Shorter, S. | bioRxiv Science

bioRxiv2024

Distinct neutrophil effector functions in response to different isolates of Leishmania aethiopica

BackgroundIn Ethiopia, cutaneous leishmaniasis is mainly caused by Leishmania (L.) aethiopica parasites and presents in three main clinical forms. It is still not clear if the host immune response plays a role in the development of these different presentations. Since neutrophils are likely to be one of the first immune cells present at the site of the sand fly bite, we set up an in vitro model of infection of neutrophils with L. aethiopica and assessed neutrophil effector functions. We used freshly isolated clinical isolates and one isolate that has been kept in culture for decades. ResultsOur results showed by flow cytometry that up to a quarter of neutrophils were associated with L. aethiopica; and confocal microscopy demonstrated that all isolates can be internalised. The clinical isolates of L. aethiopica associated more efficiently with neutrophils than the long-term cultured L. aethiopica. At 18hrs, two distinct populations of neutrophils were identified that associated with L. aethiopica, CD15high and CD15low neutrophils. Our results also showed that all parasites induced apoptosis in L. aethiopica-associated neutrophils. Moreover, our results showed that after 2 hrs, L. aethiopica-associated neutrophils upregulated their production of ROS, but to a greater extent with the long-term cultured L. aethiopica. After 18 hrs of incubation, CD15lowparasite+ showed an impaired ability to produce ROS as compared to CD15highparasite+. ConclusionUsing this in vitro model, our results show that different L. aethiopica parasite isolates, most notably long-term cultured parasites, impacted differently on neutrophil effector functions.

immunology↗

bioRxiv2021

Autism-associated CHD8 keeps proliferation of human neural progenitors in check by lengthening the G1 phase of the cell cycle

CHD8 (Chromodomain Helicase DNA Binding Protein 8) is a chromatin remodeler that preferentially regulates expression of genes implicated in early development of the cerebral cortex. De novo mutations (DNMs) in CHD8 are strongly associated with a specific subtype of autism characterized by enlarged foreheads and distinct cranial features. The vast majority of these DNMs are heterozygous loss-of-function mutations with high penetrance for autism. How CHD8 haploinsufficiency alters the normal developmental trajectory of the human cortex is poorly understood and debated. Previous studies in the mammalian developing cortex have shown progressive lengthening of the G1 phase of the cell cycle as neural stem cells transition from proliferative to neurogenic divisions. G1 length has been proposed to operate as a molecular clock that controls timing of this crucial developmental switch. To determine the influence of CHD8 on cell cycle timing, we disrupted one allele of CHD8 in human embryonic stem cells (hESCs), differentiated these cells into neural precursor cells (NPCs), and imaged cell cycle progression of individual CHD8+/- NPCs -- in parallel with their isogenic CHD8+/+ counterparts -- during several rounds of cell division. We found a specific and marked decrease in G1 duration in CHD8+/- NPCs, resulting in an overall shortening of the cell cycle. Consistent with faster progression of CHD8+/- NPCs through G1 and the G1/S checkpoint, we observed increased expression of E cyclins and elevated phosphorylation of Erk in these mutant cells -- two central signalling pathways involved in S phase entry. Together, our findings show dysregulated proliferation of NPCs in a human stem cell model of CHD8 haploinsufficiency and predict enlargement of the neural progenitor pool in CHD8+/- developing brains, a phenotype that may explain macrocephaly in individuals with CHD8 DNMs. Furthermore, our work provides further evidence for a link between autism and cancer and identifies MAPK signaling as a potential therapeutic target for the treatment of this autism subtype.

neuroscience↗