Systematic expression profiling of Dpr and DIP genes reveals cell surface codes in Drosophila larval motor and sensory neurons

Abstract

In complex nervous systems, neurons must identify their correct partners to form synaptic connections. The prevailing model to ensure correct recognition posits that cell surface proteins (CSPs) in individual neurons act as identification tags. Thus, knowing what cells express which CSPs would provide insights into neural development, synaptic connectivity, and nervous system evolution. Here, we investigated expression of dprs and DIPs, two CSP subfamilies belonging to the immunoglobulin superfamily, in Drosophila larval motor neurons (MNs), muscles, glia, and sensory neurons (SNs), using a collection of GAL4 driver lines. We found that dprs are more broadly expressed than DIPs in MNs and SNs, and each examined neuron expresses a unique combination of dprs and DIPs. Interestingly, many dprs and DIPs are not robustly expressed, but instead, are found in gradient and temporal expression patterns. In addition, the unique expression patterns of dprs and DIPs revealed three uncharacterized MNs. This study sets the stage for exploring the functions of dprs and DIPs in Drosophila MNs and SNs and provides genetic access to subsets of neurons.

Neuronal wiring receptors Dprs and DIPs are GPI anchored and this modification contributes to their cell surface organization

“…DIP-α is expressed in a subset of motor neurons called the Is type and localizes to the axon terminals. 23,24,49 Using a Is motor neuron-specific driver, A8-GAL4, 27,52 we confirmed that Myc-DIP-α localizes to puncta in the motor axon terminal (Figure 6A-B'). However, when the GPI anchor was replaced with a TM domain, DIP-α was redistributed and fewer puncta formed, suggesting that clustered presynaptic localization is partially due to the GPI anchor (Figure 6C-D').…”

“…The larval Drosophila neuromuscular junction (NMJ) is an excellent system to examine cell surface proteins, as the circuit is well characterized and easily imaged. Moreover, Dprs and DIPs are endogenously expressed at the larval NMJ, 49 and several Dprs and DIPs are implicated in NMJ development. DIP-α and Dpr10 are known to function in motor axon pathfinding and innervation, 23, 31 and DIP-γ and Dpr11 regulate synaptic growth through the BMP pathway.…”

“…All flies were kept at 25°C except when otherwise noted. Crosses were set at medium density and crawling third instar larvae were dissected as before 49 in Phosphate Buffered Saline (PBS, pH 7.4) on Sylgard dishes. Briefly, after fixing for 30 minutes in 4% paraformaldehyde, fillets were washed 3 times for 10 minutes in PBST (PBS + 0.05% Triton X-100, pH 7.4).…”

Ca2+and cAMP open differentially dilating synaptic fusion pores

“…For these experiments, initial attempts to express Dilp2-FAP and a PKA-R2 RNAi with the motor neuron driver OK6-GAL4 did not produce viable progeny. Therefore, PKA-R2 RNAi was expressed only in type Ib boutons with the Dip-β-GAL4 driver (Wang et al , 2022). Strikingly, the forskolin effect on emptying frequency was eliminated, while kiss and run events were unchanged (Fig.…”

Glial Draper signaling triggers cross-neuron plasticity in bystander neurons after neuronal cell death

“…Most Drosophila larval muscles are innervated by two excitatory glutamatergic MNs, known as type-I big MN (Ib MN) and type-I small MN (Is MN) based on their terminal bouton size (Choi et al, 2004;Lnenicka and Keshishian, 2000). In each hemisegment, ~29 Ib MNs innervate thirty muscle fibers mostly in a one-to-one manner (Hoang and Chiba, 2001;Wang et al, 2022), whereas two Is MNs innervate separate groups of muscles and therefore, are known as the common exciters (Takizawa et al, 2007). Genetic ablation of Is MNs led to an expanded NMJ and an elevated excitatory post-synaptic potential (EPSP) amplitude in healthy bystander Ib MNs Han et al, 2022;Wang et al, 2021).…”