Embryology Lecture Overview Vertebrate Development 2310- Hearing Dr Mark Hill (room G20) Development of Hearing Larson- chapter 12 p352-360 Structures outer, middle inner Functions Origins Development Regulatory genes (mainly from KO studies) Abnormalities- congenital deafness http://anatomy.med.unsw.edu.au/cbl/embryo/Notes/senses.htm Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Hearing- 3 divisions of ear outer external auditory meatus (ear canal) functions to collect sound and gude it to the tympanic membrane Organ of Corti middle tympanic cavity functions to convert sound pressure waves into mechanical waves of typanic membrane ossicles reduce amplitude but increase force to drive fluidfilled <a href="/keyword/inner-ear/" >inner ear</a> eustacian tube allows equalization of pressure (into oral cavity) Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev inner Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Hair Cells Pinna- Auricle develops from six aural hillocks 3 on first arch 3 on second arch originally on neck, moves cranially during mandible development stage 18 stage 19 stage 20 Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Outer- external auditory meatus derived from first pharyngeal cleft ectodermal diverticulum week 5 extends inwards to pharynx Outer Ear Genes controlled by genes that regulate arch 1 and 2 development related to hindbrain segmentation (rhombomere 4) Mouse Hox a1/Hoxb1, goosecoid, Endothelin1, dHAND until week 18 has ectodermal plug plug forms stratified squamous epithelia of canal and outer eardrum Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Middle- tympanic cavity derived from first pharyngeal pouch extends as tubotympanic recess during week 5 recess contacts outer ear canal mesoderm between 2 canals forms tympanic membrane Middle- Ossicles develop from first and second pharyngeal arches tympanic cavity enlarges to incorporate coats with epithelia expands to form tympanic recess stalk of recess forms eustacian tube pharyngotympanic tube first arch mesoderm tensor tympani muscle malleus and incus second arch mesoderm stapedius muscle and stapes Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Middle Ear Genes gooscoid, RARs, Prx1, Otx2, Hoxa1, Hoxb1, endothelian related molecules Scanning Electron Microscopy Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Ear- Otic placode week 4 first component to be generated forms <a href="/keyword/inner-ear/" >inner ear</a> forms at the level of the myelencephalon surface ectoderm invaginates forms otic pit otic pit pinches off from surface forms otic vesicle otocyst Ear- Otocyst forms membranous labyrinth endolymphatic duct and sac utricule and saccule semicircular ducts cochlear ducts vestibulocochlear nerve (VIII) differentiates from wall of otocyst includes cells from the neural crest Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev 1/11/02 Dr Mark Hill, CBL, Anatomy, UNSW 4:45 PM ANAT 2310- Hearing Dev Inner- otocyst week 3 otic placode forms on surface ectoderm otic placode sinks into mesoderm forms otocyst (otic vesicle) Otic Vesicle to Labyrinth 1 Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Pig stage 13/14 Otocyst Otocyst branches form and generate endolymphatic duct and sac forms vestibular and cochlear sac Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Vestibular sac generates 3 expansions form semicircular ducts remainder forms utricle epithelia lining generates hair cells ampullary cristae utricular macula Otic Vesicle to Labyrinth Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Human Stage 22 Otoconin- <a href="/keyword/inner-ear/" >inner ear</a> biominerals FIG. 1. Expression of Ocn-95 at early embryonic stages. E9.5 E10.5: the growing endolymphatic duct (arrowhead) and the dorsal part of the otic vesicle are strongly labeled. E12: the endolymphatic duct, the forming semicircular canals (sc), and the cochlea (c) are stained. Magnification: 325 (E9.5), 317 (E10.5), and 36 (E12). FIG. 4. Distribution of otoconin-95 in the developing <a href="/keyword/inner-ear/" >inner ear</a> . (A) Section through the three ampullae and part of the utriculo-saccular complex at E14.5. (B) Four sections of the cochlear duct at P0. Note that cochlear cell differentiation proceeds with a base-to-apex gradient Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Cochlear sac generates coiled cochlear duct humans 2 1/2 turns remainder forms saccule epithelia lining generates hair cells structures of organ of corti saccular macula Human Stage 22- cochlear Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Human Stage 22- cochlear Cochlea Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Bony Labyrinth formed from chrondified mesoderm Periotic Capsule mesenchyme within capsule degenerates to form space filled with perilymph Vestibulocochlear Nerve forms beside otocyst from wall of otocyst and neural crest cells bipolar neurons Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev vestibular neurons outer end of internal acoustic meatus innervate hair cells in membranous labyrinth axons project to brain stem and synapse in vestibular nucleus cochlear neurons cell bodies lie in modiolus central pillar of cochlear innervate hair cells of spiral organ axons project to cochlear nucleus Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Ear- Middle Ear 3 ear ossicles (maleus, incus, stapes) 2nd arch cartilage Ear- Middle Ear tubotympanic recess surrounds ossicles approaches ectoderm near meatal plug 1/11/02 Dr Mark Hill, CBL, Anatomy, UNSW 4:45 PM ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev <a href="/keyword/inner-ear/" >inner ear</a> Genes hindbrain segmentation occurs at same time placode arises otocyst adjacent to rhombomere 5 may influence development Gene Expression-<a href="/keyword/inner-ear/" >inner ear</a> In situ hybridization analysis of cDNAs expressed in the <a href="/keyword/inner-ear/" >inner ear</a> . (A) On a cross-section of the basilar papilla, b-tectorin mRNA occurs in clear cells (CC), supporting cells (SC), and cuboidal cells (CuC). (B) Calbindin mRNA is abundant in supporting cells (SC) and detectable in hair cells (HC). (C) Strong signals for type II collagen mRNAare visible in the superior fibrocartilaginous plate (SFP) and inferior fibrocartilaginous plate (IFP) and, as indicated by the arrow, between the auditory ganglion (AG) and sensory epithelium (SE). All collagen mRNAs found in the <a href="/keyword/inner-ear/" >inner ear</a> were expressed in a similar manner. (D) Coch-5B2 mRNA occurs in spindle-shaped cells (arrow) marking the path of neurites between the auditory ganglion (AG) and sensory epithelium (SE). Weaker expression is detectable in the superior and inferior fibrocartilaginous plates (SFP and IFP). (E and F) Coch-5B2 mRNAdisplays strong labeling of muscle spindles in the gastrocnemius muscle; note the encapsulation and the nuclear chain in (F). (G) Connexin 31 mRNA is expressed robustly in cells of the tegmentum vasculosum (TV), cuboidal cells (CuC), supporting cells (SC), and clear cells (CC). (H) Homogenin mRNA is detectable in homogene cells (HoC). (I) The intense yellow f luorescence of rhodamine-coupled phalloidin signals a high abundance of filamentous actin in homogene cells (HoC) as well as in hair bundles of the sensory epithelium (SE). (J) Otokeratin mRNA occurs in cells of the tegmentum vasculosum (TV). Hoxa1, kreisler, Fgf3 genes regulating neural crest cells (neural genes) Pax2 Ko affects cochlear and spiral ganglion, but not vestibular apparatus nerogenin 1 affects both ganglia Semicircular canal Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Otx1- cochlear and vestibular normal H 3 P 1 P 2 Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Brn-3c and Hair cell development The Brn-3 subfamily of POU domain tran-scription factor genes consists of three highly homologous members Brn-3a, Brn-3b, and Brn-3c that are expressed in sensory neurons and in a small number of brainstem nuclei. Supporting Cells- p27kip Cyclin-dependent kinase inhibitor p27 Kip1 is selectively expressed in the supporting-cell population of the organ of Corti. Effects of p27 Kip1 -gene disruption include ongoing cell proliferation in postnatal and adult mouse organ Absence of hair cells in the organ of Corti and defects in the spiral ganglion in Brn3c (2y2) mice. (A) Organ of Corti from a Brn-3c (1y2) mouse. The single inner hair cell, the three outer hair cells, and the three underlying Deiter s cells are clearly visible. (B) Part of a spiral ganglion from a Brn-3c (1y2) mouse showing a dense packing of myelinated axons and neuronal cell bodies. (C) Organ of Corti from a Brn-3c (2y2) mouse. Inner and outer hair cells are missing and the epithelium beneath the tectorial membrane contains only supporting cells. (D) The spiral ganglion from a Brn-3c (2y2) mouse contains fewer than one-tenth as many myelinated axons and neuronal cell bodies than the spiral ganglia of Brn-3c (1y1)or (1y2) mice. Tissues were embedded in Spurr s resin and 1 mm sections were stained with methylene blue. (Scale bar 5 25 mm.) Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Developmental expression of p27 Kip1 in the mouse organ of Corti revealed by immunocytochemistry in radial sections. Absence of hair cells in the otolith organs and cristae of Brn-3c (2y2) mice. (A) An otolith organ from a Brn-3c (1y2) mouse. The organ of Corti is composed of two sensory cell types arranged in one row ofIHCs and three rows of OHCs. There are five different types ofsupporting cells whose nuclei lie below or adjacent to the hair-cell nuclei. These types include inner phalangeal cells (IPC), inner and outer pillar cells (PC), Deiters cells (DC), and Hensen s cells (HC). Hair-cell and supporting-cell regions are indicated by arrows. Labeling with antibodies against p27 Kip1 shows that the protein is expressed onlyin the supporting-cell nuclei and not in the hair-cell nuclei. (A) Wild-type (p271y1) mouse at postnatal day 0. (B) p271y1 mouse Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Thyroid Hormone Thyroid hormone receptor b-dependent expression of a potassium conductance in inner hair cells at the onset of hearing Ganglion neurons require growth factors vestibular neurons- BDNF, NT3 survival not development Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Congenital Deafness conductive- disease of outer and middle ear sensorineural- cochlear or central auditory pathway Outer ear Malformation rare meatal atresia canal narrow or not formed part of first arch syndrome Congenital malformations Statistics Middle ear Malformation also rare can be part of first arch syndrome malformed maleus or incus congenital fixation of stapes Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev stapes anchored to oval window (annular ligament fails to develop) Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Congenital sensorineural hereditary or acquired Hereditary recessive- severe dominant- mild can be associated with abnormal pigmentation hair and irises Vestibular Development Acquired rubella (German measles) maternal infection during 2nd month of pregnancy vaccination of young girls streptomycin antibiotic thalidomide Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev Dr Mark Hill, CBL, Anatomy, UNSW ANAT 2310- Hearing Dev