Background The centrosome is the primary site for microtubule nucleation in cells and orchestrates reorganization of the microtubule cytoskeleton during the cell cycle. The activities of the centrosome must be closely aligned with progression of the cell cycle; misregulation of centrosome separation and duplication is a hallmark of cancer. In a subset of cells, including the developing spermatid, the centrosome becomes specialized to form the basal body thereby supporting growth of the axoneme in morphogenesis of cilia and flagella, structures critical for signaling and motility. Mammalian spermatogenesis is an excellent model system to investigate the transformations in cellular architecture that accompany these changes including formation of the flagellum. We have previously identified a leucine rich repeat protein (PPP1R42) that contains a protein phosphatase-1 (PP1) binding site and translocates from the apical nucleus to the centrosome at the base of the flagellum during spermiogenesis. In this manuscript we examine localization and function of PPP1R42 in a ciliated epithelial cell model as a first step in understanding the role of this protein in centrosome function and flagellar formation. Results We demonstrate that PPP1R42 localizes to the basal body in ARPE-19 retinal epithelial cells. Colocalization and co-immunoprecipitation experiments further show that PPP1R42 interacts with γ-tubulin. Inhibition of PPP1R42 with small interfering RNAs (siRNAs) causes accumulation of centrosomes indicating premature centrosome separation. Importantly, the activity of two signaling molecules that regulate centrosome separation, PP1 phosphatase and NEK2 kinase, changes when PPP1R42 is inhibited: PP1 activity is reduced with a corresponding increase in NEK2 activity. Conclusions We have identified a role for the PP1-binding protein, PPP1R42, in centrosome separation in ciliated ARPE-19 cells. Our finding that inhibition of PPP1R42 expression increases the number of centrosomes per cell is consistent with our model that PPP1R42 is a positive regulator of PP1. PPP1R42 depletion reduces the activity of PP1 leading to activation of NEK2, the kinase responsible for phosphorylation of centrosomal linker proteins promoting centrosome separation. This work identifies a new molecule localized to the centrosome and basal body with a role in the complex signaling network responsible for controlling centrosome activities.

Purpose The number of medical science educators, who commit the majority of their time to education‐related duties, is ostensibly on the rise. Given the growing role separation between teaching and biomedical research faculty in medical education, it is timely to examine how institutions communicate their promotion criteria related to educational excellence and scholarship. This study investigates the extent to which medical schools' promotion criteria align with published standards for documenting educational activities. Methods Promotion guidelines from U.S. allopathic and osteopathic medical schools were collected mostly from institutional websites and were systematically analyzed according to a predefined data extraction rubric adapted from previously published standards for documenting educational activities. After 10 researchers each independently reviewed and extracted data from 1/5 of all guidelines, researchers compared their findings in pairs and reached consensus on all identified discrepancies prior to final data submission. Descriptive statistics were used to determine the frequency of cited promotion criteria. Results Promotion‐related documents were retrieved for 110 (59%) of the 185 allopathic and osteopathic U.S. medical schools. Fifteen percent of schools were cited as lacking explicit direction for education focused faculty to attain academic advancement. Across seven education‐related domains, ‘educational measurement and evaluation’ was the least represented with only 37% of schools referencing this domain in their guidelines. The other domains including teaching, curriculum/program development, mentoring/advising, educational leadership/administration, research/scholarship, and service were referenced by at least 59% of schools. Overall, only 20% of schools were judged to have above average or very comprehensive criteria for excellence in education. Conclusions While most medical schools acknowledge education within their promotion criteria, only three fully embraced the educational excellence standards recommended in the literature. These data should be concerning to current teaching faculty who may be evaluated for promotion based on vague and/or incomplete promotion criteria. With greater awareness of how educational excellence is currently documented and how promotion criteria can be improved, more schools may be compelled to embrace change and to follow recommended best practices. Support or Funding Information None This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

BackgroundThe primary cilium is an extension of the cell membrane that encloses a microtubule-based axoneme. Primary cilia are essential for transmission of environmental cues that determine cell fate. Disruption of primary cilia function is the molecular basis of numerous developmental disorders. Despite their biological importance, the mechanisms governing their assembly and disassembly are just beginning to be understood. Cilia growth and disassembly are essential events when cells exit and reenter into the cell cycle. The kinases never in mitosis-kinase 2 (Nek2) and Aurora A (AurA) act to depolymerize cilia when cells reenter the cell cycle from G0.ResultsCoexpression of either kinase with its kinase dead companion [AurA with kinase dead Nek2 (Nek2 KD) or Nek2 with kinase dead AurA (AurA KD)] had different effects on cilia depending on whether cilia are growing or shortening. AurA and Nek2 are individually able to shorten cilia when cilia are growing but both are required when cilia are being absorbed. The depolymerizing activity of each kinase is increased when coexpressed with the kinase dead version of the other kinase but only when cilia are assembling. Additionally, the two kinases act additively when cilia are assembling but not disassembling. Inhibition of AurA increases cilia number while inhibition of Nek2 significantly stimulates cilia length. The complex functional relationship between the two kinases reflects their physical interaction. Further, we identify a role for a PP1 binding protein, PPP1R42, in inhibiting Nek2 and increasing ciliation of ARPE-19 cells.ConclusionWe have uncovered a novel functional interaction between Nek2 and AurA that is dependent on the growth state of cilia. This differential interdependence reflects opposing regulation when cilia are growing or shortening. In addition to interaction between the kinases to regulate ciliation, the PP1 binding protein PPP1R42 directly inhibits Nek2 independent of PP1 indicating another level of regulation of this kinase. In summary, we demonstrate a complex interplay between Nek2 and AurA kinases in regulation of ciliation in ARPE-19 cells.Electronic supplementary materialThe online version of this article (10.1186/s12860-017-0149-5) contains supplementary material, which is available to authorized users.

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