Localization of the germ cell-specific protein, hnRNP G-T, in testicular biopsies of azoospermic men

The increasing interest in the application of in vitro fertilization techniques in human reproduction has led to a wide use of testicular biopsies to identify the presence of spermatogenic foci in testes of azoospermic men. Histopathologic evaluation of these testicular biopsies is required to determine the spermatogenic state with respect to fertility potential and to rule out preinvasive testicular lesions. Heterogeneous nuclear ribonucleoprotein G-T (hnRNP G-T) is a germ cell-specific protein expressed most prominently during meiosis. We studied the usefulness of hnRNP G-T antibody in the evaluation of these biopsies and reasoned that its germ cell-restricted expression pattern might provide a marker to improve accuracy of diagnosis. Testicular biopsies with various spermatogenic impairments were evaluated immunohistochemically for hnRNP G-T expression. In biopsies exhibiting normal spermatogenesis (obstructive azoospermia), hnRNP G-T was localized in meiotic pachytene spermatocytes and round spermatids. Immunostaining was barely detected when maturation was arrested at the spermatocyte level and not at all in cases of Sertoli cell-only syndrome. Biopsies with a mixed histologic phenotype and minute concentrations of spermatogenesis demonstrated strong immunostaining only in tubules with full spermatogenesis. This distribution pattern of hnRNP G-T enabled instant identification of spermatogenic foci. Thus, exploitation of the hnRNP G-T marker, which is expressed preferentially as meiosis proceeds, enhances sensitivity and accuracy of diagnosis in the histologic evaluation of testicular biopsies.