Defining dysfunction due to loss of MECP2 in Rett Patient Brain

Rett Syndrome is characterized by a postnatal loss of neurophysiological function and regression of childhood development. Because the syndrome is X-linked and males with MECP2 mutations generally do not survive birth, the study of this syndrome has been complicated by the fact that in female brain, a portion of neurons express wild type MECP2, and another portion express a non-functional allele of MECP2. Therefore, bulk-RNA-sequencing of Rett brain is confounded by the presence of chimerism of neurons for functional MECP2 in neurons. We developed an approach that allows for single-nuclei transcriptional profiling of individual neurons and a direct comparison between neurons that express functional MECP2 with those that express the disease-causing allele. We found that mutant neurons from Rett brain show patterns of aberrant expression of synaptic and metabolic genes, both of which can be detected in in vitro models of Rett Syndrome. We used these resources to identify a role for POU2F1/OCT1 transcription factor in mediating the response to stress due to loss of MECP2, highlighting a potential key molecular regulator of stress in Rett neurons. Together, our new sorting approach enables us to highlight defective molecular and metabolic pathways in Rett brain neurons and suggests that in vitro models could serve as valuable tools to further study this syndrome and potentially for development of novel therapeutics.