Goodlett, C. R. | bioRxiv Science

bioRxiv2025

DYRK1A ortholog mbk-1 knockout in Caenorhabditis elegans as a tool for genetics research of developmental disorders

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a dosage sensitive gene located on human chromosome 21 (Hsa21) that contributes to phenotypes associated with developmental disorders like Down syndrome and DYRK1A haploinsufficiency syndrome. Complete genetic knockout of Dyrk1a from conception is embryonic lethal, presenting a barrier in its study. The mbk-1 gene in Caenorhabditis elegans has been identified as an ortholog to mammalian Dyrk1a, and genetic knockout of mbk-1 in C. elegans is not lethal. We hypothesized that deletion of the mbk-1 gene would alter chemosensory function, learning, and motility in C. elegans, and that these phenotypes would be recovered using a humanized DYRK1A replacement at the endogenous mbk-1 locus. Using behavioral preference index assays, analyses of locomotion, and learning in classical conditioning procedures, an mbk-1 knockout strain of C. elegans, EK228, was characterized to identify potential behavioral roles of mbk-1. Preference index assays assessing chemosensory capabilities determined that mbk-1 deletion yielded no detrimental effects. Thrashing and foraging behavior analyses uncovered significant deficits in movement in the EK228 C. elegans, which were not present in two mbk-1 replacement strains containing humanized DYRK1A, suggesting an essential role of mbk-1 in locomotion and motility. Lastly, classical conditioning revealed no significant deficits in the abilities of the EK228 strain in forming associative connections between stimuli. Overall, these results imply functional conservation of the mbk-1/DYRK family kinases, and provide support for the use of humanized replacement strains of C. elegans for the study of mammalian genes. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/686526v2_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@13616f4org.highwire.dtl.DTLVardef@1d2d64org.highwire.dtl.DTLVardef@18f36a9org.highwire.dtl.DTLVardef@14da275_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract (Created with BioRender) C_FIG Article summaryThis work provides insight into evolutionarily conserved functions of the protein kinase DYRK1A, which is linked to developmental disorders including Down syndrome and DYRK1A syndrome. Caenorhabditis elegans with a genetic ablation of the DYRK1A ortholog, mbk-1, were used to examine potential roles in movement, chemosensing, and associative learning and memory, and demonstrated selective deficits in thrashing and foraging locomotion that were not observed in strains with mbk-1 replacement with humanized DYRK1A at the endogenous loci. The findings indicate a role of mbk-1 in C. elegans in adaptive movement, which may provide insight into some of the cellular and neural mechanisms being influenced by DYRK1A. Understanding of the protein kinase DYRK1A may help to elucidate novel therapeutic pathways for developmental disorders.

genetics↗

bioRxiv2025

Genetic analysis of triplicated genes affecting sex-specific skeletal deficits in Down syndrome model mice

Down syndrome (DS) is caused by the triplication of human chromosome 21 (Hsa21), resulting in skeletal insufficiency and altered bone development. DS mouse models recapitulate these deficits, including sexual dimorphism in long bone alterations. Historically, Ts65Dn mice provided much of the insight behind DS-related skeletal deficits with [~]100 trisomic orthologous genes, but there are concerns about genetic fidelity in this model due to included triplication of genes not homologous to Hsa21. A new DS mouse model, Ts66Yah, subtracted the non-Hsa21 homologous trisomic genes from Ts65Dn but has not been evaluated for long bone deficits. Comparing skeletal phenotypes between these models can indicate the contributions of non-Hsa21 trisomic genes and whether the Ts66Yah mouse is relevant as a model for DS-associated skeletal deficits. After assessing individual densitometric, morphometric, and mechanical variables in male and female Ts66Yah femurs at similar ages to when skeletal deficits had been observed in Ts65Dn mice, structural phenotypes were directly compared to those of Ts65Dn mice using a novel multivariate principal components analysis (PCA) method to generate composite scores. Overall, structural and mechanical bone phenotypes of the femur appear milder in Ts66Yah compared to Ts65Dn mice. The appearance of developmental trabecular microarchitecture deficits, but not other abnormalities, were evident earlier in Ts65Dn than Ts66Yah mice. Dyrk1a, a gene triplicated in both models, affected skeletal structure differently in each model, likely through differing gene interactions. The novel component score analysis incorporating PCA detected subclinical phenotypes lost in individual analyses, which could be advantageous when determining overall skeletal deficits. Article summaryMouse models are essential for understanding mechanisms behind human conditions, such as Down syndrome (DS). This study evaluates long bone morphology and strength at key timepoints of development in a new DS mouse model and introduces a novel method derived from principal component analysis (PCA) to compare phenotypes between two different DS models. While both models generally exhibit similar sex-specific deficits, the window of efficacy for genetic and pharmacological intervention on a therapeutic target varies. This illustrates the importance of validating DS phenotypes and mechanisms in multiple mouse models. The method developed could be used in broader scientific applications.

genetics↗