Table 1.

Piwi-RNA sequence read libraries

					Percent of mapped reads covering:
Library	Stage		Raw reads (× 1000)	Mapped reads (× 1000)	LINE (19.6)	SINE (7.6)	LTRint (3.0)	LTRter (7.4)
MIWI2 early	16.5 dpc	prenatal	1,940	1,934	30.2	5.2	34.8	17.0
MILI early	16.5 dpc	prenatal	472	470	19.2	5.3	16.3	11.9
MILI late	10 dpp	postnatal	1,327	1,324	7.7	19.9	15.9	13.3

Three piRNA libraries from reference [31] were used for this study (accession numbers: MIWI2 early, GSM319957; MILI early, GSM319956; MILI late, GSM319953). Mapped reads denote the number of RNA reads mapping perfectly at least once to the mouse genome. The percentage of mapped reads mapping to loci of annotated RTEs are shown to the right. In parentheses under the RTE type the fractions of the mouse genome (mm9) occupied by the RTE sequences according to the RepeatMasker [15] annotation at the UCSC Genome Browser [67] are shown.