Fig. 2. Xist and Tsix expression during spermatogenesis analysed by strand-specific RTPCR using primer pair JT4/MIX20 (product 230 bp). ES cells serve as Xist and Tsix positive controls, and testes from Xist^trun males serve as negative controls. Hprt serves as RTPCR control. (a) In the male mouse, Xist is expressed in the testis and at very low levels in the heart, while Tsix is detected only in the testis. (b) Expression of both Xist and Tsix is detectable from 11.5 dpc. (c) Germ cell-dependency of Xist and Tsix, with germ cells detected by Dazla RTPCR. Wild-type adult testis, 13.5 dpc wild type and W^e/+ heterozygous testis all express Xist and Tsix, while neither are detectable in adult XOSry and embryonic W^e/W^e testes that lack germ cells as evidenced by the absence of Dazla transcripts.