CEP164C regulates flagellum length in stable flagella

Cilia and flagella are required for cell motility and sensing the external environment and can vary in both length and stability. Stable flagella maintain their length without shortening and lengthening and are proposed to “lock” at the end of growth, but molecular mechanisms for this lock are unknown. We show that CEP164C contributes to the locking mechanism at the base of the flagellum in Trypanosoma brucei . CEP164C localizes to mature basal bodies of fully assembled old flagella, but not to growing new flagella, and basal bodies only acquire CEP164C in the third cell cycle after initial assembly. Depletion of CEP164C leads to dysregulation of flagellum growth, with continued growth of the old flagellum, consistent with defects in a flagellum locking mechanism. Inhibiting cytokinesis results in CEP164C acquisition on the new flagellum once it reaches the old flagellum length. These results provide the first insight into the molecular mechanisms regulating flagella growth in cells that must maintain existing flagella while growing new flagella

Pinning of quantized vortices in helium drop by dopant atoms and molecules

Using a density functional method, we investigate the properties of liquid 4He droplets doped with atoms (Ne and Xe) and molecules (SF_6 and HCN). We consider the case of droplets having a quantized vortex pinned to the dopant. A liquid drop formula is proposed that accurately describes the total energy of the complex and allows one to extrapolate the density functional results to large N. For a given impurity, we find that the formation of a dopant+vortex+4He_N complex is energetically favored below a critical size N_cr. Our result support the possibility to observe quantized vortices in helium droplets by means of spectroscopic techniques.Comment: Typeset using Revtex, 3 pages and 5 figures (4 Postscript, 1 jpeg

CEP164C regulates flagellum length in stable flagella

Cilia and flagella are required for cell motility and sensing the external environment and can vary in both length and stability. Stable flagella maintain their length without shortening and lengthening and are proposed to “lock” at the end of growth, but molecular mechanisms for this lock are unknown. We show that CEP164C contributes to the locking mechanism at the base of the flagellum in Trypanosoma brucei. CEP164C localizes to mature basal bodies of fully assembled old flagella, but not to growing new flagella, and basal bodies only acquire CEP164C in the third cell cycle after initial assembly. Depletion of CEP164C leads to dysregulation of flagellum growth, with continued growth of the old flagellum, consistent with defects in a flagellum locking mechanism. Inhibiting cytokinesis results in CEP164C acquisition on the new flagellum once it reaches the old flagellum length. These results provide the first insight into the molecular mechanisms regulating flagella growth in cells that must maintain existing flagella while growing new flagella

The Time to Act Is Now: Addressing the Challenges of Being a Student, Staff, or Faculty Member at DU While Also Being a Parent to Young Children

The growing number of undergraduate and graduate students who are simultaneously raising children while attending school requires the attention of institutions that want to support their students through the completion of their intended program. Compared to traditional students, these students have greater time and financial restraints, lower graduation rates, and require accommodation, support, and resources to help them maintain their academic standing. This issue is not isolated to just students however. Staff and faculty at academic institutions are also balancing their family and work responsibilities. With an increase in the number of households where one or two adults work full time, more institutional employees are having to negotiate issues of childcare, parental leave, and the ways in which their family responsibilities are perceived by colleagues and employers. In 2017, it was found that many DU community members were struggling with issues of childcare, a child friendly environment at work, and institutional policies related to childcare at the University. These findings led to a study, conducted by the Applied Anthropology class of 2018, aimed at identifying solutions and recommendations for the aforementioned challenges. The study was exploratory and utilized mixed qualitative data collection and analysis methods. The class conducted interviews, surveys, and archival research and used thematic analysis techniques to identify overarching themes that informed the findings and suggestions of this project. Through this research three major needs were identified: clear communication of policies, accommodations for students, and on-site day care. Respondents from this and previous studies at DU identified that classroom policies, policies regarding parental leave, available childcare, and Fisher were being communicated either ineffectively or inaccurately. This has led to confusion, frustration, feelings of job insecurity, and unmet expectations regarding what resources and support DU actually offers parents. There is also a lack of policies in place for student parents, which makes creating schedules and fulfilling academic requirements more challenging for these nontraditional students. The most significant issue identified however was the lack of childcare at DU and the desire for an on-site daycare center. Respondents explained that Denver has a limited number of available, convenient, and affordable daycare options, that Fisher is not meeting their needs, and that they would like to see a facility designed specifically for DU students, staff, and faculty. In response to these challenges, this study suggests the assemblage and dissemination of accurate and clearly communicated childcare related policies, the creation of policies for student parents, and an on-site daycare facility for the DU community. Research and efforts to understand and alleviate these challenges have occurred at DU since the 1970s, and many of the identified needs and desired solutions have not changed over the past fifty years. However, because previous efforts have been powered by those in need of services, the momentum behind each effort has inevitably dissolved. A way to accomplish and sustain these suggestions and actively work towards making DU a more child and family friendly campus is by creating a permanent employee position at DU to handle these issues. This would help centralize information and policies, assist with their clear communication, and focus consistent and sustainable efforts towards helping DU students, staff, and faculty balance their work and family life

INVESTIGATION OF THE DISTAL APPENDAGE PROTEIN CEP164 IN Trypanosoma brucei

Cilia and flagella are highly conserved organelles required for eukaryotic cells to perform sensory and motility functions. They are found in many cells of the human body and are essential for the survival of single celled protozoans. These organelles are nucleated from a basal body after docking to the plasma membrane and are structurally similar to centrioles. Docking of the basal body requires the presence of transitional fibres, which mature from distal appendages on the centriole. These structures rely on the presence of the Cep164 protein to carry out docking and ciliogenesis. Understanding of basal body docking and flagellum length regulation in the Trypanosoma brucei cell is limited and is thought to involve the transitional fibres and surrounding structures. Three diverse Cep164 orthologues in the T. brucei parasite have been identified, but knowledge on their function is limited as functional analysis of these proteins has not been carried out. This project, in collaboration with the TrypTag project used a bioinformatic approach to identify basal body proteins in the T. brucei cell. Candidate proteins were confirmed as basal body components through endogenous tagging and co-localisation studies. The Cep164 orthologues (Cep164A, Cep164B and Cep164C) localised to the distal section of the mature basal body only, with Cep164C showing a cell cycle dependent localisation. Functional analysis of the Cep164 proteins was performed through the generation of inducible RNAi cell lines. Ablation of these proteins showed a functional role of flagellum length regulation, or formation of the transitional fibres and correct basal body docking. This work provides further understanding on the three Cep164 proteins in the T. brucei cell and proposes how the cell regulates its flagellum length

Parental favoritism in a wild bird population

In most taxa with altricial young, offspring solicit food from their parents using a combination of visual and acoustic stimuli, but exactly what these young are communicating, and how selection shapes parental responses, remains unresolved. Theory posits that parents’ interpretation and response to begging should vary with the likelihood of a return on their investment. We tested this in a wild population of prothonotary warblers (Protonotaria citrea), predicting that parents bias food non-randomly toward certain individuals within their broods depending on both the size and number of offspring. We observed parent–offspring interactions and detected strong dependence between brood size and nestling size in shaping parental responses to begging. Larger siblings were less likely to solicit food during feeding events than their smaller siblings, but they received a disproportionate share from parents in nests containing fewer-than-average young, whereas the smaller-than-average nestlings were disproportionately fed in broods containing a greater-than-average number of young. These findings suggest that parents respond to begging signals according to multiple social cues, favoring the stronger siblings with greater survival prospects when few copies of their genes are present, but overtly favoring runts to ensure whole-brood survival when capable of fledging more young. Future experimental studies may shed light on the contributions of parental decision-making and memory, how young nestlings learn in parent–offspring communication systems, and the adaptive significance of these behaviors

A key regulatory protein for flagellum length control in stable flagella

Cilia and flagella are highly conserved microtubule-based organelles that have important roles in cell motility and sensing [1]. They can be highly dynamic and short lived such as primary cilia or Chlamydomonas [2] or very stable and long lived such as those in spermatozoa [3] photoreceptors [4] or the flagella of many protist cells [3,4]. Although there is a wide variation in length between cell types, there is generally a defined length for a given cell type [1]. Many unicellular flagellated and ciliated organisms have an additional challenge as they must maintain flagella/cilia at a defined length whilst also growing new flagella/cilia in the same cell. It is not currently understood how this is achieved