A novel de novo heterozygous DYRK1A mutation causes complete loss of DYRK1A function and developmental delay

Abstract

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-offunction of the kinase activity of DYRK1A and may contribute to the developmental delay observed in the patient. Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a member of the highly conserved DYRK kinase family that belongs to the CMGC kinase superfamily. DYRK1A phosphorylates serine and threonine residues on its target substrates and autophosphorylates its own tyrosine residues 1,2. Due to the variety of proteins that DYRK1A phosphorylates, it plays essential roles in a wide range of cellular signalling pathways and processes, including neurogenesis, neuronal differentiation and proliferation 3 , synaptic transmission 4 , cell cycle 5 , apoptosis 6 , splicing 7 , and RNA transcription 8. Many of these pathways and processes regulate neurological

Integrative approach to interpret DYRK1A variants, leading to a frequent neurodevelopmental disorder

“…Phosphorylated Tyr321 DYRK1A was visualized using rabbit anti-phospho-HIPK2 antibody (1:1000) (Widowati et al , 2018) and normalized by the level of total DYRK1A protein, visualized using rabbit anti-DYRK1A antibody (1:1000; Cohesion Biosciences, #CPA1357). Kinase activity was investigated by co-transfecting DYRK1A plasmids and MAPT in HEK293 cells (MAPT_OHu28029C_pcDNA3.1(+)-C-HA from geneScript), adapted from what previously done (Lee et al , 2020b). DYRK1A, MAPT and pMAPT (Thr212) were visualized using anti-FLAG antibody, anti-TAU-5 antibody (LAS-12808 Thermofisher) and anti-pTAU-T212 antibody (44-740G Thermofisher) and their level normalized with GAPDH (MAB374 Merck).…”

“…Few years after, the first frameshift variant was described in a patient with similar features (Courcet et al , 2012). The clinical spectrum associated with DYRK1A pathogenic variants ( MRD7 for Mental Retardation 7 in OMIM ) was further refined with the publication of additional patients, presenting suggestive facial dysmorphism, severe speech impairment and feeding difficulty, while epilepsy and prenatal microcephaly were not always present (Bronicki et al , 2015; Blackburn et al , 2019a; van Bon et al , 2011, 2016; O’Roak et al , 2012; Courcet et al , 2012; Okamoto et al , 2015; Iglesias et al , 2014; Ruaud et al , 2015; Ji et al , 2015; Rump et al , 2016; Luco et al , 2016; Murray et al , 2017; Evers et al , 2017; Lee et al , 2020a; Dang et al , 2018; Qiao et al , 2019; Ernst et al , 2020; Tran et al , 2020; Møller et al , 2008; Fujita et al , 2010; Oegema et al , 2010; Yamamoto et al , 2011; Valetto et al , 2012; Kim et al , 2017; Meissner et al , 2020; Matsumoto et al , 1997). Pathogenic variants were also identified in cohorts of individuals with ASD (O’Roak et al , 2012), but all have ID (Earl et al , 2017).…”

DYRK1a Inhibitor Mediated Rescue of Drosophila Models of Alzheimer’s Disease-Down Syndrome Phenotypes

“…Due to human DYRK1A and fly mnb sharing 82% amino acid identity which is even greater the kinase domains, many of the phenotypes and pharmacological sensitivity is conserved across species. For instance, conserved loss of function mutations reduced brain size in humans and flies, hence the name minibrain ( Hämmerle et al, 2003 ; Lee et al, 2020a ). With the DYRK1A-E396term being demonstrated to be loss of function mutation as it decreases the canonical phosphorylation of human Tau by DYRK1A.…”

A novel inhibitor rescues cerebellar defects in a zebrafish model of Down syndrome–associated kinase Dyrk1A overexpression

“…Here a number of potent pharmacological Dyrk kinase inhibitors such as Harmine, ProINDY or Leucettine L41 have been identified and successfully tested in vitro and in vivo to rescue behavioral or cognitive defects. Although haploinsufficiency of Dyrk1A also causes severe neurological symptoms and developmental delay (15)(16)(17), these pharmacological inhibitors, when dosed well, appear to rescue Dyrk1A hyperactivity phenotypes only down to the wild type level. Some common first generation Dyrk1A inhibitors like Harmine produce significant side effects such as inhibiting monoamine J o u r n a l P r e -p r o o f oxidase (18,19).…”