Dynamic paraspeckle component localisation during spermatogenesis

Abstract

Expression profiles and subcellular localisations of core Drosophila behaviour/human splicing (DBHS) proteins (PSPC1, SFPQ and NONO) and NEAT1, a long noncoding RNA (lncRNA), are investigated in developing and adult mouse testes. Core DBHS proteins are markers for the distinct subnuclear domain termed paraspeckles, while a long NEAT1 isoform scaffold facilitates paraspeckle nucleation. Paraspeckles contain many proteins (>40) and are broadly involved in RNA metabolism, including transcriptional regulation by protein sequestration, nuclear retention of A-to-I edited RNA transcripts to regulate translation and promoting survival during cellular stress. Immunohistochemistry reveals cell-specific profiles for core DBHS paraspeckle protein expression, indicating their functional diversity. PSPC1 is an androgen receptor co-activator, and it is detected in differentiating Sertoli cell nuclei from day 15 onwards, as they develop androgen responsiveness. PSPC1 is nuclear in the most mature male germ cell type present at each age, from foetal to adult life. In adult mouse testes, PSPC1 and SFPQ are present in Sertoli cells, spermatocytes and round spermatids, while the NEAT1 lncRNA appears in the punctate nuclear foci delineating paraspeckles only within Leydig cells. Identification of NEAT1 in the cytoplasm of spermatogonia and spermatocytes must reflect non-paraspeckle-related functions. NONO was absent from germ cells but nuclear in Sertoli cells. Reciprocal nuclear profiles of PSPC1 and γ-H2AX in spermatogenic cells suggest that each performs developmentally regulated roles in stress responses. These findings demonstrate paraspeckles and paraspeckle-related proteins contribute to diverse functions during testis development and spermatogenesis.