Biology subjects

Herath, M.

Publications and source records attributed to Herath, M..

3 recordsLinked to original sources

bioRxiv2022

The autism-associated Neuroligin-3 R451C mutation alters mucus density and the spatial distribution of bacteria in the mouse gastrointestinal tract

The intestinal mucus layer protects the host from invading pathogens and is essential for maintaining a healthy mucosal microbial community. Alterations in the mucus layer and composition of mucus-residing microbiota in people diagnosed with Autism Spectrum Disorder (ASD; autism) may contribute to dysbiosis and gastrointestinal (GI) dysfunction. Although microbial dysbiosis based on sequencing data is frequently reported in autism, spatial profiling of microbes adjacent to the mucosa is needed to identify changes in bacterial subtypes in close contact with host tissues. Here, we analysed the spatial distribution of the MUC-2 protein using immunofluorescence as well as total bacteria, Bacteroidetes, Firmicutes phyla and Akkermansia muciniphila (A. muciniphila) using fluorescent in situ hybridization in mice expressing the autism-associated R451C mutation in the Neuroligin-3 (Nlgn3) gene. We show that the Nlgn3 R451C mutation increases mucus density adjacent to the distal ileal epithelium in mice. The relative density of total bacteria, Firmicutes and A. muciniphila was increased whereas the density of Bacteroidetes was decreased closer to the epithelium in Nlgn3R451C mice. In summary, this study suggests that increased mucus density could contribute to mucosal microbial dysbiosis in ASD.

neuroscience↗

bioRxiv2022

Caecal dysfunction in the NL3R451C mouse model of autism

The mouse caecum is a pouch-like structure that is anatomically similar to the human appendix and is hypothesised to serve as a reservoir for commensal bacteria. The gastrointestinal tract is also home to the largest immunological organ of the body and the enteric nervous system (ENS), which regulates gut motility and secretion. The caecum is therefore an ideal location to study neuro-immune-microbe interactions in gut-brain communication. Individuals with Autism Spectrum Disorder (ASD; autism) frequently present with gastrointestinal symptoms in addition to core diagnostic behavioural features, implying a gut-brain link. More broadly, changes in gut-brain connectivity are now thought to play a critical role in a range of neurodevelopmental disorders. Here, we employed a mouse model of autism expressing a missense mutation in the neuroligin-3 post-synaptic protein that affects brain and enteric neuronal activity (NL3R451C mice). We previously observed abnormal caecal ENS architecture and immune cell morphology in the caecal patch in this model, however it is unknown if caecal function is altered in NL3R451C mice. Using a tri-cannulation approach to record motility patterns in the mouse caecum, we identified novel caecal motor complexes in ex vivo preparations. Caecal permeability and neurally-evoked secretion levels were also studied. Key immune populations including gut macrophages and dendritic cells within the caecal patch were stained using immunofluorescence to investigate shifts in immune activity. Caecal motility patterns in NL3R451C mice differed from wildtype littermates. Specifically, caecal motor complexes occurred at a higher frequency and for a shorter duration in NL3R451C mice than in wildtype littermates. In NL3R451C mice, neurally-evoked caecal secretion was reduced in response to the nicotinic acetylcholine receptor agonist (DMPP), but permeability was unchanged. Increased numbers of caecal patches were observed in NL3R451C mice compared to wildtype, with no alterations in morphology of selected immune populations. Future research is warranted to better understand caecal function and how neuro-immune interactions in the caecum affect health and influence GI function in neurodevelopmental disorders via the gut-brain axis.

neuroscience↗

bioRxiv2022

Quantitative analysis of neuroligin-3 expression in the enteric nervous system of the Neuroligin-3R451C mouse model of autism

Mutations in the Neuroligin-3 (Nlgn3) gene are implicated in autism spectrum disorder (ASD) and gastrointestinal (GI) dysfunction but its cellular expression in the GI tract remains to be characterised. Localisation of NLGN3 protein is challenging in intestinal tissue due to the lack of target-specific antibodies. Here, we combined RNAScope in situ hybridization for Nlgn3 mRNA and immunofluorescence for markers of all enteric neurons, cholinergic submucosal neurons, non-cholinergic submucosal neurons, nitregic and calretinin-containing myenteric neurons as well as glial cells. We also developed a quantitative 3-dimensional image analysis method to measure Nlgn3 mRNA cellular expression levels in enteric neurons and glia. We show that Nlgn3 mRNA is expressed in most submucosal and myenteric neurons as well as in enteric glia. The R451C mutation reduces Nlgn3 mRNA expression levels in cholinergic, nitrergic and calretinin enteric neuronal subpopulations but does not affect Nlgn3 mRNA expression in VIPergic submucosal neurons. In summary, we show that the autism-associated R451C mutation in Nlgn3 reduces Nlgn3 mRNA expression in the mouse ENS. These findings could shed light on the pathophysiology of GI dysfunction in ASD.

neuroscience↗