Division of Biological and Biomedical Sciences (BBS), College of Health & Life Sciences (CHLS), Hamad Bin Khalifa University (HBKU), Doha, Qatar.
HBKU Core Labs, Hamad Bin Khalifa University (HBKU): Doha, Qatar.
PLoS Biol. 2023 Jul 24;21(7):e3002210. doi: 10.1371/journal.pbio.3002210. eCollection 2023 Jul.
1p32.3 microdeletion/duplication is implicated in many neurodevelopmental disorders-like phenotypes such as developmental delay, intellectual disability, autism, macro/microcephaly, and dysmorphic features. The 1p32.3 chromosomal region harbors several genes critical for development; however, their validation and characterization remain inadequate. One such gene is the single-stranded DNA-binding protein 3 (SSBP3) and its Drosophila melanogaster ortholog is called sequence-specific single-stranded DNA-binding protein (Ssdp). Here, we investigated consequences of Ssdp manipulations on neurodevelopment, gene expression, physiological function, and autism-associated behaviors using Drosophila models. We found that SSBP3 and Ssdp are expressed in excitatory neurons in the brain. Ssdp overexpression caused morphological alterations in Drosophila wing, mechanosensory bristles, and head. Ssdp manipulations also affected the neuropil brain volume and glial cell number in larvae and adult flies. Moreover, Ssdp overexpression led to differential changes in synaptic density in specific brain regions. We observed decreased levels of armadillo in the heads of Ssdp overexpressing flies, as well as a decrease in armadillo and wingless expression in the larval wing discs, implicating the involvement of the canonical Wnt signaling pathway in Ssdp functionality. RNA sequencing revealed perturbation of oxidative stress-related pathways in heads of Ssdp overexpressing flies. Furthermore, Ssdp overexpressing brains showed enhanced reactive oxygen species (ROS), altered neuronal mitochondrial morphology, and up-regulated fission and fusion genes. Flies with elevated levels of Ssdp exhibited heightened anxiety-like behavior, altered decisiveness, defective sensory perception and habituation, abnormal social interaction, and feeding defects, which were phenocopied in the pan-neuronal Ssdp knockdown flies, suggesting that Ssdp is dosage sensitive. Partial rescue of behavioral defects was observed upon normalization of Ssdp levels. Notably, Ssdp knockdown exclusively in adult flies did not produce behavioral and functional defects. Finally, we show that optogenetic manipulation of Ssdp-expressing neurons altered autism-associated behaviors. Collectively, our findings provide evidence that Ssdp, a dosage-sensitive gene in the 1p32.3 chromosomal region, is associated with various anatomical, physiological, and behavioral defects, which may be relevant to neurodevelopmental disorders like autism. Our study proposes SSBP3 as a critical gene in the 1p32.3 microdeletion/duplication genomic region and sheds light on the functional role of Ssdp in neurodevelopmental processes in Drosophila.
1p32.3 微缺失/重复与许多神经发育障碍表型有关，如发育迟缓、智力障碍、自闭症、大头畸形/小头畸形和发育不良特征。1p32.3 染色体区域包含几个对发育至关重要的基因；然而，它们的验证和表征仍然不足。其中一个基因是单链 DNA 结合蛋白 3（SSBP3），其果蝇同源物称为序列特异性单链 DNA 结合蛋白（Ssdp）。在这里，我们使用果蝇模型研究了 Ssdp 操作对神经发育、基因表达、生理功能和自闭症相关行为的影响。我们发现 SSBP3 和 Ssdp 在大脑中的兴奋性神经元中表达。Ssdp 过表达导致果蝇翅膀、机械感觉刚毛和头部的形态改变。Ssdp 操作还影响幼虫和成年果蝇中神经丛脑体积和神经胶质细胞数量。此外，Ssdp 过表达导致特定脑区的突触密度发生差异变化。我们观察到 Ssdp 过表达果蝇头部的 Armadillo 水平降低，以及幼虫翅膀盘的 Armadillo 和 Wingless 表达减少，表明经典 Wnt 信号通路参与了 Ssdp 的功能。RNA 测序显示 Ssdp 过表达果蝇头部氧化应激相关途径受到干扰。此外，Ssdp 过表达的大脑表现出增强的活性氧 (ROS)、神经元线粒体形态改变、以及上调的分裂和融合基因。Ssdp 水平升高的果蝇表现出焦虑样行为增强、决策力改变、感觉知觉和习惯形成缺陷、异常社交互动和摄食缺陷，这些表型在 pan-neuronal Ssdp 敲低果蝇中得到复制，表明 Ssdp 是剂量敏感的。当 Ssdp 水平正常化时，观察到行为缺陷的部分恢复。值得注意的是，仅在成年果蝇中敲低 Ssdp 不会产生行为和功能缺陷。最后，我们表明 Ssdp 表达神经元的光遗传学操作改变了自闭症相关行为。总的来说，我们的研究结果提供了证据表明，1p32.3 染色体区域中的剂量敏感基因 Ssdp 与各种解剖学、生理学和行为缺陷有关，这些缺陷可能与自闭症等神经发育障碍有关。我们的研究提出 SSBP3 是 1p32.3 微缺失/重复基因组区域中的一个关键基因，并揭示了 Ssdp 在果蝇神经发育过程中的功能作用。
