Evolution and Development of Mammalian Brains
PROGRAMME

09:00: Coffee

09:15: Introduction by Professor Zoltán Molnár

09:30: ‘Astrocyte evolution – from vertebrates to human’ by Professor Verónica Martínez-Cerdeño

10:00: ‘Intrinsic and extrinsic factors that impact the function of neural precursor cells in the fetal cerebral cortex under normal and pathological conditions’ by Stephen Charles Noctor

10:30: ‘Molecular mechanisms underlying the subplate layer expansion in primates during brain evolution’ by Professor Chiaki Ohtaka-Maruyama

11:00: Coffee

11:30: ‘Neurothermodynamics and global geometry of the mammalian brain’ by Professor Paul R. Manger

12:00: ‘A common space approach to comparative neuroscience’ by Associate Professor Rogier B. Mars

12:30: ‘Effects of lifestyle and phylogeny on the vertebrate visual system’ by Wellcome Trust DPhil Student Jasper E. Hunt

ABSTRACTS

‘Astrocyte evolution – from vertebrates to human’ by Professor Verónica Martínez-Cerdeño PhD

Two major types of astrocytes have been broadly described in mammals, the protoplasmic and fibrous astrocytes. Two other astrocyte types with distinct morphology are known to localize to specific layers of the cerebral cortex in primates, interlaminar astrocytes (ILAs) and varicose-projection astrocytes (VP-As). ILAs possess a cell body in cortical layer I, and long processes traveling perpendicular to the pia towards deeper layers of the cortex. We examined cerebral cortex from 46 species that encompassed most orders of therian mammalians, including 22 primate species. Pial ILA were present in all mammalian species analyzed, and that while the density of pial ILA somata only varied slightly, the complexity of ILA processes varied greatly across species. Primates, specifically bonobo, chimpanzee, orangutan, and human, exhibited pial ILA with the highest complexity. We described two distinct cell types with interlaminar processes that have been referred to as ILA, that we termed pial ILA and supial ILA (Falcone et al., 2019). VP-As have a cell body in layers V-VI, short spiny processes, and one to five long processes with prominent, evenly spaced varicosities. We found that VP-As were present only in human and other apes (hominoids) and were absent in all other species. The presence of VP-As was concomitant with the presence of interlaminar astrocytes that also have varicosities along the interlaminar process (Falcone et al., 2022).

‘Intrinsic and extrinsic factors that impact the function of neural precursor cells in the fetal cerebral cortex under normal and pathological conditions’ by Professor Stephen Charles Noctor, PhD

The Noctor Lab investigates development of the cerebral cortex, with a special focus on factors that regulate neural and glial precursor cells and the migration of cortical cells. Goals of the lab include establishing a firm foundation for understanding signaling systems that control normal brain development to better understand the origins of neurodevelopmental disorders. We investigate brain development in a variety of vertebrates, including rodents and mammalian species that possess gyrencephalic cerebral cortex. Our current work investigates the complex milieu in cortical proliferative zones, and how cellular interactions regulate normal developmental programs that include cell genesis and cellular migration.

‘Molecular mechanisms underlying the subplate layer expansion in primates during brain evolution’ by Professor Chiaki Ohtaka-Maruyama PhD

The subplate(SP) layer of the mammalian neocortex plays an essential role in the embryonic cortical formation, including establishing a thalamocortical connection and radial neuronal migration. Primates such as monkeys and humans have a transiently highly expanded SP layer during the embryonic period compared to mice. However, its biological significance and the molecular mechanisms responsible for this expansion still need to be understood. We aimed to elucidate the mechanism by performing Visium spatial transcriptomic analysis using the embryonic cerebrum of marmosets and humans. By comparing these data with mouse data to identify genes specifically expressed in the SP layer of the primate. I want to discuss the candidate genes identified in this analysis an d their functional roles in expanding the SP layer in primates.

‘Neurothermodynamics and global geometry of the mammalian brain’ by Professor Paul R. Manger PhD

The mammalian brain produces heat independently of the body, indicating that thermodynamics specifically the relationship between heat production and heat loss might be an important factor in the evolution of global brain shape. Mammalian neurons need to be maintained at around 37 degrees C in order to function properly, and this temperature requirement might be a significant factor in mammalian brain evolution. By examining the relationship between a proxy for heat production in the brain (the endocranial volume) and heat loss (endocranial surface area) across over 450 mammal species, interesting findings emerge. For “most mammals” there is a distinct relationship between these two parameters indicating an ancestral balance between heat production and loss that appears to work for the spheroid shaped mammalian brain. In rodents the brain takes on a more tubular shape than other mammals, indicating the potential need to increase heat production in the brain to counter the increased rate of heat loss. In cetaceans, the brain takes on a more spherical shape, reducing surface area by around 10%, indicating a lowering in the rate of heat loss. In primates, there is a clear relationship between increasing brain size and increasing sphericity of the brain, culminating in hominins having quite spheroidal shaped brains, with a reduction in surface area of around 15%. Thus, both cetaceans and larger-brained primates can reduce the energetic costs required to heat the brain, although they achieve this in different ways. Energetic savings may be quite useful in the context of natural selection.

‘A common space approach to comparative neuroscience’ by Associate Professor Rogier B. Mars, PhD

Our laboratory is interested in developing a large-scale approach to comparative neuroscience. Using neuroimaging, we are able to get whole-brain, multi-modal images of post-mortem specimens, which allow us to sample an unprecedented range of species at high anatomical specificity. We have concentrated on developing approaches to quantitatitvely compare the organization of mammalian brains, even if they differ strongely in size and morphology. In this talk I will report our recent progress.

‘Effects of lifestyle and phylogeny on the vertebrate visual system’ by Jasper E. Hunt, MSc

Comparing CNS development and organisation between animals has yielded new insights into animals’ evolutionary histories, yet the role of ecological considerations in shaping CNS evolution is relatively underexplored. Nonetheless, ecological considerations play a considerable role in driving selection and thus shape evolution of the nervous system. My DPhil aims to fill this gap, underscoring the importance of an animal’s environment and behavioural lifestyle for the evolution of its nervous system.

Vision enables vertebrates from across the animal kingdom to interact with their environments, presenting a fantastic opportunity to examine how ecological pressures have shaped these animals’ behaviours and their developmental strategies. To begin exploring how the environment shapes visual system evolution, I develop a theoretical framework wherein ethological considerations are used to generate testable hypotheses regarding visual system development and organisation across species.

First, I use this ethological framework to advance a novel interpretation of the cross-species significance of retinal waves, a well-characterised phenomenon in visual system development. This theoretical work has led to a new collaboration with the Ruthazer Lab, which will result in my theory’s predictions being tested in an understudied species.

Using the same ethological framework, I develop hypotheses regarding the organisation of occipital white matter tracts in the primate lineage. Having validated a data-driven tractographic technique that is well-suited for cross-species comparisons, I will begin to test these ethologically-motivated hypotheses regarding primate visual organisation.
Date: 26 June 2023, 9:00 (Monday, 10th week, Trinity 2023)
Venue: Sherrington Building, off Parks Road OX1 3PT
Venue Details: Sherrington Room (second floor)
Speakers: Professor Zoltan Molnar (DPAG, University of Oxford), Professor Verónica Martínez-Cerdeño (Institute for Paediatric Regenerative Medicine at Shriners Hospitals for Children, Institute for Medical Investigation of Neurodevelopmental Disorders - MIND, School of Medicine, University of California, Davis), Professor Stephen Charles Noctor (Department of Psychiatry and Behavioural Sciences, UC Davis), Professor Chiaki Ohtaka-Maruyama (Developmental Neuroscience Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan), Professor Paul R. Manger (School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa), Associate Professor Rogier B. Mars (Wellcome Centre for Integrative Neuroimaging, University of Oxford and Donders Institute for Brain, Cognition and Behavior, Radboud University Nijmegen), Jasper E. Hunt (Nuffield Department of Clinical Neurosciences, University of Oxford)
Organising department: Department of Physiology, Anatomy and Genetics (DPAG)
Organiser: Professor Zoltan Molnar (DPAG, University of Oxford)
Organiser contact email address: zoltan.molnar@dpag.ox.ac.uk
Host: Professor Zoltan Molnar (DPAG, University of Oxford)
Part of: Neuroscience Theme Guest Speakers (DPAG)
Booking required?: Not required
Audience: Members of the University only
Editor: Talitha Smith