Ten simple rules for students navigating summer research experiences for undergraduates (REU) programs: From application to program completion.

For many emerging scientists, research experiences for undergraduates (REU) programs are an important gateway to graduate school and a career in science, technology, engineering, and mathematics (STEM). REUs provide guided mentorship and learning experiences in a summer-long program where students develop research skills, build scientific knowledge, and strengthen their scientific identity. While the benefits of REUs are abundant, the process is not always easy to navigate, especially for students who come from first-generation and/or low-income (FLI) backgrounds. This paper provides two-fold guidance for undergraduate students interested in participating in REUs. Rules 1 to 5 focus on demystifying the application process from beginning to end, and Rules 6 to 10 guide students who are on the other side of the application process. Thus, this paper will be most helpful for undergraduate students who are either considering applying for an REU or have been accepted into one and want to learn more about what to expect. It can also be a shareable resource for faculty, staff, and mentors who work directly with STEM undergraduates.

Postmitotic centriole disengagement and maturation leads to centrosome amplification in polyploid trophoblast giant cells.

DNA replication is normally coupled with centriole duplication in the cell cycle. Trophoblast giant cells (TGCs) of the placenta undergo endocycles resulting in polyploidy but their centriole state is not known. We used a cell culture model for TGC differentiation to examine centriole and centrosome number and properties. Before differentiation, trophoblast stem cells (TSCs) have either two centrioles before duplication or four centrioles after. We find that the average nuclear area increases approximately eight-fold over differentiation, but most TGCs do not have more than four centrioles. However, these centrioles become disengaged, acquire centrosome proteins, and can nucleate microtubules. In addition, some TGCs undergo further duplication and disengagement of centrioles, resulting in substantially higher numbers. Live imaging revealed that disengagement and separation are centriole autonomous and can occur asynchronously. Centriole amplification, when present, occurs by the standard mechanism of one centriole generating one procentriole. PLK4 inhibition blocks centriole formation in differentiating TGCs but does not affect endocycle progression. In summary, centrioles in TGC endocycles undergo disengagement and conversion to centrosomes. This increases centrosome number but to a limited extent compared with DNA reduplication.

Cyclin-dependent kinase control of motile ciliogenesis.

Cycling cells maintain centriole number at precisely two per cell in part by limiting their duplication to S phase under the control of the cell cycle machinery. In contrast, postmitotic multiciliated cells (MCCs) uncouple centriole assembly from cell cycle progression and produce hundreds of centrioles in the absence of DNA replication to serve as basal bodies for motile cilia. Although some cell cycle regulators have previously been implicated in motile ciliogenesis, how the cell cycle machinery is employed to amplify centrioles is unclear. We use transgenic mice and primary airway epithelial cell culture to show that Cdk2, the kinase responsible for the G1 to S phase transition, is also required in MCCs to initiate motile ciliogenesis. While Cdk2 is coupled with cyclins E and A2 during cell division, cyclin A1 is required during ciliogenesis, contributing to an alternative regulatory landscape that facilitates centriole amplification without DNA replication.