Presentation on theme: "Embryogenesis of the human eye Bharesh Chauhan, PhD"— Presentation transcript:
1 Embryogenesis of the human eye Bharesh Chauhan, PhD 8-wkBharesh Chauhan, PhDResearch Assistant ProfessorDept. of Ophthalmology, UPSOM
2 Examples of inborn errors in human eye development AniridiaAnophthalmiaColoboma(Dr. K. Ramaesh, FRCS FRCOphthUniversity of Edinburgh)(Dr. W.C. Caccamise, Sr, MDPittsford, NY)(Dr. B.P. Brooks, MD PhDNEI, MD)
3 Stages in animal development GametogenesisFertilizationCleavageGastrulationOrganogenesisGrowthsperm (spermatogenesis) and ovum (oogenesis) form.fusion of a sperm and ovum to generate a zygote.to form morula (solid ball of blastomeres) and thenblastula (ball of cells surrounding blastocoele).reorganization of blastocyst into a gastrula, consisting of endoderm, mesoderm and ectoderm.organ formation from the trilaminar gastrula through the processes ofpatterning, differentiation, morphogenesis and growth.correct size and shape of organs are determined by growth increating the fetus.
4 Organogenesis – the process Regional specificationcell differentiationmorphogenesisgrowth
5 Mammalian eye development Optic stalkThe genetic and molecular basis of congenital eye defects.Graw J.Nat Rev Genet Nov;4(11):Kismet/CHD7 regulates axon morphology, memory and locomotion in a Drosophila model of CHARGE syndrome.Melicharek DJ, Ramirez LC, Singh S, Thompson R, Marenda DR.Hum Mol Genet Nov 1;19(21):PhotoreceptorneuronsDevelopingbrain
7 Neurulation and head patterning Neural plate patterning: upstream and downstream of the isthmic organizer.Wurst W, Bally-Cuif L.Nat Rev Neurosci Feb;2(2):Neural crest specification: migrating into genomics.Gammill LS, Bronner-Fraser M.Nat Rev Neurosci Oct;4(10):Prior to retinal development, the following occurs during the first 3 weeks of embryogenesis:- neural induction of the competent ectoderm- anterior-posterior subdivision of the resulting neural plate.
9 Placode stageSpecification of the eye field in the diencephalon occurs at this stage by signaling between the closely-apposed:- epithelia of the surface ectoderm- the lateral diverticuli of the budding diencephalon.
10 Lens pit stageThe first morphological sign of eye development in vertebrates is the bilateral evagination of the diencephalon to form the optic vesicles.Continued evagination leads to the formation of the optic pits with elongation of the optic stalk driving the back of the eye further.Mesenchyme between the optic vesicle and the surface ectoderm is displaced as the two tissues come into close physical contact.Coronal section of the embryonic head
11 Optic cup stageThe continued evagination of the optic vesicle leads to the formation of the optic cup, which is bilayered.The upper layers differentiate to form the neural retinas and the lower layers differentiate to form the retinal pigment epithelium (RPE).
12 Differentiation of RPCs into retinal cell types Intrinsically different retinal progenitor cells produce specific types of progeny.Cepko C.Nat Rev Neurosci Sep;15(9):human neural retina of the optic cup inner layer differentiates within first monthganglion cells start first (7-8 wks) and centrally, while bipolar and horizontal cells start peripherally and migrate centrally,primitive fovea is formed from the thinning of the GCL and INL at wks .
13 Optic stalk (OS) – choroidal fissure closure occurs at 6 weeks,molecular mechanism has been partially deciphered (eg., FGF, RA).
14 Optic nerve development Four phases of development1.2.3.optic stalk extensionchoroidal fissure closure (coloboma),migration of the RGC axons into the optic stalk towards the LGN,reduction of axons by apoptosis (megalopapilla)Myelination of the axons occurs later in gestation, 32 wks in humans
15 Hyaloid vasculature development Three stage processdeposition of hyaloid cells aroundlens area and generation of a loop,branched networks form,vessel refinement occurs.In vivo analysis of hyaloid vasculature morphogenesis in zebrafish: A role for the lens in maturation and maintenance of the hyaloid.Hartsock A, Lee C, Arnold V, Gross JM.Dev Biol Aug 13. pii: S (14)
16 Four stages of morphogenesis in lens development placodepitvesiclefibera critical phase for co-ordinated morphogenesis betweentwo epithelia, the optic vesicle and presumptive lens
17 Mechanism of invagination RhoARac1Balanced Rac1 and RhoA activities regulate cell shape and drive invagination morphogenesis in epithelia.Chauhan BK, Lou M, Zheng Y, Lang RA.Proc Natl Acad Sci U S A Nov 8;108(45):• RhoA promotes apical constriction• Rac1 promotes cell lengthening
18 Inter-epithelial processes during lens placode invagination Mann I. (1950) The Development of the Human Eye. 2nd Ed. Grune & Stratton,Inc. New York.
19 Lens pit filopodia contain active myosin II Cdc42- and IRSp53-dependent contractile filopodia tether presumptive lens and retina to coordinate epithelial invagination.Chauhan BK, Disanza A, Choi SY, Faber SC, Lou M, Beggs HE, Scita G, Zheng Y, Lang RA.Development Nov;136(21):
20 Does the developing lens shape the optic cup? 1)Self-organizing optic-cup morphogenesis in three-dimensional culture.Eiraku M, Takata N, Ishibashi H, Kawada M, Sakakura E, Okuda S, Sekiguchi K, Adachi T, Sasai Y.Nature Apr 7;472(7341):51-6.Shape of the cultured optic cup is different from the naturally developing optic cup next to the lens.Uncoupled developing lens and optic cups do not conform to canonical shape forms.Cdc42- and IRSp53-dependent contractile filopodia tether presumptive lens and retina to coordinate epithelial invagination.Chauhan BK, Disanza A, Choi SY, Faber SC, Lou M, Beggs HE, Scita G, Zheng Y, Lang RA.Development Nov;136(21):2)
21 Maturation of the lens and sutures Fiber cell differentiation begins during early vesicle stage to form primary fibers in the posterior lens,lens continues enlarging by proliferation and elongation of the lens equator epithelial cells to form secondary fibers,The fibers adopt a hexagonal shape, a ball-socket mid-arrangement and are bound to the lens capsule by a foot processeshttps://mutagenetix.utsouthwestern.edu/phenotypic/phenotypic_rec.cfm?pk=309Understanding the role of growth factors in embryonic development: insights from the lens.Lovicu FJ, McAvoy JW, de Iongh RU. Philos Trans R Soc Lond B Biol Sci Apr 27;366(1568): doi: /rstb Review.Three-dimensional organization of primary lens fiber cells. Shestopalov VI, Bassnett S. Invest Ophthalmol Vis Sci Mar;41(3):
22 Corneal developmentNeuroblastoma book edited by Hiroyuki Shimada, ISBN , Published: May 29, 2013Chapter 4 Neurotrophin and Neurotrophin Receptor Involvement in Human NeuroblastomaPierdomenico Ruggeri, Antonietta R. Farina, Lucia Cappabianca, Natalia Di Ianni, Marzia Ragone, Stefania Merolle, Alberto Gulino and Andrew R. Mackay
23 Angle developmentThe next step: detailed assessment of an adult glaucoma patient.Philippin H, Shah P, Burton M.Community Eye Health. 2012;25(79-80):50-3.