The MacBrain Resource Center (MBRC) rhesus macaque embryonic brain histology datasets

Datasets for the study of developing Non-Human Primate (NHP) brain are scarce. Some of the reasons are related to the financial and technical obstacles that make the production of these datasets logistically challenging. NHP embryos of different and verified developmental ages require timed pregnancies and the maintenance of expensive and highly regulated breeding colonies. Here, we document our efforts to provide digital datasets of rhesus macaque (Macaca mulatta) embryonic brain histological series of sections that can be used and reused for research. These efforts fall well within the primary mission of the MacBrain Resource Center (MBRC, https://medicine.yale.edu/neuroscience/macbrain/mission/), which targets a reduction in the need to sacrifice animals, improved efficiency in the use of resources, the use of male (M) and female (F) specimens to conduct developmental research, and increase archival and sharing of materials for the advancement of neuroscience. First, we describe the already existent tritiated thymidine (³H-TdR) cases in MBRC Collection 1 and the electron microscopy (EM) blocks of Collection 5, which together contain >100 specimens of different developmental ages. We also report methodological details on, as of July 2025, n = 24 histo- and immunohistochemically processed embryonic brains that enrich Collection 6 with thousands of coronal sections stained for n = 38 different cellular and fiber markers. These datasets provide NHP brain histo- and immunohistology for comparison with other species and hence help close a gap in the availability of suitable materials for comparative evolution and neurodevelopmental studies. Through examples, we illustrate how different materials are currently being used in de novo research. Finally, we advocate the absolute need to continue using NHPs in the study of neurodevelopment because of the unparalleled molecular, genetic, and anatomical similarities between these animal models and humans.