Characterization of a Mouse Model of Börjeson-Forssman-Lehmann Syndrome

Mutations of the transcriptional regulator PHF6 cause the X-linked intellectual disability disorder Börjeson-Forssman-Lehmann syndrome (BFLS), but the pathogenesis of BFLS remains poorly understood. Here, we report a mouse model of BFLS, generated using a CRISPR-Cas9 approach, in which cysteine 99 within the PHD domain of PHF6 is replaced with phenylalanine (C99F). Mice harboring the patient-specific C99F mutation display deficits in cognitive functions, emotionality, and social behavior, as well as reduced threshold to seizures. Electrophysiological studies reveal that the intrinsic excitability of entorhinal cortical stellate neurons is increased in PHF6 C99F mice. Transcriptomic analysis of the cerebral cortex in C99F knockin mice and PHF6 knockout mice show that PHF6 promotes the expression of neurogenic genes and represses synaptic genes. PHF6-regulated genes are also overrepresented in gene signatures and modules that are deregulated in neurodevelopmental disorders of cognition. Our findings advance our understanding of the mechanisms underlying BFLS pathogenesis. Cheng et al. generated a mouse model of Börjeson-Forssman-Lehmann syndrome containing a patient-specific mutation of PHF6. PHF6 knockin mice display cognitive impairments, neuronal hyperexcitability, and seizure susceptibility. PHF6 promotes neurogenic and repressed synaptic genes in the cortex. This study advances understanding of the cellular and molecular underpinnings of BFLS.