Alternative splicing can contribute to functional diversity by creating multiple isoforms of a single gene. Alternative splicing has been widely observed but it is often unknown whether specific isoforms are expressed in unique cell types, and whether they are functionally relevant. Neuron-specific RNA sequencing (RNA-seq) of C. elegans in our lab showed that the conserved membrane protein
mec-2 exhibits unique splicing patterns in specific neurons. We found that the canonical long
mec-2A isoform is expressed in mechanosensory neurons and was regulated by the
mec-8 RNA binding protein, but the non-canonical short
mec-2B isoform was detected in neurons other than mechanosensory neurons. We have recently validated our RNA-Seq results using isoform-specific endogenous fluorescent tags, and determined that the
mec-2B isoform is present in chemosensory neurons as well as mechanosensory neurons. We then tested whether there was a functional role for the
mec-2B isoform in chemosensory neurons. Chemotaxis assays show that
mec-2 mutants have a significant deficiency in chemotaxis to various organic volatile odorants. Using the CRISPR-Cas9 system we forced the expression of one or the other isoform of
mec-2 to see whether there is a difference in behaviors. We found worms expressing only the short
mec-2B isoform can sense odors but not soft touch, while worms expressing long
mec-2 can sense both odors and soft touch. When we re-introduced the long
mec-2 isoform into
mec-8 mutant, the
mec-8 touch insensitivity phenotype was rescued. These experiments therefore demonstrate regulation of
mec-2 alternative splicing resulting in isoforms with differential expression and function in different neuron types.