Spermatid Perinuclear RNA Binding Protein (STRBP)

SPNR is both an RNA-binding protein and a microtubule-associated protein.The deduced 649-amino acid protein contains a central leucine zipper motif, followed by a short basic region and 2 RNA-binding domains. Northern blot analysis detected tissue-specific expression of several Spnr splice variants, including 4 variants in testis. RNase protection assays showed highest expression in testis, lower expression in ovary, thymus, and brain, and weak expression in all other tissues examined. Western blot analysis detected Spnr expression in testis only. Immunofluorescence analysis of adult mouse testis revealed stage-specific Spnr expression in elongating spermatids that coincided with formation of the manchette, a testis-specific microtubular array.