Rnf6 messenger is preferentially expressed in testicular cells. (A) Northern blot analysis of total RNA prepared from brain (lane1), heart (lane 2), liver (lane 3), intestine (lane 4), lung (lane 5), spleen (lane 6), adult testis (lane 7), testis of a 10-day-old mouse (lane 8), testis of a 20-day-old mouse (lane 9), testis of a 25-day-old mouse (lane 10), testis of a 30-day-old mouse (lane 11), testis of a 2-month-old mouse (lane 12), and freshly isolated Sertoli cells from 3-week-old mice (lane 13). Hybridization was performed in succession with probes for Rnf6 cDNA and for the ubiquitous ribosomal S26 protein cDNA (28). (B) Northern blot analysis of total RNA prepared from germinal fractions purified (≥90% pure) by elutriation centrifugation. Fractions: 1 and 2, spermatozoa and elongated spermatids; 3 and 4, round spermatids; 5 and 6, spermatocytes. Hybridization was performed in succession with probes for cDNAs of the Rnf6 and S26 proteins. (C) Top, in situ hybridization performed on testis section with Rnf6 antisense riboprobe. Bottom, same section stained with Hoechst 33258. The germinal differentiation stage (2) is indicated for each tubule section in roman numerals. Bar, 50 μm.