Damaging DNA variants in PRICKLE genes cause epilepsy from flies to humans. While classic work, primarily in flies, has demonstrated that PRICKLE proteins work with other planar cell polarity proteins to polarize epithelial sheets, the function of PRICKLE proteins in the nervous system is still unclear and may play distinct roles in the nervous system of different organisms. We thus sought to compare and contrast Drosophila prickle with PRICKLE genes in vertebrate systems in order to identify unifying roles across species. First, we find that similar to expression of the mouse Prickles, fly prickle is expressed in a wide variety of CNS neurons, in particular post-mitotic maturing neuroblasts and neurons. However, unlike in the mouse, fly prickle is not enriched in the axon initial segment (AIS) but is broadly distributed across the entire length of the expressing neurons. Second, we find that targeted expression of the prickle-spiny-legs (pksple) isoform in a) glutamatergic neurons or b) a region analogous to the human brain stem in pksple mutant animals suppresses seizures, implicating dysfunction of these neurons in seizure progression. Strikingly, targeting prickle expression to only larval/pupal stages can fully rescue adult seizures, demonstrating that this form of epilepsy can be considered a neurodevelopmental defect such that an abnormality that occurs during development leads to a disorder that is late-onset. Finally, targeting pksple expression exclusively in pksple mutant brains suppresses seizures, demonstrating that, similar to humans, prickle-associated epilepsy arises in the brain. Consistent with this result, removal of the head of pksple mutants also significantly reduces seizures, confirming that brain neuronal dysfunction contributes to fly seizures.
Neurite outgrowth and motility are essential for neuronal development and migration, and they play crucial roles in nervous system formation and axonal regeneration. Cytosolic scaffold proteins are key regulators of these processes, and their dysregulation can lead to neurodevelopmental disorders. In flies, Bruchpilot (Brp), an ortholog of the mammalian active zone scaffold protein ELKS/CAST, is a key factor in synapse formation and maintenance and in neurotransmitter release at chemical synapses. Although mammalian ELKS has been implicated in the growth and motility of both neuronal and non-neuronal cells, the roles of Brp beyond synaptic function remain unclear. Here, we show that Brp contributes to neurite outgrowth and cell motility in dissociated embryonic cell cultures of Drosophila. We detected Brp formed discrete cytoplasmic puncta at early developmental stages in dissociated giant neurons derived from cytokinesis-arrested neuroblasts. During neurite extension and branching, the density of Brp puncta increased over time prior to growth events. Consistently, Brp downregulation impeded cell growth. Brp accumulated in the growth cone, the most motile region of dissociated neurons. Brp was also expressed in non-neuronal cell types, such as highly motile hemocytes, raising the possibility that Brp may have broader context-dependent roles in motile cells. Our findings provide the first evidence of a novel functional link between the Brp scaffold and neuronal growth and cell motility, highlighting the conserved multifunctionality of this scaffold protein.
The muscle of Lawrence (MOL) is a pair of male-specific longitudinal muscles located below the tergite of the fifth abdominal segment in adult Drosophila melanogaster. For the MOL to form, the innervating motor neuron (MOL-inducing neuron: Mind neuron) must express male-specific products of the fruitless (fru) gene, collectively called FruM. We localized a cis-regulatory element of the fru gene that promotes its expression in the Mind neuron to a short genomic interval lying between -4.3 and -5.7 kb upstream of the distal promotor P1 of the fru gene. Comparisons of the sequences of this genomic interval between D. melanogaster, which carries a single MOL pair and D. subobscura, a distant relative that carries two MOL pairs, revealed five conserved stretches, Boxes A-E, tandemly aligned in a single copy (D. melanogaster) or in duplicate (D. subobscura). The Gal4 transgenes carrying Boxes A, B, and E together were able to induce the MOL when used to drive UAS-fruM. Deleting Boxes A, B and E from the genome resulted in loss of the MOL, with occasional formation of vestigial MOL-like muscles. Conversely, reintroducing Boxes A, B, and E into the deletant restored the MOL. We conclude that Boxes A, B, and E comprise a major element that promotes fru expression in the Mind neuron for MOL induction, and we propose to call it the cis-element for MOL induction (ceMOi).
Developmental and epileptic encephalopathies (DEEs) are severe early-onset disorders featuring refractory seizures, abnormal EEGs, and developmental delays. Clinically and etiologically heterogeneous, they include subtypes such as Dravet syndrome and EIMFS. An increasing number are recognized as etiology-specific, with distinct genetic causes corresponding to characteristic phenotypes, highlighting the need for thorough diagnostic evaluation. This study utilized a multidisciplinary diagnostic approach to investigate DEE. In this descriptive case series, the reported novel variants include a PLPBP duplication (c.596dup), an SCN1A insertion (c.3879dup), and an SLC6A1 in-frame deletion (c.943_945del). Bioinformatics and segregation analysis supported their pathogenicity, with each variant linked to a distinct clinical phenotype. The reported novel variants broaden the phenotypic and genotypic spectrum of these disorders and inform clinical management and genetic counseling.
Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by both motor and non-motor dysfunctions. Although the underlying mechanisms are multifactorial, oxidative stress, inflammation, and dopaminergic deficits are central to its pathogenesis. D-Ribose-L-Cysteine (DRLC), a glutathione (GSH) precursor, has shown potential protective effects in models of human diseases. This study investigates the neuroprotective effects of DRLC against rotenone (ROT)-induced PD-like pathology in Drosophila melanogaster. Adult Drosophila (Harwich strain) were segregated into five groups and administered either a control diet, 500 μM ROT, or ROT in conjunction with DRLC (125, 250, or 500 μM) for a duration of 14 days. Longevity, locomotor, and olfactory assays were performed. Biochemical analysis of dissected fly brains assessed redox status markers, pro-inflammatory cytokines, apoptosis indicators, neurotransmitter levels, and dopa-decarboxylase (DDC) gene expression. ROT exposure reduced survival by 25%, significantly impaired motor and olfactory functions, increased reactive oxygen species (ROS) levels, disrupted neurotransmission, elevated TNF-α and caspase-3 levels, and downregulated DDC gene expression. DRLC co-treatment improved survival and motor performance in a dose-dependent manner while also decreasing ROS, TNF-α, and caspase-3 expression. DRLC restored dopamine and acetylcholine levels and GSH concentrations compared to the ROT-only group. DRLC also upregulated DDC gene expression. In conclusion, DRLC mitigates ROT-induced PD-like neurotoxicity in Drosophila through antioxidant, anti-inflammatory, and anti-apoptotic mechanisms, possibly via enhanced GSH synthesis and dopamine regulation. Although we cannot fully rule out the possibility that DRLC affected rotenone ingestion or feeding behavior, the fact that ROT-dependent phenotypes persisted in the absence of DRLC and were only selectively reversed by DRLC suggests a neuroprotective effect.
