Dynamic expression of long noncoding RNAs reveals their potential roles in spermatogenesis and fertility.

Mammalian reproduction requires that males and females produce functional haploid germ cells through complex cellular differentiation processes known as spermatogenesis and oogenesis, respectively. While numerous studies have functionally characterized protein-coding genes and small noncoding RNAs (microRNAs and piRNAs) that are essential for gametogenesis, the roles of regulatory long noncoding RNAs (lncRNAs) are yet to be fully characterized. Previously, we and others have demonstrated that intergenic regions of the mammalian genome encode thousands of long noncoding RNAs, and many studies have now demonstrated their critical roles in key biological processes. Thus, we postulated that some lncRNAs may also impact mammalian spermatogenesis and fertility. In this study, we identified a dynamic expression pattern of lncRNAs during murine spermatogenesis. Importantly, we identified a subset of lncRNAs and very few mRNAs that appear to escape meiotic sex chromosome inactivation, an epigenetic process that leads to the silencing of the X- and Y-chromosomes at the pachytene stage of meiosis. Further, some of these lncRNAs and mRNAs show a strong testis expression pattern suggesting that they may play key roles in spermatogenesis. Lastly, we generated a mouse knockout of one X-linked lncRNA, Tslrn1 (testis-specific long noncoding RNA 1), and found that males carrying a Tslrn1 deletion displayed normal fertility but a significant reduction in spermatozoa. Our findings demonstrate that dysregulation of specific mammalian lncRNAs is a novel mechanism of low sperm count or infertility, thus potentially providing new biomarkers and therapeutic strategies.

Candida albicans Sap6 amyloid regions function in cellular aggregation and zinc binding, and contribute to zinc acquisition.

Candida albicans is an opportunistic fungal pathogen colonizing the oral cavity. C. albicans secreted aspartic protease Sap6 is important for virulence during oral candidiasis since it degrades host tissues to release nutrients and essential transition metals. We found that zinc specifically increased C. albicans autoaggregation induced by Sap6; and that Sap6 itself bound zinc ions. In silico analysis of Sap6 predicted four amyloidogenic regions that were synthesized as peptides (P1-P4). All peptides, as well as full length Sap6, demonstrated amyloid properties, and addition of zinc further increased amyloid formation. Disruption of amyloid regions by Congo red significantly reduced auotoaggregation. Deletion of C. albicans genes that control zinc acquisition in the ZAP1 regulon, including zinc transporters (Pra1 and Zrt1) and other zinc-regulated surface proteins, resulted in lower autoaggregation and reduction of surface binding of Sap6. Cells with high expression of PRA1 and ZRT1 also showed increased Sap6-mediated autoaggregation. C. albicans ∆sap6 deletion mutants failed to accumulate intracellular zinc comparable to ∆zap1, ∆zrt1, and ∆pra1 cells. Thus Sap6 is a multi-functional molecule containing amyloid regions that promotes autoaggregation and zinc uptake, and may serve as an additional system for the community acquisition of zinc.