Genetic variation and pesticide exposure influence blood DNA methylation signatures in females with early-stage Parkinson's disease.

Although sex, genetics, and exposures can individually influence risk for sporadic Parkinson's disease (PD), the joint contributions of these factors to the epigenetic etiology of PD have not been comprehensively assessed. Here, we profiled sex-stratified genome-wide blood DNAm patterns, SNP genotype, and pesticide exposure in agricultural workers (71 early-stage PD cases, 147 controls) and explored replication in three independent samples of varying demographics (n = 218, 222, and 872). Using a region-based approach, we found more associations of blood DNAm with PD in females (69 regions) than in males (2 regions, Δßadj| ≥0.03, padj ≤ 0.05). For 48 regions in females, models including genotype or genotype and pesticide exposure substantially improved in explaining interindividual variation in DNAm (padj ≤ 0.05), and accounting for these variables decreased the estimated effect of PD on DNAm. The results suggested that genotype, and to a lesser degree, genotype-exposure interactions contributed to variation in PD-associated DNAm. Our findings should be further explored in larger study populations and in experimental systems, preferably with precise measures of exposure.

The genetic landscape of Parkinson's disease.

The cause of Parkinson's disease (PD) remains unknown in most patients. Since 1997, with the first genetic mutation known to cause PD described in SNCA gene, many other genes with Mendelian inheritance have been identified. We summarize genetic, clinical and neuropathological findings related to the 27 genes reported in the literature since 1997, associated either with autosomal dominant (AD): LRRK2, SNCA, VPS35, GCH1, ATXN2, DNAJC13, TMEM230, GIGYF2, HTRA2, RIC3, EIF4G1, UCHL1, CHCHD2, and GBA; or autosomal recessive (AR) inheritance: PRKN, PINK1, DJ1, ATP13A2, PLA2G6, FBXO7, DNAJC6, SYNJ1, SPG11, VPS13C, PODXL, and PTRHD1; or an X-linked transmission: RAB39B. Clinical and neuropathological variability among genes is great. LRRK2 mutation carriers present a phenotype similar to those with idiopathic PD whereas, depending on the SNCA mutations, the phenotype ranges from early onset typical PD to dementia with Lewy bodies, including many other atypical forms. DNAJC6 nonsense mutations lead to a very severe phenotype whereas DNAJC6 missense mutations cause a more typical form. PRKN, PINK1 and DJ1 cases present with typical early onset PD with slow progression, whereas other AR genes present severe atypical Parkinsonism. RAB39B is responsible for a typical phenotype in women and a variable phenotype in men. GBA is a major PD risk factor often associated with dementia. A growing number of reported genes described as causal genes (DNAJC13, TMEM230, GIGYF2, HTRA2, RIC3, EIF4G1, UCHL1, and CHCHD2) are still awaiting replication or indeed have not been replicated, thus raising questions as to their pathogenicity. Phenotypic data collection and next generation sequencing of large numbers of cases and controls are needed to differentiate pathogenic dominant mutations with incomplete penetrance from rare, non-pathogenic variants. Although known genes cause a minority of PD cases, their identification will lead to a better understanding their pathological mechanisms, and may contribute to patient care, genetic counselling, prognosis determination and finding new therapeutic targets.

The potential of Antheraea pernyi silk for spinal cord repair.

One of the most challenging applications for tissue regeneration is spinal cord damage. There is no cure for this, partly because cavities and scar tissue formed after injury present formidable barriers that must be crossed by axons to restore function. Natural silks are considered increasingly for medical applications because they are biocompatible, biodegradable and in selected cases promote tissue growth. Filaments from wild Antheraea pernyi silkworms can support axon regeneration in peripheral nerve injury. Here we presented evidence that degummed A. pernyi filaments (DAPF) support excellent outgrowth of CNS neurons in vitro by cell attachment to the high density of arginine-glycine-aspartic acid tripeptide present in DAPF. Importantly, DAPF showed stiffness properties that are well suited to spinal cord repair by supporting cell growth mechano-biology. Furthermore, we demonstrated that DAPF induced no activation of microglia, the CNS resident immune cells, either in vitro when exposed to DAPF or in vivo when DAPF were implanted in the cord. In vitro DAPF degraded gradually with a corresponding decrease in tensile properties. We conclude that A. pernyi silk meets the major biochemical and biomaterial criteria for spinal repair, and may have potential as a key component in combinatorial strategies for spinal repair.

An orthologous non-MHC locus in rats and mice is linked to CD4+ and CD8+ T-cell proportion.

CD4+ and CD8+ T cells have a central role in the immune system due to their ability to protect against infection and cancer development without targeting self. Consequently, changes in CD4+ and CD8+ T-cell homeostasis can be indicative of an array of serious illnesses, ranging from viral infections to autoimmune diseases. In addition to environmental influences, there is evidence for a genetic component regulating the proportion of CD4+ and CD8+ T cells in lymphoid organs. Indeed, identifying the genetic determinants defining the frequency of the T-cell subsets is critical as it may reveal a targetable genetic pathway to modulate CD4+ and CD8+ T-cell numbers, which could be of clinical relevance for multiple disease settings. In this study, we aim to uncover non-MHC genetic factors regulating the proportion of CD4+ and CD8+ T cells in lymphoid tissues. By investigating linkage analyses on three independent F2 cohorts, namely a rat F2 (BBDP × ACI.1U.LYP) cohort, a mouse 3A9 TCR transgenic F2 (B10.BR × NOD.H2k) cohort and a mouse F2 (C57BL/6 × FVB/N) cohort, we uncover an orthologous non-MHC locus on rat chromosome 1 and mouse chromosome 7 that is linked to T-cell proportion amongst total lymphocytes.

High-level intrathymic thyrotrophin receptor expression in thyroiditis-prone mice protects against the spontaneous generation of pathogenic thyrotrophin receptor autoantibodies.

The thyrotrophin receptor (TSHR) A-subunit is the autoantigen targeted by pathogenic autoantibodies that cause Graves' hyperthyroidism, a common autoimmune disease in humans. Previously, we reported that pathogenic TSHR antibodies develop spontaneously in thyroiditis-susceptible non-obese diabetic (NOD).H2h4 mice bearing a human TSHR A-subunit transgene, which is expressed at low levels in both the thyroid and thymus (Lo-expressor transgene). The present study tested recent evidence that high intrathymic TSHR expression protects against the development of pathogenic TSHR antibodies in humans. By successive back-crossing, we transferred to the NOD.H2h4 background a human TSHR A-subunit transgene expressed at high levels in the thyroid and thymus (Hi-expressor transgene). In the sixth back-cross generation (> 98% NOD.H2h4 genome), only transgenic offspring produced spontaneously immunoglobulin (Ig)G class non-pathogenic human TSHR A-subunit antibodies. In contrast, both transgenic and non-transgenic offspring developed antibodies to thyroglobulin and thyroid peroxidase. However, non-pathogenic human TSHR antibody levels in Hi-expressor offspring were lower than in Lo-expressor transgenic mice. Moreover, pathogenic TSHR antibodies, detected by inhibition of TSH binding to the TSHR, only developed in back-cross offspring bearing the Lo-expressor, but not the Hi-expressor, transgene. High versus low expression human TSHR A-subunit in the NOD.H2h4 thymus was not explained by the transgene locations, namely chromosome 2 (127-147 Mb; Hi-expressor) and chromosome 1 (22.9-39.3 Mb; low expressor). Nevertheless, using thyroiditis-prone NOD.H2h4 mice and two transgenic lines, our data support the association from human studies that low intrathymic TSHR expression is associated with susceptibility to developing pathogenic TSHR antibodies, while high intrathymic TSHR expression is protective.

Evidence that MHC I-E dampens thyroid autoantibodies and prevents spreading to a second thyroid autoantigen in I-A(k) NOD mice.

NOD.H2(k) and NOD.H2(h4) mice carry the major histocompatibility complex (MHC) class II molecule I-A(k) associated with susceptibility to experimentally induced thyroiditis. Dietary iodine-enhanced spontaneous thyroid autoimmunity, well known in NOD.H2(h4) mice, has not been investigated in NOD.H2(k) mice. We compared NOD.H2(h4) and NOD.H2(k) strains for thyroiditis and autoantibodies to thyroglobulin (TgAb) and thyroid peroxidase (TPOAb) without or with dietary sodium iodide (NaI) for up to 32 weeks. TgAb levels were significantly higher in NOD.H2(h4) compared with NOD.H2(k) mice on NaI, and TPOAb developed in NOD.H2(h4) mice but not in NOD.H2(k) mice. DNA exome analysis revealed, in addition to the differences in the chromosome (Chr) 17 MHC regions, that NOD.H2(k) mice, and particularly NOD.H2(h4) mice, have substantial non-MHC parental DNA. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis highlighted thyroid autoimmunity and immune-response genes on Chr 17 but not on Chr 7, and 15 parental B10.A4R DNA. Studies of parental strains provided no evidence for non-MHC gene contributions. The exon 10 Tg haplotype, associated with experimentally induced thyroiditis, is absent in NOD.H2(h4) and NOD.H2(k) mice and is not a marker for spontaneous murine thyroid autoimmunity. In conclusion, the absence of I-E is a likely explanation for the difference between NOD.H2(h4) and NOD.H2(k) mice in TgAb levels and, as in humans, autoantibody spreading to TPO.

Idd13 is involved in determining immunoregulatory DN T-cell number in NOD mice.

Immunoregulatory T cells have been identified as key modulators of peripheral tolerance and participate in preventing autoimmune diseases. CD4(-)CD8(-) (double negative, DN) T cells compose one of these immunoregulatory T-cell subsets, where the injection of DN T cells confers protection from autoimmune diabetes progression. Interestingly, genetic loci defining the function and number of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) coincide with at least some autoimmune disease susceptibility loci. Herein, we investigate the impact of major insulin-dependent diabetes (Idd) loci in defining the number of DN T cells. We demonstrate that although Idd3, Idd5 and Idd9 loci do not regulate DN T-cell number, NOD mice congenic for diabetes resistance alleles at the Idd13 locus show a partial restoration in DN T-cell number. Moreover, competitive and non-competitive bone marrow chimera experiments reveal that DN T-cell number is defined by a bone marrow-intrinsic, but DN T-cell-extrinsic, factor. This suggests that non-autonomous candidate genes define DN T-cell number in secondary lymphoid organs. Together, our results show that the regulation of DN T-cell number in NOD mice is at least partially conferred by alleles at the Idd13 locus.

Penetrance of Parkinson disease in glucocerebrosidase gene mutation carriers.

OBJECTIVE: Glucocerebrosidase (GBA) gene mutations represent a strong risk factor for Parkinson disease (PD). PD penetrance in GBA mutation carriers, which represents a key issue for genetic counseling, especially for relatives of patients with Gaucher disease (GD), is unknown. Our objective was to estimate PD penetrance in a familial study of GBA mutation carriers. METHODS: Probands with familial PD were recruited through the French Parkinson Disease Genetic Study Group. All GBA exons were sequenced in probands and their relatives. To estimate the age-specific cumulative PD risk (i.e., penetrance) in GBA mutation carriers, we used the proband's phenotype exclusion likelihood method and corrected for selection of familial cases by considering the status of one affected relative per family as unknown. RESULTS: Of 525 probands with familial PD, 24 (4.6%) were GBA mutation carriers. Of their 256 relatives, 43 (16.8%) had PD and 26 of 32 affected relatives tested for GBA mutations were mutation carriers; 213 relatives did not have PD and 31 of 71 of unaffected relatives tested for GBA mutations were mutation carriers. Under a dominant model, penetrance was estimated as 7.6%, 13.7%, 21.4%, and 29.7% at 50, 60, 70, and 80 years, respectively. There was no significant difference in penetrance at 70 years between N370S carriers, L444P carriers, and carriers of rarer mutations. CONCLUSION: The relatively high penetrance estimate in GBA carriers obtained in this study should lead to consideration of GBA as a dominant causal gene with reduced penetrance and should be taken into account for genetic counseling in relatives of patients with GD and patients with GBA-associated PD.

Genetic bases and phenotypes of autosomal recessive Parkinson disease in a Turkish population.

BACKGROUND AND PURPOSE: To evaluate the phenotype and the frequencies of mutations in PRKN, DJ1 and PINK1 genes in patients with Parkinson disease (PD) in Turkey. METHODS: Eighty-six patients from 77 PD families participated in the study. Seventy-four families were originating from Turkey, two families from Greece and one family from Bulgaria. All patients underwent detailed neurological examination. PRKN, PINK1 and DJ1 genes were sequenced, and dosage analysis was performed by multiplex ligation-dependent probe amplification. RESULTS: Sixteen patients with PD were found to carry homozygous (n = 14) or compound heterozygous (n = 2) PRKN mutations. We identified exon rearrangements, three point mutations and one new point mutation in exon 2 (p.K27del). In two families, two new PINK1 point mutations (L31X and P416L) were identified. No pathogenic mutations were found in DJ1 gene. Clinical phenotypes of PRKN patients were comparable to previously described features, but only in four of 13 families, the pedigree structure was clearly consistent with an autosomal recessive (AR) mode of inheritance in comparison with nine families where also different pattern of transmission could have been possible. CONCLUSIONS: Our data suggest that the PRKN gene mutation is the most frequent form of ARPD in Turkey. The proportion of mutations with regard to the age of onset in our population is in the range of those previously described, but our pedigrees are characterized by high rate of consanguinity, which might explain the high proportion of families with homozygous mutations and of patients in more than one generation. Pathogenic DJ1 mutations do not seem to play a major role in Turkey.

Regenerative potential of silk conduits in repair of peripheral nerve injury in adult rats.

Various attempts have been made to develop artificial conduits for nerve repair, but with limited success. We describe here conduits made from Bombyx mori regenerated silk protein, and containing luminal fibres of Spidrex(®), a silk-based biomaterial with properties similar to those of spider silk. Assessment in vitro demonstrated that Spidrex(®) fibres support neurite outgrowth. For evaluation in vivo, silk conduits 10 mm in length and containing 0, 100, 200 or 300 luminal Spidrex(®) fibres, were implanted to bridge an 8 mm gap in the rat sciatic nerve. At 4 weeks, conduits containing 200 luminal Spidrex(®) fibres (PN200) supported 62% and 59% as much axon growth as autologous nerve graft controls at mid-conduit and distal nerve respectively. Furthermore, Spidrex(®) conduits displayed similar Schwann cell support and macrophage response to controls. At 12 weeks, animals implanted with PN200 conduits showed similar numbers of myelinated axons (81%) to controls, similar gastrocnemius muscle innervation, and similar hindpaw stance assessed by Catwalk footprint analysis. Plantar skin innervation was 73% of that of controls. PN200 Spidrex(®) conduits were also effective at bridging longer (11 and 13 mm) gaps. Our results show that Spidrex(®) conduits promote excellent axonal regeneration and function recovery, and may have potential for clinical application.

Multicenter analysis of glucocerebrosidase mutations in Parkinson's disease.

BACKGROUND: Recent studies indicate an increased frequency of mutations in the gene encoding glucocerebrosidase (GBA), a deficiency of which causes Gaucher's disease, among patients with Parkinson's disease. We aimed to ascertain the frequency of GBA mutations in an ethnically diverse group of patients with Parkinson's disease. METHODS: Sixteen centers participated in our international, collaborative study: five from the Americas, six from Europe, two from Israel, and three from Asia. Each center genotyped a standard DNA panel to permit comparison of the genotyping results across centers. Genotypes and phenotypic data from a total of 5691 patients with Parkinson's disease (780 Ashkenazi Jews) and 4898 controls (387 Ashkenazi Jews) were analyzed, with multivariate logistic-regression models and the Mantel-Haenszel procedure used to estimate odds ratios across centers. RESULTS: All 16 centers could detect two GBA mutations, L444P and N370S. Among Ashkenazi Jewish subjects, either mutation was found in 15% of patients and 3% of controls, and among non-Ashkenazi Jewish subjects, either mutation was found in 3% of patients and less than 1% of controls. GBA was fully sequenced for 1883 non-Ashkenazi Jewish patients, and mutations were identified in 7%, showing that limited mutation screening can miss half the mutant alleles. The odds ratio for any GBA mutation in patients versus controls was 5.43 across centers. As compared with patients who did not carry a GBA mutation, those with a GBA mutation presented earlier with the disease, were more likely to have affected relatives, and were more likely to have atypical clinical manifestations. CONCLUSIONS: Data collected from 16 centers demonstrate that there is a strong association between GBA mutations and Parkinson's disease.

Retinal microvascular abnormalities and cognitive decline: the ARIC 14-year follow-up study.

BACKGROUND: Because retinal and cerebral arterioles share similar pathologic processes, retinal microvascular changes are expected to be markers of cerebral small vessel disease (SVD). To better understand the role of SVD in cognitive function, we investigated the relationship between retinal microvascular abnormalities and longitudinal changes in cognitive function in a community-based study. METHODS: A total of 803 participants underwent 4 cognitive assessments between 1990-1992 and 2004-2006, using the Word Fluency (WF) test, Digit Symbol Substitution (DSS), and Delayed Word Recall as well as retinal photography in 1993-1995. Covariate adjusted random effects linear models for repeated measures were used to determine the associations of cognitive change with specific retinal vascular abnormalities. RESULTS: Individuals with retinopathy showed declines in executive function and psychomotor speed, with 1) an average decline in WF of -1.64 words per decade (95% confidence interval [CI] -3.3, -0.02) compared to no decline in those without retinopathy +0.06 (95% CI -0.6, 0.8) and 2) a higher frequency of rapid decliners on the DSS test. CONCLUSION: Signs of retinal vascular changes, as markers of the cerebral microvasculature, are associated with declines in executive function and psychomotor speed, adding to the growing evidence for the role of microvascular disease in cognitive decline in the elderly.

Molecular analyses of the LRRK2 gene in European and North African autosomal dominant Parkinson's disease.

BACKGROUND: Mutations in the leucine-rich-repeat kinase 2 (LRRK2) gene have been identified in families with autosomal dominant Parkinson's disease (ADPD), the most common of which is the p.G2019S substitution that has been found at varying frequencies worldwide. Because of the size of the LRRK2 gene, few studies have analysed the entire gene in large series of ADPD families. METHODS: We performed extensive mutation analyses of all 51 coding exons of the LRRK2 gene in index cases from 226 Parkinson's disease families compatible with autosomal dominant inheritance, mostly from France (n = 182) and North Africa (n = 14). RESULTS: We found 79 sequence variants, 29 of which were novel. Eight potentially or proven pathogenic mutations were found in 22 probands (9.7%). There were four novel amino acid substitutions that are potentially pathogenic (p.S52F, p.N363S, p.I810V, p.R1325Q) and two novel variants, p.H1216R and p.T1410M, that are probably not causative. The common p.G2019S mutation was identified in 13 probands (5.8%) including six from North Africa (43%). The known heterozygous p.R1441H and p.I1371V mutations were found in two probands each, and the p.E334K variant was identified in one single patient. Most potentially or proven pathogenic mutations were located in the functional domains of the Lrrk2 protein. CONCLUSION: This study leads us to conclude that LRRK2 mutations are a common cause of autosomal dominant Parkinson's disease in Europe and North Africa.

A LRRK2 G2019S mutation carrier from Turkey shares the Japanese haplotype.

The leucine-rich repeat kinase 2 (LRRK2) G2019S mutation is recognized as the most common cause of familial autosomal dominant and also sporadic forms of Parkinson disease (PD). A common founder has been described for most Europeans and all North Africans and Jews; besides, two distinct G2019S LRRK2 haplotypes were found in a small proportion of European families and in Japanese PD patients. This study revealed a Turkish patient heterozygous for the G2019S mutation sharing the Japanese haplotype. To the best of our knowledge, it is the first time that the G2019S-associated Japanese haplotype has been reported in a different population.