Periodic Reporting for period 1 - RADIOGUT (Radial Glia as Neurodevelopmental Mediators Of Gut Microbiota Signals)
Reporting period: 2022-06-01 to 2024-11-30
Increasing evidence points to the importance of gut microbiota in the aetiology of neurodevelopmental and neuropsychiatric conditions. However, the mechanisms and conduits through which microbiota influences brain development in the critical perinatal period, potentially leading to cognitive deficits in later life, remain largely unknown.
My hypothesis is that the dynamic early-life gut microbiota modulates the primary brain neural stem cells, the radial glia (RG), thereby sculpting the concurrently maturing neurodevelopmental trajectory. RG are in direct contact with cerebrospinal fluid (CSF), whose composition relies on a functional blood-CSF barrier (BCSFB) at the choroid plexus. BCSFB-RG interface is thus ideally positioned to receive peripheral circulating signals, such as those from gut microbiota. My preliminary data indicating alterations in RG dynamics and BCSFB integrity in neonatal mice with disrupted gut microbiota provides credence to my hypothesis. Building on this, RADIOGUT aims to mechanistically understand the interactions between gut microbiota, RG-led neurodevelopment and BCSFB function at molecular and cellular levels. To accomplish this, I will employ distinct models of early-life microbiota disruption in mice and assess the impact on RG and BCSFB using in vivo tracer imaging, ex vivo models combining explant cultures with microbial metabolites from a faecal fermenter, and an integrated multi-omics analysis. We will identify key microbial metabolites that operate at the BCSFB RG interface, discern their signalling mechanisms and their potential to rescue RG-derived neurodevelopmental deficits as well as later life aberrant behaviours.
RADIOGUT will explore for the first time how RG can act as cellular sensors of microbial signals that modulate neurodevelopment. It will fill a large gap in the understanding of microbiota-gut-brain axis development and its communication code, as well as deliver tangible future translational value.
My hypothesis is that the dynamic early-life gut microbiota modulates the primary brain neural stem cells, the radial glia (RG), thereby sculpting the concurrently maturing neurodevelopmental trajectory. RG are in direct contact with cerebrospinal fluid (CSF), whose composition relies on a functional blood-CSF barrier (BCSFB) at the choroid plexus. BCSFB-RG interface is thus ideally positioned to receive peripheral circulating signals, such as those from gut microbiota. My preliminary data indicating alterations in RG dynamics and BCSFB integrity in neonatal mice with disrupted gut microbiota provides credence to my hypothesis. Building on this, RADIOGUT aims to mechanistically understand the interactions between gut microbiota, RG-led neurodevelopment and BCSFB function at molecular and cellular levels. To accomplish this, I will employ distinct models of early-life microbiota disruption in mice and assess the impact on RG and BCSFB using in vivo tracer imaging, ex vivo models combining explant cultures with microbial metabolites from a faecal fermenter, and an integrated multi-omics analysis. We will identify key microbial metabolites that operate at the BCSFB RG interface, discern their signalling mechanisms and their potential to rescue RG-derived neurodevelopmental deficits as well as later life aberrant behaviours.
RADIOGUT will explore for the first time how RG can act as cellular sensors of microbial signals that modulate neurodevelopment. It will fill a large gap in the understanding of microbiota-gut-brain axis development and its communication code, as well as deliver tangible future translational value.
We've made significant progress in our RADIOGUT project, which studies how early-life gut microbes influence brain development. We focused on two main areas: how changes in gut microbes during pregnancy affect brain cells and how these changes might impact the communication between the maternal gut microbes and the developing brain.
During our research, we've conducted experiments on which included both embryos and early postnatal mice in the context of a disrupted normal gut microbiota. We observed the effects on brain development at various stages of embryonic development and after birth. Our findings suggest that, at least in mice, a mother's gut microbes during pregnancy directly influence the development of her offspring's brain cells, particularly in a structure called the choroid plexus, which is involved in producing the fluid surrounding the brain and spinal cord. We also noticed differences between male and female embryos, even at the early stages of development. We also observed changes in specific brain cells known as radial glial cells, which play a key role in brain development. These changes were linked to the mother’s gut microbiota srarus. We also noticed that different regions of the brain, like the cortex and more ancient brain areas like the hypothalamus and amygdala (more involved in emotions and hormone regulation), were affected in distinct ways. Overall, this supports our theory that gut microbes during pregnancy can influence how the brain develops.
We also studied the protective barriers of the developing brain, particularly in a structure named the choroid plexus, which helps regulate what substances can enter the brain. We found changes in the integrity of these barriers when the mother's gut microbes were disrupted. This suggests that the gut microbes may also play a role in how the brain protects itself during development. We are now investigating whether these changes could contribute to brain development and how they might relate to brain disorders.
We also identified several chemical changes in the blood and brain fluid of embryos, which were linked to changes in the mother's gut microbiota. For instance, a brain chemical called N-acetylaspartate (NAA), which is important for brain health, was found to decrease when the mother’s gut bacteria were disrupted. We are now working to understand how these changes might impact brain development.
In terms of technological and methodological advancements, we have developed several new techniques:
- A method to extract and study cerebrospinal fluid from embryos, which helps us understand which signals from the maternal gut could reach the embryonic brain, thereby influencing brain cells and their development.
- We also created a cellular model consisting of cells cultured in a dish, which helps us to study the brain’s protective barriers ex vivo. We can culture these cells in different conditions, for example adding specific microbial signals of interest, that have the potential to modulate the brain barriers.
- Embryonic brain tissue preparation: we have optimised methods of embryonic tissue processing, specific to the study of the different brain structures of interest for our studies.
- Working with Germ-Free Animals: To ensure our results are accurate, we used a special group of animals that were completely free of gut bacteria. This allowed us to closely study the role of maternal gut bacteria in brain development.
During our research, we've conducted experiments on which included both embryos and early postnatal mice in the context of a disrupted normal gut microbiota. We observed the effects on brain development at various stages of embryonic development and after birth. Our findings suggest that, at least in mice, a mother's gut microbes during pregnancy directly influence the development of her offspring's brain cells, particularly in a structure called the choroid plexus, which is involved in producing the fluid surrounding the brain and spinal cord. We also noticed differences between male and female embryos, even at the early stages of development. We also observed changes in specific brain cells known as radial glial cells, which play a key role in brain development. These changes were linked to the mother’s gut microbiota srarus. We also noticed that different regions of the brain, like the cortex and more ancient brain areas like the hypothalamus and amygdala (more involved in emotions and hormone regulation), were affected in distinct ways. Overall, this supports our theory that gut microbes during pregnancy can influence how the brain develops.
We also studied the protective barriers of the developing brain, particularly in a structure named the choroid plexus, which helps regulate what substances can enter the brain. We found changes in the integrity of these barriers when the mother's gut microbes were disrupted. This suggests that the gut microbes may also play a role in how the brain protects itself during development. We are now investigating whether these changes could contribute to brain development and how they might relate to brain disorders.
We also identified several chemical changes in the blood and brain fluid of embryos, which were linked to changes in the mother's gut microbiota. For instance, a brain chemical called N-acetylaspartate (NAA), which is important for brain health, was found to decrease when the mother’s gut bacteria were disrupted. We are now working to understand how these changes might impact brain development.
In terms of technological and methodological advancements, we have developed several new techniques:
- A method to extract and study cerebrospinal fluid from embryos, which helps us understand which signals from the maternal gut could reach the embryonic brain, thereby influencing brain cells and their development.
- We also created a cellular model consisting of cells cultured in a dish, which helps us to study the brain’s protective barriers ex vivo. We can culture these cells in different conditions, for example adding specific microbial signals of interest, that have the potential to modulate the brain barriers.
- Embryonic brain tissue preparation: we have optimised methods of embryonic tissue processing, specific to the study of the different brain structures of interest for our studies.
- Working with Germ-Free Animals: To ensure our results are accurate, we used a special group of animals that were completely free of gut bacteria. This allowed us to closely study the role of maternal gut bacteria in brain development.
RADIOGUT has been an incredibly exciting research project with groundbreaking findings. While we have successfully confirmed our main hypothesis, we’ve also discovered some unexpected but important results:
- We found that a decrease in a brain chemical called N-acetylaspartate (NAA) might be linked to gut microbes during early development. Since NAA is mainly produced in brain cells' powerhouses (mitochondria), this suggests that gut microbes could play a role in supporting brain energy production. Understanding this connection could help develop strategies aimed at protecting the brain.
- We discovered specific proteins in the blood vessels of a brain structure called the choroid plexus, which acts as a barrier. Even though these vessels are usually permissive to circulating substances, the presence of these proteins suggest they have a protective function and the capacity to have barrier properties. This finding could help us understand how the brain keeps a stable environment and what could go wrong in certain disorders.
- We found that maternal gut microbes during gestation affect brain cells differently depending on the brain region of the embryo. For example, cells in the cortex and hypothalamus seem to react differently to these signals. This could mean that more 'ancient' brain regions (from an evolutionary perspective), have been influenced by gut microbes for a longer time than the evolutionarily newer brain areas such as the cortex. Understanding these differences could be crucial in studying brain development disorders that affect different parts of the brain.
- We found that a decrease in a brain chemical called N-acetylaspartate (NAA) might be linked to gut microbes during early development. Since NAA is mainly produced in brain cells' powerhouses (mitochondria), this suggests that gut microbes could play a role in supporting brain energy production. Understanding this connection could help develop strategies aimed at protecting the brain.
- We discovered specific proteins in the blood vessels of a brain structure called the choroid plexus, which acts as a barrier. Even though these vessels are usually permissive to circulating substances, the presence of these proteins suggest they have a protective function and the capacity to have barrier properties. This finding could help us understand how the brain keeps a stable environment and what could go wrong in certain disorders.
- We found that maternal gut microbes during gestation affect brain cells differently depending on the brain region of the embryo. For example, cells in the cortex and hypothalamus seem to react differently to these signals. This could mean that more 'ancient' brain regions (from an evolutionary perspective), have been influenced by gut microbes for a longer time than the evolutionarily newer brain areas such as the cortex. Understanding these differences could be crucial in studying brain development disorders that affect different parts of the brain.