The initial aim of this study on Balb/C mice was to investigate the putative effects on feeding and appetite of isopentenyl pyrophosphate (IPP) and E-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), also known as phosphoantigens (pAgs). HMBPP was recently shown to increase blood meal appetite in malaria mosquitoes. Both IPP and HMBPP are metabolites produced by the normal gut microbiota and apicomplexan parasites such as Plasmodium. To explore potential effects on appetite, male and female mice were treated by gavage with these metabolites, and body mass and gene expression were monitored in brain, stomach and small intestine at 3 h and 7 weeks. Body mass gain did not clearly differ between pAg-treated and water control mice. However, beginning between 4 and 7 weeks, the salivary glands of IPP-treated males began to swell. With the autoimmune Sjögren disease (SjD) in mind, we subsequently investigated the salivary glands after 1, 4 and 7 weeks of IPP treatment. Fast gene set enrichment analysis (FGSEA) of marginal zone B-cell (MZB) transcripts from salivary glands, together with B-cell infiltration in both sexes at 4 weeks, suggested similarities to SjD pathology. Using ELISA, we measured serum autoantibodies against Ro52, Ro60 and La. Multivariate analysis at 7 weeks showed treatment-associated trends: levels of anti-Ro52 and anti-La tended to increase in IPP-treated males, but not in females. Notably, IL-6 serum levels displayed a sex-dependent pattern, and PCA analyses of transcriptomic data from brain, stomach and small intestine—though with some exceptions—also indicated differential responses to pAgs between males and females.

In male mice, the transcription factor A-MYB initiates the transcription of pachytene piRNA genes during meiosis. Here, we report that A-MYB activates the transcription factor Tcfl5 produced in pachytene spermatocytes. Subsequently, A-MYB and TCFL5 reciprocally reinforce their own transcription to establish a positive feedback circuit that triggers pachytene piRNA production. TCFL5 regulates the expression of genes required for piRNA maturation and promotes transcription of evolutionarily young pachytene piRNA genes, whereas A-MYB activates the transcription of older pachytene piRNA genes. Intriguingly, pachytene piRNAs from TCFL5-dependent young loci initiate the production of piRNAs from A-MYB-dependent older loci, ensuring the self-propagation of pachytene piRNAs. A-MYB and TCFL5 act via a set of incoherent feedforward loops that drive regulation of gene expression by pachytene piRNAs during spermatogenesis. This regulatory architecture is conserved in rhesus macaque, suggesting that it was present in the last common ancestor of placental mammals.

In male mice, the transcription factors STRA8 and MEISON initiate meiosis I. We report that STRA8/MEISON activates the transcription factors A-MYB and TCFL5, which together reprogram gene expression after spermatogonia enter into meiosis. TCFL5 promotes the transcription of genes required for meiosis, mRNA turnover, miR-34/449 production, meiotic exit, and spermiogenesis. This transcriptional architecture is conserved in rhesus macaque, suggesting TCFL5 plays a central role in meiosis and spermiogenesis in placental mammals. Tcfl5(em1/em1) mutants are sterile, and spermatogenesis arrests at the mid- or late-pachytene stage of meiosis. Moreover, Tcfl5(+/em1) mutants produce fewer motile sperm.