Autism-associated Dyrk1a truncation mutants impair neuronal dendritic and spine growth and interfere with postnatal cortical development.
ABSTRACT: Autism is a prevailing neurodevelopmental disorder with a large genetic/genomic component. Recently, the dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1 A (DYRK1A) gene was implicated as a risk factor for autism spectrum disorder (ASD). We identified five DYRK1A variants in ASD patients and found that the dose of DYRK1A protein has a crucial role in various aspects of postnatal neural development. Dyrk1a loss of function and gain of function led to defects in dendritic growth, dendritic spine development and radial migration during cortical development. Importantly, two autism-associated truncations, R205X and E239X, were shown to be Dyrk1a loss-of-function mutants. Studies of the truncated Dyrk1a mutants may provide new insights into the role of Dyrk1a in brain development, as well as the role of Dyrk1a loss of function in the pathophysiology of autism.
Project description:Dendritic arborization patterns are consistent anatomical correlates of genetic disorders such as Down syndrome (DS) and autism spectrum disorders (ASDs). In a screen for abnormal dendrite development, we identified Minibrain (MNB)/DYRK1a, a kinase implicated in DS and ASDs, as a regulator of the microtubule cytoskeleton. We show that MNB is necessary to establish the length and cytoskeletal composition of terminal dendrites by controlling microtubule growth. Altering MNB levels disrupts dendrite morphology and perturbs neuronal electrophysiological activity, resulting in larval mechanosensation defects. Using in vivo and in vitro approaches, we uncover a molecular pathway whereby direct phosphorylation of ?-tubulin by MNB inhibits tubulin polymerization, a function that is conserved for mammalian DYRK1a. Our results demonstrate that phosphoregulation of microtubule dynamics by MNB/DYRK1a is critical for dendritic patterning and neuronal function, revealing a previously unidentified mode of posttranslational microtubule regulation in neurons and uncovering a conserved pathway for a DS- and ASD-associated kinase.
Project description:Dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1 A (DYRK1A) maps to the Down syndrome critical region; copy number increase of this gene is thought to have a major role in the neurocognitive deficits associated with Trisomy 21. Truncation of DYRK1A in patients with developmental delay (DD) and autism spectrum disorder (ASD) suggests a different pathology associated with loss-of-function mutations. To understand the phenotypic spectrum associated with DYRK1A mutations, we resequenced the gene in 7162 ASD/DD patients (2446 previously reported) and 2169 unaffected siblings and performed a detailed phenotypic assessment on nine patients. Comparison of our data and published cases with 8696 controls identified a significant enrichment of DYRK1A truncating mutations (P=0.00851) and an excess of de novo mutations (P=2.53 × 10(-10)) among ASD/intellectual disability (ID) patients. Phenotypic comparison of all novel (n=5) and recontacted (n=3) cases with previous case reports, including larger CNV and translocation events (n=7), identified a syndromal disorder among the 15 patients. It was characterized by ID, ASD, microcephaly, intrauterine growth retardation, febrile seizures in infancy, impaired speech, stereotypic behavior, hypertonia and a specific facial gestalt. We conclude that mutations in DYRK1A define a syndromic form of ASD and ID with neurodevelopmental defects consistent with murine and Drosophila knockout models.
Project description:DYRK1A maps to the Down syndrome critical region at 21q22. Mutations in this kinase-encoding gene have been reported to cause microcephaly associated with either intellectual disability or autism in humans. Intellectual disability accompanied by microcephaly was recapitulated in a murine model by overexpressing Dyrk1a which mimicked Down syndrome phenotypes. However, given embryonic lethality in homozygous knockout (KO) mice, no murine model studies could present sufficient evidence to link Dyrk1a dysfunction with autism. To understand the molecular mechanisms underlying microcephaly and autism spectrum disorders (ASD), we established an in vivo dyrk1aa KO model using zebrafish.We identified a patient with a mutation in the DYRK1A gene using microarray analysis. Circumventing the barrier of murine model studies, we generated a dyrk1aa KO zebrafish using transcription activator-like effector nuclease (TALEN)-mediated genome editing. For social behavioral tests, we have established a social interaction test, shoaling assay, and group behavior assay. For molecular analysis, we examined the neuronal activity in specific brain regions of dyrk1aa KO zebrafish through in situ hybridization with various probes including c-fos and crh which are the molecular markers for stress response.Microarray detected an intragenic microdeletion of DYRK1A in an individual with microcephaly and autism. From behavioral tests of social interaction and group behavior, dyrk1aa KO zebrafish exhibited social impairments that reproduce human phenotypes of autism in a vertebrate animal model. Social impairment in dyrk1aa KO zebrafish was further confirmed by molecular analysis of c-fos and crh expression. Transcriptional expression of c-fos and crh was lower than that of wild type fish in specific hypothalamic regions, suggesting that KO fish brains are less activated by social context.In this study, we established a zebrafish model to validate a candidate gene for autism in a vertebrate animal. These results illustrate the functional deficiency of DYRK1A as an underlying disease mechanism for autism. We also propose simple social behavioral assays as a tool for the broader study of autism candidate genes.
Project description:DYRK1A is a gene recurrently disrupted in 0.1-0.5% of the ASD population. A growing number of case reports with DYRK1A haploinsufficiency exhibit common phenotypic features including microcephaly, intellectual disability, speech delay, and facial dysmorphisms.Phenotypic information from previously published DYRK1A cases (n = 51) and participants in an ongoing study at the University of Washington (UW, n = 10) were compiled. Frequencies of recurrent phenotypic features in this population were compared to features observed in a large sample with idiopathic ASD from the Simons Simplex Collection (n = 1981). UW DYRK1A cases were further characterized quantitatively and compared to a randomly subsampled set of idiopathic ASD cases matched on age and gender (n = 10) and to cases with an ASD-associated disruptive mutation to CHD8 (n = 12). Contribution of familial genetic background to clinical heterogeneity was assessed by comparing head circumference, IQ, and ASD-related symptoms of UW DYRK1A cases to their unaffected parents.DYRK1A haploinsufficiency results in a common phenotypic profile including intellectual disability, speech and motor difficulties, microcephaly, feeding difficulties, and vision abnormalities. Eighty-nine percent of DYRK1A cases ascertained for ASD presented with a constellation of five or more of these symptoms. When compared quantitatively, DYRK1A cases presented with significantly lower IQ and adaptive functioning compared to idiopathic cases and significantly smaller head size compared to both idiopathic and CHD8 cases. Phenotypic variability in parental head circumference, IQ, and ASD-related symptoms corresponded to observed variability in affected child phenotype.Results confirm a core clinical phenotype for DYRK1A disruptions, with a combination of features that is distinct from idiopathic ASD. Cases with DYRK1A mutations are also distinguishable from disruptive mutations to CHD8 by head size. Measurable, quantitative characterization of DYRK1A haploinsufficiency illuminates clinical variability, which may be, in part, due to familial genetic background.
Project description:Dual-specificity tyrosine phosphorylation-regulated kinase 1?A (DYRK1A) is essential for human development, and DYRK1A haploinsufficiency is associated with a recognizable developmental syndrome and variable clinical features. Here, we present a patient with DYRK1A haploinsufficiency syndrome, including facial dysmorphism, delayed motor development, cardiovascular system defects, and brain atrophy. Exome sequencing identified a novel de novo heterozygous mutation of the human DYRK1A gene (c.1185dup), which generated a translational termination codon and resulted in a C-terminally truncated protein (DYRK1A-E396ter). To study the molecular effect of this truncation, we generated mammalian cell and Drosophila models that recapitulated the DYRK1A protein truncation. Analysis of the structure and deformation energy of the mutant protein predicted a reduction in protein stability. Experimentally, the mutant protein was efficiently degraded by the ubiquitin-dependent proteasome pathway and was barely detectable in mammalian cells. More importantly, the mutant kinase was intrinsically inactive and had little negative impact on the wild-type protein. Similarly, the mutant protein had a minimal effect on Drosophila phenotypes, confirming its loss-of-function in vivo. Together, our results suggest that the novel heterozygous mutation of DYRK1A resulted in loss-of-function of the kinase activity of DYRK1A and may contribute to the developmental delay observed in the patient.
Project description:The dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) gene, located on chromosome 21q22.13 within the Down syndrome critical region, has been implicated in syndromic intellectual disability associated with Down syndrome and autism. DYRK1A has a critical role in brain growth and development primarily by regulating cell proliferation, neurogenesis, neuronal plasticity and survival. Several patients have been reported with chromosome 21 aberrations such as partial monosomy, involving multiple genes including DYRK1A. In addition, seven other individuals have been described with chromosomal rearrangements, intragenic deletions or truncating mutations that disrupt specifically DYRK1A. Most of these patients have microcephaly and all have significant intellectual disability. In the present study, we report 10 unrelated individuals with DYRK1A-associated intellectual disability (ID) who display a recurrent pattern of clinical manifestations including primary or acquired microcephaly, ID ranging from mild to severe, speech delay or absence, seizures, autism, motor delay, deep-set eyes, poor feeding and poor weight gain. We identified unique truncating and non-synonymous mutations (three nonsense, four frameshift and two missense) in DYRK1A in nine patients and a large chromosomal deletion that encompassed DYRK1A in one patient. On the basis of increasing identification of mutations in DYRK1A, we suggest that this gene be considered potentially causative in patients presenting with ID, primary or acquired microcephaly, feeding problems and absent or delayed speech with or without seizures.
Project description:We have identified and characterized two unrelated patients with prenatal onset of microcephaly, intrauterine growth retardation, feeding problems, developmental delay, and febrile seizures/epilepsy who both carry a de novo balanced translocation that truncates the DYRK1A gene at chromosome 21q22.2. DYRK1A belongs to the dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) family, which is highly conserved throughout evolution. Given its localization in both the Down syndrome critical region and in the minimal region for partial monosomy 21, the gene has been studied intensively in animals and in humans, and DYRK1A has been proposed to be involved in the neurodevelopmental alterations associated with these syndromes. In the present study, we show that truncating mutations of DYRK1A result in a clinical phenotype including microcephaly.
Project description:PURPOSE:Haploinsufficiency of DYRK1A causes a recognizable clinical syndrome. The goal of this paper is to investigate congenital anomalies of the kidney and urinary tract (CAKUT) and genital defects (GD) in patients with DYRK1A variants. METHODS:A large database of clinical exome sequencing (ES) was queried for de novo DYRK1A variants and CAKUT/GD phenotypes were characterized. Xenopus laevis (frog) was chosen as a model organism to assess Dyrk1a's role in renal development. RESULTS:Phenotypic details and variants of 19 patients were compiled after an initial observation that one patient with a de novo pathogenic variant in DYRK1A had GD. CAKUT/GD data were available from 15 patients, 11 of whom presented with CAKUT/GD. Studies in Xenopus embryos demonstrated that knockdown of Dyrk1a, which is expressed in forming nephrons, disrupts the development of segments of embryonic nephrons, which ultimately give rise to the entire genitourinary (GU) tract. These defects could be rescued by coinjecting wild-type human DYRK1A RNA, but not with DYRK1AR205* or DYRK1AL245R RNA. CONCLUSION:Evidence supports routine GU screening of all individuals with de novo DYRK1A pathogenic variants to ensure optimized clinical management. Collectively, the reported clinical data and loss-of-function studies in Xenopus substantiate a novel role for DYRK1A in GU development.
Project description:DYRK1A is a serine/threonine kinase that has been linked to mental retardation associated with Down syndrome. In the present report, we describe a previously unknown role for DYRK1A in bone homeostasis. The protein expression of DYRK1A increased during osteoclast differentiation. In vitro studies in osteoclasts revealed that DYRK1A inhibited osteoclastogenesis. Whereas DYRK1A phosphorylated and inhibited the osteoclastogenic transcription factor NFATc1, forced expression of NFATc1 induced DYRK1A expression, suggesting a negative feedback loop. Transgenic mice overexpressing DYRK1A by the extent of the increased gene dosage in Down syndrome exhibited significantly reduced bone mass despite the decreased osteoclastogenesis, which is reminiscent of osteoporotic bone phenotype in Down syndrome patients. In these mice, attenuated osteoblast differentiation and function in the presence of extra DYRK1A overrode the effect of impaired osteoclastogenesis. However, impeded osteoclastogenesis in DYRK1A transgenic mice was proven to be beneficial in protecting bone loss induced by inflammation or estrogen deficiency. These results provide novel insight into the role for DYRK1A in bone homeostasis as well as in bone destructive diseases, in which modulation of DYRK1A might be used as a strategy to treat unregulated bone resorption.
Project description:DYRK1A (the dual specificity tyrosine phosphorylation-regulated kinase 1A) plays an important role in body growth and brain physiology. Overexpression of this kinase has been associated with the development of Down syndrome in both human and animal models, whereas single copy loss-of-function of DYRK1A leads to increased apoptosis and decreased brain size. Although more than a dozen of DYRK1A targets have been identified, the molecular basis of its involvement in neuronal development remains unclear. Here we show that DYRK1A and another pro-survival member of the DYRK family, DYRK3, promote cell survival through phosphorylation and activation of SIRT1, an NAD(+)-dependent protein deacetylase that is essential in a variety of physiological processes including stress response and energy metabolism. DYRK1A and DYRK3 directly phosphorylate SIRT1 at Thr(522), promoting deacetylation of p53. A SIRT1 phosphorylation mimetic (SIRT1 T522D) displays elevated deacetylase activity, thus inhibiting cell apoptosis. Conversely, a SIRT1 dephosphorylation mimetic (SIRT1 T522V) fails to mediate DYRK-induced deacetylation of p53 and cell survival. We show that knockdown of endogenous DYRK1A and DYRK3 leads to hypophosphorylation of SIRT1, sensitizing cells to DNA damage-induced cell death. We also provide evidence that phosphorylation of Thr(522) activates SIRT1 by promoting product release, thereby increasing its enzymatic turnover. Taken together, our findings provide a novel mechanism by which two anti-apoptotic DYRK members promote cell survival through direct modification of SIRT1. These findings may have important implications in understanding the molecular mechanisms of tumorigenesis, Down syndrome, and aging.