Interrogating interneuron migratory streams in development and neuropathogenesis

Objective

The development of cortical neural networks requires the migration and integration of ventrally-born inhibitory neurons (INs). Many diverse IN subtypes are regionally and temporally specified throughout development, but late-born INs derived from the CGE have recently received increased attention due to their expansion in humans and strong associations with neurodevelopmental disorder (NDD) pathogenesis. Recent studies have found that CGE INs form distinct migratory streams late in gestation and which persist postnatally. One such stream, the EC Stream, delivers INs to the entorhinal cortex up to 1 year after birth in humans, but was not found in macaques. This has implicated late IN migratory streams as a potential human-specific vulnerability in late and postnatal development. Despite this, the inaccessibility of tissue and lack of model systems has made genetic studies difficult. The Knoblich Lab has recently modeled the emergence of late migratory streams in long-term cultures of CGE-patterned organoids derived from human iPSCs. We find that organoid streams undergo chain migration, recapitulating the molecular and cellular phenotypes of the in vivo postnatal EC Stream. I propose to leverage this novel system to identify the transcriptional networks and genetic dependencies that postnatal migratory streams, while interrogating their potential role in neuropathogenesis. To do this, I will conduct multiomic single-cell characterization of early and late migratory IN populations to identify gene regulatory networks (GRNs) driving late migration. I will then conduct a multiplexed loss-of-function screen to identify stream-specific dependencies. Finally, I will leverage multiregional assembloid models of IN migration to interrogate the effects EC Stream perturbation in functional cortical maturation. Together, these objectives will uncover the transcriptomic drivers of the postnatal EC Stream and its previously unknown roles in neurodevelopment and disease.