Dp(10)2Yey mice were tested on a battery of object recognition memory test that assessed object novelty detection, novel location detection and associative object-in place memory. Following behavioral testing, hippocampal and frontal cortical tissue was analysed for expression of glutamatergic receptor proteins using standard immunoblot techniques. Conclusion: Our results show that distinct Hsa21-orthologous regions contribute differentially to cognitive dysfunction in DS mouse models and that aging interacts with triplication of Hsa21-orthologous genes on Mmu10.
RESUMEN
Down syndrome (DS) is caused by trisomy of human chromosome 21 (Hsa21). DS is a gene dosage disorder that results in multiple phenotypes including congenital heart defects. This clinically important cardiac pathology is the result of a third copy of one or more of the approximately 230 genes on Hsa21, but the identity of the causative dosage-sensitive genes and hence mechanisms underlying this cardiac pathology remain unclear. Here, we show that hearts from human fetuses with DS and embryonic hearts from the Dp1Tyb mouse model of DS show reduced expression of mitochondrial respiration genes and cell proliferation genes. Using systematic genetic mapping, we determined that three copies of the dual-specificity tyrosine phosphorylation-regulated kinase 1A (Dyrk1a) gene, encoding a serine/threonine protein kinase, are associated with congenital heart disease pathology. In embryos from Dp1Tyb mice, reducing Dyrk1a gene copy number from three to two reversed defects in cellular proliferation and mitochondrial respiration in cardiomyocytes and rescued heart septation defects. Increased dosage of DYRK1A protein resulted in impairment of mitochondrial function and congenital heart disease pathology in mice with DS, suggesting that DYRK1A may be a useful therapeutic target for treating this common human condition.
Asunto(s)
Síndrome de Down , Cardiopatías Congénitas , Animales , Humanos , Ratones , Modelos Animales de Enfermedad , Síndrome de Down/genética , Genes Mitocondriales , Cardiopatías Congénitas/genética , Miocitos Cardíacos , TrisomíaRESUMEN
Down syndrome (DS), trisomy of human chromosome 21 (Hsa21), occurs in 1 in 800 live births and is the most common human aneuploidy. DS results in multiple phenotypes, including craniofacial dysmorphology, which is characterised by midfacial hypoplasia, brachycephaly and micrognathia. The genetic and developmental causes of this are poorly understood. Using morphometric analysis of the Dp1Tyb mouse model of DS and an associated mouse genetic mapping panel, we demonstrate that four Hsa21-orthologous regions of mouse chromosome 16 contain dosage-sensitive genes that cause the DS craniofacial phenotype, and identify one of these causative genes as Dyrk1a. We show that the earliest and most severe defects in Dp1Tyb skulls are in bones of neural crest (NC) origin, and that mineralisation of the Dp1Tyb skull base synchondroses is aberrant. Furthermore, we show that increased dosage of Dyrk1a results in decreased NC cell proliferation and a decrease in size and cellularity of the NC-derived frontal bone primordia. Thus, DS craniofacial dysmorphology is caused by an increased dosage of Dyrk1a and at least three other genes.
Asunto(s)
Síndrome de Down , Ratones , Humanos , Animales , Síndrome de Down/genética , Cráneo , Mapeo Cromosómico , Fenotipo , Modelos Animales de EnfermedadRESUMEN
Down syndrome (DS) phenotypes result from triplicated genes, but the effects of three copy genes are not well known. A mouse mapping panel genetically dissecting human chromosome 21 (Hsa21) syntenic regions was used to investigate the contributions and interactions of triplicated Hsa21 orthologous genes on mouse chromosome 16 (Mmu16) on skeletal phenotypes. Skeletal structure and mechanical properties were assessed in femurs of male and female Dp9Tyb, Dp2Tyb, Dp3Tyb, Dp4Tyb, Dp5Tyb, Dp6Tyb, Ts1Rhr and Dp1Tyb;Dyrk1a+/+/- mice. Dp1Tyb mice, with the entire Hsa21 homologous region of Mmu16 triplicated, display bone deficits similar to those of humans with DS and served as a baseline for other strains in the panel. Bone phenotypes varied based on triplicated gene content, sex and bone compartment. Three copies of Dyrk1a played a sex-specific, essential role in trabecular deficits and may interact with other genes to influence cortical deficits related to DS. Triplicated genes in Dp9Tyb and Dp2Tyb mice improved some skeletal parameters. As triplicated genes can both improve and worsen bone deficits, it is important to understand the interaction between and molecular mechanisms of skeletal alterations affected by these genes.
Asunto(s)
Síndrome de Down , Humanos , Ratones , Masculino , Femenino , Animales , Síndrome de Down/genética , Cromosomas Humanos Par 21 , Modelos Animales de Enfermedad , FenotipoRESUMEN
Down syndrome (DS), trisomy 21, results in many complex phenotypes including cognitive deficits, heart defects and craniofacial alterations. Phenotypes arise from an extra copy of human chromosome 21 (Hsa21) genes. However, these dosage-sensitive causative genes remain unknown. Animal models enable identification of genes and pathological mechanisms. The Dp1Tyb mouse model of DS has an extra copy of 63% of Hsa21-orthologous mouse genes. In order to establish whether this model recapitulates DS phenotypes, we comprehensively phenotyped Dp1Tyb mice using 28 tests of different physiological systems and found that 468 out of 1800 parameters were significantly altered. We show that Dp1Tyb mice have wide-ranging DS-like phenotypes, including aberrant erythropoiesis and megakaryopoiesis, reduced bone density, craniofacial changes, altered cardiac function, a pre-diabetic state, and deficits in memory, locomotion, hearing and sleep. Thus, Dp1Tyb mice are an excellent model for investigating complex DS phenotype-genotype relationships for this common disorder.
Asunto(s)
Síndrome de Down/patología , Péptidos beta-Amiloides/metabolismo , Anemia/complicaciones , Animales , Desarrollo Óseo , Modelos Animales de Enfermedad , Síndrome de Down/genética , Síndrome de Down/fisiopatología , Eritropoyesis , Potenciales Evocados Auditivos del Tronco Encefálico , Regulación de la Expresión Génica , Genes Duplicados , Audición , Pruebas de Función Cardíaca , Hipocampo/patología , Locomoción , Memoria/fisiología , Ratones Endogámicos C57BL , Otitis Media/complicaciones , Otitis Media/patología , Otitis Media/fisiopatología , Fenotipo , Estado Prediabético/complicaciones , Estado Prediabético/patología , Estado Prediabético/fisiopatología , Respiración , Sueño/fisiología , Bazo/patología , Esplenomegalia/complicacionesRESUMEN
Congenital heart disease (CHD) is the most common class of human birth defects, with a prevalence of 0.9% of births. However, two-thirds of cases have an unknown cause, and many of these are thought to be caused by in utero exposure to environmental teratogens. Here we identify a potential teratogen causing CHD in mice: maternal iron deficiency (ID). We show that maternal ID in mice causes severe cardiovascular defects in the offspring. These defects likely arise from increased retinoic acid signalling in ID embryos. The defects can be prevented by iron administration in early pregnancy. It has also been proposed that teratogen exposure may potentiate the effects of genetic predisposition to CHD through gene-environment interaction. Here we show that maternal ID increases the severity of heart and craniofacial defects in a mouse model of Down syndrome. It will be important to understand if the effects of maternal ID seen here in mice may have clinical implications for women.
Asunto(s)
Sistema Cardiovascular/embriología , Embrión de Mamíferos/patología , Deficiencias de Hierro , Animales , Aorta Torácica/anomalías , Biomarcadores/metabolismo , Diferenciación Celular , Vasos Coronarios/embriología , Vasos Coronarios/patología , Suplementos Dietéticos , Edema/patología , Embrión de Mamíferos/anomalías , Desarrollo Embrionario , Femenino , Perfilación de la Expresión Génica , Interacción Gen-Ambiente , Proteínas Fluorescentes Verdes/metabolismo , Hierro/metabolismo , Vasos Linfáticos/embriología , Vasos Linfáticos/patología , Ratones Endogámicos C57BL , Miocardio/patología , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/patología , Penetrancia , Fenotipo , Embarazo , Transducción de Señal , Células Madre/patología , Transgenes , Tretinoina/metabolismoRESUMEN
All individuals with Down syndrome (DS), which results from trisomy of human chromosome 21 (Ts21), present with skeletal abnormalities typified by craniofacial features, short stature and low bone mineral density (BMD). Differences in skeletal deficits between males and females with DS suggest a sexual dimorphism in how trisomy affects bone. Dp1Tyb mice contain three copies of all of the genes on mouse chromosome 16 that are homologous to human chromosome 21, males and females are fertile, and therefore are an excellent model to test the hypothesis that gene dosage influences the sexual dimorphism of bone abnormalities in DS. Dp1Tyb as compared to control littermate mice at time points associated with bone accrual (6 weeks) and skeletal maturity (16 weeks) showed deficits in BMD and trabecular architecture that occur largely through interactions between sex and genotype and resulted in lower percent bone volume in all female and Dp1Tyb male mice. Cortical bone in Dp1Tyb as compared to control mice exhibited different changes over time influenced by sex × genotype interactions including reduced cortical area in both male and female Dp1Tyb mice. Mechanical testing analyses suggested deficits in whole bone properties such as bone mass and geometry, but improved material properties in female and Dp1Tyb mice. Sexual dimorphisms and the influence of trisomic gene dosage differentially altered cellular properties of male and female Dp1Tyb bone. These data establish sex, gene dosage, skeletal site and age as important factors in skeletal development of DS model mice, paving the way for identification of the causal dosage-sensitive genes. Skeletal differences in developing male and female Dp1Tyb DS model mice replicated differences in less-studied adolescents with DS and established a foundation to understand the etiology of trisomic bone deficits.
Asunto(s)
Síndrome de Down , Animales , Densidad Ósea/genética , Modelos Animales de Enfermedad , Síndrome de Down/genética , Femenino , Dosificación de Gen , Masculino , Ratones , Caracteres SexualesRESUMEN
Down syndrome (DS), trisomy of human chromosome 21 (Hsa21), results in a broad range of phenotypes. A recent study reported that DS cells show genome-wide transcriptional changes in which up- or down-regulated genes are clustered in gene expression dysregulation domains (GEDDs). GEDDs were also reported in fibroblasts derived from a DS mouse model duplicated for some Hsa21-orthologous genes, indicating cross-species conservation of this phenomenon. Here we investigate GEDDs using the Dp1Tyb mouse model of DS, which is duplicated for the entire Hsa21-orthologous region of mouse chromosome 16. Our statistical analysis shows that GEDDs are present both in DS cells and in Dp1Tyb mouse fibroblasts and hippocampus. However, we find that GEDDs do not depend on the DS genotype but occur whenever gene expression changes. We conclude that GEDDs are not a specific feature of DS but instead result from the clustering of co-regulated genes, a function of mammalian genome organisation.
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Síndrome de Down/genética , Fibroblastos/metabolismo , Expresión Génica/genética , Hipocampo/metabolismo , Animales , Modelos Animales de Enfermedad , Perfilación de la Expresión Génica , Genoma , Genotipo , Ratones , Familia de Multigenes , FenotipoRESUMEN
Down Syndrome (DS) is caused by trisomy of chromosome 21 (Hsa21) and results in a spectrum of phenotypes including learning and memory deficits, and motor dysfunction. It has been hypothesized that an additional copy of a few Hsa21 dosage-sensitive genes causes these phenotypes, but this has been challenged by observations that aneuploidy can cause phenotypes by the mass action of large numbers of genes, with undetectable contributions from individual sequences. The motor abnormalities in DS are relatively understudied-the identity of causative dosage-sensitive genes and the mechanism underpinning the phenotypes are unknown. Using a panel of mouse strains with duplications of regions of mouse chromosomes orthologous to Hsa21 we show that increased dosage of small numbers of genes causes locomotor dysfunction and, moreover, that the Dyrk1a gene is required in three copies to cause the phenotype. Furthermore, we show for the first time a new DS phenotype: loss of motor neurons both in mouse models and, importantly, in humans with DS, that may contribute to locomotor dysfunction.
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Síndrome de Down/genética , Actividad Motora/genética , Neuronas Motoras/metabolismo , Degeneración Nerviosa/genética , Adulto , Anciano , Animales , Autopsia , Modelos Animales de Enfermedad , Expresión Génica , Humanos , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Persona de Mediana Edad , Proteínas Serina-Treonina Quinasas/genética , Proteínas Tirosina Quinasas/genética , Médula Espinal/metabolismo , Médula Espinal/patología , Quinasas DyrKRESUMEN
Altered concentrations of monoamine neurotransmitters and metabolites have been repeatedly found in people with Down syndrome (DS, trisomy 21). Because of the limited availability of human post-mortem tissue, DS mouse models are of great interest to study these changes and the underlying neurobiological mechanisms. Although previous studies have shown the potential of Ts65Dn mice - the most widely used mouse model of DS - to model noradrenergic changes, a comprehensive monoaminergic characterization in multiple brain regions has not been performed so far. Here, we used RP-HPLC with electrochemical detection to quantify (nor)adrenergic (NA, adrenaline and MHPG), dopaminergic (DA, HVA and DOPAC), and serotonergic compounds (tryptophan, 5-HT and 5-HIAA) in ten regionally dissected brain regions of Ts65Dn mice, as well as in Dp1Tyb mice - a novel DS mouse model. Comparing young adult aneuploid mice (2.5-5.5months) with their euploid WT littermates did not reveal generalized monoaminergic dysregulation, indicating that the genetic overload in these mice barely affected the absolute concentrations at this age. Moreover, we studied the effect of aging in Ts65Dn mice: comparing aged animals (12-13months) with their younger counterparts revealed a large number of significant changes. In general, the (nor)adrenergic system appeared to be reduced, while serotonergic compounds were increased with aging. Dopaminergic alterations were less consistent. These overall patterns appeared to be relatively similar for Ts65Dn and WT mice, though more observed changes were regarded significant for WT mice. Similar human post-mortem studies are necessary to validate the monoaminergic construct validity of the Ts65Dn and Dp1Typ mouse models.
Asunto(s)
Envejecimiento , Aneuploidia , Monoaminas Biogénicas/metabolismo , Encéfalo/metabolismo , Síndrome de Down/patología , Animales , Cromatografía Líquida de Alta Presión , Modelos Animales de Enfermedad , Síndrome de Down/genética , Técnicas Electroquímicas , Masculino , Ratones , Ratones Endogámicos C57BL , Neurotransmisores/metabolismo , Estadísticas no ParamétricasRESUMEN
Down syndrome (DS), caused by trisomy of human chromosome 21 (Hsa21), is the most common cause of congenital heart defects (CHD), yet the genetic and mechanistic causes of these defects remain unknown. To identify dosage-sensitive genes that cause DS phenotypes, including CHD, we used chromosome engineering to generate a mapping panel of 7 mouse strains with partial trisomies of regions of mouse chromosome 16 orthologous to Hsa21. Using high-resolution episcopic microscopy and three-dimensional modeling we show that these strains accurately model DS CHD. Systematic analysis of the 7 strains identified a minimal critical region sufficient to cause CHD when present in 3 copies, and showed that it contained at least two dosage-sensitive loci. Furthermore, two of these new strains model a specific subtype of atrio-ventricular septal defects with exclusive ventricular shunting and demonstrate that, contrary to current hypotheses, these CHD are not due to failure in formation of the dorsal mesenchymal protrusion.
Down syndrome is a condition caused by having an extra copy of one of the 46 chromosomes found inside human cells. Specifically, instead of two copies, people with Down syndrome are born with three copies of chromosome 21. This results in many different effects, including learning and memory problems, heart defects and Alzheimer's disease. Each of these different effects is caused by having a third copy of one or more of the approximately 230 genes found on chromosome 21. However, it is not known which of these genes cause any of these effects, and how an extra copy of the genes results in such changes. Now, Lana-Elola et al. have investigated which genes on chromosome 21 cause the heart defects seen in Down syndrome, and how those heart defects come about. This involved engineering a new strain of mouse that has an extra copy of 148 mouse genes that are very similar to 148 genes found on chromosome 21 in humans. Like people with Down syndrome, this mouse strain developed heart defects when it was an embryo. Using a series of six further mouse strains, Lana-Elola et al. then narrowed down the potential genes that, when in three copies, are needed to cause the heart defects, to a list of just 39 genes. Further experiments then showed that at least two genes within these 39 genes were required in three copies to cause the heart defects. The next step will be to identify the specific genes that actually cause the heart defects, and then work out how a third copy of these genes causes the developmental problems.
Asunto(s)
Síndrome de Down/patología , Cardiopatías Congénitas/genética , Animales , Mapeo Cromosómico , Modelos Animales de Enfermedad , Dosificación de Gen , Sitios Genéticos , RatonesRESUMEN
Down Syndrome (DS) is a highly prevalent developmental disorder, affecting 1/700 births. Intellectual disability, which affects learning and memory, is present in all cases and is reflected by below average IQ. We sought to determine whether defective morphology and connectivity in neurons of the cerebral cortex may underlie the cognitive deficits that have been described in two mouse models of DS, the Tc1 and Ts1Rhr mouse lines. We utilised in utero electroporation to label a cohort of future upper layer projection neurons in the cerebral cortex of developing mouse embryos with GFP, and then examined neuronal positioning and morphology in early adulthood, which revealed no alterations in cortical layer position or morphology in either Tc1 or Ts1Rhr mouse cortex. The number of dendrites, as well as dendrite length and branching was normal in both DS models, compared with wildtype controls. The sites of projection neuron synaptic inputs, dendritic spines, were analysed in Tc1 and Ts1Rhr cortex at three weeks and three months after birth, and significant changes in spine morphology were observed in both mouse lines. Ts1Rhr mice had significantly fewer thin spines at three weeks of age. At three months of age Tc1 mice had significantly fewer mushroom spines--the morphology associated with established synaptic inputs and learning and memory. The decrease in mushroom spines was accompanied by a significant increase in the number of stubby spines. This data suggests that dendritic spine abnormalities may be a more important contributor to cognitive deficits in DS models, rather than overall neuronal architecture defects.
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Corteza Cerebral/patología , Espinas Dendríticas/patología , Síndrome de Down/patología , Animales , Espinas Dendríticas/metabolismo , Modelos Animales de Enfermedad , Femenino , Proteínas Fluorescentes Verdes/metabolismo , Ratones , FenotipoRESUMEN
Down syndrome (DS) is caused by trisomy of human chromosome 21 (Hsa21) and results in a large number of phenotypes, including learning difficulties, cardiac defects, distinguishing facial features and leukaemia. These are likely to result from an increased dosage of one or more of the â¼310 genes present on Hsa21. The identification of these dosage-sensitive genes has become a major focus in DS research because it is essential for a full understanding of the molecular mechanisms underlying pathology, and might eventually lead to more effective therapy. The search for these dosage-sensitive genes is being carried out using both human and mouse genetics. Studies of humans with partial trisomy of Hsa21 have identified regions of this chromosome that contribute to different phenotypes. In addition, novel engineered mouse models are being used to map the location of dosage-sensitive genes, which, in a few cases, has led to the identification of individual genes that are causative for certain phenotypes. These studies have revealed a complex genetic interplay, showing that the diverse DS phenotypes are likely to be caused by increased copies of many genes, with individual genes contributing in different proportions to the variance in different aspects of the pathology.
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Síndrome de Down/genética , Encéfalo/crecimiento & desarrollo , Encéfalo/fisiopatología , Síndrome de Down/complicaciones , Síndrome de Down/fisiopatología , Humanos , Memoria/fisiología , Actividad Motora/fisiologíaRESUMEN
Holoprosencephaly (HPE) is a heterogeneous craniofacial and neural developmental anomaly characterized in its most severe form by the failure of the forebrain to divide. In humans, HPE is associated with disruption of Sonic hedgehog and Nodal signaling pathways, but the role of other signaling pathways has not yet been determined. In this study, we analyzed mice which, due to the lack of the Bmp antagonist Noggin, exhibit elevated Bmp signaling. Noggin(-/-) mice exhibited a solitary median maxillary incisor that developed from a single dental placode, early midfacial narrowing as well as abnormalities in the developing hyoid bone, pituitary gland and vomeronasal organ. In Noggin(-/-) mice, the expression domains of Shh, as well as the Shh target genes Ptch1 and Gli1, were reduced in the frontonasal region at key stages of early facial development. Using E10.5 facial cultures, we show that excessive BMP4 results in reduced Fgf8 and Ptch1 expression. These data suggest that increased Bmp signaling in Noggin(-/-) mice results in downregulation of the hedgehog pathway at a critical stage when the midline craniofacial structures are developing, which leads to a phenotype consistent with a microform of HPE.
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Alelos , Proteínas Portadoras/genética , Holoprosencefalia/genética , Animales , Proteína Morfogenética Ósea 4/metabolismo , Proteínas Portadoras/metabolismo , Cara/embriología , Factor 8 de Crecimiento de Fibroblastos/metabolismo , Regulación del Desarrollo de la Expresión Génica , Proteínas Hedgehog/metabolismo , Holoprosencefalia/embriología , Holoprosencefalia/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Boca/embriología , Boca/metabolismo , Hueso Paladar/embriología , Hueso Paladar/metabolismo , Receptores Patched , Receptor Patched-1 , Fenotipo , Hipófisis/anomalías , Receptores de Superficie Celular/metabolismo , Transducción de Señal , Órgano Vomeronasal/anomalíasRESUMEN
Gli3 is a zinc-finger transcription factor whose activity is dependent on the level of hedgehog (Hh) ligand. Hh signaling has key roles during endochondral ossification; however, its role in intramembranous ossification is still unclear. In this study, we show that Gli3 performs a dual role in regulating both osteoprogenitor proliferation and osteoblast differentiation during intramembranous ossification. We discovered that Gli3Xt-J/Xt-J mice, which represent a Gli3-null allele, exhibit craniosynostosis of the lambdoid sutures and that this is accompanied by increased osteoprogenitor proliferation and differentiation. These cellular changes are preceded by ectopic expression of the Hh receptor Patched1 and reduced expression of the transcription factor Twist1 in the sutural mesenchyme. Twist1 is known to delay osteogenesis by binding to and inhibiting the transcription factor Runx2. We found that Runx2 expression in the lambdoid suture was altered in a pattern complimentary to that of Twist1. We therefore propose that loss of Gli3 results in a Twist1-, Runx2-dependent expansion of the sutural osteoprogenitor population as well as enhanced osteoblastic differentiation which results in a bony bridge forming between the parietal and interparietal bones. We show that FGF2 will induce Twist1, normalize osteoprogenitor proliferation and differentiation and rescue the lambdoid suture synostosis in Gli3Xt-J/Xt-J mice. Taken together, we define a novel role for Gli3 in osteoblast development; we describe the first mouse model of lambdoid suture craniosynostosis and show how craniosynostosis can be rescued in this model.
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Diferenciación Celular , Proliferación Celular , Craneosinostosis/fisiopatología , Factores de Transcripción de Tipo Kruppel/genética , Proteínas del Tejido Nervioso/genética , Osteogénesis , Cráneo/anomalías , Células Madre/citología , Animales , Craneosinostosis/embriología , Craneosinostosis/genética , Craneosinostosis/metabolismo , Modelos Animales de Enfermedad , Femenino , Regulación del Desarrollo de la Expresión Génica , Humanos , Factores de Transcripción de Tipo Kruppel/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas del Tejido Nervioso/metabolismo , Osteoblastos/citología , Osteoblastos/metabolismo , Cráneo/citología , Cráneo/embriología , Cráneo/metabolismo , Células Madre/metabolismo , Proteína Gli3 con Dedos de ZincRESUMEN
AIMS: Cardiac malformations are prevalent in trisomies of human chromosome 21 [Down's syndrome (DS)], affecting normal chamber separation in the developing heart. Efforts to understand the aetiology of these defects have been severely hampered by the absence of an accurate mouse model. Such models have proved challenging to establish because synteny with human chromosome Hsa21 is distributed across three mouse chromosomes. None of those engineered so far accurately models the full range of DS cardiac phenotypes, in particular the profound disruptions resulting from atrioventricular septal defects (AVSDs). Here, we present analysis of the cardiac malformations exhibited by embryos of the transchromosomic mouse line Tc(Hsa21)1TybEmcf (Tc1) which contains more than 90% of chromosome Hsa21 in addition to the normal diploid mouse genome. METHODS AND RESULTS: Using high-resolution episcopic microscopy and three-dimensional (3D) modelling, we show that Tc1 embryos exhibit many of the cardiac defects found in DS, including balanced AVSD with single and separate valvar orifices, membranous and muscular ventricular septal defects along with outflow tract and valve leaflet abnormalities. Frequencies of cardiac malformations (ranging from 38 to 55%) are dependent on strain background. In contrast, no comparable cardiac defects were detected in embryos of the more limited mouse trisomy model, Dp(16Cbr1-ORF9)1Rhr (Ts1Rhr), indicating that trisomy of the region syntenic to the Down's syndrome critical region, including the candidate genes DSCAM and DYRK1A, is insufficient to yield DS cardiac abnormalities. CONCLUSION: The Tc1 mouse line provides a suitable model for studying the underlying genetic causes of the DS AVSD cardiac phenotype.
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Anomalías Múltiples , Cromosomas Humanos Par 21 , Síndrome de Down/genética , Defectos de la Almohadilla Endocárdica/genética , Corazón Fetal/anomalías , Defectos del Tabique Interatrial/genética , Defectos del Tabique Interventricular/genética , Animales , Aorta/anomalías , Modelos Animales de Enfermedad , Síndrome de Down/embriología , Embrión de Mamíferos/anomalías , Defectos de la Almohadilla Endocárdica/embriología , Genotipo , Edad Gestacional , Defectos del Tabique Interatrial/embriología , Defectos del Tabique Interventricular/embriología , Humanos , Imagenología Tridimensional , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Microscopía/métodos , Morfogénesis , FenotipoRESUMEN
Runx1 is highly expressed in chondroprogenitor and osteoprogenitor cells and in vitro experiments suggest that Runx1 is important in the early stages of osteoblast and chondrocyte differentiation. However, because Runx1 knockout mice are early embryonic lethal due to failure of hematopoiesis, the role of Runx1 in skeletogenesis remains unclear. We studied the role of Runx1 in skeletal development using a Runx1 reversible knockout mouse model. By crossing with Tie2-Cre deletor mice, Runx1 expression was selectively rescued in the endothelial and hematopoietic systems but not in the skeleton. Although Runx1(Re/Re) embryos survived until birth and had a generally normal skeleton, the development of mineralization in the sternum and some skull elements was significantly disrupted. In contrast to wild-type embryos, the sternum of E17.5 Runx1(Re/Re) embryos showed high levels of Sox-9 and collagen type II expression and lack of development of hypertrophic chondrocytes. In situ hybridization analysis demonstrated that, in contrast to the vertebrae and long bones, the sternum of wild-type embryos expresses high levels of Runx1, but not Runx2, the master regulator of skeletogenesis. Thus, although Runx1 is not essential for major skeletal development, it does play an essential role in the development of the sternum and some skull elements.
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Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Esternón/metabolismo , Animales , Huesos/metabolismo , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Embrión de Mamíferos/metabolismo , Desarrollo Embrionario/genética , Regulación del Desarrollo de la Expresión Génica , Hibridación in Situ , Ratones , Ratones Noqueados , Esternón/embriologíaRESUMEN
Sporadic diseases, which occur as single, scattered cases, are among the commonest causes of human morbidity and death. They result in a variety of diseases, including many cancers, premature aging, neurodegeneration and skeletal defects. They are often pathogenetically complex, involving a mosaic distribution of affected cells, and are difficult to model in the mouse. Faithful models of sporadic diseases require innovative forms of genetic manipulation to accurately recreate their initiation and pathogenesis. Such modelling is crucial to understanding these diseases and, by extension, to the development of therapeutic approaches to treat them. This article focuses on sporadic diseases with a genetic aetiology, the challenges they pose to biomedical researchers, and the different current and developing approaches used to model such disorders in the mouse.
Asunto(s)
Modelos Animales de Enfermedad , Enfermedades Genéticas Congénitas/patología , Técnicas Genéticas , Animales , Núcleo Celular/genética , Quimera , Humanos , Ratones , Mutación/genéticaRESUMEN
Apert syndrome (AS) is a severe congenital disease caused by mutations in fibroblast growth factor receptor-2 (FGFR2), and characterised by craniofacial, limb, visceral, and neural abnormalities. AS-type FGFR2 molecules exert a gain-of-function effect in a ligand-dependent manner, but the causative FGFs and their relative contribution to each of the abnormalities observed in AS remains unknown. We have generated mice that harbour an AS mutation but are deficient in or heterozygous for Fgf10. The genetic knockdown of Fgf10 can rescue the skeletal as well as some of the visceral defects observed in this AS model, and restore a near normal level of FgfR2 signaling involving an apparent switch between ERK(p44/p42) and p38 phosphorylation. Surprisingly, it can also yield de novo cleft palate and blind colon in a subset of the compound mutants. These findings strongly suggest that Fgf10 contributes to AS-like pathologies and highlight a complexity of Fgf10 function in different tissues.