Transcriptomic profiling of murine GnRH neurons reveals developmental trajectories linked to human reproduction and infertility

<b>Rationale:</b> Neurons producing Gonadotropin-Releasing Hormone (GnRH) are essential for human reproduction and have to migrate from nose to brain during prenatal life. Impaired GnRH neuron biology results in alterations of the reproductive axis, including delayed puberty and infertility, with considerable effects on quality of life and metabolic health. Although various genes have been implicated, the molecular causes of these conditions remain elusive, with most patients lacking a genetic diagnosis. <b>Methods:</b> GnRH neurons and non-GnRH cells were FACS-isolated from mouse embryo microdissections to perform high-resolution transcriptomic profiling during mouse embryonic development. We analyzed our dataset to reveal GnRH neuron molecular identity, gene expression dynamics, and cell-to-cell communication. The spatial context of candidate genes was validated using <i>in situ</i> hybridization and spatial transcriptomic analysis. The possible links with human reproduction in health and disease were explored using enrichment analysis on GWAS data and analyzing the genetic burden of patients with congenital GnRH deficiency. <b>Results:</b> GnRH neurons undergo a profound transcriptional shift as they migrate from the nose to the brain and display expression trajectories associating with distinct biological processes, including cell migration, neuronal projections, and synapse formation. We revealed a timely and spatially restricted modulation of signaling pathways involving known and novel molecules, including Semaphorins and Neurexins, respectively. A particular set of genes, whose expression in GnRH neurons timely rises in late developmental stages, showed a strong association with GWAS genes linked with human reproductive onset. Finally, some of the identified trajectories harbor a diagnostic potential for congenital hypogonadism. This is supported by genetic analysis in a large cohort of patients affected by congenital GnRH deficiency, revealing a high mutation burden in patients compared to healthy controls. <b>Conclusion:</b> We charted the landscape of gene expression dynamics underlying murine GnRH neuron embryonic development. Our study highlights new genes in GnRH neuron development and provides novel insights linking those genes with human reproduction.