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Basic morphogenetic processes
Lecture, 21.3.2012
Aim
• mechanisms, participating during
ontogenesis, creating multicellular organism
from one cell, zygote
• terminology, theoretical background
• normal development example
• abnormal development example
Ontogenesis – development of individual being
• begins by fertilisation (oocyte and sperm) - zygote culminates by maturity : physical, structural, functional,
sexual, mental, emotional – terminates by death
• time of birth - divides ontogenesis prenatal and postnatal
• prenatal period: 40 weeks
blastogenesis - embryonal - fetal - perinatal
0-2 weeks
3.-8.w
9.-.38.w around 40w
1. trimester
2.a 3. trimester
blastogenesis
embryonic period
fetal period
Ontogenesis - prenatal - zygote development
toward multicellular organism)
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mechanisms operate…at different levels
cells - differentiation
cell populations - morphogenesis - structure development
cell populations set - morphogenetic system – realizes
structure and function programme in organ or part of the
body – basic morphogenetic processes
Cell level
• differentiaton - process that cause cell specialisation
• different cell types develop from totipotent zygote, by
specific and different proteins synthesis, underlying specific
morphology (structure) and function of particular cell
Oocyt , sperm
Oocyt
Oocyte and sperms
Goblet cells and cilliated cells
Blood cells
Chondrocytes
Different cell types – different proteins
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Cilliated cell - tubulin a dynein
Neuron - neurotransmitter, tubulin a kinesin
B- cell of pankreas
Red blood cell - hemoglobin
Differentiation
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differentiation is dependent on signals from cell
environment (regulatory differentiation) – in case of higher
species (e.c.-human)
Differentiation and determination
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gene - RNA - DNA - protein = differentiation
regulatory genes
control the expression of one or more other genes
they are activated by the signal from environment
a cell can become specified for a particular fate – it becomes
determined – the cell fate determination
• determination is followed by differentiation
mesenchymal cell
chondroblast
cartilage
lipoblast
fat
fibroblast
osteoblast
myoblast
bone
muscle
hemocytoblast
endothelium
blood cells
connective tissue, ligaments, tendons
Diferenciace buněk neuroepitelu
Cell populations level
• development of structures/ organs - morphogenesis
• 1. induction – one cell population induces the change of the
fate in another cell population
• epithelial-mesenchymal interactions
examples: limbs, lens, nephrons, teeth
cross-talk
• 2. cell-signalling, signalising cell x target cell (must be
sensitive to this signal)
paracrine interactions, contact interactions
• neuroectoderm induction / target is surface
ectoderm – lens placode
Morphogenetic systems level
= group of cell populations developmental programme
• basic morphogenetic processes - 4 processes play out at the
cell population level to essentially create the final organism
• proliferation
• migration
• asociation
• Programmed cell death - apoptosis
Proliferation (mitotic activity)
• characteristic feature of development – the embryo grows
+ cavity formation a extracellular material increase (interstitial
growth in cartilage) + cell increase
• considerable in embryonic period 3.-8. week , 3mm – 30 mm
• in adult tissues proliferation in regeneration process
(hematopoeisis, epithelial tissues..)
• programmed structure growth (limb is preformed as
miniature in 4th week of development, followed by its
growth)
• growth/proliferation is regulated – growth factor – insulin,
insulin-like-growth faktor, PDGF, VEGF…
• mitotic activity is localised in the centres of proliferation
Cell migration
• cell movements from original site to the target site
• passive – the cells are pushed from the proliferation centre
• activní – movements thank to cell itself systém of locomotion
(philopodium, train)
• Neural crest derived cells, germ layer cells, somites
Neural crest cell derivates
Cell association
• association to the groups, for synchronisation of their function
• CAM – cell adhesive molecules, cadherins, gap-junctions
• syncytium in skeletal muscle, neurons, angiogenesis
2 multipolar neurons associated by synapse
biomedicalengineering.yolasite.com
Apoptosis
• fysiological process
• elimination of defect cells
mutation or supranumeral
elements (neurons)
• creating of the shape interdigital spaces in hands
and feets
Limb development
• Limb bud - mesenchyme, ectoderm
• AED - apical ectodermal ridge - proliferation
• ZPA – zone of polarisation activity- retinoid acid –
morphogene – transcriptional factor- for axis pattern (SHH,
BMP, WNT, HOX genes - postion)
• differentiation – bones, connectives
• migration – muscle cells from somites, melanocytes, Schwann
cells from neural crest
• growth of axons from spinal cord , angiogenesis association• apoptosis – interdigital spaces formation
Affected limb development
• critical period 4.-7.week
• thalidomide - 20% risk of defects
phokomelia, amelia
• proximal part of limb is missing ,
stylopodium and zeugopodium
• mechanism
• block of growth factor for
angiogenesis and integrins
Neural tube differentiation in CNS development
neuroepithelial cells - proliferation, neuroblast migration,
neuron association to neuronal net. Solitary neurons die by
apoptosis
Embryology
• developmental processes during prenatal period of
development
• morfogenesis
• organogenesis
• teratogenesis