Department of Biological Sciences and Purdue Institute for Integrative Neuroscience, Purdue University, West Lafayette, IN 47907, USA.
Dis Model Mech. 2022 Aug 1;15(8). doi: 10.1242/dmm.049507. Epub 2022 Aug 19.
Dendritic spines are the principal site of excitatory synapse formation in the human brain. Several neurodevelopmental disorders cause spines to develop abnormally, resulting in altered spine number and morphology. Although spine development has been thoroughly characterized in the mammalian brain, spines are not unique to mammals. We have developed a genetic system in zebrafish to enable high-resolution in vivo imaging of spine dynamics during larval development. Although spiny neurons are rare in the larval zebrafish, pyramidal neurons (PyrNs) of the zebrafish tectum form an apical dendrite containing a dense array of dendritic spines. To characterize dendritic spine development, we performed mosaic genetic labeling of individual PyrNs labeled by an id2b:gal4 transgene. Our findings identify a developmental period during which PyrN dendrite growth is concurrent with spine formation. Throughout this period, motile, transient filopodia gradually transform into stable spines containing postsynaptic specializations. The utility of this system to study neurodevelopmental disorders was validated by examining spine development in fmr1 mutant zebrafish, a model of fragile X syndrome. PyrNs in fmr1 mutants exhibited pronounced defects in dendrite growth and spine stabilization. Taken together, these findings establish a genetic labeling system to study dendritic spine development in larval zebrafish. In the future, this system could be combined with high-throughput screening approaches to identify genes and drug targets that regulate spine formation.
树突棘是人类大脑中兴奋性突触形成的主要部位。一些神经发育障碍导致棘突异常发育，导致棘突数量和形态改变。尽管哺乳动物大脑中的棘突发育已经得到了充分的描述，但棘突并不是哺乳动物所特有的。我们在斑马鱼中开发了一种遗传系统，使我们能够在幼虫发育过程中进行高分辨率的体内棘突动态成像。尽管幼虫斑马鱼中的棘突神经元很少，但斑马鱼顶盖的锥体神经元（PyrNs）形成一个含有密集树突棘的顶树突。为了描述树突棘的发育，我们对单个由 id2b:gal4 转基因标记的 PyrNs 进行了嵌合遗传标记。我们的发现确定了一个发育时期，在此期间 PyrN 树突的生长与棘突的形成同时发生。在整个发育过程中，运动的、短暂的丝状伪足逐渐转化为含有突触后特化结构的稳定棘突。该系统在研究神经发育障碍方面的有效性通过检查脆性 X 综合征模型的 fmr1 突变体斑马鱼的棘突发育得到了验证。fmr1 突变体中的 PyrNs 表现出树突生长和棘突稳定的明显缺陷。总之，这些发现建立了一个遗传标记系统来研究幼虫斑马鱼的树突棘发育。在未来，该系统可以与高通量筛选方法相结合，以鉴定调节棘突形成的基因和药物靶点。
