HEN1 is required for piRNA stability.

(A) The piRNA read counts were normalized, each dot represents the abundance of an individual piRNA analyzed from HEN1 MO vs. control MO. piRNAs that showed a depletion ≥ two fold are indicated in green. The data represent the mean of two independent biological replicates. (B) The Relative abundance of Nematostella piRNAs between HEN1 MO and control MO, in HEN1 MO the piRNA read counts were significantly reduced (P < .0001, Wilcoxon Signed-Rank Test). (C) Scatter plot presenting the change in normalized read counts of individual piRNAs upon periodate treatment. ~90% of piRNAs remained unchanged in abundance upon periodate treatment (indicated in blue). (D) The percentage of nucleotide length distribution plotted for piRNAs reads mapped at 22–28 nt in length. In HEN1 MO data the percentage of 27 and 28 nt sizes was reduced (indicated with red arrows) compared to the control.