Precocious neuronal differentiation and disrupted oxygen responses in Kabuki syndrome
Giovanni A. Carosso, … , Loyal A. Goff, Hans T. Bjornsson
Giovanni A. Carosso, … , Loyal A. Goff, Hans T. Bjornsson
Published August 29, 2019
Citation Information: JCI Insight. 2019;4(20):e129375. https://doi.org/10.1172/jci.insight.129375.
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Research Article Genetics Neuroscience

Precocious neuronal differentiation and disrupted oxygen responses in Kabuki syndrome

Abstract

Chromatin modifiers act to coordinate gene expression changes critical to neuronal differentiation from neural stem/progenitor cells (NSPCs). Lysine-specific methyltransferase 2D (KMT2D) encodes a histone methyltransferase that promotes transcriptional activation and is frequently mutated in cancers and in the majority (>70%) of patients diagnosed with the congenital, multisystem intellectual disability disorder Kabuki syndrome 1 (KS1). Critical roles for KMT2D are established in various non-neural tissues, but the effects of KMT2D loss in brain cell development have not been described. We conducted parallel studies of proliferation, differentiation, transcription, and chromatin profiling in KMT2D-deficient human and mouse models to define KMT2D-regulated functions in neurodevelopmental contexts, including adult-born hippocampal NSPCs in vivo and in vitro. We report cell-autonomous defects in proliferation, cell cycle, and survival, accompanied by early NSPC maturation in several KMT2D-deficient model systems. Transcriptional suppression in KMT2D-deficient cells indicated strong perturbation of hypoxia-responsive metabolism pathways. Functional experiments confirmed abnormalities of cellular hypoxia responses in KMT2D-deficient neural cells and accelerated NSPC maturation in vivo. Together, our findings support a model in which loss of KMT2D function suppresses expression of oxygen-responsive gene programs important to neural progenitor maintenance, resulting in precocious neuronal differentiation in a mouse model of KS1.

Authors

Giovanni A. Carosso, Leandros Boukas, Jonathan J. Augustin, Ha Nam Nguyen, Briana L. Winer, Gabrielle H. Cannon, Johanna D. Robertson, Li Zhang, Kasper D. Hansen, Loyal A. Goff, Hans T. Bjornsson

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Figure 4

Transcriptional suppression of metabolic genes in cycling cells and precocious neuronal differentiation in KS1 patient–derived NSPCs.

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Transcriptional suppression of metabolic genes in cycling cells and prec...
(A) scRNA-Seq profiling in patient and healthy control iPSC-derived NSPCs (~5000 cells per patient), with Uniform Manifold Approximation Projection (UMAP) to visualize gene expression differences between cells. (B) NSPCs partitioned by maturation stage as defined by stage-specific marker expression and (C) enriched gene networks, analyzed exclusively among DEGs for each NSPC subset (cycling, transitioning, and differentiating). (D and E) Representative UMAPs annotated by relative expression intensities of NSPC markers, revealing the maturation trajectory from early NSPCs (PAX6+) to differentiating NSPCs (MAP2+). (F) Heatmap comparing density of NSPCs along the maturation trajectory, defined by binned marker expression from earliest (first) to most differentiated (10th) deciles, with KS1 cells disproportionately occupying the most mature bins. (G and H) Protein-level experimental validation of marker expression differences by flow cytometry in NSPCs from KS1 patient and controls, plotting fluorescence intensities of PAX6 and MAP2. Fisher’s exact test (†FDR < 0.05, ††FDR < 0.01, and †††FDR < 0.001).