National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.
PLoS Genet. 2023 Sep 20;19(9):e1010941. doi: 10.1371/journal.pgen.1010941. eCollection 2023 Sep.
Transcription factors (TFs) play critical roles in specifying many aspects of neuronal cell fate including dendritic morphology. How TFs are accurately regulated during neuronal morphogenesis is not fully understood. Here, we show that LIM homeodomain protein MEC-3, the key TF for C. elegans PVD dendrite morphogenesis, is regulated by both alternative splicing and an E3 ubiquitin ligase. The mec-3 gene generates several transcripts by alternative splicing. We find that mbl-1, the orthologue of the muscular dystrophy disease gene muscleblind-like (MBNL), is required for PVD dendrite arbor formation. Our data suggest mbl-1 regulates the alternative splicing of mec-3 to produce its long isoform. Deleting the long isoform of mec-3(deExon2) causes reduction of dendrite complexity. Through a genetic modifier screen, we find that mutation in the E3 ubiquitin ligase EEL-1 suppresses mbl-1 phenotype. eel-1 mutants also suppress mec-3(deExon2) mutant but not the mec-3 null phenotype. Loss of EEL-1 alone leads to excessive dendrite branches. Together, these results indicate that MEC-3 is fine-tuned by alternative splicing and the ubiquitin system to produce the optimal level of dendrite branches.
转录因子（TFs）在指定神经元细胞命运的许多方面起着关键作用，包括树突形态。TFs 在神经元形态发生过程中如何被精确调节还不完全清楚。在这里，我们表明 LIM 同源域蛋白 MEC-3 是秀丽隐杆线虫 PVD 树突形态发生的关键 TF，它受到选择性剪接和 E3 泛素连接酶的调节。mec-3 基因通过选择性剪接产生几个转录本。我们发现，肌肉营养不良疾病基因 muscleblind-like（MBNL）的同源物 mbl-1，是 PVD 树突分支形成所必需的。我们的数据表明，mbl-1 调节 mec-3 的选择性剪接以产生其长型异构体。删除 mec-3 的长型异构体（deExon2）会导致树突复杂性降低。通过遗传修饰筛，我们发现 E3 泛素连接酶 EEL-1 的突变抑制了 mbl-1 表型。eel-1 突变体也抑制 mec-3（deExon2）突变体，但不抑制 mec-3 缺失表型。单独缺失 EEL-1 会导致树突分支过多。这些结果表明，MEC-3 通过选择性剪接和泛素系统进行微调，以产生最佳水平的树突分支。
