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The formation of mammalian synapses entails the precise alignment of presynaptic release sites with postsynaptic receptors but how nascent cell–cell contacts translate into assembly of presynaptic specializations remains unclear. Guided by pioneering work in invertebrates, we hypothesized that in mammalian synapses, liprin-? proteins directly link trans-synaptic initial contacts to downstream steps. Here we show that, in human neurons lacking all four liprin-? isoforms, nascent synaptic contacts are formed but recruitment of active zone components and accumulation of synaptic vesicles is blocked, resulting in ‘empty’ boutons and loss of synaptic transmission. Interactions with presynaptic cell adhesion molecules of either the LAR-RPTP family or neurexins via CASK are required to localize liprin-? to nascent synaptic sites. Liprin-? subsequently recruits presynaptic components via a direct interaction with ELKS proteins. Thus, assembly of human presynaptic terminals is governed by a hierarchical sequence of events in which the recruitment of liprin-? proteins by presynaptic cell adhesion molecules is a critical initial step. This paper identifies the evolutionarily conserved liprin-? protein family as key mediators of presynaptic assembly in human neurons. Their recruitment to sites formed by contacting neurons is the critical initial step that triggers presynaptic differentiation.

Differentiation of induced pluripotent stem cells (iPSCs) into specialized cell types is essential for uncovering cell-type specific molecular mechanisms and interrogating cellular function. Transcription factor screens have enabled efficient production of a few cell types; however, engineering cell types that require complex transcription factor combinations remains challenging. Here, we report an iterative, high-throughput single-cell transcription factor screening method that enables the identification of transcription factor combinations for specialized cell differentiation, which we validated by differentiating human microglia-like cells. We found that the expression of six transcription factors, SPI1, CEBPA, FLI1, MEF2C, CEBPB, and IRF8, is sufficient to differentiate human iPSC into cells with transcriptional and functional similarity to primary human microglia within 4 days. Through this screening method, we also describe a novel computational method allowing the exploration of single-cell RNA sequencing data derived from transcription factor perturbation assays to construct causal gene regulatory networks for future cell fate engineering. Liu et al. developed a platform to identify transcription factors (TFs) that turn stem cells into desired cell types. They discovered six key TFs that produce microglia efficiently, enhancing cell differentiation methods.

AbstractSpinal cord injury (SCI) elicits a hostile microenvironment characterized by inflammation, gliosis, and disrupted signaling pathways that collectively impede neural repair. Neural progenitor cells (NPCs) represent a promising regenerative approach, yet their survival and differentiation are often compromised in this setting. Here, we investigated whether engineering NPCs to overexpress the Notch pathway modulator Delta-like non-canonical Notch ligand 1 (DLK1) could overcome these limitations and improve functional outcomes after cervical SCI in rats. NPCs were engineered to express DLK1 under a Pax6 promoter-driven expression system, ensuring elevated DLK1 levels during the progenitor state. Following transplantation of DLK1-overexpressing NPCs or control NPCs, we assessed graft survival, lineage differentiation, behavioral performance, and electrophysiological integration over 12 weeks. DLK1-expressing NPCs exhibited significantly greater retention in the injured spinal cord and showed enhanced neuronal differentiation alongside reduced astrocytic commitment compared to controls. Behavioral tests—including forelimb grip strength and CatWalk gait assessments—demonstrated that DLK1-modified NPCs conferred robust improvements in forelimb motor coordination and overall locomotion. Concordantly, electrophysiological recordings revealed increased motor-evoked potential amplitudes and area-under-the-curve values in animals receiving DLK1-transduced NPC grafts, indicative of strengthened synaptic integration within the host motor circuitry. Graphical Abstract Graphical Abstract

?-propeller protein-associated neurodegeneration (BPAN) is a rare X-linked neurodegenerative disorder caused by mutations in the WDR45 gene, yet its molecular mechanisms remain poorly understood. Here, we identify a role for WDR45 in stress granule (SG) disassembly, mediated through its phase separation with Caprin-1. We demonstrate that WDR45 forms gel-like condensates via its WD5 domain, which competitively displaces G3BP1 from Caprin-1 to promote SG disassembly. BPAN-associated WDR45 mutations impair condensate formation and Caprin-1 interaction, leading to delayed SG disassembly, which correlates with earlier disease onset. WDR45 depletion also exacerbates amyotrophic lateral sclerosis-associated pathological SGs, highlighting its broader relevance to neurodegenerative diseases. Using iPSC-derived midbrain neurons from a BPAN patient, we demonstrate delayed SG recovery, directly linking WDR45 dysfunction to neurodegeneration. These findings establish WDR45 as a critical regulator of SG dynamics, uncover a potential molecular basis of BPAN pathogenesis, and identify therapeutic targets for neurodegenerative diseases associated with SG dysregulation. BPAN is a rare neurodegenerative disease caused by WDR45 mutations. Here, the authors discover that WDR45 can competitively displace G3BP1 from Caprin-1 to promote stress granule disassembly, a function that is disrupted by BPAN-associated WDR45 mutations.

BackgroundPhotoreceptor death leads to inherited blinding retinal diseases, such as retinitis pigmentosa (RP). As disease progression often outpaces therapeutic advances, developing effective treatments is urgent. This study evaluates the efficacy of small peptides derived from pigment epithelium-derived factor (PEDF), which are known to restrict common cell death pathways associated with retinal diseases.MethodsWe tested chemically synthesized peptides (17-mer and H105A) with affinity for the PEDF receptor, PEDF-R, delivered as eye drops to two RP mouse models: rd10 (phosphodiesterase 6b mutation) and RhoP23H/+ (rhodopsin P23H mutation). Additionally, we engineered AAV-H105A vectors for intravitreal delivery in RhoP23H/+ mice. To assess peptide effects in human tissue, we used retinal organoids exposed to cigarette smoke extract, a model of oxidative stress. Photoreceptor survival, morphology and function were evaluated.ResultsHere we show that peptides 17-mer and H105A delivered via eye drops successfully reach the retina, promote photoreceptor survival, and improve retinal function in both RP mouse models. Intravitreal delivery of a AAV-H105A vector delays photoreceptor degeneration in RhoP23H/+ mice up to six months. In human retinal organoids, peptide H105A specifically prevents photoreceptor death induced by oxidative stress, a contributing factor to RP progression.ConclusionsPEDF peptide-based eye drops offer a promising, minimally invasive therapy to prevent photoreceptor degeneration in retinal disorders, with a favorable safety profile. Plain language summaryRetinitis pigmentosa (RP) is a rare inherited condition that causes the gradual death of photoreceptors (light-sensing cells) in the eye, leading to vision loss. There is currently no cure. This study tested a potential treatment using small protein fragments (peptides) from PEDF, a protective protein naturally found in the eye. Researchers delivered these peptides through eye drops or gene therapy in mouse models of RP and to human retinal organoids (lab-grown retina tissue). Mice treated early maintained healthy vision cells, while untreated mice experienced rapid cell loss and vision decline. These results suggest that peptide-based eye drops could be a simple, safe, and effective way to slow vision loss in patients with RP. Bernardo-Colón et al. evaluate small peptides derived from the neurotrophic region of pigment epithelium-derived factor (PEDF) as potential therapeutics for retinitis pigmentosa using mouse models and human retinal organoids. A significant delay in photoreceptor death with eye drop or gene therapy delivery is seen.

miRNA, short non-coding RNA, are rapidly emerging as important regulators in cell homeostasis, as well as potential players in cellular degeneration. The latter has led to interest in them as both biomarkers and as potential therapeutics. Retinal ganglion cells (RGC), whose axons connect the eye to the brain, are central nervous system cells of great interest, yet their study is largely restricted to animals due to the difficulty in obtaining healthy human RGC. Using a CRISPR/Cas9-based reporter embryonic stem cell line, human RGC were generated and their miRNA profile characterized using NanoString miRNA assays. We identified a variety of retinal specific miRNA upregulated in ESC-derived RGC, with half of the most abundant miRNA also detectable in purified rat RGC. Several miRNA were however identified to be unique to RGC from human. The findings show which miRNA are abundant in RGC and the limited congruence with animal derived RGC. These data could be used to understand miRNA’s role in RGC function, as well as potential biomarkers or therapies in retinal diseases involving RGC degeneration.