No description available.

Thesis (MSc.(Anatomy)--Faculty of Health Sciences)-University of Pretoria, 2008. / Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Additional advisors: Asim Bej, Gene Hines, Douglas Watson, Douglas Weigent. Description based on contents viewed Oct. 2, 2008; title from PDF t.p. Includes bibliographical references.

A espennatogênese é andrógeno-dependente, porém muitos homens com problemas na espermatogênese têm níveis hormonais androgênicos normais. O mau funcionamento do receptor de andrógenos (Androgen Receptor- AR) é a possível causa deste problema. O AR é membro da família dos receptores nucleares e é codificado pelo Gene do Receptor de Andrógenos, que é de cópia única, localizado no cromossomo X e possui oito éxons. O éxon 1 contém um segmento com repetições CAG, que codifica poliglutamina. O trato glutamínico é polimórfico e varia de 1 O a 35 repetições na população normal. Alterações no segmento CAG estão envolvidas na etiologia de doenças neurodegenerativas (repetições CAG > 40) e câncer de próstata (< a 16 repetições). Mutações no Gene do AR estão correlacionadas com a síndrome de insensibilidade aos andrógenos, que varia desde a completa feminilização até homens inférteis com fenótipo normal. O objetivo do presente estudo constituiu em investigar a correlação entre o polimorfismo CAG e a prevalência de mutações nos éxons 5 e 7 e a alteração dos parâmetros seminais na população da Serra Gaúcha. O segmento CAG e a região codificadora dos éxons 5 e 7 foram amplificadas pela técnica de reação da polimerase em cadeia (PCR) e analisadas pela técnica de seqüenciamento automatizado. A média das repetições CAG do grupo de pacientes (n = 45) foi de 20,04±3,94 e a média do grupo controle (n = 45) foi 20,64±3,71. Não há significânc:ia estatística entre elas (p = O, 459). Verificamos correlação entre as repetições CAG e a morfologia seminal (Organização Mundial da Saúde) (p = O, 032; r = O, 349). Porém não se verificou associação com os demais parâmetros seminais: concentração (p =O, 134; r= O, 227), motilidade (p = 0,184; r= 0,202), morfologia (Kruger) (p = 0,213; r= 0,210). Não foram detectadas mutações nos éxons 5 e 7 nos dois grupos de estudo. Nosso estudo sugere que polimorfismo CAG e a presença de mutações nos éxons 5 e 7 não estão correlacionados com alterações seminais no grupo de estudo. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-09-22T16:54:58Z No. of bitstreams: 1 Dissertacao Rafaele Frassini.pdf: 13123487 bytes, checksum: e567348e30bcf48846f22a5b5f684ada (MD5) / Made available in DSpace on 2015-09-22T16:54:58Z (GMT). No. of bitstreams: 1 Dissertacao Rafaele Frassini.pdf: 13123487 bytes, checksum: e567348e30bcf48846f22a5b5f684ada (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Spermatogenesis is androgen-dependent, but most men with impaired spermatogenisis have normal serum androgens leveis. Malfunction of androgen receptor (AR) may be a possible cause of this problem. AR is a member of the nuclear receptor family. It encodes a single copy gene in the X chromosome. The AR Gene is composed by eigth exons. The exon 1 contains a segment of CAG repeats, translated to polyglutamine. This glutamine repeat tract is polymorphic and its size varies from 10 to 35 in normal population. These changes have clinicai implications for human diseases: neurodegenerative disorders (CAG repeat > 40) and prostate cancer (CAG repeat < 16). Mutations in AR Gene cause a variety of defects related to androgen insensitivity, ranging from complete feminization to phenotypic males with infertilty. The aim of this study was to investigate the relationship between CAG repeat length and the prevalence of mutations in the exon:s 5 and 7 and impaired spermatogenesis in a Serra Gaucha population. The CAG repeat leng1th and the coding region of exons 5 and 7 was amplified by polymerase chain reaction (PCR) and analyzed by direct DNA sequencing. The mean CAG repeat length in the experimental group (n = 45) was 20.04±3.94 and in the control group (n = 45) was 20.64±3.71. No difference was found between patientes and controls in the mean values (p = 0.459). 1We found relationship between CAG repeat and morphology (World Health Organization) (p = 0.032; r = 0.349). However, the correlation was not found between CAG repeat and others seminais parameters: concentration (p = 0.134; r= 0.227), morphology (Kruger) (p = 0.213;. r= 0.210) and motility (p = 0.184; r= 0.202). No mutations were detected in the coding regions of exons 5 and 7 in both groups. Our study suggests that CAG polymorphism and mutations in the exons 5 and 7 are not likely to cause of spermatogenesis abnnormalities in our population.

A espennatogênese é andrógeno-dependente, porém muitos homens com problemas na espermatogênese têm níveis hormonais androgênicos normais. O mau funcionamento do receptor de andrógenos (Androgen Receptor- AR) é a possível causa deste problema. O AR é membro da família dos receptores nucleares e é codificado pelo Gene do Receptor de Andrógenos, que é de cópia única, localizado no cromossomo X e possui oito éxons. O éxon 1 contém um segmento com repetições CAG, que codifica poliglutamina. O trato glutamínico é polimórfico e varia de 1 O a 35 repetições na população normal. Alterações no segmento CAG estão envolvidas na etiologia de doenças neurodegenerativas (repetições CAG > 40) e câncer de próstata (< a 16 repetições). Mutações no Gene do AR estão correlacionadas com a síndrome de insensibilidade aos andrógenos, que varia desde a completa feminilização até homens inférteis com fenótipo normal. O objetivo do presente estudo constituiu em investigar a correlação entre o polimorfismo CAG e a prevalência de mutações nos éxons 5 e 7 e a alteração dos parâmetros seminais na população da Serra Gaúcha. O segmento CAG e a região codificadora dos éxons 5 e 7 foram amplificadas pela técnica de reação da polimerase em cadeia (PCR) e analisadas pela técnica de seqüenciamento automatizado. A média das repetições CAG do grupo de pacientes (n = 45) foi de 20,04±3,94 e a média do grupo controle (n = 45) foi 20,64±3,71. Não há significânc:ia estatística entre elas (p = O, 459). Verificamos correlação entre as repetições CAG e a morfologia seminal (Organização Mundial da Saúde) (p = O, 032; r = O, 349). Porém não se verificou associação com os demais parâmetros seminais: concentração (p =O, 134; r= O, 227), motilidade (p = 0,184; r= 0,202), morfologia (Kruger) (p = 0,213; r= 0,210). Não foram detectadas mutações nos éxons 5 e 7 nos dois grupos de estudo. Nosso estudo sugere que polimorfismo CAG e a presença de mutações nos éxons 5 e 7 não estão correlacionados com alterações seminais no grupo de estudo. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Spermatogenesis is androgen-dependent, but most men with impaired spermatogenisis have normal serum androgens leveis. Malfunction of androgen receptor (AR) may be a possible cause of this problem. AR is a member of the nuclear receptor family. It encodes a single copy gene in the X chromosome. The AR Gene is composed by eigth exons. The exon 1 contains a segment of CAG repeats, translated to polyglutamine. This glutamine repeat tract is polymorphic and its size varies from 10 to 35 in normal population. These changes have clinicai implications for human diseases: neurodegenerative disorders (CAG repeat > 40) and prostate cancer (CAG repeat < 16). Mutations in AR Gene cause a variety of defects related to androgen insensitivity, ranging from complete feminization to phenotypic males with infertilty. The aim of this study was to investigate the relationship between CAG repeat length and the prevalence of mutations in the exon:s 5 and 7 and impaired spermatogenesis in a Serra Gaucha population. The CAG repeat leng1th and the coding region of exons 5 and 7 was amplified by polymerase chain reaction (PCR) and analyzed by direct DNA sequencing. The mean CAG repeat length in the experimental group (n = 45) was 20.04±3.94 and in the control group (n = 45) was 20.64±3.71. No difference was found between patientes and controls in the mean values (p = 0.459). 1We found relationship between CAG repeat and morphology (World Health Organization) (p = 0.032; r = 0.349). However, the correlation was not found between CAG repeat and others seminais parameters: concentration (p = 0.134; r= 0.227), morphology (Kruger) (p = 0.213;. r= 0.210) and motility (p = 0.184; r= 0.202). No mutations were detected in the coding regions of exons 5 and 7 in both groups. Our study suggests that CAG polymorphism and mutations in the exons 5 and 7 are not likely to cause of spermatogenesis abnnormalities in our population.

The identification of victims involved in mass fatality incidents, as well as the identification of unknown individuals in criminal cases has become an increasingly important issue nowadays. Sex assessment represents a key point in forensic evaluations due to its significance in providing biological identity. Even though the availability of documented skeletal remains to forensic practitioners is a common practice in many countries, in Turkey, contemporary documented skeletal remains are not available for this purpose. For this reason, studies have been focused on living populations. Previous research has shown that modern technologies such as CT scanning present very promising potential in establishing new standards for contemporary populations. Therefore, the main aim of this project was to examine the application of the measurements taken from 3D CT images of the femur in order to assess sex, and to contribute to the establishment of discriminant function equations for the Turkish population for forensic applications. The accuracy and reproducibility of imaging methods in the assessment of the measurements taken from femora are essential when estimating sex. This research also concentrated on determining the accuracy and repeatability of CT measurements, using the femur. Prior to primary data collection, a preliminary study was performed in an effort to test the reliability of the femur measurements. The results of reliability analysis indicated no significant difference between the three observations of each measurement. Thus, the methodology employed in the current study appears reliable and reproducible. In addition, a validation study was conducted to determine the linear measurement accuracy of the 3D volume rendering models derived from a medical CT scanner and the influence of different reconstruction parameters. The differences between measurements obtained from dry bones and their 3D volume rendered models were also evaluated. The results from this study indicated that there were no statistically significant differences between measurements taken from different reconstruction parameters and measurements obtained from CT images and drybones. Using the CT data, volume-rendering function (VR), 3D Curved Multiplanar reconstruction (MPR), and Scout View on OsiriX were employed in order to compare the accuracy and reliability of each rendering method and to determine which technique is optimal for linear measurements. Overall, the measurements taken from the 3D Volume Rendering images had the highest intra-observer reliability when compared to the other two rendering methods. This research study produced data and interpretations that will inform on and improve population specific standards of sex assessment from three-dimensional postcranial osteometric landmarks. Additionally, this research is believed to provide value for a developing discipline of forensic anthropology, and integrate within the existing systems of criminal investigation and disaster victim identification practices in Turkey. A Turkish sample population, consisting of 300 adult hospital patients was examined via the interpretation of CT reconstructed images using the OsiriX software. The 3D reconstructions were then created using the volume-rendering function in OsiriX (v.5.6.). Following the 3D reconstruction, an image of each femur was segmented from the surrounding bones to ensure the correct usage of landmarks as accurately as possible. Thirteen measurements were acquired using a 3D viewer after being located and marked on each CT reconstructed femora. These thirteen anthropometric parameters were measured and analysed by basic descriptive statistics and discriminant analysis methods using the SPSS 21.0 software package. The intra-observer variation was assessed by obtaining the intraclass correlation coefficient in order to evaluate the accuracy of the linear measurements taken. Asymmetry was also tested. The results indicated that an accuracy of 92.3% was acquired from a combination of six of the measurements, and the Femur Vertical Diameter of Neck (FVDN) measurement was found to be the most dimorphic with 88.0% accuracy.

Le développement du sexe est un processus fondamental et versatile qui forme la morphologie, la physiologie et le comportement des animaux. Le processus de développement sous-jacent est composé de la détermination et de la différentiation du sexe. Les mécanismes de détermination du sexe sont souvent génétiques et nommés gènes de détermination du sexe. A l’heure actuelle, parmi les gènes de détermination connus, trois familles de gènes nommément sox, dmrt and les facteurs TGF-ß gouvernent ce processus de développement.Comme exception à cette règle, sdY « sexually dimorphic on the Y » n’appartient à aucune de ces familles puisqu’il provient d’une duplication/évolution d’un gène ancestral de l’immunité, c’est-à-dire d’un facteur lié à l’interféron, irf9. sdY est le gène maître de la détermination du sexe chez les salmonidés, un groupe de poissons incluant des espèces tel que la truite arc-en-ciel et le saumon Altantique. L’étude présentée avait pour but de premièrement caractériser les propriétés de la protéine SdY. Deuxièment, l’étude a pour but de comprendre comment SdY pouvait entraîner la différentiation testiculaire. Les résultats pris dans leur ensemble proposent que SdY pourrait entraîner la différentiation testiculaire chez les salmonidés en interagissant avec un facteur prédominant de la voie femelle. / Sexual development is a fundamental and versatile process that shapes animal morphology, physiology and behavior. The underlying developmental process is composed of the sex determination and the sex differentiation. The initial triggers are often genetics called sex determining genes. To date, among the known sex determining genes, three gene families namely sox, dmrt and TGF-ß factors govern this developmental program. As exception to this rule, sdY “sexually dimorphic on the Y” does not belong to one of these families as it comes from the duplication / evolution of an ancestor gene related to immunity, i.e., the interferon related factor 9, irf9.sdY is the master sex determining gene in salmonids, a group of fishes that include species such as rainbow trout and Atlantic salmon. The present study was aimed to firstly characterize the features of SdY protein. Results indicate that SdY is predominantly localized in the cytoplasm, composed of a ß-sandwich core surrounded by three a-helices as well specific characteristics conferring a putative protein-protein interaction site. Secondly, the study was aimed to understand how SdY could trigger testicular differentiation. Altogether results propose that SdY would trigger testicular differentiation in salmonids by interacting with a prominent female factor.

Les ressources génétiques naturelles du Tilapia du Nil (Oreochromis niloticus) se trouvent en Afrique. Ces ressources sont menacées en raison de modifications des habitats naturels des poissons et des introductions incontrôlées d'espèces ou de souches exotiques. Les populations de tilapia du Nil qui vivent dans des habitats extrêmes sont emblématiques de cette situation. Elles représentent des ressources génétiques originales et potentiellement utiles pour l'aquaculture. Cependant, les populations sont menacées soit par des modifications fortes de l'environnement soit par l'introduction d'espèces exotiques dans leur habitat. La caractérisation de ces populations constitue la première étape de leur protection et par conséquent leur utilisation en aquaculture. Dans notre étude, nous nous sommes concentré sur deux populations différentes de tilapia du Nil. L'une d'entre elles vit dans le lac alcalin ‘Crocodile Lake' (10 590 S / cm, pH 10) qui est un lac de cratère situé dans Central Island, au milieu du lac Turkana. La deuxième population (ou groupe de population) vit dans les sources chaudes (Hot Springs) du marais de loboi (Loboi Swamp) près du lac Bogoria au Kenya. Ces poissons vivent dans une eau caractérisée par des températures élevées, autour de 36 ° c. Toutes les populations ci-dessus (Crocodile Lake et Loboi swamp Hot Springs) ont connu ou connaissent un certain nombre de pressions sélectives de la part de leurs environnements difficiles. Pour le lac Crocodile, les poissons ont certainement dû trouver un moyen d'excréter leurs déchets azotés car à pH 10, l'excrétion n'est pas possible par simple diffusion. Pour les populations de sources chaudes, la plupart des individus devraient être des mâles car les hautes températures sont connues pour induire une masculinisation chez O. niloticus. Cette population doit avoir accumulé des mutations nécessaires pour lui permettre de surmonter les effets masculinisants des températures élevées.Pour étudier ces populations, nous avons utilisé la morphométrie géométrique et des marqueurs génétiques (microsatellites et 16 ADNmt) et nous les avons comparés à d'autres populations proches de la région. En outre, trois gènes liés au sexe (Cyp19a, Wt1b, AMH) ont été analysés en utilisant des marqueurs SNP dans trois populations de tilapia du Nil habitant les sources chaudes du marais de Loboi, et nous les avons comparés à ceux que l'on observe chez huit autres populations de l'Afrique de l'Est, la région soudano-sahélienne et éthiopiennes . Des différences morphologiques significatives ont été observées entre toutes les populations étudiées, y compris entre les trois populations voisines du marais Loboi, et entre les deux populations génétiquement liées du Crocodile Lake et du lac Turkana. Nous concluons de cette analyse que les différences morphologiques observées peuvent avoir comme origine pour une part des différences génétiques et pour une autre part des facteurs environnementaux. De même, toutes les populations étudiées sont génétiquement différenciées, et nous avons montré que les populations du marais Loboi et celle du lac Baringo ont été introgresséess par des gèes de O. leucostictus. Les analyses des gènes liés au sexe ont révélé que le gène AMH est un gène candidat pour la détermination du sexe chez le tilapia du Nil, avec 12 SNPs montrant de fortes associations avec le sexe phénotypique des individus. Néanmoins, il n'existe pas de modèle général de la détermination du sexe, il semble plutôt que les mécanismes de détermination du sexe sont différents suivant les populations de cette espèce et qu'il n'existe pas de mécanisme unique pour l'espèce entière. / Nile tilapia (Oreochromis niloticus) natural genetic resources are found in Africa. These resources are threatened due to modifications of the natural habitats of fishes and uncontrolled introductions of alien species or strains. Nile tilapia populations living in extreme habitats are emblematic of this situation. They represent original and potentially useful genetic resources for Aquaculture. However, the populations are threatened either by strong modifications or introduction of alien species in their habitats. Characterizing these populations constitutes the very first step of their protection and consequently their utilization in aquaculture. In our study we concentrated on two different populations of Nile Tilapia. One living in the alkaline Crocodile Lake (10,590 µS/cm, 10 pH) which is a Crater Lake located in the central Island of Lake Turkana. The second group of population inhabit the hot springs of Loboi Swamp near Lake Bogoria in Kenya. These fish are living in water characterized by high temperatures, around 36°c. All above populations (Crocodile Lake and Loboi Swamp Hot springs) may have experienced some selective pressures to cope with their challenging environments. For Crocodile Lake, fish may have found a way to excrete their nitrogenous wastes because at pH 10, excretion is not possible by simple diffusion. For the hot spring populations, most individuals should have been males as high temperature is known to induce masculinization in O. niloticus. This population may have accumulated adequate mutations to enable them overcome masculinizing effects of high water temperature. To study these populations we used geometric morphometrics and genetic markers (16 microsatellites and mtDNA) and compared them with other related populations from the region. In addition, three sex-linked genes (Cyp19a, Wt1b, amh) were analysed using SNP markers in three populations of Nile tilapia inhabiting hot springs of Loboi Swamp, and compared them to eight other populations from East Africa, Sudano-Sahelian and Ethiopian regions. Significant morphological differences were observed in all populations studied, including three closely related populations of Loboi Swamp, and two genetically related populations from Lake Turkana basin. Both genetic differences and environmental factors were responsible for the observed morphological differences. Similarly, all studied populations were genetically differentiated, and we demonstrated that populations from Loboi Swamp and Lake Baringo have been introgressed by O. leucostictus genes. Analyses of the sex-linked clustered revealed that amh gene is a candidate gene for sex determination in Nile tilapia, with 12 SNPs showing strong associations to phenotypic sex. Nevertheless there is no general pattern of sex determination, rather it seems that sex determination mechanisms are different with respect to populations, but is not characteristic or unique for the entire species.

As moscas-das-frutas são consideras pragas da fruticultura mundial, sendo que a espécie de maior importância econômica na região Neotropical é Anastrepha fraterculus. Sabe-se que na verdade A. fraterculus corresponde a um complexo de espécies crípticas; vários estudos têm se focado na caracterização destas espécies e no desenvolvimento de estratégias de controle populacional. Trabalhos anteriores mostraram que o silenciamento de genes envolvidos na determinação sexual de Anastrepha, como o transformer-2, constitui uma potencial ferramenta que pode ser usada em programas com este propósito, por gerar uma maior proporção de machos, uma vez que a proteína Transformer-2 funcional é necessária para o desenvolvimento do fenótipo feminino. Na ausência desta proteína um embrião XX se desenvolve com o fenótipo masculino (pseudomacho). Esse tipo de abordagem pode ser utilizado para otimizar a produção de moscas em biofábricas. Nesses estudos prévios o dsRNA foi injetado diretamente em ovos, o que constitui uma técnica de execução bastante complexa e que resulta em uma alta mortalidade durante o processo, inviabilizando sua utilização em um contexto aplicado. Aqui nós descrevemos os efeitos do silenciamento gênico de transformer-2 a partir da injeção parental de dsRNA em A. sp.1 affinis fraterculus, com o intuito de verificar se ocorre o silenciamento gênico na progênie. Para isso, fêmeas adultas foram injetadas com transformer-2 dsRNA em seu abdome e cruzadas com machos não tratados. Suas progênies foram coletadas ao longo de cinco semanas e analisadas quanto a (a) proporção sexual, (b) presença de pseudomachos (XX), (c) fertilidade dos machos e (d) morfologia sexual, além de análises de (e) emergência e de (f) assimetria de estruturas dos adultos, que são indicadores relevantes para a aplicação dessa técnica. A análise da proporção sexual mostrou um desvio significativo da proporção esperada de 1?:1? a favor dos machos, sendo o máximo desvio detectado entre as semanas 1 e 3 após a injeção. A análise dos cariótipos revelou a presença de pseudomachos (XX) na progênie. A maioria dos adultos apresentou morfologia das estruturas sexuais normal, exceto um pequeno número de indivíduos, que tinham gônadas assimétricas. Os testes de fertilidade revelaram que todos os machos apresentaram espermatozoides móveis em seus testículos, mas algumas fêmeas, referentes aos cruzamentos estéreis, não tinham espermatozoides em suas espermatecas. As análises de emergência dos adultos e assimetria de asas e mostraram que não há diferenças em relação ao controle, mas há aumento da assimetria de cerdas frontais da cabeça. Esses resultados indicam que alguns indivíduos da progênie de fêmeas injetadas com transformer-2 dsRNA foram afetados pelo silenciamento gênico de transformer-2. Além disso, as análises de morfologia e assimetria sugerem que esse tratamento causa perturbações no desenvolvimento desses organismos. Finalmente, os testes de fertilidade mostraram que alguns machos da progênie são funcionalmente estéreis, por serem incapazes de transferir espermatozoides para as fêmeas, possivelmente os pseudomachos (XX). A produção de uma progênie com maior número de machos a partir da interferência na expressão de um único gene pode ser bastante útil para melhorar o manejo da produção de machos em biofábricas / Fruit flies are worldwide fruticulture pest, and the economic important species in Neotropics is Anastrepha fraterculus. It is known that actually A. fraterculus corresponds to a cryptic species complex; many studies have focused in characterizing those species and development of population control strategies. Previous studies showed that silencing genes involved in sex determination of Anastrepha, such as transformer-2, are potential tools to be used in control programs that require male production in a large scale. The Transformer-2 protein is required to development of female phenotype. In the absence of this protein, an XX embryo develops in male phenotype (pseudomale). In previous studies, dsRNA was injected directly in embryos, which consists in a high complex executing technique with high rates of mortality during this process, difficulting your utility in an applied context. Herein we describe the effects of transformer-2 gene silencing by parental injection of dsRNA in A. sp.1 affinis fraterculus, to verify whether gene silencing occurs in progeny. For that, adult females were injected with transformer-2 dsRNA in its abdomen and crossed to non-treated males. Their progeny were recovered by five weeks and analysed by (a) sex ratio, (b) presence of pseudomales (XX), (c) fertility of males and (d) sexual morphology, besides analysis of (e) emergence and (f) asymmetry of wings and head setae, what consists in indicators of goodness of progeny. Sex ratio analysis showed a significant bias of expected 1:1, in favour of males, significant between weeks 1 and 3. Karyotype analysis revealed presence of pseudomales (XX) in progeny. The most of flies exhibited sexual structures morphology normal, except by a few individuals having asymmetric testes. Fertility tests showed that all males had motile spermatozoids in their testes, but some females, regarding to sterile crosses, had no spermatozoids in their spermathecae. Emergence and wing asymmetry analysis showed that there is no significant differences in relation to control, but there is a significant increase in asymmetry of head setae. The results indicate that the progeny from females treated with transformer-2 dsRNA were affected by transformer-2 gene silencing. Besides, the morphological analysis suggest that the treatment has a low impact in disturbing ontogeny of the progeny comparing to method of injection directly in eggs. Finally, fertility tests showed that some males of progeny are functionally sterile, unable to transfer spermatozoids to females, possibly the pseudomales ones (XX). The production of a male enriched progeny by interference in expression of a single gene could be very useful to improve the management of male production in biofabrics

Sexual reproduction is an evolutionary innovation that arose 1.2 billion years ago, and in that time, has allowed a rapid diversification of species outpacing that of asexually reproducing organisms. Successful sexual reproduction in animals requires the incredible coordination of complex genetic and behavioral factors; from the most fundamental levels of ensuring correct chromosome segregation and ploidy to the most complex of behavioral mating rituals, any failure can result in a complete loss of evolutionary fitness. In this thesis, I have explored the developmental programs that function to ensure somatic sex determination, sexual differentiation, and mating behaviors in C. elegans. C. elegans is an androdiecious nematode species that has been extensively characterized in regard to the sexual dimorphism of its development, nervous system, and behavioral outputs. Sex determination pathways are widely diverged across phyla, and C. elegans has coopted a Gli family transcription factor to serve as a cell autonomous global regulator of somatic sex determination. I investigated the expression of this transcription factor, tra-1, with cellular, subcellular, sex-specific, and temporal resolution in both sexes of C. elegans and found that it is dynamically regulated to control sex determination. In contrast to the upstream sex determination pathway, genes that control downstream sexual differentiation in animals display much higher functional conservation, and many of the regulators of sexual differentiation belong to a family of transcription factors known as the DMRT family. Downstream of the tra-1 global regulator, I found that the highly conserved DMRT family gene dmd-4 acts much more specifically in adult hermaphrodites to generate sexual dimorphism at the level of the phasmid sensory neurons PHA and PHB. Furthermore, the sexual dimorphism of DMD-4 is regulated post-translationally by a ubiquitin-binding domain that I also found to be functionally conserved in the human ortholog, Dmrt3. Although these transcription factors both demonstrate the high degree of genetic control that contributes to sex determination and sexual differentiation, I also described male-specific effects of early life stress on sexual dimorphic synaptic connectivity and behavior generated by the phasmid sensory neurons, indicating that sexual differentiation is also plastic to environmental cues encountered during the life of an organism. This thesis provides insight into how genetic pathways function at multiple levels to give rise to extensive sexual dimorphism in the soma of an animal, both globally and in regard to the development on individual cells, in addition to the ways in which these genetic pathways can be modified by environmental factors and organismal life history.