CRISPR activation of DLX5 drives neural progenitors to the GnRH cell fate

Gonadotropin-releasing hormone (GnRH) neurons regulate the hypothalamic pituitary-gonadal axis and are required for puberty onset and reproductive competence. However, the transcriptional regulators governing GnRH neuron specification and migration remain poorly defined. The homeodomain transcription factor DLX5 is expressed in fetal human GnRH neurons, its expression precedes that of GNRH1 in human pluripotent stem cell (hPSC)-derived GnRH neurons, and in mice it serves as a guidance cue for GnRH neuron migration. We hypothesized that DLX5 may act as an upstream regulator of human GnRH neuron fate specification and migratory capacity. Using CRISPR activation, we upregulated DLX5 during FGF8b-directed differentiation of hPSCs to GnRH neurons via dual SMAD inhibition and Notch inhibition, as previously described. DLX5 activation increased neural progenitor motility (p<0.001), upregulated FGF8 (p<0.05), and induced GABAergic markers including GAD1 and GAD2. Notably, DLX5 activation induced GNRH1 in the absence of exogenous FGF8b (p<0.05), suggesting that, in GnRH neurons, DLX5 regulates FGF8. When combined with exogenous FGF8b, DLX5 activation produced distinct neuronal patterning accompanied by upregulation of extracellular matrix genes such as SPARC, which has been implicated in neurite outgrowth. Collectively, these data indicate that activation of DLX5 promotes GnRH neurogenesis from hPSCs by driving GABAergic fate, inducing FGF8, and remodelling the extracellular matrix.