Canonical Wnt/ß-catenin activity and differential epigenetic marks direct sexually dimorphic regulation of Irx3 and Irx5 in developing mouse gonads.

Members of the Iroquois B (IrxB) homeodomain cluster genes, specifically Irx3 and Irx5, are crucial for heart, limb and bone development. Recently, we reported their importance for oocyte and follicle survival within the developing ovary. Irx3 and Irx5 expression begins after sex determination in the ovary but remains absent in the fetal testis. Mutually antagonistic molecular signals ensure ovary versus testis differentiation with canonical Wnt/ß-catenin signals paramount for promoting the ovary pathway. Notably, few direct downstream targets have been identified. We report that Wnt/ß-catenin signaling directly stimulates Irx3 and Irx5 transcription in the developing ovary. Using in silico analysis of ATAC- and ChIP-Seq databases in conjunction with mouse gonad explant transfection assays, we identified TCF/LEF-binding sequences within two distal enhancers of the IrxB locus that promote ß-catenin-responsive ovary expression. Meanwhile, Irx3 and Irx5 transcription is suppressed within the developing testis by the presence of H3K27me3 on these same sites. Thus, we resolved sexually dimorphic regulation of Irx3 and Irx5 via epigenetic and ß-catenin transcriptional control where their ovarian presence promotes oocyte and follicle survival vital for future ovarian health.

Bovine papillomavirus type 1: from clathrin to caveolin.

Viruses may infect cells through clathrin-dependent, caveolin-dependent, or clathrin- and caveolin-independent endocytosis. Bovine papillomavirus type 1 (BPV1) entry into cells has been shown to occur by clathrin-dependent endocytosis, a pathway that involves the formation of clathrin-coated pits and fusion to early endosomes. Recently, it has been demonstrated that the closely related JC virus can enter cells in clathrin-coated vesicles and subsequently traffic to caveolae, the organelle where vesicles of the caveolin-dependent pathway deliver their cargo. In this study, we use immunofluorescence staining of BPV1 pseudovirions to show that BPV1 overlaps with the endosome marker EEA1 early during infection and later colocalizes with caveolin-1. We provide evidence through the colocalization of BPV1 with transferrin and cholera toxin B that BPVl trafficking may not be restricted to the clathrin-dependent pathway. Disrupting the entry of caveolar vesicles did not affect BPV1 infection; however, we show that blocking the caveolar pathway postentry results in a loss of BPV1 infection. These data indicate that BPV1 may enter by clathrin-mediated endocytosis and then utilize the caveolar pathway for infection, a pattern of trafficking that may explain the slow kinetics of BPV1 infection.