FOXP1 differentially regulates murine vasopressin and oxytocin neuron development, disproportionately affecting OXT neurons

Hypothalamic arginine vasopressin (AVP) and oxytocin (OXT) magnocellular neurons (MCNs) are vital for fluid balance, social behavior, and stress response. Despite sharing a common developmental lineage, the specific transcription factors driving their distinct specification remain largely unknown. Understanding these developmental pathways is critical for addressing conditions linked to AVP or OXT dysregulation, such as diabetes insipidus or autism spectrum disorders. This study aimed to identify key transcriptional regulators involved in the differential development of these crucial neuron populations.

Researchers employed a multi-modal approach, beginning with gene regulatory network analysis on published single-cell RNA-sequencing data from the developing mouse hypothalamus. This identified candidate transcription factors for differential MCN specification. They then used computational cell fate mapping to model developmental gene expression dynamics. Further, in silico analysis predicted binding sites for specific factors on Avp and Oxt promoters. An in vitro reporter assay was used to validate these regulatory interactions. Finally, heterozygous FOXP1 knockout mice were generated and analyzed to assess the in vivo role of FOXP1 in AVP and OXT neuron abundance.

Gene regulatory network analysis identified RORA, EBF3, FOXP1, FOXP2, and BCL11B as candidate transcription factors. Computational cell fate mapping revealed enrichment of EBF3 and BCL11B in the Avp lineage, while FOXP1 and FOXP2 were enriched in the Oxt lineage. In silico analysis predicted binding sites for FOXP1 and FOXP2 on both Avp and Oxt genomic promoters, which was subsequently confirmed by an in vitro reporter assay demonstrating their regulatory activity. The most significant finding came from genetic manipulation:

Heterozygous FOXP1 knockout mice exhibited a significant reduction in both AVP and OXT neuron abundance. Importantly, OXT neurons were disproportionally affected compared to AVP neurons in these knockout animals. This indicates a critical and differential role for FOXP1 in MCN development.