A novel testicular
protein designated
sertolin was cloned. The full-length
sertolin cDNA consists of 853 base pairs with an open reading frame of 381 base pairs coding for a 127-amino
acid polypeptide that shares limited identities with antaxin/josephin and
thrombospondin proteins.
Sertolin (calculated molecular mass, 13,759 daltons) has two
mRNA transcripts of 2.3 and 1 kilobase. A 22-amino
acid peptide based on the deduced amino acid sequence of
sertolin (NH(2)-KKEHFNLFKAASVSHLVQVVPQ) was synthesized and used for polyclonal antibody production. Immunoblot analysis detected a 17-kDa immunoreactive band in the Sertoli cell cytosol. Using Sertoli-germ cell cocultures,
sertolin expression was found to be reduced by as much as 5-fold at the time when germ cells attach onto Sertoli cells but preceding the establishment of specialized inter-Sertoli-germ cell junctions. Neither FSH nor
17beta-hydroxy-5alpha-androstan-3-one was able to affect
sertolin expression, whereas
estradiol-17beta and
progesterone induced a significant increase in Sertoli cell
sertolin expression in vitro. In addition,
interleukin-1alpha, a germ cell-derived
cytokine, was also able to elicit a transient but significant increase in Sertoli cell
sertolin expression.
Sertolin expression was also shown to increase with testicular development and is likely to be associated with the onset of spermatogenesis. In addition,
sertolin expression increased in the testis when generalized
inflammation was induced in adult rats by injection of fermented yeast. These results show that
sertolin will be useful in characterizing cell-cell interactions in the testis.