Den här uppsatsen handlar om elever med Ushers syndrom och inkludering i klassrummet. Ushers syndrom består av en kombinerad syn- och hörselnedsättning och synen försämras med tiden framförallt i synfältet. Med Ushers syndrom innebär det även svårigheter att se i mörkret. Syftet med uppsatsen är att undersöka hur inkludering kan skapas i klassrummet utifrån elever på aktörsnivå och skolan och lärare på institutionell nivå. Anpassningarna är viktiga faktorer för att eleverna ska bli inkluderade och jag undersöker även vilka anpassningar som uppstår och hur går de tillväga för att lösa problem i klassrummet. Denna uppsats utgår från en etnografisk ansats och studiens empiri består av intervjuer med elever, läraren, dövblindsamordnaren, en klassrumsobservation och styrdokument. Dessa empirier presenteras i resultatredovisningen med fokus på elever med Ushers syndrom och inkludering på olika nivåer som skolan, läraren och klassrummet. Studien har visat att skolan och lärarens bemötande är en betydande faktor för inkluderingsprocessen. Forskningen har betonat att det är hela verksamheten som ska förändras i ett inkluderingsarbete. Ett bra bemötande innebär att dessa aktörer med anpassningar ser till att eleverna med Ushers syndrom får uppleva inkludering. Anpassningarna som visats i studien är lärarens klädsel, belysning, turtagning i samtal och tekniska hjälpmedel. Det har konstaterats att elever med Ushers syndrom också själva har en del i inkluderingsarbetet genom att framföra sina behov eftersom behovet varierar från elev till elev. Det har framträtt i studien att det inte är lätt att framföra sina behov direkt eftersom elever inte vill avvika från normen i klassrummet som består av döva elever och teckenspråk.

Human Usher syndrome is a severe and congenital form of syndromic deafness that affects 1 person in 25,000 people in the world population. Normally the stereocilia, microvillar protrusions of the apical membrane of inner ear hair cells, are organized into coherent bundles. This precise organization is critical for mechanosensing, i.e. for hearing. Mutation in any of the five known Usher syndrome genes is sufficient to alter the precise organization of stereocilia, a condition that results in deafness. To date, however, the molecular mechanisms responsible for the splaying of stereocilia and genesis of the disease are not well understood. Here, I identified Drosophila melanogaster genes related to human Usher syndrome and characterized some of them (Cad99C, DSANS and crinkled) during Drosophila development, in the processes of microvilli morphogenesis in the follicular and wing imaginal disc epithelia. Cadherin Cad99C is a transmembrane protein with putative cell adhesion properties. Similar to its human ortholog Protocadherin 15, Drosophila Cad99C localizes to microvillar protrusions in the follicular epithelium. In this epithelium, Cad99C is required for the proper morphogenesis and organization of microvilli into bundles, similar to human Protocadherin 15. Further, overexpression of the full-length Cad99C or of a deleted version, devoid of the cytoplasmic region, promotes microvilli bundling. This finding suggests that Cad99C establishes adhesive interactions between microvilli via its extracellular region. Interestingly, morphological alteration of follicle cell microvilli associates with defective deposition of the vitelline membrane, an extracellular matrix that protects the embryo from osmotic stresses. These findings suggest that microvilli are normally required for the even deposition of the extracellular matrix. In order to test whether Cad99C is involved in microvilli morphogenesis and bundling in other tissues, I analyzed the function of Cad99C in a larval tissue, the wing imaginal disc. Cad99C overexpression, but not Cad99C removal, is sufficient to alter microvilli morphology and organization in the columnar epithelium of the wing imaginal disc. Likely, other molecules can compensate for Cad99C loss of function in this tissue. To possibly get some insights on the molecular function of other Usher syndrome proteins, I analyzed the function of Drosophila SANS and crinkled in the follicular epithelium, where both these genes are expressed. crinkled is the ortholog of myosinVIIa, that encodes a motor protein of the actin cytoskeleton. DSANS is related to human SANS and encodes a cytoplasmic protein of unknown function. It has been puzzling how removal of SANS, a cytoplasmic protein, could impair adhesion and bundling of stereocilia. To study the function of DSANS, I generated null mutant flies and observed that, in the absence of DSANS, delivery of Cad99C to microvilli is impaired. Cad99C localization is however unperturbed in crinkled mutant follicle cells. By immunostaining, DSANS immunoreactivity was detected diffusively in the cytoplasm and in dot-like structures, possibly corresponding to vesicles. In conclusion, DSANS is a cytoplasmic protein that is required for the efficient delivery of Cad99C to microvilli protrusions. Taken together, the analysis that I here performed of Drosophila Usher syndrome related genes indicates two novel molecular mechanisms of function for the corresponding human Usher syndrome proteins. First, human Protocadherin 15, like Drosophila Cad99C, could be involved in establishing adhesive interactions between microvilli protrusions of the inner ear (stereocilia). Removal of Protocadherin 15 would then cause splaying of stereocilia due to lack of inter-stereocilia adhesive links. Second, the analysis here performed suggests that SANS is involved in the efficient delivery of Protocadherin 15 to stereocilia. Mutations in SANS would then lead to splaying of stereocilia and deafness due to poor localization of Protocadherin 15 to stereocilia.

Human Usher syndrome is a severe and congenital form of syndromic deafness that affects 1 person in 25,000 people in the world population. Normally the stereocilia, microvillar protrusions of the apical membrane of inner ear hair cells, are organized into coherent bundles. This precise organization is critical for mechanosensing, i.e. for hearing. Mutation in any of the five known Usher syndrome genes is sufficient to alter the precise organization of stereocilia, a condition that results in deafness. To date, however, the molecular mechanisms responsible for the splaying of stereocilia and genesis of the disease are not well understood. Here, I identified Drosophila melanogaster genes related to human Usher syndrome and characterized some of them (Cad99C, DSANS and crinkled) during Drosophila development, in the processes of microvilli morphogenesis in the follicular and wing imaginal disc epithelia. Cadherin Cad99C is a transmembrane protein with putative cell adhesion properties. Similar to its human ortholog Protocadherin 15, Drosophila Cad99C localizes to microvillar protrusions in the follicular epithelium. In this epithelium, Cad99C is required for the proper morphogenesis and organization of microvilli into bundles, similar to human Protocadherin 15. Further, overexpression of the full-length Cad99C or of a deleted version, devoid of the cytoplasmic region, promotes microvilli bundling. This finding suggests that Cad99C establishes adhesive interactions between microvilli via its extracellular region. Interestingly, morphological alteration of follicle cell microvilli associates with defective deposition of the vitelline membrane, an extracellular matrix that protects the embryo from osmotic stresses. These findings suggest that microvilli are normally required for the even deposition of the extracellular matrix. In order to test whether Cad99C is involved in microvilli morphogenesis and bundling in other tissues, I analyzed the function of Cad99C in a larval tissue, the wing imaginal disc. Cad99C overexpression, but not Cad99C removal, is sufficient to alter microvilli morphology and organization in the columnar epithelium of the wing imaginal disc. Likely, other molecules can compensate for Cad99C loss of function in this tissue. To possibly get some insights on the molecular function of other Usher syndrome proteins, I analyzed the function of Drosophila SANS and crinkled in the follicular epithelium, where both these genes are expressed. crinkled is the ortholog of myosinVIIa, that encodes a motor protein of the actin cytoskeleton. DSANS is related to human SANS and encodes a cytoplasmic protein of unknown function. It has been puzzling how removal of SANS, a cytoplasmic protein, could impair adhesion and bundling of stereocilia. To study the function of DSANS, I generated null mutant flies and observed that, in the absence of DSANS, delivery of Cad99C to microvilli is impaired. Cad99C localization is however unperturbed in crinkled mutant follicle cells. By immunostaining, DSANS immunoreactivity was detected diffusively in the cytoplasm and in dot-like structures, possibly corresponding to vesicles. In conclusion, DSANS is a cytoplasmic protein that is required for the efficient delivery of Cad99C to microvilli protrusions. Taken together, the analysis that I here performed of Drosophila Usher syndrome related genes indicates two novel molecular mechanisms of function for the corresponding human Usher syndrome proteins. First, human Protocadherin 15, like Drosophila Cad99C, could be involved in establishing adhesive interactions between microvilli protrusions of the inner ear (stereocilia). Removal of Protocadherin 15 would then cause splaying of stereocilia due to lack of inter-stereocilia adhesive links. Second, the analysis here performed suggests that SANS is involved in the efficient delivery of Protocadherin 15 to stereocilia. Mutations in SANS would then lead to splaying of stereocilia and deafness due to poor localization of Protocadherin 15 to stereocilia.

Les cellules ciliées internes (CCIs) de la cochlée encodent les signaux acoustiques en impulsions électriques au niveau des synapses à ruban formées avec les fibres afférentes du nerf auditif. L'exocytose des vésicules glutamatergiques par les CCIs est déclenchée par l'activation des canaux calciques Cav1.3 et par l'otoferline, le senseur calcique intracellulaire présumé. Les mécanismes moléculaires précis régulant cette exocytose restent encore mal compris, notamment ceux à l’origine de sa précision temporelle, sa vitesse élevée en phase avec le signal acoustique("phase-locking" jusqu'à 1-2 kHz) et son infatigabilité. Nous montrons que la spécificité des synapses à ruban auditive et vestibulaire passe par une organisation spatiale spécifique des canaux Cav1.3 dans les zones actives. Les CCIs utilisent différentes isoformes de canaux Cav1.3, notamment des isoformes courtes tronquées dans leur partie C-terminale. Ces isoformes courtes (Cav1.343S et Cav1.342A) sont essentiellement impliquées dans le déclenchement et dans l'adaptation rapide de l'exocytose. Cette adaptation se réalise au niveau des canaux Cav1.3 à la fois en intracellulaire par le Ca2+ et en extracellulaire parles protons secrétés lors de l'exocytose. Les isoformes longues (Cav1.342L et Cav1.3∆44),positionnées en périphérie du ruban, réguleraient le recrutement vésiculaire. Par ailleurs, nous montrons que l'organisation spatiale des canaux Cav1.3 est dépendante d'un cytosquelette d'actine-F au ruban synaptique. La clarine 1 (protéine Usher IIIA) interagirait avec l'actine-F, l'harmonine (protéine PDZ, Usher IC) et la sous-unité β2 des canaux calciques pour organiser les canaux Cav1.3 dans les zones actives. / Cochlear inner hair cells (IHCs) encode acoustic signals into nerve impulses at their ribbon synapses formed with the auditory afferent fibers. The exocytosis of glutamatergic vesicles is triggered by voltage activation of Cav1.3 channels and requires otoferlin, the putative intracellular Ca2+ sensor. The precise molecular mechanisms of exocytosis still remain elusive, notably the mechanisms allowing the temporal precision, the high rates of vesicular fusion (high frequency phase-locking with sound) and the indefatigability of the process. We show here that exocytosis in auditory and vestibular hair cells relies on a specific tight spatial organization of Cav1.3 channels at the active zones. Auditory IHCs use different Cav1.3isoforms, notably short C-terminal isoforms (Cav1.343S et Cav1.342A). These short Cav1.3isoforms essentially trigger the RRP exocytosis (Readily Releasable Pool of vesicles) and are at the origin of its fast adaptation. This fast exocytotic adaptation is based both on an intracellularCa2+ dependant inactivation of the Ca2+ current and on its extracellular block by exocytosed protons. Long Cav1.3 isoforms (Cav1.342L et Cav1.3∆44) regulate the vesicular recruitment at the active zones. Furthermore, our results show that a synaptic actin cytoskeleton is essential for the tight spatial organization of the Cav1.3 channels at the ribbons. Clarin 1 (Usher IIIA protein),through its interactions with the F-actin network, harmonin (PDZ protein, Usher IC) and the Ca2+channel β2 subunit, is required to maintain the tight organization of Cav1.3 channels at the ribbon synapses.