Systematic analysis of long intergenic non-coding RNAs in <i>C. elegans</i> germline uncovers roles in somatic growth

Long intergenic non-coding RNAs (lincRNAs) are transcripts longer than 200 nucleotides that are transcribed from non-coding loci yet undergo biosynthesis similar to coding mRNAs. The disproportional number of lincRNAs expressed in testes suggests that lincRNAs are important during gametogenesis, but experimental evidence has implicated very few lincRNAs in this process. We took advantage of the relatively limited number of lincRNAs in the genome of the nematode <i>Caenorhabditis elegans</i> to systematically analyse the functions of lincRNAs during meiosis. We deleted six lincRNA genes that are highly and dynamically expressed in the <i>C. elegans</i> gonad and tested the effects on central meiotic processes. Surprisingly, whereas the lincRNA deletions did not strongly impact fertility, germline apoptosis, crossovers, or synapsis, <i>linc-4</i> was required for somatic growth. Slower growth was observed in <i>linc-4</i>-deletion mutants and in worms depleted of <i>linc-4</i> using RNAi, indicating that <i>linc-4</i> transcripts are required for this post-embryonic process. Unexpectedly, analysis of worms depleted of <i>linc-4</i> in soma versus germline showed that the somatic role stems from <i>linc-4</i> expression in germline cells. This unique feature suggests that some lincRNAs, like some small non-coding RNAs, are required for germ-soma interactions.