The tubulin repertoire of Caenorhabditis elegans sensory neurons and its context-dependent role in process outgrowth

Microtubules contribute to many cellular processes, including transport, signaling, and chromosome separation during cell division. They comprise alpha beta-tubulin heterodimers arranged into linear protofilaments and assembled into tubes. Eukaryotes express multiple tubulin isoforms, and there has been a longstanding debate as to whether the isoforms are redundant or perform specialized roles as part of a tubulin code. Here we use the well-char-acterized touch receptor neurons (TRNs) of Caenorhabditis elegans to investigate this question through genetic dissection of process outgrowth both in vivo and in vitro. With single-cell RNA-seq, we compare transcription profiles for TRNs with those of two other sensory neurons and present evidence that each sensory neuron expresses a distinct palette of tubulin genes. In the TRNs, we analyze process outgrowth and show that four tubulins (tba-1, tba-2, tbb-1, and tbb-2) function partially or fully redundantly, whereas two others (mec-7 and mec-12) perform specialized, context-dependent roles. Our findings support a model in which sensory neurons express overlapping subsets of tubulin genes whose functional redundancy varies among cell types and in vivo and in vitro contexts.