The molecular characterization of a human testicular proteoglycan, the progenitor of a seminal plasma glycosaminoglycan-bearing peptide, was achieved by cDNA cloning, Its protein core encompasses several domains encountered in various proteins associated with adhesion, migration and cell proliferation. An osteonectin-like domain, a Kazal-like sequence and a 46-amino-acid motif around a Cys-Trp-Cys-Val peptide encountered in cell-surface antigens, cell-adhesion molecules and growth-factor-binding proteins are distributed within the testican protein core. Testican is the progenitor of the unique heparadchondroitin-sulfate-bearing peptide present in human seminal plasma, a feature which might confer additional potentialities to this hybrid proteoglycan.Proteoglycans belong to a versatile protein family (Ruoslahti, 1988) whose potential functions proceed from either the glycosaminoglycan chains they bear or from specific regions of their protein cores (Wight et al., 1991 ; Kjelltn and Lindahl, 1991); they contribute to maintain an essential microenvironment for cell adhesion, migration and proliferation (Wight et al., 1992) through their ability to function as linkers between cells and the extracellular matrix (ECM) and as growth-factor binders (Ruoslahti, 1989;Ruoslahti and Yamaguchi, 1991). ECM components of the testis regulate, in vitro, Sertoli-cell differentiation, testicular-cord formation and germ-cell development, mimicking the original testicular structure (Hadley et al., 1985). Among the components of testicular ECM, only proteoglycans synthesized by rat peritubular cells and Sertoli cells in culture have so far been partially characterized ; while peritubular cells only produce proteochondroitin, Sertoli cells produce proteochondroitin, proteoheparan and a hybrid proteoglycan (Skinner and Fritz, 1985) bearing both chondroitin (CS) and heparan-sulfate (HS) chains. On the basis of the recent isolation of a single and unique glycosaminoglycan-bearing peptide (Bonnet et al., 1992) from human seminal plasma, (S.GP), substituted with both HS and CS, the characterization of its progenitor, speculated to be synthesized in the testis, was achieved by cDNA cloning. Abbreviations. S.GP, glycosaminoglycan-bearing peptide from human seminal plasma; RA-S.GP, reduced and alkylated glycosaminoglycan-bearing peptide from human seminal plasma; ECM, extracellular matrix; CS, chondroitin-sulfate chain; HS heparan-sulfate chain. EXPERIMENTAL PROCEDURES6 X lo5 clones of a human testicular DNA library in Agtll (Clontech) were screened with a 38-nucleotide ~'~P-labelled probe (5'-GTCTCCTGCTCCTCGCAGGACACGGCGCCC-TGCTT-3'), corresponding to the first 13 amino acids identified in the purified reduced and alkylated form of S.GP (RA-S.GP; Bonnet et al., 1992). Hybond N+ (Amersham) filter hybridization was carried out in 6 X NaCVCit. (0.15 M NaCI, 0.015 M sodium citrate), 5 X Denhardt, 0.5% SDS and 250 pg/ml salmon-sperm DNA for 18 h at 42°C. The filters were washed five times at 48°C for 10 min in 4 X NaCKit. and subjected to autorad...

Mutations affecting developmental processes may allow some insight into the complexity of the biological processes involved. In mice, two mutants that affect myelin formation in the central nervous system, jimpy and shiverer, have proved to be useful models for the study of this process. The predominant proteins in myelin are the major myelin proteolipid (PLP) and the myelin basic proteins (MBP), which together account for 80-90% of total myelin proteins. It has recently been shown that the shiverer mutation is located in the MBP structural gene, but the site of the jimpy mutation, which is X-chromosome-linked and may be similar to the sex-linked dismyelinization human disease, Pelizaeus-Merzbacher disease, remains unclear. Here we provide evidence, based on a combined genetic and biochemical approach, that the sex-linked recessive mutation jimpy is located in the structural gene coding for PLP.