Transcript cells
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) • • • • 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 • • • • Cilliated cell - tubulin a dynein Neuron - neurotransmitter, tubulin a kinesin B- cell of pankreas Red blood cell - hemoglobin Differentiation • differentiation is dependent on signals from cell environment (regulatory differentiation) – in case of higher species (e.c.-human) Differentiation and determination • • • 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