Lecture 8 - Neural development

Lecture 8 - Neural development

1. Structure

   • 100,000,000,000 neurons
   • 2,500,000,000,000,000 connections
   • 40 known transmitters

2. Embryonic development

   • Zygote surrounded by zona pellucida
     • Cleavage (cell division) of cell with no growth
       • When it reaches ~16 cells --> undergoes compaction, cells are connected by gap junctions (cells become less distinct) = morula (takes around 4 days)
         • Start of differentiation: blastomere cells
           • These cells secrete fluid --> formation of a vacuole which is a fluid filled cavity called the blastocoel
             • Some of blastocyst near the top and form the Inner Cell Mass (ICM) - these cells are pluripotent = whole thing is now a blastocyst and the cells around the edge form trophoblasts
               • Zona pellucida is now lost and new cavity forms within ICM cells called the amniotic cavity
                 • A new layer of cells forms to form the epiblast (top layer) and hypoblast (bottom layer) cells in a bilamina disk
                   • Development of groove along bilamina disk resulting from the migration of cells towards the groove and downwards to form the primitive streak = gastrulation --> goes from bilamina disk to trilamina (3 layers) disk
                     • This trilamina disk forms the 3 primary germ layers ectoderm (top layer), mesoderm (middle) and endoderm (bottom)
                       • Ectoderm layer goes on to form skin, nails, hair, lens of eye etc. and all parts of nervous system --> more info on slide about mesoderm and endoderm
                       • Notochord starts to form in the mesoderm
                         • Ectoderm starts to thicken in the middle to form the neural plate
                           • Signals from the notochord act on the neural plate cells which then start to invaginate, dipping down slightly into the mesoderm --> beginning on neural tube formation
                             • The action of BMP4 (bone morphogenic protein 4, TGFB family) induces ectodermal cultures to differentiate into epidermis - BMP4 inhibits ...
                               • • Neural plate induction:
                                   • 1. Neuroectodermal cells from the neural plate with neural crest on either side
                     • Gastrulation also creates the anterior-posterior body axis
                     • Henson's node is the 'organiser' for the process of infolding during gastrulation
                       • The order in which the cells enter the blastocoel through Henson's node determines their specification in the embryo
                       • Henson's node = birds; Spemann's organiser = amphibians; primitive knot = mammals
                         • Confirming the role of the organiser in embryogenesis
                           • Took dorsal lip of blastopore from a pigmented gastrula and transported it into unpigmented gastrula --> formation of 2 embryos conjoined
                         • Molecular basis of the organiser can be found in notes from last years embryogenesis bit (about B-catenin)
                           • The axin/GSK-3/APC 'destruction complex' normally promotes the proteolytic degradation of B-catenin
                             • Need to go back and look at this