Granulin loss of function in human mature brain organoids implicates astrocytes in TDP-43 pathology

Loss of function (LoF) of TAR-DNA binding protein 43 (TDP-43) and mis-localization, together with TDP-43-positive and hyperphosphorylated inclusions, are found in post-mortem tissue of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) patients, including those carrying LoF variants in the progranulin gene (GRN). Modeling TDP-43 pathology has been challenging in vivo and in vitro. We present a three-dimensional induced pluripotent stem cell (iPSC)-derived paradigm-mature brain organoids (mbOrg)-composed of cortical-like-astrocytes (iA) and neurons. When devoid of GRN, mbOrgs spontaneously recapitulate TDP-43 mis-localization, hyperphosphorylation, and LoF phenotypes. Mixing and matching genotypes in mbOrgs showed that GRN-/- iA are drivers for TDP-43 pathology. Finally, we rescued TDP-43 LoF by adding exogenous progranulin, demonstrating a link between TDP-43 LoF and progranulin expression. In conclusion, we present an iPSC-derived platform that shows striking features of human TDP-43 proteinopathy and provides a tool for the mechanistic modeling of TDP-43 pathology and patient-tailored therapeutic screening for FTD and ALS.

Genome-wide CRISPRi/a screens in human neurons link lysosomal failure to ferroptosis

Single-cell transcriptomics provide a systematic map of gene expression in different human cell types. The next challenge is to systematically understand cell-type-specific gene function. The integration of CRISPR-based functional genomics and stem cell technology enables the scalable interrogation of gene function in differentiated human cells. Here we present the first genome-wide CRISPR interference and CRISPR activation screens in human neurons. We uncover pathways controlling neuronal response to chronic oxidative stress, which is implicated in neurodegenerative diseases. Unexpectedly, knockdown of the lysosomal protein prosaposin strongly sensitizes neurons, but not other cell types, to oxidative stress by triggering the formation of lipofuscin, a hallmark of aging, which traps iron, generating reactive oxygen species and triggering ferroptosis. We also determine transcriptomic changes in neurons after perturbation of genes linked to neurodegenerative diseases. To enable the systematic comparison of gene function across different human cell types, we establish a data commons named CRISPRbrain.

Characterization of the Drosophila atlastin interactome reveals VCP as a functionally related interactor

At least 25 genes, many involved in trafficking, localisation or shaping of membrane organelles, have been identified as causative genes for the neurodegenerative disorder hereditary spastic paraplegia (HSP). One of the most commonly mutated HSP genes, atlastin-1, encodes a dynamin-like GTPase that mediates homotypic fusion of endoplasmic reticulum (ER) membranes. However, the molecular mechanisms of atlastin-1-related membrane fusion and axonopathy remain unclear. To better understand its mode of action, we used affinity purification coupled with mass spectrometry to identify protein interactors of atlastin in Drosophila. Analysis of 72 identified proteins revealed that the atlastin interactome contains many proteins involved in protein processing and transport, in addition to proteins with roles in mRNA binding, metabolism and mitochondrial proteins. The highest confidence interactor from mass spectrometry analysis, the ubiquitin-selective AAA-ATPase valosin-containing protein (VCP), was validated as an atlastin-interacting protein, and VCP and atlastin showed overlapping subcellular distributions. Furthermore, VCP acted as a genetic modifier of atlastin: loss of VCP partially suppressed an eye phenotype caused by atlastin overexpression, whereas overexpression of VCP enhanced this phenotype. These interactions between atlastin and VCP suggest a functional relationship between these two proteins, and point to potential shared mechanisms between HSP and other forms of neurodegeneration.

Tsetse fly control and trypanosomiasis in Africa, quo vadis?

National and international efforts to eradicate tsetse fly-borne human and animal trypanosomiasis are critically evaluated, and possible reasons for their failure in many cases are discussed. Some formerly performed campaigns in specific areas with positive results cannot be taken as examples to solve the main problems. In future, a significant reduction of trypanosomiasis cases will be possible to achieve only if a concerted long-term Pan-African approach, based on financial security, the continuity of expert staff, and a well-planned, ecologically sound land use, is generally accepted.

On the immobilization of hartebeest and kob in Upper Volta

24 hartebeests (Alcelaphus buselaphus major), one waterbuck (Kobus defassa) and 16 kobs (Kobus kob) were immobilized during field work in Upper Volta. The use of the newly developed piperidine derivative R 33799 at weight treated dosage levels can be strongly recommended for the immobilisation of hartebeest. In this species the drug produces a sufficient deep analgesia within a reasonable short period for all handling purposes. It is safe, has a wide therapeutic index, can be used in syringes of not more than 1 ml capacity and is quickly reversed by the antidote (nalorphine hydrobromide). No fatalities occurred. The limited number of kobs immobilized did not allow final conclusions to be drawn on the compatibility of the drug for this game species unless the central nervous side effects as described can be explained better and overcome. Further investigation should be undertaken to study the reaction of kob to lower dosages of R 33799 and other combinations of this analgesic with other neuroleptics. Nalorphine hydrobromide proved to be a useful antidote in hartebeest, but less effective in kob.

Demodicosis in African Buffalo (Syncerus caffer caffer) in Botswana

Demodex cafferi causes a nodular skin disease in African buffalo (Syncerus caffer caffer) resulting in eczematous lesions in severely affected animals. Average prevalence in 193 animals was 28%, infection rates being highest in animals 1 to 3 years old and equal in both sexes. A granulomatous reaction occurred in the lumina of infected hair follicles with numerous mites developing in the follicles and associated sebaceous glands. The Demodex in buffalo probably is not transmitted to cattle.

Investigations on the prevalence of trypanosome carriers and the antibody response in wildlife in Northern Botswana

605 buffalo, 60 lechwe, 23 kudu, 23 impala, 15 tsessebe, 22 sable and two reedbuck from Northern Botswana were examined for trypanosome infections by serological and/or parasitological means. The indirect fluorescent antibody test (IFAT), the haematocrit centrifugation technique (HCT) and rodent subinoculation were used. The overall prevalence of patent infection with trypanosomes in buffalo, lechwe and reedbuck was 15,7%. In the case of buffalo and lechwe it was possible to classify their origin into high and low tsetse fly density areas. Serological and parasitological results showed a significantly higher prevalence of infections in areas with a high fly density. Buffalo showed a predominance of infections with Trypanosoma (Duttonella) vivax and T. (Nannomonas) congolense, while in lechwe infections with T. (Trypanozoon) brucei were as frequent. Strains of T. (T.) brucei isolated from buffalo, unlike those from lechwe, failed to infect rodents, 6 strains from lechwe proved sensitive to human serum (Blood Incubation Infectivity Test). Parasitological positive cases, antibody response and the age of buffalo were correlated. The number of patent infections in animals over one year rose to a peak at the age of 2 1/2 years and dropped steadily in the older buffalo. The frequency of positive antibody titres and their levels also increased after the first years of age, reached its peak at the age of four years an then persisted for the rest of the animals' life. Serological tests carried out on serum samples of the remaining species showed that kudu were more frequently infected than impala, tsessebe or sable.