Deletion of Hnrnpk Gene Causes Infertility in Male Mice by Disrupting Spermatogenesis

Abstract

HnRNPK is a heterogeneous nuclear ribonucleoprotein (hnRNP) that has been firmly implicated in transcriptional and post-transcriptional regulation. However, the molecular mechanisms by which hnRNPK orchestrates transcriptional or post-transcriptional regulation are not well understood due to early embryonic lethality in homozygous knockout mice, especially in a tissue-specific context. Strikingly, in this study, we demonstrated that hnRNPK is strongly expressed in the mouse testis and mainly localizes to the nucleus in spermatogonia, spermatocytes, and round spermatids, suggesting an important role for hnRNPK in spermatogenesis. Using a male germ cell-specific hnRNPK-depleted mouse model, we found that it is critical for testicular development and male fertility. The initiation of meiosis of following spermatogenesis was not affected in Hnrnpk cKO mice, while most germ cells were arrested at the pachytene stage of the meiosis and no mature sperm were detected in epididymides. The further RNA-seq analysis of Hnrnpk cKO mice testis revealed that the deletion of hnRNPK disturbed the expression of genes involved in male reproductive development, among which the meiosis genes were significantly affected, and Hnrnpk cKO spermatocytes failed to complete the meiotic prophase. Together, these results identify hnRNPK as an essential regulator of spermatogenesis and male fertility.

Deficiency of IQCH causes male infertility in humans and mice

“…5E), implicating this subset of genes as direct targets. Among the 76 proteins, 21 were RNA-binding proteins (RBPs), 10 of which were suggested to be involved in spermatogenesis (Kuroda et al 2000, Yang et al 2012, Chapman et al 2013, Fukuda et al 2013, Legrand et al 2019, Sechi et al 2019, Liang et al 2021, Tian and Petkov 2021, Wang et al 2022, Xu et al 2022); 8 were involved in mitochondrial function; and 4 were calcium channel activity-related proteins (Fig. 5F).…”

“…We focused on SYNCRIP, HNRNPK, FUS, EWSR1, ANXA7, SLC25A4, and HNRPAB, the loss of which showed the greatest influence on the phenotype of the Iqch KO mice. Specifically, SYNCRIP, HNRNPK, FUS, EWSR1, and HNRPAB are RBPs that are linked to spermatogenesis by controlling mRNA translation or spermatid post-meiotic transcription (Kuroda et al 2000, Fukuda et al 2013, Sechi et al 2019, Tian and Petkov 2021, Xu et al 2022). ANXA7 is a calcium-dependent phospholipid-binding protein that is a negative regulator of mitochondrial apoptosis (Du et al 2015).…”

HnRNPK is essential for Sertoli cells development and male fertility in mice

“…In recent times, hnRNPK has attracted signi cant attention for its involvement in regulation of cell proliferation and differentiation in different tissues [26][27][28] . Notably, our recent study revealed a high expression level of hnRNPK protein in the mouse testis, particularly in SCs and germ cells [17,20] . Male mice with a targeted deletion of the pre-meiotic male germ speci c hnRNPK (Hnrnpk cKO) exhibited reproductive abnormalities and compromised spermatogenesis, ultimately leading to infertility [17] .…”

“…Notably, our recent study revealed a high expression level of hnRNPK protein in the mouse testis, particularly in SCs and germ cells [17,20] . Male mice with a targeted deletion of the pre-meiotic male germ speci c hnRNPK (Hnrnpk cKO) exhibited reproductive abnormalities and compromised spermatogenesis, ultimately leading to infertility [17] . Nevertheless, the exact physiological function and potential mechanism of hnRNPK in SCs with respect to spermatogenesis and male fertility remain unidenti ed.…”

“…The Heterogeneous nuclear ribonucleoproteins (hnRNPs) family, consisting of a diverse group of RNA binding proteins, plays a crucial role in regulating various aspects of nucleic acid metabolism, including mRNA transcription, alternative splicing, RNA stability, and translation regulation [13,14] . Previous studies have shown that certain members of the hnRNP family are highly expressed in male germ cells and SCs and are involved in spermatogenesis [15][16][17][18][19][20] . Among these family members, hnRNPK is a multifunctional protein consisting three K-homology domains (KH1, KH2, and KH3), a K-protein interactive region (KI), an N-terminal bipartite nuclear localization signal (NLS), and a nuclear shuttling domain (KNS).…”