TRANSCRIPTION AND TRANSLATION OF THE OUTER DENSE FIBER GENE (ODF1) DURING SPERMIOGENESIS IN THE RAT - A STUDY BY IN-SITU ANALYSES AND POLYSOME FRACTIONATION

Transcription and translation of the Odf1 gene encoding the major prot ein of sperm tail outer dense fibers has been investigated in rat sper matogenesis. Odf1 mRNA was detected by in situ hybridization from step 6 round spermatids up to step 17. The protein was detected immunohist ochemically in the cytoplasm of step 7 spermatids up to step 18 and in the sperm tails. The distribution of Odf1 mRNA and the respective tra nscript sizes in polysomes and translationally inactive nonpolysomal r ibonucleoproteinparticles has been investigated by fractionation on su crose gradients and Northern blot analysis of the isolated RNA. In adu lt rat testis about 30% of Odf1 mRNA is associated with the polysomal fraction, but the bulk is stored in translationally inactive ribonucle oprotein particles. In 35-day old rat testis, in which spermatids have reached step 15 of spermiogenesis, only about 10% of Odf1 mRNA can be found in the polysomal fraction. It seems therefore, that translation of Odf1 is greatly enhanced in the maturation phase of spermiogenesis during which a marked increase in diameter of outer dense fibers take s place. In the polysomal fraction, Odf1 transcripts are of heterogene ous size. Northern blot analysis of fractionated RNA digested with RHa seH revealed the presence of both Odf1 transcripts (Burfeind and Hoyer -Fender, 1991: Dev Biol 148:195-204; Burfeind et al., 1993: fur J Bioc hem 216:497-505) on polysomes. While the larger transcript population is heterogeneous in size due to variable polyA-shortening, the smaller transcript population is not deadenylated compared to those present i n nonpolysomal fractions. (C) 1996 Wiley-Liss, Inc.