IDENTIFICATION OF A UNIQUE MU-CLASS GLUTATHIONE-S-TRANSFERASE IN MOUSE SPERMATOGENIC CELLS

The fibrous sheath is a major cytoskeletal structure in the principal piece of the mammalian sperm flagellum. Two peptide sequences obtained from a tryptic digest of mouse fibrous sheath proteins exhibited high homology with mu-class glutathione S-transferases (GSTs). Using a DNA probe amplified from degenerate polymerase chain reaction (PCR) prime rs predicted from these two peptide sequences, a similar to 1.1 kb cDN A clone for fibrous sheath component 2 (Fsc2) was isolated which had 8 4% nucleic acid and 89% amino acid sequence identity with a previously reported mu-class human GST gene (hGSTM3; Campbell et al., 1990: J Bi ol Chem 265:4188-9193). Sequences corresponding to those of the two fi brous sheath peptides were present in the protein encoded by the Fsc2 cDNA. Northern analysis with the full length Fsc2 cDNA detected a simi lar to 1.1 kb mRNA in 12 of 15 somatic tissues examined, as well as in testis and isolated spermatogenic cells. However, 5'(nt -96 to 12) or 3' (nt 637 to 808) Fsc2 probes, containing mostly noncoding sequences , detected a similar to 1.1 kb mRNA abundant in testis and isolated sp ermatogenic cells, but absent or present at low levels in somatic tiss ues. Northern analysis with RNA from testes of mice of different postn atal ages and purified spermatogenic cell populations indicated that t his transcript is first present during the meiotic phase of germ cell development. These results suggest that a previously unreported mu-cla ss GST gene (mGSTM5) is expressed at a specific time during the devel opment of spermatogenic cells in the mouse. Immunoblot analysis indica ted that a mu-class GST protein is associated with the fibrous sheath, suggesting that it becomes an integral part of the mouse sperm cytosk eleton. (C) 1995 Wiley-Liss, Inc.