Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA 01605, USA.
Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
Genetics. 2023 Apr 6;223(4). doi: 10.1093/genetics/iyad026.
The nematode Caenorhabditis elegans utilizes chemosensation to navigate an ever-changing environment for its survival. A class of secreted small-molecule pheromones, termed ascarosides, play an important role in olfactory perception by affecting biological functions ranging from development to behavior. The ascaroside #8 (ascr#8) mediates sex-specific behaviors, driving avoidance in hermaphrodites and attraction in males. Males sense ascr#8 via the ciliated male-specific cephalic sensory (CEM) neurons, which exhibit radial symmetry along dorsal-ventral and left-right axes. Calcium imaging studies suggest a complex neural coding mechanism that translates stochastic physiological responses in these neurons to reliable behavioral outputs. To test the hypothesis that neurophysiological complexity arises from differential expression of genes, we performed cell-specific transcriptomic profiling; this revealed between 18 and 62 genes with at least twofold higher expression in a specific CEM neuron subtype vs both other CEM neurons and adult males. These included two G protein-coupled receptor (GPCR) genes, srw-97 and dmsr-12, that were specifically expressed in nonoverlapping subsets of CEM neurons and whose expression was confirmed by GFP reporter analysis. Single CRISPR-Cas9 knockouts of either srw-97 or dmsr-12 resulted in partial defects, while a double knockout of both srw-97 and dmsr-12 completely abolished the attractive response to ascr#8. Together, our results suggest that the evolutionarily distinct GPCRs SRW-97 and DMSR-12 act nonredundantly in discrete olfactory neurons to facilitate male-specific sensation of ascr#8.
秀丽隐杆线虫利用化学感觉来导航不断变化的环境以生存。一类分泌的小分子信息素，称为ascarosides，通过影响从发育到行为的各种生物功能，在嗅觉感知中发挥重要作用。ascaroside #8 (ascr#8) 介导性别特异性行为，在雌雄同体中引起回避，在雄性中引起吸引。雄性通过有纤毛的雄性特异性头感器 (CEM) 神经元感知 ascr#8，这些神经元沿背腹和左右轴呈现放射状对称。钙成像研究表明，一种复杂的神经编码机制将这些神经元中的随机生理反应转化为可靠的行为输出。为了测试神经生理学复杂性源于基因差异表达的假设，我们进行了细胞特异性转录组分析；这表明至少有 18 到 62 个基因在特定的 CEM 神经元亚型中表达至少两倍以上，而在其他 CEM 神经元和成年雄性中则表达较少。其中包括两个 G 蛋白偶联受体 (GPCR) 基因，srw-97 和 dmsr-12，它们在 CEM 神经元的非重叠亚群中特异性表达，并且通过 GFP 报告基因分析得到了证实。srw-97 或 dmsr-12 的单个 CRISPR-Cas9 敲除导致部分缺陷，而 srw-97 和 dmsr-12 的双敲除则完全消除了对 ascr#8 的吸引力反应。总之，我们的结果表明，进化上不同的 GPCRs SRW-97 和 DMSR-12 在离散的嗅觉神经元中非冗余地发挥作用，以促进雄性对 ascr#8 的特异性感觉。
