Dissecting the enhancer gene regulatory network in early Drosophila spermatogenesis.

Cellular decision-making and tissue homeostasis are governed by transcriptional networks shaped by chromatin accessibility. Using single-nucleus multi-omics, we jointly profile gene expression and chromatin accessibility in 10,335 cells from the Drosophila testis apical tip. This enables inference of 147 cell type-specific enhancer-gene regulons using SCENIC + . We functionally validate key transcription factors, including ovo and klumpfuss, known from other stem cell systems but not previously linked to spermatogenesis. CRISPR-mediated knockout reveals their essential roles in germline stem cell regulation, and we provide evidence that they co-regulate shared targets through overlapping enhancer elements. We further uncover a critical role for canonical Wnt signaling, with Pangolin/Tcf activating lineage-specific targets in the germline, soma, and niche. The Pan eRegulon links Wnt activity to cell adhesion, intercellular signaling and germline stem cell maintenance. Together, our study defines the enhancer-driven regulatory landscape of early spermatogenesis and reveals conserved, combinatorial mechanisms of niche-dependent stem cell control.