La epilepsia lateral temporal de herencia autosómica dominante, es una forma de epilepsia parcial, con crisis secundariamente generalizadas, causada por mutaciones en LGI1. Este gen fue inicialmente descrito en 1998 en relación a la aparición de glioblastomas malignos y se ha visto que su expresión, se relaciona inversamente con el grado de malignidad de estos tumores. El análisis in silico de la secuencia primaria de LGI1, permitió identificar una familia génica compuesta por cuatro elementos, que compartían una misma organización en dominios proteicos: la familia LGI. La existencia de formas clínicas de epilepsia similares a aquellas debidas a mutaciones en LGI1 pero sin relación con este gen, permite establecer la hipótesis de que algún otro componente de la misma familia génica podría estar implicado en la aparición de la enfermedad. Además, la existencia de varios parálogos sugiere que se da un cierto grado de redundancia funcional, que podría ser explicado por una distinta distribución anatómica de los elementos de la familia LGI. En este trabajo se presentan los resultados del análisis de expresión de los ARNm de los componentes de la familia LGI en cerebro de ratón adulto. La distribución de transcritos de los genes de la familia LGI es regionalmente heterogénea, lo que hace pensar que desde su origen a partir de un gen ancestral común, sufrieron una subfuncionalización. Además, en este trabajo se trata de indagar, en la posible función o funciones de estos genes. / Autosomic dominant lateral temporal epilepsy (ADLTE) is a form of partial epilepsy with secondary generalized seizures, caused by mutations in LGI1. This gene was initially identified in 1998, as a tumour suppressor in multiform glioblastoma, affecting to the malignancy of these tumours. In silico analysis of the primary sequence of LGI1, revealed four paralogues of the gene, which shared a very similar domain structure and were named as LGI1, LGI2, LGI3 and LGI4. The existence of similar types of epilepsy with common features for that seen for ADLTE, suggests that some other members of this gene family could be involved in these pathologies. Moreover, the presence of four paralogues, makes the idea of a certain degree of functional redundancy, possible. This fact, could be explained by the complementary distribution of cells expressing the genes of this family in the brain. In this work, we show a detailed expression analysis of the mRNA of the members of the LGI family in adult mouse brain. The distribution of these genes is regionally heterogeneous, suggesting that since their origin as a common ancestral gene, a subfunctionalization might have occurred. In this work, we try to shed light on these possible functions.

A lo largo del desarrollo embrionario las células que forman el embrión deben dividirse numerosas veces hasta alcanzar la cantidad celular capaz de asegurar la diferenciación de todos los tejidos y órganos. Por tanto, la correcta regulación de la proliferación y diferenciación celular es fundamental para evitar defectos durante el desarrollo embrionario y la aparición de enfermedades en el individuo adulto. Aprovechando las numerosas ventajas que ofrece el pez Medaka (Oryzias latipes; Ol), hemos estudiado los mecanismos moleculares que regulan la proliferación y diferenciación en los embriones de Medaka en dos momentos distintos del desarrollo, uno temprano durante la segmentación y otro tardío durante la organogénesis. El estudio en la etapa temprana de desarrollo se ha centrado, por una parte, en describir el patrón de expresión de Nanog y Oct4 a lo largo del desarrollo embrionario, y por otra parte, en estudiar la función endógena de Nanog. Tanto Ol-Nanog como Ol-Oct4 presentan patrones de expresión muy similares a los de mamífero, localizándose en el núcleo de los blastómeros durante la segmentación y más tardíamente, concentrándose principalmente en las células del primordio germinal. En el adulto, ambos se expresan en las células germinales de las gónadas de Medaka. El estudio funcional de Ol-Nanog reveló que es necesario para la transición de la fase de síntesis del ciclo celular al regular la expresión de Ciclina A, así como para la proliferación del embrión, sin embargo, no parece desempeñar un papel directo en la diferenciación de las capas germinales embrionarias. Además, Ol-Nanog media la migración de las células del primordio germinal mediante la regulación directa de la expresión de Cxcr4b. Por otra parte, centramos el estudio de la etapa tardía del desarrollo en conocer la función de la vía de señalización canónica de Wnt sobre los progenitores neurales de la retina. Para realizar este estudio utilizamos una aproximación con animales transgénicos y otra farmacológica que nos permitió manipular la señalización de Wnt en distintos momentos del desarrollo de la retina de Medaka. De este modo, determinamos que la vía de señalización de Wnt tiene dos funciones temporales distintas sobre los progenitores neurales de la retina, una temprana donde regula la progresión del ciclo celular a través de Ciclina D1, proliferación, apoptosis y diferenciación; y otra tardía, donde sólo regula la expresión del gen Vsx1, que es un marcador de células bipolares. Por tanto, la respuesta de los progenitores neurales de la retina a la vía de Wnt es dependiente del estadio de desarrollo. / During embryonic development, cells must divide many times until reaching the number required to ensure the correct differentiation of all tissues. The proper regulation of cell proliferation and differentiation is essential to avoid defects during development and the emergence of diseases in the adult. Due to the favourable experimental characteristics of Medaka fish (Oryzias latipes; Ol), we used it to study the molecular mechanisms that regulate proliferation and differentiation at two different times of development. The study undertaken during the early stage of development has focused on characterising the expression pattern of two key factors involved in maintaining pluripotency, Nanog and Oct4, and also investigating the function of the Medaka Nanog homologue (Ol-Nanog) during development. Both transcripts in medaka are expressed in a similar pattern to the mammalian Nanog and Oct4. Both proteins are located in the nucleus of the blastomeres during segmentation and later in primordial germ cells. In adults, both are expressed in the gonadal germ cells. Ol-Nanog is required for the correct transition of cells within the synthesis phase of the cell cycle by regulating the expression of Cyclin A. Although having an important role in proliferation, Ol-Nanog does not appear to play a direct role in the differentiation of embryonic germ layers. In addition, Ol-Nanog mediates correct primordial germ cell migration by directly regulating the expression of Cxcr4b, the receptor for Sdf1. To study the mechanisms that regulate proliferation and differentiation in later stages, we focused on investigating the role of canonical Wnt signalling using retina neural progenitors as a model system. To perform this study we used a transgenic and pharmacological approach to manipulate Wnt signalling at different stages. We determined that Wnt has two functions on the retina neural progenitors which depend on the stage of development. During early development Wnt controls the progression of the cell cycle by regulating the expression of Cyclin D1. During a later stage of development Wnt regulates the expression of Vsx1, a bipolar cell marker.

The identification of factors underlying complex trait variation is a major goal in the field of genetics. For normally distributed, fully observed trait data there are many well established statistical methods for partitioning phenotypic variation and for mapping quantitative trait loci (QTL). Survival or time-to-event traits often follow non-normal distributions and frequently contain partially-known (or censored) trait data. If standard statistical methods are used to analyse age at onset data a bias can be introduced through a failure to account for the non-normal distribution of the data and the presence of censoring. Complex statistical methods have been developed to partition trait variation and map QTL for age at onset or survival traits. In this thesis, the use of these survival analysis methods is compared to more established statistical methods for the analysis of age-at-onset data. A brief introduction to the analysis of human variation and the issues associated with the analysis of age at onset data is given. The methods currently used to partition trait variation and map QTL for survival traits are discussed (Chapter 1). Age-specific penetrances can be used to model the age-at-onset of disease in unaffected individuals. This parametric method is used to identify loci underlying susceptibility to a novel co-morbid psychiatric phenotype (depression and unexplained swelling). The method is compared to a non-parametric variance component (VC) QTL mapping method that does not account for the age at onset of the disease. Parametric linkage analysis identified two suggestive loci, neither of which were supported by the standard variance component analysis. VC analysis identified a suggestive linkage region on chromosome 14 which decreased upon fine mapping (Chapter 2). Many of the current methods used to analyse survival data in human genetics are based on methods originally derived by animal geneticists. The analysis of survival traits in some experimental populations is simplified by the presence of fully inbred lines. However, for complex traits the methods are both computationally intensive and not widely available. A grouped linear regression method is proposed for the analysis of continuous survival data in fully inbred lines. Using simulation the method is compared to both the Cox and Weibull proportional hazards models and a standard linear regression method that ignores censoring. The grouped linear regression method is of equivalent power to both the Cox and Weibull proportional hazards methods, is significantly better than the standard linear regression method when censored observations are present and is computationally simple (Chapter 3). A sample of 446 monozygotic (MZ) twins, 633 dizygotic (DZ) twins and 223 siblings was used to partition the inter-individual variance in age at menarche. The analysis was carried out using both a standard method which failed to account for the censored nature of the data and a mixed effects Cox model which fits a frailty model to the random effects. The standard methodology suggested that an additive genetic model best described the data. The most parsimonious model when using the frailty method included additive genetic and common environmental effects (ACE). The difference between the two models was caused by the different ascertainment of the siblings. The frailty model estimated the heritability of age at menarche to be 0.57 (Chapter 4). In Chapter 5, a sample of 2,685 pseudo-independent sib-pairs is used in a genomewide linkage scan for QTL underlying variation in age-at-menarche. The sample comprises of the adolescent sample discussed in chapter 4, and three adult cohorts. The proportion of censoring in the sample is 1.20% so a standard QTL mapping method is used. Two QTL of suggestive significance are identified on chromosomes 11p and 3p. The candidate genes WT1 and FSHB are located within the linkage peak on 11p. After the removal of bivariate outliers a locus on chromosome 12q was identified. No significant QTL were detected which suggests age-at-menarche is influenced by multiple genes of small effect. The thesis concludes with a general discussion (Chapter 6).

The first phylogeny reconstructed solely for amblyceran genera is presented. This study, based on an extensive comparison of adult morphology and a rigorous cladistic analysis, considers generic exemplars from 4 families of amblyceran lice (Menoponidae, Boopiidae, Laemobothriidae and Ricinidae). The monophyly and evolutionary relationships of these families are strongly supported and there is good support for Menoponidae and Boopiidae as sister taxa. The relationships of the families are not concordant with the traditional hypothesis of a basal Menoponidae. The study identifies 4 supra-generic groups within the Menoponidae, which are discussed with reference to previous classifications and studies which have included amblyceran taxa. A preliminary assessment of host-parasite cospeciation is also provided. Whether a similar phylogeny would be produced from molecular data is investigated. The relationships of genera based on morphology are compared with phylogenies generated from the nuclear gene elongation factor 1a and the mitochondrial gene cytochrome oxidase I. Different methods of reconstruction used to assess their phylogeny and raw signal find that the data are largely incongruent, although there is little support for the topologies generated from the sequence data. The monophyly and relationships of families are compared between datasets and differences in rate heterogeneity between the data are also discussed. A first phylogeny for the genus Austromenopon (Amblycera: Menoponidae) and their close allies (based on the results of the morphological analysis) is reconstructed from molecular data using the mitochondrial genes COI and 12S rRNA. The molecular phylogenies obtained are generally incongruent, with most branch support located nearer the tips of the tree. No analysis recovered a monophyletic Austromenopon, although there is good support for a subset of the Austromenopon taxa, which repeatedly group together.

Plant pathogens secrete effector proteins in order to overcome immunity in plants stimulated by common microbial patterns. The genomes of oomycete pathogens including Hyaloperonospora arabidopsidis (Hpa) are predicted to contain a large number of effectors. These experiments focussed on characterising an interaction between predicted Hpa effector HaRxL14 and Arabidopsis protein phosphatase type-2CA (PP2CA), which functions as a co-receptor in response to the phytohormone abscisic acid (ABA). This interaction was previously identified in a yeast two-hybrid screen. Bimolecular fluorescence complementation experiments verified an interaction in the nucleus. Over-expression of the effector in planta enhances susceptibility of Arabidopsis to Hpa, although knocking-out PP2CA in the host did not have a clear effect on infection. Furthermore, a potential role for the interaction in enhancing host signalling associated with ABA was highlighted from microarray analysis of Arabidopsis lines over-expressing the effector. The up-regulation of various ABA-related genes supports previous findings that ABA may disrupt host response to biotrophic pathogens. Furthermore, it was hypothesised that phytohormones including jasmonic acid (JA), ABA, and salicylic acid (SA) could have a role in coordinating host transcription at the level of chromosome conformation. Progress was made towards optimising a method for use with Arabidopsis related to chromosome conformation capture (3C). These experiments began to examine the spatial interactions of JA-induced genes in Arabidopsis. This method could be used to determine if related genes co-localise at specialised transcription factories. These transcription factories have previously been studied in other models including mammals, although their potential role in plants is currently not well understood. Overall, a Hpa effector was shown to interact with host protein PP2CA potentially to up-regulate ABA-related genes. It remains to be established if phytohormones have a role in coordinating transcription through manipulating spatial interactions of genes.

Understanding how virus strains offer protection against closely related emerging strains is vital for creating effective vaccines. For many viruses, including Foot-and-Mouth Disease Virus (FMDV) and the Influenza virus where multiple serotypes often co-circulate, in vitro testing of large numbers of vaccines can be infeasible. Therefore the development of an in silico predictor of cross-protection between strains is important to help optimise vaccine choice. Vaccines will offer cross-protection against closely related strains, but not against those that are antigenically distinct. To be able to predict cross-protection we must understand the antigenic variability within a virus serotype, distinct lineages of a virus, and identify the antigenic residues and evolutionary changes that cause the variability. In this thesis we present a family of sparse hierarchical Bayesian models for detecting relevant antigenic sites in virus evolution (SABRE), as well as an extended version of the method, the extended SABRE (eSABRE) method, which better takes into account the data collection process. The SABRE methods are a family of sparse Bayesian hierarchical models that use spike and slab priors to identify sites in the viral protein which are important for the neutralisation of the virus. In this thesis we demonstrate how the SABRE methods can be used to identify antigenic residues within different serotypes and show how the SABRE method outperforms established methods, mixed-effects models based on forward variable selection or l1 regularisation, on both synthetic and viral datasets. In addition we also test a number of different versions of the SABRE method, compare conjugate and semi-conjugate prior specifications and an alternative to the spike and slab prior; the binary mask model. We also propose novel proposal mechanisms for the Markov chain Monte Carlo (MCMC) simulations, which improve mixing and convergence over that of the established component-wise Gibbs sampler. The SABRE method is then applied to datasets from FMDV and the Influenza virus in order to identify a number of known antigenic residue and to provide hypotheses of other potentially antigenic residues. We also demonstrate how the SABRE methods can be used to create accurate predictions of the important evolutionary changes of the FMDV serotypes. In this thesis we provide an extended version of the SABRE method, the eSABRE method, based on a latent variable model. The eSABRE method takes further into account the structure of the datasets for FMDV and the Influenza virus through the latent variable model and gives an improvement in the modelling of the error. We show how the eSABRE method outperforms the SABRE methods in simulation studies and propose a new information criterion for selecting the random effects factors that should be included in the eSABRE method; block integrated Widely Applicable Information Criterion (biWAIC). We demonstrate how biWAIC performs equally to two other methods for selecting the random effects factors and combine it with the eSABRE method to apply it to two large Influenza datasets. Inference in these large datasets is computationally infeasible with the SABRE methods, but as a result of the improved structure of the likelihood, we are able to show how the eSABRE method offers a computational improvement, leading it to be used on these datasets. The results of the eSABRE method show that we can use the method in a fully automatic manner to identify a large number of antigenic residues on a variety of the antigenic sites of two Influenza serotypes, as well as making predictions of a number of nearby sites that may also be antigenic and are worthy of further experiment investigation.

Airborne pollens and, more recently, spores, which occur in the rooftop airstream over Edinburgh have been monitored and the data analysed, since 1988. The thesis describes the developing organisation, methodologies and resources which underpin the daily pollen count, data of which are transmitted daily to the UK National Pollen Research Unit at Worcester for the British Aerobiology Federation's database. The data of birch (Betula) and grass (POACEJE), two highly allergenic components of the pollen circulating, are forwarded daily to the European Aeroallergy Network's database in Vienna. Each of the nine selected publications presented are of significance both nationally and internationally. Both the birch and grass pollen studies revealed problems associated with geographical location, varying heights of trapping sites and determination of start dates for pollen seasons. Likewise, the factors involved in asthma mortality within Scotland, the effect on human health that may be passed by high concentrations of bracken spores and the impact of Dutch Elm disease on the elm population, all highlighted problems in determining which environmental factors are significant and, possibly, causative. The paper which dealt with the possible use of pollen rain analysis on vegetation surfaces, was a response to an hypothesis, which could have proved useful had it been positive. The two papers on the technique of pollen analysis of animal faeces has proved to be of value in determining preferred diet, habitat and cause of pollinosis. Lastly, the biographical paper on Dr Cunningham once again underlined the importance of an individual's contribution to the gradual development of techniques for measuring, evaluating and understanding of the roles of various parameters and their interaction in the discharge, aerial movement and impact ofbiopartic1es. The thesis concludes with a description and evaluation of the author's contribution to the science of Aerobiology.

The ecology and evolution of pathogens are key factors in predicting the severity and spread of disease, as well as treatment outcomes. However, the effects of multiple trophic levels that include host, microbial competitors and viruses are typically overlooked. In this thesis I develop our understanding of bacteria-phage coevolution, microbial dispersal and the role of the microbiome in disease. The results of these experiments have direct implications for phage therapy: the use of bacteriophages to treat bacterial infections. Firstly, I explore the risks of phage application in the environment and draw parallels with the misuse of antibiotics in selecting for bacterial resistance. I then demonstrate that the evolution of resistance to phages in a plant pathogenic bacterium is context-dependent. Notably, I find a fitness cost in plant infections that is absent when the bacteria are cultured solely in the laboratory. I then characterize four novel phages and use a simple laboratory based assay to predict their potential as phage therapy agents in an agricultural context. Next I show that reservoir species of plant hosts can affect the evolution of virulence, when bacteria are passaged on both a focal and distant host, but find no evidence of local adaptation. I also show that the evolution of such traits can occur in a parallel manner at the genetic level. I then determine a compositional shift in the microbiota associated with the symptoms of bleeding canker disease in Horse Chestnut trees across the length of the UK. Finally, I find an age-elated decline in bacterial species richness and evidence for niche-assembly theories by investigating bacterial dispersal in UK Oak trees in a single woodland.

Trotz der rasanten Entwicklung molekulargenetischer Analysemethoden sind die Auslöser vieler Erbrankheiten bislang ungeklärt. Eine Identifikation der genetischen Ursache einer Erkrankung ist jedoch essenziell, um zusätzliche invasive Tests vermeiden, adäquate Therapiemaßnahmen in die Wege leiten, akkurate Prognosen stellen und eine entsprechende genetische Beratung anbieten zu können. Next Generation Sequencing (NGS)-basierte Techniken wie die Whole Exome Sequenzierung (WES) haben die humangenetische Forschung und Diagnostik in den letzten Jahren revolutioniert. Die WES ermöglicht die Sequenzierung der Exons aller proteincodierenden Gene von mehreren Individuen gleichzeitig und stellt ein hilfreiches Werkzeug bei der Suche nach neuen kranheitsrelevanten Genen im Menschen dar. Die vorliegende Arbeit beschäftigt sich mit der Aufklärung genetischer Ursachen verschiedenster Erkrankungen in konsanguinen Familien aus dem nahen und mittleren Osten mittels WES. Insgesamt wurden 43 Patienten mit unterschiedlichen Krankheitsbildern untersucht, darunter viele mit Skelettdysplasien oder Neuropathien. In 22 Fällen (51%) konnte die entsprechende krankheitsverursachende Mutation ausfindig gemacht werden. In 21% der aufgeklärten Fälle wurden Sequenzvarianten detektiert, die in der Literatur bereits als pathogen beschrieben wurden, während 63% bisher noch unbekannte Mutationen in bereits als krankheitsrelevant beschriebenen Genen darstellten. Zudem konnten im Rahmen dieser Arbeit drei neue, für den Menschen krankheitsrelevante Gene identifiziert werden, solute carrier family 10 member 7 (SLC10A7), T-box 4 (TBX4) und MIA SH3 domain ER export factor 3 (MIA3). SLC10A7 codiert für einen Transporter aus der Familie der solute carrier, der in der Plasmamembran verankert ist. In dieser Arbeit geleistete Analyseergebnisse konnten zu der Erstbeschreibung von homozygoten pathogenen SLC10A7-Mutationen als Ursache für eine Skelettdysplasie mit Amelogenesis imperfecta beitragen. Bei TBX4 handelt es sich um einen hochkonservierten Transkriptionsfaktor, der während der embryonalen Entwicklung an der Ausbildung der unteren Extremitäten beteiligt ist. Homozygote pathogene TBX4-Mutationen wurden im Kontext dieser Arbeit erstmalig mit einer posterioren Amelie mit Becken- und Lungenhypoplasie in Verbindung gebracht. MIA3 ist ein Transmembranprotein des endoplasmatischen Retikulums, das eine essenzielle Rolle bei der Proteinsekretion spielt. Die hier vorgestellten Patienten mit homozygoten pathogenen MIA3-Mutationen zeigen eine komplexe syndromale Erkrankung, die sich hauptsächlich in einer Kollagenopathie, Diabetes mellitus und milder mentaler Retardierung manifestiert und ein neues Krankheitsbild darstellt. Die im Rahmen dieser Arbeit erzielten Ergebnisse erweitern somit zum einen das Mutationsspektrum verschiedener bekannter Krankheitsbilder und offenbaren zum anderen neue krankheitsrelevante Gene im Menschen. / Despite the rapid development of molecular genetic analysis methods, the causes of many hereditary diseases are still unknown. However, it is essential to identify the genetic cause of a disease in order to avoid additional invasive tests, to initiate adequate therapeutic measures, to be able to provdide accurate prognoses, and to offer appropriate genetic counselling. Over the past years, Next Generation Sequencing (NGS)-based technologies such as Whole Exome Sequencing (WES) have revolutionized research and diagnostics in human genetics. WES enables sequencing of the exons of all protein-coding genes from several individuals simultaneously and is a powerful tool in identifying new disease-relevant genes in humans. The present work deals with the elucidation of genetic disease causes in consanguineous families from the Near and Middle East by means of WES. A total of 43 patients with various clinical phenotypes were examined, including many with skeletal dysplasias or neuropathies. In 22 cases (51%), the genetic cause of the disease could be found. In 21% of the solved cases, sequence variants were detected that were already described as pathogenic in the literature, while 63% showed previously unknown mutations in genes already described as disease-relevant in humans. In addition, three new disease-relevant genes could be identified within the scope of this work: solute carrier family 10 member 7 (SLC10A7), T-box 4 (TBX4) and MIA SH3 domain ER export factor 3 (MIA3). SLC10A7 encodes a transporter from the family of solute carriers, which is anchored in the plasma membrane. The analysis results performed in this study could contribute to the first description of homozygous pathogenic SLC10A7 mutations as the cause of a novel skeletal dysplasia with amelogenesis imperfecta. TBX4 is a highly conserved transcription factor that is involved in the formation of the lower extremities during embryonic development. Homozygous pathogenic TBX4 mutations were associated for the first time with posterior amelia with pelvic and pulmonary hypoplasia in the context of this study. MIA3 is a transmembrane protein of the endoplasmic reticulum that plays an essential role in the secretory pathway. The patients presented here with homozygous pathogenic MIA3 mutations show a complex syndromal disease manifesting mainly in a collagenopathy, diabetes mellitus, and mild mental retardation, representing a novel clinical picture. The results obtained within the scope of this work expand on the one hand the range of mutations of various known diseases and on the other hand reveal novel disease-relevant genes in humans.

Laut des aktuellen Reports der Weltgesundheitsorganisation sind ca. 466 Millionen Menschen weltweit von einer Hörstörung (HS) betroffen. Durch die enorme Heterogenität und die klinische Variabilität, die diese Erkrankung ausmacht, und viele bisher nicht mit HS assoziierte Gene, bleibt ein großer Teil der erblich bedingten HS in vielen Familien unaufgeklärt. Die Entwicklung moderner Techniken, wie die Next-Generation Sequenzierung (NGS) und der Fortschritt bei der Untersuchung von Modellorganismen trugen jedoch in den letzten Jahren immens dazu bei, neue Gene zu identifizieren, die innerhalb des auditorischen Signalwegs oder damit assoziierten Strukturen beteiligt sind. Die vorliegende Arbeit umfasst Ergebnisse dreier Veröffentlichungen, in denen iranische und pakistanische Familien und eine deutsche Familie mit erblich bedingter HS untersucht und neue, krankheitsverursachende Varianten identifiziert und funktionell charakterisiert wurden. Im ersten Abschnitt konnten zwei neue rezessive Varianten im CDC14A-Gen als krankheitsverursachend identifiziert werden, die zu einem potentiellen Funktionsverlust des kodierten Proteins in einer iranischen und einer pakistanischen Familie führen. Mit Hilfe einer funktionellen Charakterisierung auf RNA-Ebene (Spleiß-Assay und RT-qPCR) konnte der Funktionsverlust beider Varianten bestätigt werden. Der zweite Abschnitt umfasst eine deutsche Familie mit sieben von einer HS betroffenen Familienmitgliedern, in der eine heterozygote missense Variante in MYO3A identifiziert wurde. In der vorliegenden Arbeit konnte somit die erste autosomal dominante Variante in einer europäischen Familie mit einer bilingualen, sensorineuralen Hochtonschwerhörigkeit beschrieben werden und der dominante Charakter von MYO3A bestätigt werden. Im dritten Abschnitt konnten die krankheitsverursachenden Varianten in 13 Familien aus einer Kohorte mit 21 pakistanischen Familien mit einer syndromalen und nicht-syndromalen HS ausfindig gemacht werden. Hierbei wurden sowohl bekannte, als auch bisher nicht beschriebene Varianten detektiert. Die Aufklärungsrate innerhalb dieser Kohorte betrug 61,9% und es konnte somit das Spektrum syndromaler und nicht-syndromaler HS erweitert werden. Der letzte Abschnitt dieser Arbeit beschreibt eine iranische Familie mit einer milden HS und milden Intelligenzminderung, in der eine homozygote missense Variante im Kandidatengen DBN1 ausfindig gemacht wurde. Um die Funktion und die Auswirkungen eines potentiellen Verlusts des codierten Proteins Drebrin zu untersuchen, wurden immunhistochemische Färbungen und auditorische Messungen an Dbn1 Knockout (KO)-Mäusen durchgeführt. Hierbei konnte eine Expression innerhalb der Nervenfasern, die innere Haarzellen innervieren, nachgewiesen werden. Eine leicht verlängerte Latenz für die ABR-Welle IV in KO-Mäusen im Vergleich zum Wildtyp ergab den Hinweis auf einen Defekt innerhalb des zentralen auditorischen Signalwegs, der möglicherweise mit einer Sprachverarbeitungsstörung im Menschen korreliert. / According to the latest World Health Organization report, approximately 466 million people are affected by hearing loss (HL) worldwide. Due to the enormous heterogeneity and clinical variability that comes with this disorder and the previously unassociated HL genes, a large proportion of hereditary HL remains unexplained in many families. However, the development of modern techniques such as next-generation sequencing (NGS) and constant progress in the study of model organisms contributed immensely to the identification of new genes involved within the auditory pathway or associated structures. This thesis includes results of three publications in which Iranian and Pakistani families and a German family with HL were studied and novel disease-causing variants were identified and characterized. In the first section, two novel recessive variants in the CDC14A gene were identified as disease-causing, leading to a loss-of-function of the encoded protein in an Iranian and a Pakistani family. Functional characterization on RNA level (splice assay and RT-qPCR) confirmed the loss of function of both variants. The second section includes a German family with seven family members affected by HL, in which a heterozygous missense variant in MYO3A was identified. Thus, the first autosomal dominant variant in a European family with a bilingual sensorineural high-frequency hearing loss could be described in the current work. In the third section, the disease-causing variants were established in 13 families from a cohort of 21 Pakistani families with syndromic and non-syndromic HL. Both known and previously undescribed variants were detected. The detection rate within this cohort was 61.9% and thus the spectrum of syndromic and non-syndromic HL could be expanded. The final section of this work describes an Iranian family with mild HL and mild intellectual disability in which a homozygous missense variant in the candidate gene DBN1 was detected. To investigate the function and effects of a potential loss of the encoded protein Drebrin, immunohistochemical staining and auditory measurements were performed in Dbn1 knockout mice. Here, expression within nerve fibers innervating inner hair cells was detected. A slightly prolonged latency for ABR wave IV in the auditory pathway in KO mice compared to wild type mice provided evidence for a defect within the central auditory pathway that might correlate with a speech processing disorder in humans.