A MYT1L Syndrome mouse model recapitulates patient phenotypes and reveals altered brain development due to disrupted neuronal maturation

Human genetics have defined a new autism-associated syndrome caused by loss-of-function mutations in MYT1L , a transcription factor known for enabling fibroblast-to-neuron conversions. However, how MYT1L mutation causes autism, ADHD, intellectual disability, obesity, and brain anomalies is unknown. Here, we develop a mouse model of this syndrome. Physically, Myt1l haploinsufficiency causes obesity, white-matter thinning, and microcephaly in the mice, mimicking clinical phenotypes. During brain development we discovered disrupted gene expression, mediated in part by loss of Myt1l gene target activation, and identified precocious neuronal differentiation as the mechanism for microcephaly. In contrast, in adults we discovered that mutation results in failure of transcriptional and chromatin maturation, echoed in disruptions in baseline physiological properties of neurons. This results in behavioral anomalies including hyperactivity, muscle weakness and fatigue, and social alterations with more severe phenotypes in males. Overall, our findings provide insight into the mechanistic underpinnings of this disorder and enable future preclinical studies.