MSJ-1, a Mouse Testis-Specific DnaJ Protein, Is Highly Expressed in Haploid Male Germ Cells and Interacts with the Testis-Specific Heat Shock Protein Hsp70-2

• Published in: Biology of reproduction 2001-08, Vol.65 (2), p.488-495
• Main Authors: BERRUTI, Giovanna, MARTEGANI, Enzo
• Format: Article
• Language: English
• Subjects: Aging; Animals; Biological and medical sciences; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Haploidy; Heat-Shock Proteins - analysis; Heat-Shock Proteins - metabolism; HSP40 Heat-Shock Proteins; HSP70 Heat-Shock Proteins - analysis; HSP70 Heat-Shock Proteins - metabolism; Immunoblotting; Immunohistochemistry; Immunosorbent Techniques; Male; Mammalian male genital system; Meiosis; Mice; Microscopy, Confocal; Microscopy, Fluorescence; Morphology. Physiology; Spermatids - chemistry; Spermatozoa - chemistry; Testis - chemistry; Testis - growth & development; Vertebrates: reproduction
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod65.2.488

The MSJ-1 gene encodes a murine DnaJ homologue that is expressed specifically in adult testis. DnaJ proteins act as cochaperones of Hsp70 proteins in promoting diverse cellular functions. In this study we used recombinant MSJ-1 proteins to produce MSJ-1 antiserum and to carry out in vitro binding assays. In a wide immunoscreening of mouse tissues, affinity-purified MSJ-1 antibodies recognize a unique protein of 30 kDa in male germ cells only. MSJ-1 is able to interact with the testis-specific Hsp70-2 protein and can be coimmunoprecipitated with Hsp70-2 from spermatogenic cells; binding of these two chaperones is consistent with the presence of a third component, which is so far unknown. MSJ-1 is weakly detected in early round spermatids, and its protein content increases in cytodifferentiating spermatids where it colocalizes with the developing acrosome and their postnuclear region. Hsp70-2, which is known to be highly expressed in meiotic cells, shows a subcellular localization in late differentiating spermatids that overlaps that of MSJ-1. MSJ-1 is also maintained in testicular and epididymal spermatozoa, where it sharply demarcates into two distinct cell areas; the outer surface of the acrosomal vesicle, and the centrosomal area. On the whole, our findings are consistent with a role for MSJ-1 in acrosome formation and centrosome adjustment during spermatid development, whereas its presence in mature spermatozoa suggests a special function during fertilization, shortly afterward, or both.