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The segregation of embryonic endomesoderm into separate endoderm and mesoderm fates is not well understood in deuterostomes. Using sea urchin embryos, we showed that Notch signaling initiates segregation of the endomesoderm precursor field by inhibiting expression of a key endoderm transcription factor in presumptive mesoderm. The regulatory circuit activated by this transcription factor subsequently maintains transcription of a canonical Wnt (cWnt) ligand only in endoderm precursors. This cWnt ligand reinforces the endoderm state, amplifying the distinction between emerging endoderm and mesoderm. Before gastrulation, Notch-dependent nuclear export of an essential ß-catenin transcriptional coactivator from mesoderm renders it refractory to cWnt signals, insulating it against an endoderm fate. Thus, we report that ' endomesoderm segregation is a progressive process, requiring a succession of regulatory interactions between cWnt and Notch signaling.

Sexually transmitted infection (STI) in lesbian and bisexual women is a relatively unexplored topic, particularly for women from low- and middle-income countries. Despite perceptions that women who have sex with women (WSW) are at negligible risk of contracting STI, existing research demonstrates that WSW do become infected with STI. Given the opposition between assumptions of invulnerability and the observed risks, we explored how WSW would respond to symptoms of STI (i.e., wait until symptoms passed, see a medical doctor, and inform sexual partners). We used data collected as part of a collaboration between academic researchers and community-based LGBTQ organizations in Botswana, Namibia, South Africa, and Zimbabwe. Chi-squared tests were used to test whether participants’ responses to hypothetical STI symptoms varied in relation to several intrapersonal, interpersonal, and structural factors. Multivariable logistic regression (backward) was used to assess whether these variables were independently associated with women’s responses. Most women would be proactive in response to potential STI symptoms and would see a medical doctor. However, most women would not inform their sexual partner of symptoms of STI. Findings demonstrate several intrapersonal, interpersonal, and structural factors that influence WSW’s health agency, and show a clustering of high-risk factors among women who would not be proactive about their health. Our findings suggest the need for improved health and health care of WSW in Southern Africa.