Branch-restricted regulation of synaptic organization in MSNs. a) Schematic of the Drosophila adult CNS. A single dorsocentral MSN (in box) is diagrammed in the thoracic ganglia [figure panel modeled after Chen et al. (2006)]. b) MSNs exhibit a highly stereotyped branching pattern with distinct synaptic organization: the anterior branches exhibit uniformly distributed synapses while the posterior branches exhibit interspersed areas of high synaptic density [black arrowheads; figure adapted from Urwyler et al. (2015, 2019)]. The contralateral branch is unique in that it contains high synaptic density throughout the entire length of that specific branch. Local enrichment of the membrane-anchored phosphatase, Prl-1 (orange), in the contralateral branch is required for normal synaptogenesis, terminal arborization, and this increased local synaptic density. c) Prl-1 controls synapse formation in the contralateral branch of MSNs by antagonizing PTEN function and synergizing with the InR-Akt signaling pathway (Urwyler et al. 2019).