Illumina HiSeq 2500 sequencing
3' adapter sequence TGGAATTCTCGGGTGCCAAG
A small RNA fraction, from 18nt to 30nt in length, was obtained by separating it on a denaturing polyacrylamide gel from total RNA extracted from dissected ovaries. This fraction was used to generate multiplexed libraries with Illumina TruSeq Small RNA library preparation kits (RS-200-0012, RS200-0024, RS-200-036 or RS-200-048) at Fasteris (http://www.fasteris.com). A house protocol based on TruSeq, which reduces 2S RNA (30nt) contamination in the final library, was performed (except for libraries whose GRH number is below #40)