Cell cultures were examined for percentage of fragile sites seen in straight-stained, Q-stained and reverse fluorescent-stained preparations. In all cases, percentage of fragile site expression was decreased when compared to straight-stained preparations. However, fragile sites seen in Q- and RF-stain could be identified as on X chromosomes.

Thesis (Ph. D. in Biological Science)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.

by Priscilla Miu-kuen Poon. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (p. 176-193). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

The accurate development of the wiring between the billions of neurons in our brain is fundamental to brain function. Development of this connectivity relies on activity-dependent modification of synapses similar to those that underlie learning and memory. Glutamate is the principal excitatory neurotransmitter in the mammalian brain and several brain disorders result from altered glutamatergic receptor signalling (Catania et al., 2007; Lau and Zukin, 2007). Genes encoding glutamate receptor associated proteins have a high incidence of mutation in cognitive disorders, especially X-linked mental retardation (MR)(Laumonnier et al., 2007). MR has long been associated with altered cortical connectivity, particularly dendritic spine dysgenesis. There is also an emerging view that aberrant local protein synthesis within dendrites and protein trafficking to dendrites underlies some forms of MR (Kelleher and Bear, 2008; Pfeiffer and Huber, 2006; Zalfa and Bagni, 2005). Most studies examining the role of glutamatergic receptors in MR have focused on adults. Little is known about how these MR genes regulate brain development despite their neurodevelopmental aetiology. Fragile X mental retardation (FXS) is the most common form of inherited MR and results from the loss of fragile X mental retardation protein (FMRP). FMRP is a RNA binding protein and is hypothesised to have a role in protein trafficking from nucleus to sites of synapses, and regulating local protein synthesis at sites of synapses (Bagni and Greenough, 2005). A prevalent theory of FXS causation is ‘metabotropic glutamate receptor (mGluR) theory of fragile X’, which postulates that all functional consequences of mGluR (predominantly mGluR5)-dependent protein synthesis maybe exaggerated in FXS (Bear et al., 2004). Primary somatosensory cortex (S1) of rodents provides an excellent model system to study the role of MR genes in development because of its stereotypic, glutamate receptor-dependent, anatomical development (Barnett et al., 2006b; Erzurumlu and Kind, 2001). Hannan et al., (2001) reported that genetic deletion of mGluR5 results in loss of ‘barrels’, the anatomical correlates of rodent whiskers in S1. Chapter 3 extends these findings to show that there is expression of mGluR5 as early as P4 in S1 prior to segregation of layer 4 cells into barrels suggesting a tropic role for glutamate in barrel formation. The expression of mGluR5 is postsynaptic during barrel formation and does not regulate tangential or radial cortical development. Its effects on barrel segregation are dose dependent and are not due to a developmental delay. During late S1 development, loss of mGluR5 results in decreased spine density suggesting a role in synaptogenesis. Supporting this hypothesis in mGluR5 mutant mice there is a general decrease in expression of synaptic markers in early S1 development. Chapter 4 explores the role of FMRP in cortical development. FMRP is expressed early in S1 development with peak expression prior to synaptogenesis at P14. It is expressed postsynaptically at P7 and pre and postsynaptically at P14. FMRP does not regulate cortical arealisation during barrel formation but results in decreased barrel segregation. In the absence of FMRP, biochemical studies show altered expression of glutamatergic receptors in the neocortex P7 and P14 suggesting altered glutamatergic receptor composition at synaptic sites. During late S1 development, loss of FMRP results in increased spine density in layer 4 spiny cells. Together these data indicate a role for FMRP during early and late S1 development. Chapter 5 directly tests the mGluR theory of FXS by examining whether genetic reduction of mGluR5 levels rescues anatomical phenotypes characterised in Fmr1-/y mice. The defect in barrel formation in Fmr1-/y mice is partially rescued by reducing mGluR5 levels. However, layer 4 spine density in Fmr1-/y mice does not appear to be rescued. Chapter 6 explores the expression patterns of three key synaptic MAGUKs (Membrane associated guanylate kinases) PSD95, SAP102 and PSD93, one of which (PSD95) is regulated by FMRP (Zalfa et al., 2007) and the others which have putative binding sites for FMRP. MAGUKs tether glutamatergic receptors to their associated signalling complexes at the postsynaptic membrane and also regulate glutamatergic receptor trafficking (Collins and Grant, 2007; Kim and Sheng, 2004). The immunohistochemical expression profiles of PSD95, SAP102 and PSD93 show dynamic regulation during S1 development that is unaffected by loss of FMRP (at P7), and biochemical data indicates that basal levels of these MAGUKs in neocortex are unaltered at P7 and P14 in Fmr1-/y mice. In Sap102-/y and Psd95-/- mice, there is altered expression of several synaptic proteins biochemically providing evidence for differential roles of SAP102 and PSD95 in regulating expression of glutamatergic receptors at synaptic sites during early S1 development. This thesis demonstrates that synaptic proteins associated with MR are expressed early in development and display regulatory roles in cellular processes governing S1 formation. An understanding of their role in early brain development would be critical in fully appreciating when and where they exert their regulatory effects, and this in turn would be beneficial in designing therapeutic interventions.

The purpose of this study was to explore what contributes to resilience in females diagnosed with Fragile X Syndrome. Fragile X Syndrome can be defined as an inherited (genetic) condition that causes mental impairment, attention deficit and hyperactivity, anxiety and unstable mood, autistic behaviours, hyper-extensible joints, and seizures. I became aware of Fragile X Syndrome during my time as a live-in caretaker to an adolescent female who was diagnosed with Fragile X Syndrome. Because she coped with her disability so resiliently, I was encouraged to explore what contributes to resilience in females diagnosed with Fragile X Syndrome. I followed a qualitative approach, anchored in the interpretivist paradigm. This means that I tried to understand the resilience of females diagnosed with Fragile X Syndrome through the meanings that the participants in my study assigned to them. Furthermore, I worked from a transformative paradigm, which meant that I was interested in changing the traditionally negative ways in which females diagnosed with Fragile X Syndrome are seen. I followed a multiple case study approach, which included four case studies. I conveniently selected the first participant, but realised that convenience sampling was not very credible for a qualitative case study. An Advisory Panel was then used to purposefully recruit three more participants. In order to explore what contributed to their resilience, I made use of interviews, observations, and visual data collection. I also interviewed adults (e.g. parents, teachers and consulting psychologists) who were significantly involved in the lives of my participants. My findings suggest that resilience in females with Fragile X Syndrome is rooted in protective processes within the individual as well as within her family and environment. Because my findings do not point to one specific resource, my study underscores newer understandings of resilience as an Eco systemic transaction. Most of the resilience-promoting resources noted by the participants in my study as contributing to their resilience have been identified as resilience-promoting in previous studies. Although the themes that emerged in my study have been reported in resilience previously, I make a contribution to theory because I link traditional resilience-promoting resources to resilience in females diagnosed with Fragile X Syndrome. Peer support was previously reported as a resilience-promoting resource, but in my study I noticed that the main source of peer support came from peers who were also disabled. Furthermore, my study transforms how we see females diagnosed with Fragile X Syndrome. This transformation encourages communities and families to work together towards resilience in females diagnosed with Fragile X Syndrome. / Ph.D, North-West University, Vaal Triangle Campus, 2011

How do the brain and the immune system interact, and what are the consequences of this interaction on the physiology of an organism during infection? The main focus of my thesis is neuroimmune interaction, as studied in the following: (1) circadian regulation of immune system function, specifically phagocytosis by immune cells during bacterial infection; (2) the impact of circadian-regulated metabolism and feeding behavior on immunity and host tolerance of bacterial infection; and (3) immune system function in the context of Fragile X syndrome, a neurological disease known to cause circadian dysregulation. To investigate the interactions between these complex physiologies, I use the well-characterized and genetically tractable Drosophila melanogaster animal model. Each topic is briefly introduced in Chapter 1. Chapter 2 focuses on the body of work identifying the circadian regulation of the immune system, particularly phagocytosis, by immune cells during bacterial infection. Chapter 3 highlights findings regarding how diet and host metabolic state impact survival after infection. Chapter 4 illustrates phagocytic immune cell defects both systemically and in the brain in the Drosophila model of Fragile X syndrome. Lastly the conclusions discuss how these three works have built on our fund of knowledge of neuroimmune interactions and the future implications for these results.

Fragile X syndrome (FXS) is a neurogenetic syndrome characterized by cognitive impairments and high rates of autism spectrum disorder (ASD). FXS is often used as a model for exploring mechanisms and pathways of symptom expression in ASD due to the high prevalence of ASD in this population and the known single-gene cause for ASD in FXS. Early vocalization features – including volubility, canonical complexity, vocalization duration and vocalization pitch – have shown promise in detecting ASD in idiopathic ASD populations but have yet to be extensively studied in a population with a known cause for ASD, such as FXS. The present study characterizes early vocalization features in FXS, demonstrating how these features are associated with language ability and ASD outcomes, as well as highlighting how these features in FXS may diverge from patterns observed in typically developing (TD) populations. We coded vocalization features during a standardized child-examiner interaction in 39 nine-month-old infants (22 FXS, 17 TD) who were then followed up at 24 months to determine developmental and clinical outcomes. Although many findings did not reach statistical significance in this small sample, our results provide preliminary evidence that infants with FXS may demonstrate patterns of associations with 24-month language outcomes that diverge from those observed in typical development, and that certain vocalization features may be associated with later ASD outcomes in the FXS group. These findings warrant more research exploring these features as potential early markers of ASD in FXS. Characterizing the associations of early vocalization features with ASD outcomes in FXS can inform mechanisms of ASD development that can then be tested broadly with other etiologically-distinct populations at risk for ASD. Thus, further characterization of these early vocalization features in typical and atypical development may lead to improved early identification methods, treatment approaches, and overall well-being of individuals in the ASD population.

Fragile X syndrome (FXS) is the leading single gene cause of intellectual disability and Autism Spectrum Disorder (ASD). It is caused by epigenetic silencing of the fragile X mental retardation gene (FMR1), causing a loss of Fragile-X Mental Retardation Protein (FMRP). Over the last 2 decades, much has been learned about the pathophysiology related to the loss of FMRP from mouse models of FXS. The recent generation of a rat model of FXS opens the door to: validate phenotypes across mammalian species, address cognitive dysfunction using paradigms that are more difficult to address in mice and explore candidate therapeutics more accurately. This thesis explored the validity of a new rat model for FXS (Fmr1 KO rat). I showed that Fmr1 KO rats exhibit normal spatial navigation memory, social interactions and anxiety levels. On the contrary, when subjects were tested in a battery of spontaneous exploration tasks: object recognition (OR), object-context (OC), object-place (OP), and object-place-context (OPC) recognition, which assess associative memory, Fmr1 KO rats showed a severe deficit in remembering the most complex (episodic-like) associations. Following these results, I sought to explore the development of associative memory from postnatal day 25 (P25) to adulthood (P71). Subjects were tested in the four spontaneous exploration tasks, previously mentioned, 8 times between P25 and P71 to assess the development of their ability to discriminate novel from familiar associations between objects, contexts and places. Fmr1 KO rats’ ability to discriminate novel from familiar object-place (spatial) and object-place-context (episodic-like) associations was significantly impaired (OP was delayed, and OPC ability did not develop). In the last part of this thesis I examined whether early therapeutic intervention with lovastatin can restore the cognitive deficits I observed. Subjects were fed either a diet containing lovastatin (“lovachow”) or an identically looking control diet, between P29 and P64, and tested in the four spontaneous exploration tasks, previously mentioned. Fmr1 KO rats demonstrated a developmental profile of associative memory indistinguishable from that of WT animals. At P64, lovachow was replaced with standard laboratory chow and the animals were tested 1 and 3 months later. Surprisingly, lovastatin treated Fmr1 KO animals maintained the ability to perform the OPC task even at 3 months after the end of treatment, whereas Fmr1 KO animals on control chow showed no improvement with age. The findings of this work indicate that transgenic rats can complement existing mouse models of FXS, providing valuable insights into the effects of FMRP loss on cognitive function. Furthermore, the results from the treatment study show that not only can lovastatin treatment prevent the emergence of cognitive deficits associated with Fragile X Syndrome but also that lovastatin (and perhaps pharmaceutical interventions more generally) may prevent the developmental deficits in neuronal circuit formation which can be maintained into adulthood.

The Indonesian archipelago comprises more than 17,000 islands, inhabited by ~200 million people constituting more than 350 recognizable ethnic and tribal groups which can be classified into two broad ethno-linguistic groups [the Austronesian (AN) and non-Austronesian (NAN) speaking peoples] and 3 physical anthropology groups (Deutero Malay, Proto Malay and Papuan). The origins of these groups are of considerable anthropological interest. The anthropology of Indonesia is extremely complex and still controversial. The present populations of Indonesia show very great diversity. The data presented below result from an investigation of the Fragile X A syndrome and the size and distribution of alleles at fragile sites on the X chromosome among Javanese males with developmental disability (DD) and unselected males from 10 major Indonesian ethnic groups. The Fragile X syndrome is caused by expansion of a CGG trinucleotide repeat array in the 5' untranslated region of the FMR-1 gene at Xq27.3. Normal X chromosomes have between 6-54 CGG trinucleotide repeats, whereas premutation alleles have 55-230 and full mutation alleles more than 230 repeats. In a study of predominantly Caucasian males with intellectual disability, the prevalence of Fragile X syndrome is estimated to be approximately 1:4,000. FRAXE mental retardation syndrome is caused by an expansion of a GCC trinucleotide repeat in the 5'UTR of FMR2 gene located 600 kb telomeric to FMR1. The prevalence of FMR2 is 1-2 per 100,000 live births. FMR2 common alleles consist of 11-30 GGC repeats; intermediate alleles between 31-60 GCC repeats; premutation alleles with 61-200 repeats and full mutation alleles have over 200 repeats with attendant methylation of the repeat array The first Indonesian screening program aimed at determining the presence and prevalence of fragile XA syndrome among individuals with mild DD (IQ above 50) from special schools (N=205) and isolated areas (N=50) of Java was undertaken in 1994-1996 by cytogenetic and molecular studies. In this first study 4 fragile X positive children were found among 255 males with DD. The estimated prevalence of fragile-X in males with mild DD from special schools was 1.95% (5/205) and the overall prevalence was 1.57% (4/255). The number of trinucleotide repeats in the 5' untranslated regions of the FMR1 and FMR2 genes were determined by PCR in 254 Fragile XA-negative Javanese male children with DD. The distribution of FMR1 and FMR2 trinucleotide repeat alleles was found to be significantly different in the Indonesian population with DD compared to that in equivalent Caucasian populations. The trimodal distribution of Indonesian FMR1 alleles (29, 30 and 36 repeats) is largely in agreement with findings from other Asian populations). This provides supportive evidence that the origin of Indonesians could be the same as that of the Chinese and Japanese. Sequence analysis was performed on the trinucleotide repeat arrays of the 27 individuals' FMR1 alleles in the 'grey zone' (35-52 repeats). The identification of 16 unrelated individuals with a (CGG)36 allele that also contains a (CGG)6 segment [(CGG)9AGG(CGG)9AGG(CGG)6 AGG(CGG)9 or 9A9A6A9 pattern] is in agreement with earlier observations in the Japanese population. It is proposed that this FMR1 array pattern may be specific for Asian populations and that Javanese and Japanese populations may have arisen from a single progenitor population. The presence of pure 25, 33 and 34 CGGs in FMR1 alleles with 36, 44 and 45 repeats respectively, suggests that these may represent alleles at high risk for instability and may therefore be at early stages of expansion to a premutation. The lack of the characteristic (CGG)6 in all three alleles with ?? 25 pure CGG arrays suggests that the most common Asian 36 repeat allele is not predisposed to slippage expansion. Seven of the 8 alleles with 36 CGG repeats could be sequenced. Seven of 36 CGG repeats FMR1 alleles from the Hiri population has been sequenced and 4 alleles indicated 9A9A6A9 pattern, 1 sample with 10A25 pattern Two of the remaining alleles showed 12A6A6A9 structure, which consisted of a tandem duplication of the (CGG)6 segment. The presence of a tandem duplication of (CGG)6 segments has never been reported in any other population. The other major findings of this study are that FRAXE syndrome is a rare cause of developmental disability in this predominantly-Javanese population. The most common FMR2 (GCC)20 allele in this selected Asian population is significantly longer than that previously reported for Caucasian populations. There was a weak correlation between the overall length of the FMR1 and FMR2 repeat arrays within the normal range (Spearman's Rank Correlation = 0.130, p-value=0.042) in the Indonesian population, which have been no previous associations reported for alleles within the normal range. One approach to studying the origins of the human populations is to study the genetic structure of polymorphic alleles such as those at the FMR1 locus and its linked microsatellite markers DXS548 and FRAXAC1. Length polymorphisms of the FMR1 gene (CGG)n repeat array, DXS548 and FRAXAC1 were studied in a total of 1,008 unselected males from 10 different Indonesian ethnic groups. FMR1 alleles were identified ranging from 8 to 57 CGG repeats. The most common CGG repeat allele was 29 (45.6%) followed by 30 (27.4%) and 36 repeats (8.0%). One hundred and forty four grey zone (3-52 CGG) alleles were found in the study population. Four people of the same ethnic group from an isolated island in Eastern Indonesia (Hiri, Ternate), a representative of the NAN ethnolinguistic group, had CGG repeat lengths of 55-57. The prevalence of these alleles is estimated to be 3.3% (4/120) in the population of Hiri or 0.4% (4/1008) of whole Indonesian population. Thirteen different alleles were found at the DXS548 locus, of which allele numbers 7 [194 bp] (44.1%), 6.5 [195bp] (43.5%) and 6 [196bp] (7.5%) are the most common. Seven rare alleles, some of which have not been previously found in Asian peoples were also identified (190, 191,192, 193, 197,198, 199, 202, 204 and 206) and accounted for 3.9% of the total. The odd number alleles were dominantly found in this study whereas almost none found in Caucasian. The finding of many "odd numbered" alleles DXS548 has never been found in other Asian population and has only been documented extremely rarely in Caucasians and Africans. Five different alleles of FRAXAC1 identified with alleles D [106 bp] (62.2%) and C [108bp] (35.6%) accounting for 97.8% of FRAXAC1 alleles in the population. Three rare alleles (104, 110, 112 bp = 2.2%) were identified that have not been previously found in other Asian populations (1-3). There is a striking linkage disequilibrium of FMR1 alleles with FRAXAC1 (p=0.0001), 88% of 29 (CGG)n repeats alleles associated with FRAXAC1 allele D (106bp) versus only 17% with the 30 (CGG)n repeat alleles, which is in agreement with other studies. The value of D' was calculated to be 0.7. The longer alleles of both DXS548 and FRAXAC1 were found mostly in the NAN ethnolinguistic group. Moreover the Irian Jaya people also showed a higher percentage of people with 30 CGG repeats and the 108 bp FRAXAC1. The Eastern Indonesian NAN groups demonstrate a different genetic background probably due to the contribution of Melanesian peoples. The Analysis of Molecular Variance (AMOVA) identified that the vast majority of genetic diversity occurs within, rather than between, ethnic groups. These data are consistent with a model where there is sufficient migration (~20 per generation) between populations to minimise differentiation of population through genetic drift. The results obtained are consistent with three clusters of populations that share similar allele frequencies at the fragile X locus. The most clearly defined cluster is based in the east of Indonesia and includes the two Irian populations, Minahasans and Hiri. A surprising finding was that the Minahasan who are Deutero-Malay in origin and physical appearance are genetically closer to the Irianese. This may reflect the admixture of Melanesian alleles or other eastern Indonesian alleles as a result of their geographic location in that part of Indonesia. The second major cluster is largely based in the west of the country and is composed of the following Deutero-Malay populations; Javanese, Balinese, Acehnese but which also includes people from Ternate (not including those from Hiri). Using Delta Mu and Nei's genetic distance for FMR1 locus in this study the Javanese were shown to have the closest distance to Balinese which is consistent with anthropological data and with published data. The third group is a "western and central" group composed of Bimanese, Dayak and Sundanese who share some features of the western and eastern clusters but mostly resemble the western Indonesian populations. Bima is located in the lesser Sunda in between west Indonesia and east Indonesia. The Bimanese are of mixed Deutero & Proto Malay origin that is consistent with their geographic location. The Bataks are distinctive and sit somewhat apart in this scheme. In this study, Bataks were found not to resemble the other Proto-Malay group studied (the Dayak). The Dayaks were found to have fewer alleles than the Bataks at FRAXAC1 and DXS548. In all four methods of calculating genetic distance Bataks showed a large genetic distance to almost all other ethnic groups. There are differences in allele frequency between east and west Indonesia as well as other Asian nations, but the genetic similarities between these groups are also very impressive. The findings from this study are consistent with other genetic anthropological evidence that the people of Indonesia have the same origin as North-east Asian groups. This model is referred to as the "express train from Taiwan" in which the Austronesian speakers are proposed to have radiated from Taiwan bringing the Malayo-Polynesian language group to the Philippines, Borneo and Sulawesi around 5000-4500 B.P.E. However Richards et al.(1998) have used the diversity in the mtDNA D Loop to propose an alternative to the "express train" model. The "two train7quot; model proposes that the Austronesian languages originated within eastern Indonesia during the Pleistocene era and spread through Melanesia and into the remote Pacific within the past 6,000 years. Unfortunately the high migration rates between population groups that were demonstrated in this thesis and the known migration patterns of populations through Indonesia preclude determining whether the observed allelic heterogeneity is a function of the original population or due to the admixture of several gene pools in more recent times.

The Indonesian archipelago comprises more than 17,000 islands, inhabited by ~200 million people constituting more than 350 recognizable ethnic and tribal groups which can be classified into two broad ethno-linguistic groups [the Austronesian (AN) and non-Austronesian (NAN) speaking peoples] and 3 physical anthropology groups (Deutero Malay, Proto Malay and Papuan). The origins of these groups are of considerable anthropological interest. The anthropology of Indonesia is extremely complex and still controversial. The present populations of Indonesia show very great diversity. The data presented below result from an investigation of the Fragile X A syndrome and the size and distribution of alleles at fragile sites on the X chromosome among Javanese males with developmental disability (DD) and unselected males from 10 major Indonesian ethnic groups. The Fragile X syndrome is caused by expansion of a CGG trinucleotide repeat array in the 5' untranslated region of the FMR-1 gene at Xq27.3. Normal X chromosomes have between 6-54 CGG trinucleotide repeats, whereas premutation alleles have 55-230 and full mutation alleles more than 230 repeats. In a study of predominantly Caucasian males with intellectual disability, the prevalence of Fragile X syndrome is estimated to be approximately 1:4,000. FRAXE mental retardation syndrome is caused by an expansion of a GCC trinucleotide repeat in the 5'UTR of FMR2 gene located 600 kb telomeric to FMR1. The prevalence of FMR2 is 1-2 per 100,000 live births. FMR2 common alleles consist of 11-30 GGC repeats; intermediate alleles between 31-60 GCC repeats; premutation alleles with 61-200 repeats and full mutation alleles have over 200 repeats with attendant methylation of the repeat array The first Indonesian screening program aimed at determining the presence and prevalence of fragile XA syndrome among individuals with mild DD (IQ above 50) from special schools (N=205) and isolated areas (N=50) of Java was undertaken in 1994-1996 by cytogenetic and molecular studies. In this first study 4 fragile X positive children were found among 255 males with DD. The estimated prevalence of fragile-X in males with mild DD from special schools was 1.95% (5/205) and the overall prevalence was 1.57% (4/255). The number of trinucleotide repeats in the 5' untranslated regions of the FMR1 and FMR2 genes were determined by PCR in 254 Fragile XA-negative Javanese male children with DD. The distribution of FMR1 and FMR2 trinucleotide repeat alleles was found to be significantly different in the Indonesian population with DD compared to that in equivalent Caucasian populations. The trimodal distribution of Indonesian FMR1 alleles (29, 30 and 36 repeats) is largely in agreement with findings from other Asian populations). This provides supportive evidence that the origin of Indonesians could be the same as that of the Chinese and Japanese. Sequence analysis was performed on the trinucleotide repeat arrays of the 27 individuals' FMR1 alleles in the 'grey zone' (35-52 repeats). The identification of 16 unrelated individuals with a (CGG)36 allele that also contains a (CGG)6 segment [(CGG)9AGG(CGG)9AGG(CGG)6 AGG(CGG)9 or 9A9A6A9 pattern] is in agreement with earlier observations in the Japanese population. It is proposed that this FMR1 array pattern may be specific for Asian populations and that Javanese and Japanese populations may have arisen from a single progenitor population. The presence of pure 25, 33 and 34 CGGs in FMR1 alleles with 36, 44 and 45 repeats respectively, suggests that these may represent alleles at high risk for instability and may therefore be at early stages of expansion to a premutation. The lack of the characteristic (CGG)6 in all three alleles with ?? 25 pure CGG arrays suggests that the most common Asian 36 repeat allele is not predisposed to slippage expansion. Seven of the 8 alleles with 36 CGG repeats could be sequenced. Seven of 36 CGG repeats FMR1 alleles from the Hiri population has been sequenced and 4 alleles indicated 9A9A6A9 pattern, 1 sample with 10A25 pattern Two of the remaining alleles showed 12A6A6A9 structure, which consisted of a tandem duplication of the (CGG)6 segment. The presence of a tandem duplication of (CGG)6 segments has never been reported in any other population. The other major findings of this study are that FRAXE syndrome is a rare cause of developmental disability in this predominantly-Javanese population. The most common FMR2 (GCC)20 allele in this selected Asian population is significantly longer than that previously reported for Caucasian populations. There was a weak correlation between the overall length of the FMR1 and FMR2 repeat arrays within the normal range (Spearman's Rank Correlation = 0.130, p-value=0.042) in the Indonesian population, which have been no previous associations reported for alleles within the normal range. One approach to studying the origins of the human populations is to study the genetic structure of polymorphic alleles such as those at the FMR1 locus and its linked microsatellite markers DXS548 and FRAXAC1. Length polymorphisms of the FMR1 gene (CGG)n repeat array, DXS548 and FRAXAC1 were studied in a total of 1,008 unselected males from 10 different Indonesian ethnic groups. FMR1 alleles were identified ranging from 8 to 57 CGG repeats. The most common CGG repeat allele was 29 (45.6%) followed by 30 (27.4%) and 36 repeats (8.0%). One hundred and forty four grey zone (3-52 CGG) alleles were found in the study population. Four people of the same ethnic group from an isolated island in Eastern Indonesia (Hiri, Ternate), a representative of the NAN ethnolinguistic group, had CGG repeat lengths of 55-57. The prevalence of these alleles is estimated to be 3.3% (4/120) in the population of Hiri or 0.4% (4/1008) of whole Indonesian population. Thirteen different alleles were found at the DXS548 locus, of which allele numbers 7 [194 bp] (44.1%), 6.5 [195bp] (43.5%) and 6 [196bp] (7.5%) are the most common. Seven rare alleles, some of which have not been previously found in Asian peoples were also identified (190, 191,192, 193, 197,198, 199, 202, 204 and 206) and accounted for 3.9% of the total. The odd number alleles were dominantly found in this study whereas almost none found in Caucasian. The finding of many "odd numbered" alleles DXS548 has never been found in other Asian population and has only been documented extremely rarely in Caucasians and Africans. Five different alleles of FRAXAC1 identified with alleles D [106 bp] (62.2%) and C [108bp] (35.6%) accounting for 97.8% of FRAXAC1 alleles in the population. Three rare alleles (104, 110, 112 bp = 2.2%) were identified that have not been previously found in other Asian populations (1-3). There is a striking linkage disequilibrium of FMR1 alleles with FRAXAC1 (p=0.0001), 88% of 29 (CGG)n repeats alleles associated with FRAXAC1 allele D (106bp) versus only 17% with the 30 (CGG)n repeat alleles, which is in agreement with other studies. The value of D' was calculated to be 0.7. The longer alleles of both DXS548 and FRAXAC1 were found mostly in the NAN ethnolinguistic group. Moreover the Irian Jaya people also showed a higher percentage of people with 30 CGG repeats and the 108 bp FRAXAC1. The Eastern Indonesian NAN groups demonstrate a different genetic background probably due to the contribution of Melanesian peoples. The Analysis of Molecular Variance (AMOVA) identified that the vast majority of genetic diversity occurs within, rather than between, ethnic groups. These data are consistent with a model where there is sufficient migration (~20 per generation) between populations to minimise differentiation of population through genetic drift. The results obtained are consistent with three clusters of populations that share similar allele frequencies at the fragile X locus. The most clearly defined cluster is based in the east of Indonesia and includes the two Irian populations, Minahasans and Hiri. A surprising finding was that the Minahasan who are Deutero-Malay in origin and physical appearance are genetically closer to the Irianese. This may reflect the admixture of Melanesian alleles or other eastern Indonesian alleles as a result of their geographic location in that part of Indonesia. The second major cluster is largely based in the west of the country and is composed of the following Deutero-Malay populations; Javanese, Balinese, Acehnese but which also includes people from Ternate (not including those from Hiri). Using Delta Mu and Nei's genetic distance for FMR1 locus in this study the Javanese were shown to have the closest distance to Balinese which is consistent with anthropological data and with published data. The third group is a "western and central" group composed of Bimanese, Dayak and Sundanese who share some features of the western and eastern clusters but mostly resemble the western Indonesian populations. Bima is located in the lesser Sunda in between west Indonesia and east Indonesia. The Bimanese are of mixed Deutero & Proto Malay origin that is consistent with their geographic location. The Bataks are distinctive and sit somewhat apart in this scheme. In this study, Bataks were found not to resemble the other Proto-Malay group studied (the Dayak). The Dayaks were found to have fewer alleles than the Bataks at FRAXAC1 and DXS548. In all four methods of calculating genetic distance Bataks showed a large genetic distance to almost all other ethnic groups. There are differences in allele frequency between east and west Indonesia as well as other Asian nations, but the genetic similarities between these groups are also very impressive. The findings from this study are consistent with other genetic anthropological evidence that the people of Indonesia have the same origin as North-east Asian groups. This model is referred to as the "express train from Taiwan" in which the Austronesian speakers are proposed to have radiated from Taiwan bringing the Malayo-Polynesian language group to the Philippines, Borneo and Sulawesi around 5000-4500 B.P.E. However Richards et al.(1998) have used the diversity in the mtDNA D Loop to propose an alternative to the "express train" model. The "two train7quot; model proposes that the Austronesian languages originated within eastern Indonesia during the Pleistocene era and spread through Melanesia and into the remote Pacific within the past 6,000 years. Unfortunately the high migration rates between population groups that were demonstrated in this thesis and the known migration patterns of populations through Indonesia preclude determining whether the observed allelic heterogeneity is a function of the original population or due to the admixture of several gene pools in more recent times.