The effects of tubulin post-translational modifications on the flagellar motility of Trypanosoma brucei

Trypanosoma brucei is a parasitic kinetoplastid that causes African trypanosomiasis and is transmitted to a mammalian host by the tsetse fly (Glossina spp.). T. brucei relies on its flagellar motility to carry out its morphological changes from the procyclic form (predominant in the fly vector) to the bloodstream form (infectious form in mammals) and navigate the bloodstream of its host. The driving structure within the flagellum is the axoneme, which is composed of microtubules and dynein motor proteins. The tubulin code hypothesis suggests that cells regulate microtubule motor protein activity through post-translational modifications (PTMs) of alpha and beta tubulin. However, the regulatory role of tubulin PTMs on the flagellar beat and structural effects on the subpellicular microtubules that dictate T. brucei’s unique morphology remain largely unknown. To characterize the importance of tubulin PTMs, I targeted the enzymes responsible for tubulin acetylation (alpha-tubulin acetyltransferase 1) and detyrosination (vasohibin) using two different strategies. First, we generated knockdowns of both enzymes through a well-developed RNAi system using the pZJM vector which revealed a \u3e50% decrease in transcript and PTM presence. Second, we modified a CRISPR/Cas9 system to knock out both enzymes to compare gene expression and modification presence between cell lines. RT-qPCR and western blot analysis revealed complete absence of PTM enzyme transcripts and PTM presence in whole cell lysate. Confocal immunofluorescence revealed the subpellicular microtubules are highly acetylated and detyrosinated. Cell tracking and sedimentation assays revealed a significant increase in motility and swimming speed in non-acetylated cell lines. However, cells containing heavily tyrosinated microtubules displayed an insignificant motility decrease in comparison to wild type. These results indicate acetylation negatively-regulates the dynein-driven flagellar motility of T. brucei, whereas detyrosination as little to no effect. Additionally, the subpellicular-microtubule array is significantly disrupted in the absence of acetylated alpha tubulin, leading to an elongated trypanosome (\u3e14 μm). Overall, the findings from this study support the evolutionary conservation of tubulin PTMs in simple eukaryotes, such as T. brucei, and thus, can be expanded to similar Leishmania and Trypanosoma species

Light chain 2 is a Tctex-type related axonemal dynein light chain that regulates directional ciliary motility in \u3ci\u3eTrypanosoma brucei\u3c/i\u3e

Flagellar motility is essential for the cell morphology, viability, and virulence of pathogenic kinetoplastids. Trypanosoma brucei flagella beat with a bending wave that propagates from the flagellum’s tip to its base, rather than base-to-tip as in other eukaryotes. Thousands of dynein motor proteins coordinate their activity to drive ciliary bending wave propagation. Dynein-associated light and intermediate chains regulate the biophysical mechanisms of axonemal dynein. Tctex-type outer arm dynein light chain 2 (LC2) regulates flagellar bending wave propagation direction, amplitude, and frequency in Chlamydomonas reinhardtii. However, the role of Tctex-type light chains in regulating T. brucei motility is unknown. Here, we used a combination of bioinformatics, in-situ molecular tagging, and immunofluorescence microscopy to identify a Tctex-type light chain in the procyclic form of T. brucei (TbLC2). We knocked down TbLC2 expression using RNAi in both wild-type and FLAM3, a flagellar attachment zone protein, knockdown cells and quantified TbLC2’s effects on trypanosome cell biology and biophysics. We found that TbLC2 knockdown reduced the directional persistence of trypanosome cell swimming, induced an asymmetric ciliary bending waveform, modulated the bias between the base-to-tip and tip-to-base beating modes, and increased the beating frequency. Together, our findings are consistent with a model of TbLC2 as a down-regulator of axonemal dynein activity that stabilizes the forward tip-to-base beating ciliary waveform characteristic of trypanosome cells. Our work sheds light on axonemal dynein regulation mechanisms that contribute to pathogenic kinetoplastids’ unique tip-to-base ciliary beating nature and how those mechanisms underlie dynein-driven ciliary motility more generally

Timing of seasonal influenza epidemics for 25 countries in Africa during 2010-19: a retrospective analysis.

BACKGROUND: Using country-specific surveillance data to describe influenza epidemic activity could inform decisions on the timing of influenza vaccination. We analysed surveillance data from African countries to characterise the timing of seasonal influenza epidemics to inform national vaccination strategies. METHODS: We used publicly available sentinel data from African countries reporting to the WHO Global Influenza Surveillance and Response FluNet platform that had 3-10 years of data collected during 2010-19. We calculated a 3-week moving proportion of samples positive for influenza virus and assessed epidemic timing using an aggregate average method. The start and end of each epidemic were defined as the first week when the proportion of positive samples exceeded or went below the annual mean, respectively, for at least 3 consecutive weeks. We categorised countries into five epidemic patterns: northern hemisphere-dominant, with epidemics occurring in October-March; southern hemisphere-dominant, with epidemics occurring in April-September; primarily northern hemisphere with some epidemic activity in southern hemisphere months; primarily southern hemisphere with some epidemic activity in northern hemisphere months; and year-round influenza transmission without a discernible northern hemisphere or southern hemisphere predominance (no clear pattern). FINDINGS: Of the 34 countries reporting data to FluNet, 25 had at least 3 years of data, representing 46% of the countries in Africa and 89% of Africa's population. Study countries reported RT-PCR respiratory virus results for a total of 503 609 specimens (median 12 971 [IQR 9607-20 960] per country-year), of which 74 001 (15%; median 2078 [IQR 1087-3008] per country-year) were positive for influenza viruses. 248 epidemics occurred across 236 country-years of data (median 10 [range 7-10] per country). Six (24%) countries had a northern hemisphere pattern (Algeria, Burkina Faso, Egypt, Morocco, Niger, and Tunisia). Eight (32%) had a primarily northern hemisphere pattern with some southern hemisphere epidemics (Cameroon, Ethiopia, Mali, Mozambique, Nigeria, Senegal, Tanzania, and Togo). Three (12%) had a primarily southern hemisphere pattern with some northern hemisphere epidemics (Ghana, Kenya, and Uganda). Three (12%) had a southern hemisphere pattern (Central African Republic, South Africa, and Zambia). Five (20%) had no clear pattern (Côte d'Ivoire, DR Congo, Madagascar, Mauritius, and Rwanda). INTERPRETATION: Most countries had identifiable influenza epidemic periods that could be used to inform authorities of non-seasonal and seasonal influenza activity, guide vaccine timing, and promote timely interventions. FUNDING: None. TRANSLATIONS: For the Berber, Luganda, Xhosa, Chewa, Yoruba, Igbo, Hausa and Afan Oromo translations of the abstract see Supplementary Materials section

Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials

An amendment to this paper has been published and can be accessed via the original article

Designing Inflatable Pontoons as Boat Stabilizers for Dock Safety

Rowers with physical disabilities, adaptive rowers, often use pontoons to help stabilize their boats on the water, however additional problems have been recognized with entering and exiting the boat. The problem of this project is to research and design a device or system of devices to increase stability at the dock while adaptive rowers are getting in and out of the boat. This project addresses how the docking process can be made more efficient and safe through boat stabilization. It further explores how well inflatable pontoons stabilize the boat at the dock in addition to the water. Using a design process, a system was developed where an inflatable pontoon is partially deflated at the dock to provide resistance to the dock, thereby decreasing boat movement. This device helps adaptive rowers’ autonomy at the dock by eliminating the need for assistive personnel to keep their boats steady

Older age is associated with increased early mortality after transjugular intrahepatic portosystemic shunt

Introduction &amp; Aim. The role of age as a predictor of mortality after transjugular intra hepatic portosystemic shunt (TIPS) is controversial. Age has been found to be an important predictor of post-TIPS mortality in some, but not all, studies and is not a component of the MELD score. The purpose of this study was to compare the 90-day survival of subjects with cirrhosis age ≥ 70 years with younger subjects undergoing TIPS.Material and methods. A database of adult with cirrhosis undergoing TIPS from 2003-2011 was analyzed. The primary endpoint was survival 90-days post-TIPS. Survival was analyzed by the Kaplan-Meier method and proportional hazard modeling.Results. 539 subjects met study criteria. 474 (88%) were between the ages of 24-69 and 65 (12%) were age 70-89 years. The groups were similar with respect to the indication for TIPS, mean MELD score and distribution of MELD score. Survival 90-days post-TIPS was 60% in the older cohort compared with 85% in the younger cohort (p < 0.001). Proportional hazards modeling controlled for comorbidities identified age ≥ 70 and MELD score as predictors of early post-TIPS survival. The hazard ratio associated with age increased monotonically, became significant at age ≥ 70 years (HR 3.22; 95% CI 1.81-5.74; p < 0.001) and exceeded the effect of MELD on survival.Conclusions. Age ≥ 70 was associated with reduced survival within 90 days following TIPS. The findings from this study indicate that age is a relevant consideration in assessing the early mortality risk of TIPS

Light chain 2 is a Tctex-type related axonemal dynein light chain that regulates directional ciliary motility in Trypanosoma brucei.

Flagellar motility is essential for the cell morphology, viability, and virulence of pathogenic kinetoplastids. Trypanosoma brucei flagella beat with a bending wave that propagates from the flagellum's tip to its base, rather than base-to-tip as in other eukaryotes. Thousands of dynein motor proteins coordinate their activity to drive ciliary bending wave propagation. Dynein-associated light and intermediate chains regulate the biophysical mechanisms of axonemal dynein. Tctex-type outer arm dynein light chain 2 (LC2) regulates flagellar bending wave propagation direction, amplitude, and frequency in Chlamydomonas reinhardtii. However, the role of Tctex-type light chains in regulating T. brucei motility is unknown. Here, we used a combination of bioinformatics, in-situ molecular tagging, and immunofluorescence microscopy to identify a Tctex-type light chain in the procyclic form of T. brucei (TbLC2). We knocked down TbLC2 expression using RNAi in both wild-type and FLAM3, a flagellar attachment zone protein, knockdown cells and quantified TbLC2's effects on trypanosome cell biology and biophysics. We found that TbLC2 knockdown reduced the directional persistence of trypanosome cell swimming, induced an asymmetric ciliary bending waveform, modulated the bias between the base-to-tip and tip-to-base beating modes, and increased the beating frequency. Together, our findings are consistent with a model of TbLC2 as a down-regulator of axonemal dynein activity that stabilizes the forward tip-to-base beating ciliary waveform characteristic of trypanosome cells. Our work sheds light on axonemal dynein regulation mechanisms that contribute to pathogenic kinetoplastids' unique tip-to-base ciliary beating nature and how those mechanisms underlie dynein-driven ciliary motility more generally