Analysis of Long Intergenic Non-coding RNAs’ Roles in the Germline

Long intergenic non-coding RNAs (lincRNAs) are transcripts that are >200 nucleotides long and they are transcribed from loci that do not code for proteins. LincRNAs are highly expressed in mammalian testes as well as in C. elegans’ germline. In both C. elegans and humans some were shown to be bound by PUF proteins to control double-strand breaks repair (DSBR). In humans, over 10,000 lincRNAs are expressed, but only hundreds were found in worms, allowing for systematic knockout analyses.

We engineered worm strains with complete deletion of seven lincRNA genes with significant expression in the gonads. Brood size, embryonic lethality, synapsis, crossover number, bivalent formation and chromatin structure were indistinguishable from WT in all but one deletion strain: drl-1. Drl-1 is also one of the three PUF bound lincRNAs. In this strain we detected reduced progeny and higher germline apoptosis. We are currently testing the role of drl-1 in meiotic DSBR.

A strain lacking linc-4, which is also PUF bound was homozygous inviable. Yet, a second linc-4 deletion strain, harboring a shorter full deletion, was viable. We found that the lethality in the first strain is due to the downstream gene which lies on the same operon. Similar to other operon genes, the viable linc-4D as well as linc-4 knock-down worms grew slower after L1 arrest. Surprisingly, this role in growth rate is due to linc-4 activity in the germline, and not due to somatic expression. These results raise the hypothesis that some lincRNA may gap the soma to germline border.