The optimal markers for human spermatogonial stem cells (SSCs) are not known. Among the genes recently linked to SSCs in mice and other animals are the basic helix-loop-helix transcription factor ID4 and the orphan G-protein coupled receptor GPR125. While ID4 and GPR125 are considered putative markers for SSCs, they have not been evaluated for co-expression in human tissue. Further, neither the size nor the character of the human spermatogonial populations that express ID4 and GPR125, respectively, are known. A major barrier to addressing these questions is the availability of healthy adult testis tissue from donors with no known reproductive health problems. To overcome this obstacle, we have employed healthy testicular tissue from a novel set of organ donors (n=16; aged 17-68 years) who were undergoing post-mortem clinical organ procurement. Using immunolabeling, we found that ID4 and GPR125 are expressed on partially overlapping spermatogonial populations and are more broadly expressed in the normal adult human testis. Additionally, we found that expression of ID4 remained stable during aging. These findings suggest that ID4 and GPR125 could be efficacious for identifying previously unrecognized human spermatogonial subpopulations in conjunction with other putative human stem cell markers, both in younger and older donors.
The Constantinople as Palimpsest Project is a collaborative, online, interactive, topographically-indexed teaching encyclopedia of the city of Constantinople from AD 330 to 1453. It was created through and is hosted on the web 2.0 tools of ArcGIS online (https://www.arcgis.com). It is curated by Jesse W. Torgerson (College of Letters, Wesleyan University). It was and is created, maintained, and updated by the co-curatorial, editorial, and design work of research students in the Traveler’s Lab at Wesleyan University (https://travelerslab.research.wesleyan.edu). The content was written by undergraduate students as a part of their required coursework for Wesleyan University classes from 2015 to the present. The Constantinople as Palimpsest encyclopedia uses the “Map Notes” feature of ArcGIS online to provide click-able notations on a topical series of digital maps of the historical city of Constantinople during the period in which it was the capitol of the Roman Empire (AD 330-1453). These notations are written by students for students as brief encyclopedia entries on the places, structures, items, and events in the history of Constantinople. The goal of the project is to provide a tool to create a historically-informed mental topography in which to imagine figures in and events of Constantinople in a comprehensive and integrated context.
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