A multi-incident, Old-Order Amish family with PD

The GGLEAM Study: Understanding Glaucoma in the Ohio Amish

Glaucoma leads to millions of cases of visual impairment and blindness around the world. Its susceptibility is shaped by both environmental and genetic risk factors. Although over 120 risk loci have been identified for glaucoma, a large portion of its heritability is still unexplained. Here we describe the foundation of the Genetics of GLaucoma Evaluation in the AMish (GGLEAM) study to investigate the genetic architecture of glaucoma in the Ohio Amish, which exhibits lower genetic and environmental heterogeneity compared to the general population. To date, we have enrolled 81 Amish individuals in our study from Holmes County, Ohio. As a part of our enrollment process, 62 GGLEAM study participants (42 glaucoma-affected and 20 unaffected individuals) received comprehensive eye examinations and glaucoma evaluations. Using the data from the Anabaptist Genealogy Database, we found that 80 of the GGLEAM study participants were related to one another through a large, multigenerational pedigree containing 1586 people. We plan to integrate the health and kinship data obtained for the GGLEAM study to interrogate glaucoma genetics and pathophysiology in this unique population.

Parkinson's Disease-Related Motor and Nonmotor Symptoms in the Lancaster Amish

INTRODUCTION

Previous research has suggested that the Amish may experience a relatively high prevalence of Parkinson's disease (PD) and/or parkinsonian motor signs.

METHODS

In a large sample from the Amish community in Lancaster County, Pennsylvania, age ≥18 years, we assessed the prevalence of self-reported PD diagnosis. For those without self-reported PD diagnosis, we assessed the frequency of PD-related motor symptoms using a 9-item questionnaire that was designed by the PD Epidemiology Research Group. Lastly, we queried study participants for the presence of 2 nonmotor symptoms that have been commonly linked to PD: bowel movement frequency and daytime sleepiness.

RESULTS

Among 2,025 subjects who answered the PD questionnaire, 430 were older than 60 years. Of 430 participants ≥60 years, 5 (1.2%) reported a PD diagnosis. Of those without a PD diagnosis, 10.5% reported ≥1 and 1.2% ≥ 4 motor symptoms for the 9-item PD screening questionnaire. Of the 3,789 subjects who answered the question about bowel movement frequency, 0.7% reported ≤3 bowel movements per week. Among 1,710 subjects who answered the question about daytime sleepiness, 8.1% of the participants reported "always" sleepy during the day.

DISCUSSION

These data neither support a markedly higher PD prevalence in the older Lancaster Amish nor do they show dramatically higher motor and/or selected nonmotor symptoms than the general population. Future studies that employ more rigorous procedures for case identification and PD-specific preclinical symptoms/tests are needed to determine the potential differences and similarities among different Amish populations and between Amish and non-Amish populations.

Clinical, positron emission tomography, and pathological studies of DNAJC13 p.N855S Parkinsonism

BACKGROUND

Families of Dutch-German-Russian Mennonite descent with multi-incident parkinsonism have been identified as harboring a pathogenic DNAJC13 p.N855S mutation and are awaiting clinical and pathophysiological characterization.

METHODS

Family members were examined clinically longitudinally, and 5 underwent dopaminergic PET imaging. Four family members came to autopsy.

RESULTS

Of the 16 symptomatic DNAJC13 mutation carriers, 12 had clinically definite, 3 probable, and 1 possible Parkinson's disease (PD). Symptoms included bradykinesia, tremor, rigidity, and postural instability, with a mean onset of 63 years (range, 40-85) and slow progression. Eight of ten subjects who required treatment had a good levodopa response; motor complications and nonmotor symptoms were observed. Dopaminergic PET imaging revealed rostrocaudal striatal deficits typical for idiopathic PD in established disease and subtle abnormalities in incipient disease. Pathological examinations revealed Lewy body pathology.

CONCLUSION

PD associated with a DNAJC13 p.N855S mutation presents as late-onset, often slowly progressive, usually dopamine-responsive typical PD.

A population-based study of parkinsonism in an Amish community

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder with unknown cause. Genetic mutations account for a minority of cases but the role of environmental factors is unclear.

METHODS

We performed a population-based screening for PD in subjects in an Amish community over age 60. PD was diagnosed using standard clinical criteria and the Unified Parkinson Disease Rating Scale motor subsection 3 (UPDRS3). Community prevalence was calculated. We constructed a community pedigree and calculated kinship coefficients, a measure of relatedness between 2 subjects, for every pair of subjects in diagnostic categories: clinically definite PD, UPDRS3 score >9, Mini-Mental State Exam (MMSE) score <25, and normal.

RESULTS

Of 262 eligible subjects, 213 agreed to participate, 15 had PD, 43 had MMSE <25, 73 had UPDRS3 >9. The prevalence of PD was 5,703/100,000 with increasing prevalence in every decade of age. Excluding first-degree relatives, normal subjects were more related to each other (0.0102, SD = 0.0266) than subjects with clinically definite PD (0.0054, SD = 0.0100; p = 0.00003), subjects with UPDRS >9 (0.0076, SD = 0.0155; p = 0.00001), and subjects with MMSE <25 (0.0090, SD = 0.0180; p = 0.00003).

CONCLUSIONS

PD and parkinsonian signs are common in this population and the prevalence increases with age. The finding that subjects with PD were not more related than normal subjects suggests that environmental factors may contribute to the parkinsonian phenotype in this community.

A genome-wide scan in an Amish pedigree with parkinsonism

The identification of familial Parkinson Disease (PD) genes is yielding important molecular pathogenetic insights. In an effort to identify additional PD genes, we studied an eight generation Amish pedigree with apparent autosomal dominant parkinsonism with incomplete penetrance. Phenotypic variability ranged from idiopathic PD to progressive supranuclear palsy (PSP), with the average age at onset 53 years (range of 39 to 74 years). We identified markers on chromosome 3 and 7 that were significant at a genome-wide level by parametric and nonparametric criteria, lod > 3 and non-parametric P-value < 0.10, respectively. We also identified markers on chromosomes 10 and 22 with lod > 3. These data suggest that parkinsonism in this pedigree is genetically complex, with contributions from several loci.

[18F]FDOPA PET as an endophenotype for Parkinson's Disease linkage studies

Parkinson disease (PD) is a late onset disorder with age-dependent penetrance that may confound genetic studies, since affected individuals may not demonstrate clinical manifestations at the time of evaluation. The use of endophenotypes, biologic surrogates for clinical disease diagnoses, may permit more accurate classification of at-risk subjects. Positron emission tomography (PET) measurements of 6-[18F]fluorodopa ([18F]FDOPA) uptake indicate nigrostriatal neuronal integrity and may provide a useful endophenotype for PD linkage studies. We performed [18F]FDOPA PET in 11 members of a large, multi-incident Amish family with PD, 24 normals and 48 people with clinically definite idiopathic PD (PD controls). Clinical diagnoses in the Amish were clinically definite PD in four, clinically probable in one, clinically possible in five, and normal in one. Abnormal [18F]FDOPA posterior putamen uptake was defined as less than 3 standard deviations below the normal mean. The criteria were applied to the Amish sample to determine a PET endophenotype for each. We performed genetic simulations using SLINK to model the effect phenoconversion with the PET endophenotype had on logarithm of odds (LOD) scores. PET endophenotype confirmed the status of two clinically definite subjects. Two clinically definite Amish PD subjects had normal PETs. Two possible PD were converted to "PET definite PD." The remainder had normal PETs. The average maximum LOD score with the pre-PET was 6.14 +/- 0.84. Simulating phenoconversion of subjects with unknown phenotypes increased the LOD score to 7.36 +/- 1.23. The [18F]FDOPA PET endophenotype permits phenoconversion in multi-incident PD families and may increase LOD score accuracy and power of an informative pedigree.

Maternal lineages and Alzheimer disease risk in the Old Order Amish

Old Order Amish, founded by a small number of Swiss immigrants, exist in culturally isolated communities across rural North America. The consequences of genetic isolation and inbreeding within this group are evident by increased frequencies of many monogenic diseases and several complex disorders. Conversely, the prevalence of Alzheimer disease (AD), the most common form of dementia, is lower in the Amish than in the general American population. Since mitochondrial dysfunction has been proposed as an underlying cause of AD and a specific haplogroup was found to affect AD susceptibility in Caucasians, we investigated whether inherited mitochondrial haplogroups affect risk of developing AD dementia in Ohio and Indiana Amish communities. Ninety-five independent matrilines were observed across six large pedigrees and three small pedigrees then classified into seven major European haplogroups. Haplogroup T is the most frequent haplogroup represented overall in these maternal lines (35.4%) while observed in only 10.6% in outbred American and European populations. Furthermore, haplogroups J and K are less frequent (1.0%) than in the outbred data set (9.4-11.2%). Affected case matrilines and unaffected control lines were chosen from pedigrees to test whether specific haplogroups and their defining SNPs confer risk of AD. We did not observe frequency differences between AD cases compared to controls overall or when stratified by sex. Therefore, we suggest that the genetic effect responsible for AD dementia in the affected Amish pedigrees is unlikely to be of mitochondrial origin and may be caused by nuclear genetic factors.

Prevalence of parkin gene mutations and variations in idiopathic Parkinson's disease

Mutations in the parkin gene are a common cause of autosomal recessive juvenile parkinsonism (AR-JP) but their role in idiopathic Parkinson's disease (PD) is not clear. Recent studies demonstrate that most young onset PD without family history is not due to mutations in parkin. However, there is less information about the role of this gene in older onset PD. The objective of the present study was to evaluate the prevalence and frequency of parkin gene mutations and variations in the general population of patients with PD categorized on the basis of family history and age of onset. We sequenced a sample of 50 familial PD patients, screened a sample of 429 PD patients, and 115 normal controls for the previously reported mutations, deletions, single nucleotide polymorphisms (SNP) in exons 2-12 of the parkin gene, and performed RT-PCR of exon 1. A total of two heterozygous mutations in exon 7 (R275W; 0.2%) were detected in the PD group, but none were found in controls. No mutation or deletion was observed in exons 2, 3, 5, 6, 8, 9 or 12. There was also no deletion or duplication of exon 1. The SNPs in exon 4, 10, and 11 that cause amino acid changes were very rare (1-5%). We did not find the exon 4 variation in the controls while allele frequencies were similar among PD patients and controls in exon 10 and 11 polymorphisms. Mutations were not associated with a positive family history of PD or younger age of onset. We concluded that no new mutation, nor the previously described parkin polymorphisms or known mutations, are playing any direct role in the development of PD in this group of PD patients.

Suggestive linkage to chromosome 19 in a large Cuban family with late-onset Parkinson's disease

The identification of disease genes using family-based approaches has provided important insights into the pathogenesis of Parkinson's disease (PD) demonstrating the importance of genetic studies on monogenic forms of the disease. We studied a large Cuban family with typical, late-onset PD and probable autosomal dominant inheritance. Mean age at onset was 61.2 years (+/- 12.53, 45-76). Other phenotypes such as essential tremor and atypical parkinsonism were observed in this family. We carried out a genome-wide scan and linkage analyses. The genetic data were analyzed using a conservative model in which only patients with clinically definite or likely PD were considered affected, other phenotypes were regarded as "unknown." Multipoint analyses yielded a maximum LOD of 2.26 between markers D19S221 and D19S840. Haplotype analysis showed a region on chromosome 19 shared by six of seven PD patients. The essential tremor phenotype and the atypical parkinsonism do not segregate with this haplotype, suggesting a different etiology. Our findings suggest the presence of a novel locus for PD on chromosome 19p13.3-q12. We propose that an oligogenic model with moderate contribution of two or three genes rather than a "pure" monogenic model might explain better the wide range in age at onset, the reduced penetrance and the phenotypical variability observed in PD families.