Limb development genes underlie variation in human fingerprint patterns.

Fingerprints are of long-standing practical and cultural interest, but little is known about the mechanisms that underlie their variation. Using genome-wide scans in Han Chinese cohorts, we identified 18 loci associated with fingerprint type across the digits, including a genetic basis for the long-recognized "pattern-block" correlations among the middle three digits. In particular, we identified a variant near EVI1 that alters regulatory activity and established a role for EVI1 in dermatoglyph patterning in mice. Dynamic EVI1 expression during human development supports its role in shaping the limbs and digits, rather than influencing skin patterning directly. Trans-ethnic meta-analysis identified 43 fingerprint-associated loci, with nearby genes being strongly enriched for general limb development pathways. We also found that fingerprint patterns were genetically correlated with hand proportions. Taken together, these findings support the key role of limb development genes in influencing the outcome of fingerprint patterning.

'Essential Tremor' Phenotype in FMR1 Premutation/Gray Zone Sibling Series: Exploring Possible Genetic Modifiers.

Fragile X-associated tremor/ataxia syndrome (FXTAS) occurs in carriers of fragile X mental retardation 1 (FMR1) X-linked small CGG expansion (gray zone [GZ] and premutation [PM]) alleles, containing 41-200 repeats. Major features comprise kinetic tremor, gait ataxia, cognitive decline and cerebellar peduncular white matter lesions, but atypical/incomplete FXTAS may occur. We explored the possibility of polygenic effects modifying the FXTAS spectrum phenotypes. We used three motor scales and selected cognitive tests in a series of three males and three females from a single sibship carrying PM or GZ alleles (44 to 75 repeats). The molecular profiles from these siblings were determined by genomewide association study with single-nucleotide polymorphism (SNP) genotyping by Illumina Global Screening Array. Nonparametric linkage analysis was applied and Parkinson's disease (PD) polygenic risk scores (PRSs) were calculated for all the siblings, based on 107 known risk variants. All male and female siblings manifested similar kinetic tremor phenotypes. In contrast to FXTAS, they showed negligible gait ataxia, and few white matter lesions on MRI. Cognitive functioning was unaffected. Suggestive evidence of linkage to a broad region of the short arm of chromosome 10 was obtained, and median PD PRS for the sibship fell within the top 30% of a sample of over 500,000 UK and Australian controls. The genomewide study results are suggestive of modifying effects of genetic risk loci linked to PD, on the neurological phenotype of FMR1-CGG small expansion carriers, resulting in an oligosymptomatic kinetic tremor seen in FXTAS spectrum, but also consistent with essential tremor.

Relationships between Mitochondrial Function, AMPK, and TORC1 Signaling in Lymphoblasts with Premutation Alleles of the FMR1 Gene.

The X-linked FMR1 gene contains a non-coding trinucleotide repeat in its 5' region that, in normal, healthy individuals contains 20-44 copies. Large expansions of this region (>200 copies) cause fragile X syndrome (FXS), but expansions of 55-199 copies (referred to as premutation alleles) predispose carriers to a neurodegenerative disease called fragile X-associated tremor/ataxia syndrome (FXTAS). The cytopathological mechanisms underlying FXTAS are poorly understood, but abnormalities in mitochondrial function are believed to play a role. We previously reported that lymphoblastoid cell lines (LCLs, or lymphoblasts) of premutation carriers have elevated mitochondrial respiratory activities. In the carriers, especially those not clinically affected with FXTAS, AMP-activated protein kinase (AMPK) activity was shown to be elevated. In the FXTAS patients, however, it was negatively correlated with brain white matter lesions, suggesting a protective role in the molecular mechanisms. Here, we report an enlarged and extended study of mitochondrial function and associated cellular stress-signaling pathways in lymphoblasts isolated from male and female premutation carriers, regardless of their clinical status, and healthy controls. The results confirmed the elevation of AMPK and mitochondrial respiratory activities and reduction in reactive O2 species (ROS) levels in premutation cells and revealed for the first time that target of rapamycin complex I (TORC1) activities are reduced. Extensive correlation, multiple regression, and principal components analysis revealed the best fitting statistical explanations of these changes in terms of the other variables measured. These suggested which variables might be the most "proximal" regulators of the others in the extensive network of known causal interactions amongst the measured parameters of mitochondrial function and cellular stress signaling. In the resulting model, the premutation alleles activate AMPK and inhibit both TORC1 and ROS production, the reduced TORC1 activity contributes to activation of AMPK and of nonmitochondrial metabolism, and the higher AMPK activity results in elevated catabolic metabolism, mitochondrial respiration, and ATP steady state levels. In addition, the results suggest a separate CGG repeat number-dependent elevation of TORC1 activity that is insufficient to overcome the inhibition of TORC1 in premutation cells but may presage the previously reported activation of TORC1 in FXS cells.

Evidence for the role of FMR1 gray zone alleles as a risk factor for parkinsonism in females.

Background and Objective There is convincing evidence that small CGG expansion (41-54 repeats): FMR1 "gray zone" alleles (GZ) contribute to the risk of parkinsonism in males, but there is insufficient corresponding data in females. This study intends to fill this gap. Methods We screened whole-blood-derived DNA from a cohort of 601 females diagnosed with idiopathic PD, and from dry Guthrie blood spots from a local sample of 1,005 female newborns (population controls), for the size of the FMR1 CGG repeat using a PCR technique. Results We found a significant excess (8.2%) of GZ carriers compared with 5.2% in the control sample, with a P value of 0.009 for the difference in proportions. Conclusion FMR1 gray zone alleles are a significant risk factor for parkinsonism in females. These population data and occasional reports of FXTAS-like or parkinsonian manifestations in carriers suggest possible mechanisms whereby the effects of these alleles synergize with the existing pathologies underpinning parkinsonism. © 2018 International Parkinson and Movement Disorder Society.

Novel Blood Biomarkers Are Associated with White Matter Lesions in Fragile X- Associated Tremor/Ataxia Syndrome.

BACKGROUND: The need for accessible cellular biomarkers of neurodegeneration in carriers of the fragile X mental retardation 1 (FMR1) premutation (PM) alleles. OBJECTIVE: To assess the mitochondrial status and respiration in blood lymphoblasts from PM carriers manifesting the fragile X-associated tremor/ataxia syndrome (FXTAS) and non-FXTAS carriers, and their relationship with the brain white matter lesions. METHODS: Oxygen consumption rates (OCR) and ATP synthesis using a Seahorse XFe24 Extracellular Flux Analyser, and steady-state parameters of mitochondrial function were assessed in cultured lymphoblasts from 16 PM males (including 11 FXTAS patients) and 9 matched controls. The regional white matter hyperintensity (WMH) scores were obtained from MRI. RESULTS: Mitochondrial respiratory activity was significantly elevated in lymphoblasts from PM carriers compared with controls, with a 2- to 3-fold increase in basal and maximum OCR attributable to complex I activity, and ATP synthesis, accompanied by unaltered mitochondrial mass and membrane potential. The changes, which were more advanced in FXTAS patients, were significantly associated with the WMH scores in the supratentorial regions. CONCLUSION: The dramatic increase in mitochondrial activity in lymphoblasts from PM carriers may represent either the early stages of disease (specific alterations in short-lived blood cells) or an activation of the lymphocytes under pathological situations. These changes may provide early, convenient blood biomarkers of clinical involvements.

Relationships between age and epi-genotype of the FMR1 exon 1/intron 1 boundary are consistent with non-random X-chromosome inactivation in FM individuals, with the selection for the unmethylated state being most significant between birth and puberty.

Methylation of the fragile X-related epigenetic element 2 (FREE2) located on the exon 1/intron 1 boundary of the FMR1 gene is related to FMRP expression and cognitive impairment in full mutation (FM; CGG>200) individuals. We examined the relationship between age, the size of the FMR1 CGG expansion and the methylation output ratio (MOR) at 12 CpG sites proximal to the exon 1/intron 1 boundary using FREE2 MALDI-TOF MS. The patient cohort included 119 males and 368 females, i.e. 121 healthy controls (CGG<40), 176 premutation (CGG 55-170) and 190 FM (CGG 213-2000). For all CpG units examined, FM males showed a significantly elevated MOR compared with that in hypermethylated FM females. In FM males the MOR for most CpG units significantly positively correlated with both age and CGG size (P< 0.05). In FM females the skewing towards the unmethylated state was significant for half of the units between birth and puberty (P < 0.05). The methylation status of intron 1 CpG10-12 that was most significantly related to cognitive impairment in our earlier study, did not change significantly with age in FM females. These results challenge the concept of fragile X syndrome (FXS)-related methylation being static over time, and suggest that due to the preference for the unmethylated state in FM females, X-inactivation at this locus is not random. The findings also highlight that the prognostic value of FXS methylation testing is not uniform between all CpG sites, and thus may need to be evaluated on a site-by-site basis.

Early detection of fragile X syndrome: applications of a novel approach for improved quantitative methylation analysis in venous blood and newborn blood spots.

BACKGROUND: Standard fragile X syndrome (FXS) diagnostic tests that target methylation of the fragile X mental retardation 1 (FMR1) CpG island 5' of the CGG expansion can be used to predict severity of the disease in males from birth, but not in females. METHODS: We describe methylation specific-quantitative melt analysis (MS-QMA) that targets 10 CpG sites, with 9 within FMR1 intron 1, to screen for FXS from birth in both sexes. The novel method combines the qualitative strengths of high-resolution melt and the high-throughput, quantitative real-time PCR standard curve to provide accurate quantification of DNA methylation in a single assay. Its performance was assessed in 312 control (CGG <40), 143 premutation (PM) (CGG 56-170), 197 full mutation (FM) (CGG 200-2000), and 33 CGG size and methylation mosaic samples. RESULTS: In male and female newborn blood spots, MS-QMA differentiated FM from control alleles, with sensitivity, specificity, and positive and negative predictive values between 92% and 100%. In venous blood of FM females between 6 and 35 years of age, MS-QMA correlated most strongly with verbal IQ impairment (P = 0.002). In the larger cohort of males and females, MS-QMA correlated with reference methods Southern blot and MALDI-TOF mass spectrometry (P < 0.05), but was not significantly correlated with age. Unmethylated alleles in high-functioning FM and PM males determined by both reference methods were also unmethylated by MS-QMA. CONCLUSIONS: MS-QMA has an immediate application in FXS diagnostics, with a potential use of its quantitative methylation output for prognosis in both sexes.

White matter changes in patients with Parkinson's disease carrying small CGG expansion FMR1 alleles: a pilot study.

BACKGROUND/AIMS: Alleles of the FMR1 gene containing small expansions of the CGG-trinucleotide repeat comprise premutation and grey-zone alleles. Premutation alleles may cause late-onset Fragile X-associated tremor/ataxia syndrome attributed to the neurotoxic effect of elevated FMR1 transcripts. Our earlier data suggested that both grey-zone and low-end premutation alleles might also play a significant role in the acquisition of the parkinsonian phenotype due to mitochondrial dysfunction caused by elevated FMR1 mRNA toxicity. These data were obtained through clinical and molecular comparisons between carriers of grey-zone/low-end premutation alleles and group-matched non-carrier controls from patients with idiopathic Parkinson's disease (iPD). We aimed to explore the relationship between grey-zone alleles, parkinsonism and white matter changes. METHODS: This study compared the extent and severity of white matter hyperintensity (WMH) on magnetic resonance imaging, using a semi-quantitative method, between 11 grey-zone/low-end premutation carriers and 20 non-carrier controls with iPD from our earlier study. Relationships between WMH scores, and cognitive and motor test scores were assessed for carriers and non-carriers. RESULTS: Supratentorial WMH scores, and tremor and ataxia motor scores were significantly higher in carriers compared with disease controls. Moreover, some associations between cognitive decline and WMH scores were specific for each respective carrier status category. CONCLUSIONS: The results support our earlier claim that grey-zone alleles contribute to the severity of parkinsonism and white matter changes.

Cognitive status correlates of subclinical action tremor in female carriers of FMR1 premutation.

Background: There is evidence for a significant excess of kinetic upper limb tremor in non-FXTAS female FMR1 premutation carriers. The present study explores the possibility that this tremor is associated with various other features reminiscent of those occurring in syndromic FXTAS. Sample/methods: This study analyzed the data from an Australian cohort of 48 asymptomatic premutation women. We utilized spiral drawings from CRST, representing action tremor; the CRST total tremor; and ICARS- kinetic tremors/cerebellar ataxia scales. Cognitive tests (involving executive functioning) included SDMT, TMT, two subtests of the WAIS-III: MR and Similarities. Spearman Rank correlations assessed the relationships between the above measures, and the Chi-square tested hypothesis about the association between the white matter hyperintensities (wmhs) in the splenium of corpus callosum assessed from MR images and spiral drawings scores. Results: The spiral drawing scores were significantly correlated with all three non-verbal cognitive test scores, and with the CRST scores; the latter correlated with all four cognitive test measures. Similarities (verbal) scores correlated with CRST, ICARS, and with the remaining cognitive scores. Ordered spiral scores' categories were significantly associated with the degree of splenium involvement. Conclusion: This study showed that, in non-FXTAS premutation female carriers, sub-symptomatic forms of kinetic tremor were associated with a broader motor, and cognitive (especially executive) dysfunction.

Fragile X-related element 2 methylation analysis may provide a suitable option for inclusion of fragile X syndrome and/or sex chromosome aneuploidy into newborn screening: a technical validation study.

PURPOSE: We show that a novel fragile X-related epigenetic element 2 FMR1 methylation test can be used along with a test for sex-determining region Y (SRY) to provide the option of combined fragile X syndrome and sex chromosome aneuploidy newborn screening. METHODS: Fragile X-related epigenetic element 2, SRY, and FMR1 CGG repeat analyses were performed on blood and saliva DNA, and in adult and newborn blood spots. The cohort consisted of 159 controls (CGG <40), 187 premutation (CGG 56-170), and 242 full-mutation (CGG ~200-2,000) males and females, 106 sex chromosome aneuploidy individuals, and 151 cytogenetically normal controls. RESULTS: At the 0.435 threshold, fragile X-related epigenetic element 2 analysis in males was robust on both blood DNA and newborn blood spots, with specificity and sensitivity of ~100% for full-mutation genotype. In females, the specificity was 99%, whereas half of full-mutation females were above the 0.435 threshold in both blood DNA and newborn blood spots. Furthermore, at this threshold, the test could not differentiate individuals with Klinefelter syndrome from female controls without using the SRY marker. When combined with SRY analysis, the test was consistent with most results for sex chromosome aneuploidies from karyotyping. CONCLUSION: Setting specific thresholds for fragile X-related epigenetic element 2 analysis and including the SRY marker provides the option to either include or exclude detection of sex chromosome aneuploidies as part of fragile X syndrome newborn screening.

Insight and Recommendations for Fragile X-Premutation-Associated Conditions from the Fifth International Conference on FMR1 Premutation.

The premutation of the fragile X messenger ribonucleoprotein 1 (FMR1) gene is characterized by an expansion of the CGG trinucleotide repeats (55 to 200 CGGs) in the 5' untranslated region and increased levels of FMR1 mRNA. Molecular mechanisms leading to fragile X-premutation-associated conditions (FXPAC) include cotranscriptional R-loop formations, FMR1 mRNA toxicity through both RNA gelation into nuclear foci and sequestration of various CGG-repeat-binding proteins, and the repeat-associated non-AUG (RAN)-initiated translation of potentially toxic proteins. Such molecular mechanisms contribute to subsequent consequences, including mitochondrial dysfunction and neuronal death. Clinically, premutation carriers may exhibit a wide range of symptoms and phenotypes. Any of the problems associated with the premutation can appropriately be called FXPAC. Fragile X-associated tremor/ataxia syndrome (FXTAS), fragile X-associated primary ovarian insufficiency (FXPOI), and fragile X-associated neuropsychiatric disorders (FXAND) can fall under FXPAC. Understanding the molecular and clinical aspects of the premutation of the FMR1 gene is crucial for the accurate diagnosis, genetic counseling, and appropriate management of affected individuals and families. This paper summarizes all the known problems associated with the premutation and documents the presentations and discussions that occurred at the International Premutation Conference, which took place in New Zealand in 2023.

Methylation of novel markers of fragile X alleles is inversely correlated with FMRP expression and FMR1 activation ratio.

The fragile X syndrome (FXS) is caused by silencing of the fragile X mental retardation gene (FMR1) and the absence of its product, fragile X mental retardation protein (FMRP), resulting from CpG island methylation associated with large CGG repeat expansions (more than 200) termed full mutation (FM). We have identified a number of novel epigenetic markers for FXS using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), naming the most informative fragile X-related epigenetic element 1 (FREE1) and 2 (FREE2). Methylation of both regions was correlated with that of the FMR1 CpG island detected using Southern blot (FREE1 R = 0.97; P < 0.00001, n = 23 and FREE2 R = 0.93; P < 0.00001, n = 23) and negatively correlated with lymphocyte expression of FMRP (FREE1 R = -0.62; P = 0.01, n = 15 and FREE2 R = -0.55; P = 0.03, n = 15) in blood of partially methylated 'high functioning' FM males. In blood of FM carrier females, methylation of both markers was inversely correlated with the FMR1 activation ratio (FREE1 R = -0.93; P < 0.0001, n = 12 and FREE2 R = -0.95; P < 0.0001, n = 9). In a sample set of 49 controls, 18 grey zone (GZ 40-54 repeats), 22 premutation (PM 55-170 repeats) and 22 (affected) FXS subjects, the FREE1 methylation pattern was consistent between blood and chorionic villi as a marker of methylated FM alleles and could be used to differentiate FXS males and females from controls, as well as from carriers of GZ/PM alleles, but not between GZ and PM alleles and controls. Considering its high-throughput and specificity for pathogenic FM alleles, low cost and minimal DNA requirements, FREE MALDI-TOF MS offers a unique tool in FXS diagnostics and newborn population screening.

Fragile X mental retardation 1 (FMR1) intron 1 methylation in blood predicts verbal cognitive impairment in female carriers of expanded FMR1 alleles: evidence from a pilot study.

BACKGROUND: Cognitive status in females with mutations in the FMR1 (fragile X mental retardation 1) gene is highly variable. A biomarker would be of value for predicting which individuals were liable to develop cognitive impairment and could benefit from early intervention. A detailed analysis of CpG sites bridging exon 1 and intron 1 of FMR1, known as fragile X-related epigenetic element 2 (FREE2), suggests that a simple blood test could identify these individuals. METHODS: Study participants included 74 control females (<40 CGG repeats), 62 premutation (PM) females (55-200 CGG repeats), and 18 full-mutation (FM) females assessed with Wechsler intelligence quotient (IQ) tests. We used MALDI-TOF mass spectrometry to determine the methylation status of FREE2 CpG sites that best identified low-functioning (IQ <70) FM females (>200 CGG repeats), compared the results with those for Southern blot FMR1 activation ratios, and related these assessments to the level of production of the FMR1 protein product in blood. RESULTS: A methylation analysis of intron 1 CpG sites 10-12 showed the highest diagnostic sensitivity (100%) and specificity (98%) of all the molecular measures tested for detecting females with a standardized verbal IQ of <70 among the study participants. In the group consisting of only FM females, methylation of these sites was significantly correlated with full-scale IQ, verbal IQ, and performance IQ. Several verbal subtest scores showed strong correlation with the methylation of these sites (P = 1.2 × 10(-5)) after adjustment for multiple measures. CONCLUSIONS: The data suggest that hypermethylation of the FMR1 intron 1 sites in blood is predictive of cognitive impairment in FM females, with implications for improved fragile X syndrome diagnostics in young children and screening of the newborn population.

Hypertension in FMR1 premutation males with and without fragile X-associated tremor/ataxia syndrome (FXTAS).

Fragile X-associated tremor ataxia syndrome (FXTAS) is a late onset neurodegenerative disease that affects carriers of the fragile X premutation. This study seeks to assess hypertension risk and susceptibility in male premutation carriers with FXTAS. Although many symptoms and diagnostic criteria have been identified, hypertension risk has not been examined in this population. Data from 92 premutation carriers without FXTAS, 100 premutation carriers with FXTAS, and 186 controls was collected via patient medical interview. Age-adjusted logistic regression analysis was used to examine the relative odds of hypertension. We observed a significantly elevated odds ratio (OR) of hypertension relative to controls for premutation carriers with FXTAS (OR = 3.22, 95% CI: 1.72-6.04; P = 0.0003) among participants over 40-year old. The age-adjusted estimated odds of hypertension in premutation carriers without FXTAS in the over 40-year-old age group was higher compared to controls (OR = 1.61, 95% CI: 0.82-3.16), but was not statistically significant (P = 0.164). Chronic hypertension contributes to cardiovascular complications, dementia, and increased risk of stroke. Our results indicate that the risk of hypertension is significantly elevated in male premutation carriers with FXTAS compared with carriers without FXTAS and controls. Thus, evaluation of hypertension in patients diagnosed with FXTAS should be a routine part of the treatment monitoring and intervention for this disease.

Unstable mutations in the FMR1 gene and the phenotypes.

Fragile X syndrome (FXS), a severe neurodevelopmental anomaly, and one of the earliest disorders linked to an unstable ('dynamic') mutation, is caused by the large (>200) CGG repeat expansions in the noncoding portion of the FMR1 (Fragile X Mental Retardation-1) gene. These expansions, termed full mutations, normally silence this gene's promoter through methylation, leading to a gross deficit of the Fragile X Mental Retardation Protein (FMRP) that is essential for normal brain development. Rare individuals with the expansion but with an unmethylated promoter (and thus, FMRP production), present a much less severe form of FXS. However, a unique feature of the relationship between the different sizes of CGG expanded tract and phenotypic changes is that smaller expansions (<200) generate a series of different clinical manifestations and/or neuropsychological changes. The major part of this chapter is devoted to those FMR1 alleles with small (55-200) CGG expansions, termed 'premutations', which have the potential for generating the full mutation alleles on mother-offspring transmission, on the one hand, and are associated with some phenotypic changes, on the other. Thus, the role of several factors known to determine the rate of CGG expansion in the premutation alleles is discussed first. Then, an account ofvarious neurodevelopmental, cognitive, behavioural and physical changes reported in carriers of these small expansions is given, and possible association of these conditions with a toxicity of the elevated FMR1 gene's transcript (mRNA) is discussed. The next two sections are devoted to major and well defined clinical conditions associatedwith the premutation alleles. The first one is the late onsetneurodegenerative disorder termed fragile X-associated tremor ataxia syndrome (FXTAS). The wide range of clinical and neuropsychological manifestations of this syndrome, and their relevance to elevated levels of the FMR1 mRNA, are described. Another distinct disorder linked to the CGG repeat expansions within the premutation range is fragile X-associated primary ovarian insufficiency (FXPOI) in females, and an account of the spectrum of manifestations of this disorder, together with the latest findings suggesting an early onset of the ovarian changes, is given. In the following section, the most recent findings concerning the possible contribution of FMR1 'grey zone' alleles (those with the smallest repeat expansions overlapping withthenormal rangei.e.,41-54CGGs), tothepsychologicalandclinical manifestations, already associated with premutation alleles, are discussed. Special emphasis has been placed on the possibility that the modest elevation of 'toxic' FMR1 mRNA in the carriers of grey zone alleles may present an additional risk for some neurodegenerative diseases, such as those associated with parkinsonism, by synergizing with either other susceptibility genes or environmental poisons. The present status ofthe treatment of fragile X-related disorders, especially FXS, is presented in the last section of this chapter. Pharmacological interventions in this syndrome have recently extended beyond stimulants and antipsychotic medications, and the latest trials involving a group of GluR5 antagonists aim to ascertain if these substances have the potential to reverse some of the neurobiological abnormalities of FXS.

Relationships of Motor Changes with Cognitive and Neuropsychiatric Features in FMR1 Male Carriers Affected with Fragile X-Associated Tremor/Ataxia Syndrome.

The premutation expansion of the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene on the X chromosome has been linked to a range of clinical and subclinical features. Nearly half of men with FMR1 premutation develop a neurodegenerative disorder; Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS). In this syndrome, cognitive executive decline and psychiatric changes may co-occur with major motor features, and in this study, we explored the interrelationships between these three domains in a sample of adult males affected with FXTAS. A sample of 23 adult males aged between 48 and 80 years (mean = 62.3; SD = 8.8), carrying premutation expansions between 45 and 118 CGG repeats, and affected with FXTAS, were included in this study. We employed a battery of cognitive assessments, two standard motor rating scales, and two self-reported measures of psychiatric symptoms. When controlling for age and/or educational level, where appropriate, there were highly significant correlations between motor rating score for ICARS gait domain, and the scores representing global cognitive decline (ACE-III), processing speed (SDMT), immediate memory (Digit Span), and depression and anxiety scores derived from both SCL90 and DASS instruments. Remarkably, close relationships of UPDRS scores, representing the contribution of Parkinsonism to FXTAS phenotypes, were exclusive to psychiatric scores. Highly significant relationships between CGG repeat size and most scores for three phenotypic domains suggest a close tracking with genetic liability. These findings of relationships between a constellation of phenotypic domains in male PM carriers with FXTAS are reminiscent of other conditions associated with disruption to cerebro-cerebellar circuits.

Australian Parkinson's Genetics Study (APGS): pilot (n=1532).

PURPOSE: Parkinson's disease (PD) is a neurodegenerative disorder associated with progressive disability. While the precise aetiology is unknown, there is evidence of significant genetic and environmental influences on individual risk. The Australian Parkinson's Genetics Study seeks to study genetic and patient-reported data from a large cohort of individuals with PD in Australia to understand the sociodemographic, genetic and environmental basis of PD susceptibility, symptoms and progression. PARTICIPANTS: In the pilot phase reported here, 1819 participants were recruited through assisted mailouts facilitated by Services Australia based on having three or more prescriptions for anti-PD medications in their Pharmaceutical Benefits Scheme records. The average age at the time of the questionnaire was 64±6 years. We collected patient-reported information and sociodemographic variables via an online (93% of the cohort) or paper-based (7%) questionnaire. One thousand five hundred and thirty-two participants (84.2%) met all inclusion criteria, and 1499 provided a DNA sample via traditional post. FINDINGS TO DATE: 65% of participants were men, and 92% identified as being of European descent. A previous traumatic brain injury was reported by 16% of participants and was correlated with a younger age of symptom onset. At the time of the questionnaire, constipation (36% of participants), depression (34%), anxiety (17%), melanoma (16%) and diabetes (10%) were the most reported comorbid conditions. FUTURE PLANS: We plan to recruit sex-matched and age-matched unaffected controls, genotype all participants and collect non-motor symptoms and cognitive function data. Future work will explore the role of genetic and environmental factors in the aetiology of PD susceptibility, onset, symptoms, and progression, including as part of international PD research consortia.

Evidence for the toxicity of bidirectional transcripts and mitochondrial dysfunction in blood associated with small CGG expansions in the FMR1 gene in patients with parkinsonism.

PURPOSE: Our previous results showed that both gray zone and lower end premutation range (40-85 repeats) fragile X mental retardation 1 (FMR1) alleles were more common among males with parkinsonism than in the general population. This study aimed to determine whether these alleles have a significant role in the manifestations and pathogenesis of parkinsonian disorders. METHODS: Detailed clinical assessment and genetic testing were performed in 14 male carriers of premutation and gray zone FMR1 alleles and in 24 noncarriers identified in a sample of males with parkinsonism. RESULTS: The premutation + gray zone carriers presented with more severe symptoms than disease controls matched for age, diagnosis, disease duration, and treatment. The Parkinson disease (Unified Parkinson's Disease Rating Scale) motor score and the measures of cognitive decline (Mini-Mental State Examination and/or Addenbrooke's Cognitive Examination Final Revised Version A scores) were significantly correlated with the size of the CGG repeat and the (elevated) levels of antisense FMR1 and Cytochrome C1 mRNAs in blood leukocytes. In addition, the carriers showed a significant depletion of the nicotinamide adenine dinucleotide, reduced dehydrogenase subunit 1 mitochondrial gene in whole blood. CONCLUSION: Small CGG expansion FMR1 alleles (gray zone and lower end premutation) play a significant role in the development of the parkinsonian phenotype, possibly through the cytotoxic effect of elevated sense and/or antisense FMR1 transcripts involving mitochondrial dysfunction and leading to progressive neurodegeneration.

Relationships between motor scores and cognitive functioning in FMR1 female premutation X carriers indicate early involvement of cerebello-cerebral pathways.

BACKGROUND: Smaller expansions of CGG trinucleotide repeats in the FMR1 X-linked gene termed 'premutation' lead to a neurodegenerative disorder: Fragile X Associated Tremor/Ataxia Syndrome (FXTAS) in nearly half of aged carrier males, and 8-16% females. Core features include intention tremor, ataxia, and cognitive decline, and white matter lesions especially in cerebellar and periventricular locations. A 'toxic' role of elevated and expanded FMR1 mRNA has been linked to the pathogenesis of this disorder. The emerging issue concerns the trajectory of the neurodegenerative changes: is the pathogenetic effect confined to overt clinical manifestations? Here we explore the relationships between motor and cognitive scale scores in a sample of 57 asymptomatic adult female premutation carriers of broad age range. METHODS: Three motor scale scores (ICARS-for tremor/ataxia, UPDRS-for parkinsonism, and Clinical Tremor) were related to 11 cognitive tests using Spearman's rank correlations. Robust regression, applied in relationships between all phenotypic measures, and genetic molecular and demographic data, identified age and educational levels as common correlates of these measures, which were then incorporated as confounders in correlation analysis. RESULTS: Cognitive tests demonstrating significant correlations with motor scores were those assessing non-verbal reasoning on Matrix Reasoning (p-values from 0.006 to 0.011), and sequencing and alteration on Trails-B (p-values from 0.008 to 0.001). Those showing significant correlations with two motor scores-ICARS and Clinical Tremor- were psychomotor speed on Symbol Digit Modalities (p-values from 0.014 to 0.02) and working memory on Digit Span Backwards (p-values from 0.024 to 0.011). CONCLUSIONS: Subtle motor impairments correlating with cognitive, particularly executive, deficits may occur in female premutation carriers not meeting diagnostic criteria for FXTAS. This pattern of cognitive deficits is consistent with those seen in other cerebellar disorders. Our results provide evidence that more than one category of clinical manifestation reflecting cerebellar changes - motor and cognitive - may be simultaneously affected by premutation carriage across a broad age range in asymptomatic carriers.

Delineating the Relationships Between Motor, Cognitive-Executive and Psychiatric Symptoms in Female FMR1 Premutation Carriers.

Introduction: Premutation expansions (55-200 CGG repeats) of the Fragile X Mental Retardation 1 (FMR1) gene on the X chromosome are associated with a range of clinical features. Apart from the most severe - Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS) - where the most typical white matter changes affect cerebellar peduncles, more subtle changes may include impairment of executive functioning, affective disorders and/or subtle motor changes. Here we aimed to examine whether performance in selected components of executive functioning is associated with subclinical psychiatric symptoms in non-FXTAS, adult females carrying the FMR1 premutation. Methods and Sample: A total of 47 female premutation carriers (sub-symptomatic for FXTAS) of wide age range (26-77 years; M = 50.3; SD = 10.9) were assessed using standard neuropsychological tests, three motor rating scales and self-reported measures of psychiatric symptoms using the Symptom Checklist-90-Revised (SCL-90-R). Results: After adjusting for age and educational level where appropriate, both non-verbal reasoning and response inhibition as assessed on the Stroop task (i.e., the ability to resolve cognitive interference) were associated with a range of primary psychiatric symptom dimensions, and response inhibition uniquely predicted some primary symptoms and global psychiatric features. Importantly, lower scores (worse performance) in response inhibition were also strongly correlated with higher (worse) scores on standard motor rating scales for tremor-ataxia and for parkinsonism. Conclusion: These results provide evidence for the importance of response inhibition in the manifestation of psychiatric symptoms and subtle tremor-ataxia motor features, suggestive of the presence of early cerebellar changes in female premutation carriers.