Charcot-Marie-Tooth disease: genetic subtypes in the Sardinian population.

Charcot-Marie-Tooth disease (CMT) is characterised by great variability of genetic subtypes. This study aimed to assess the genetic subtypes of CMT disease in the Sardinian population. Genetic screening was performed for CMT cases (CMT1, CMT2, and hereditary neuropathy with susceptibility to pressure palsies [HNPP]). A total of 1,043 subjects (119 index cases) were evaluated. In CMT1 index cases (69/119; 58%), PMP22 duplication at 17p11.2 was the most frequent genetic diagnosis (60/69; 87%), followed by mutations in the GJB1 gene (5/69; 7.2%), in the SH3TC2 gene (3/69; 4.4%) and PMP22 Gly107Val point mutation (1/69; 1.4%). The CMT2 group (24/119; 20.1%) comprised 10/24 (41.6%) patients carrying MPZ gene Ser44Phe mutation, 6/24 (25%) with mutations in MFN2 and HSPB1, and 1/24 (4.2%) in GJB1 and LRSAM1. In the HNPP group (26/119; 21.9%), the majority of patients reported the PMP22 deletion (25/26; 96.2%). Further studies are needed to comprehend the overall picture of the disease in Mediterranean area.

The p.A382T TARDBP gene mutation in Sardinian patients affected by Parkinson's disease and other degenerative parkinsonisms.

Based on our previous finding of the p.A382T founder mutation in ALS patients with concomitant parkinsonism in the Sardinian population, we hypothesized that the same variant may underlie Parkinson's disease (PD) and/or other forms of degenerative parkinsonism on this Mediterranean island. We screened a cohort of 611 patients with PD (544 cases) and other forms of degenerative parkinsonism (67 cases) and 604 unrelated controls for the c.1144G > A (p.A382T) missense mutation of the TARDBP gene. The p.A382T mutation was identified in nine patients with parkinsonism. Of these, five (0.9 % of PD patients) presented a typical PD (two with familiar forms), while four patients (6.0 % of all other forms of parkinsonism) presented a peculiar clinical presentation quite different from classical atypical parkinsonism with an overlap of extrapyramidal-pyramidal-cognitive clinical signs. The mutation was found in eight Sardinian controls (1.3 %) consistent with a founder mutation in the island population. Our findings suggest that the clinical presentation of the p.A382T TARDBP gene mutation may include forms of parkinsonism in which the extrapyramidal signs are the crucial core of the disease at onset. These forms can present PSP or CBD-like clinical signs, with bulbar and/or extrabulbar pyramidal signs and cognitive impairment. No evidence of association has been found between TARDBP gene mutation and typical PD.

Heat shock protein 27 R127W mutation: evidence of a continuum between axonal Charcot-Marie-Tooth and distal hereditary motor neuropathy.

BACKGROUND: Heat shock protein 27 (HSP27) mutations have been reported to cause both Charcot-Marie-Tooth disease (CMT) type 2F and distal hereditary motor neuropathy (dHMN) although never previously in a single family. OBJECTIVE: To analyse clinical and electrophysiological findings obtained in a single large Sardinian family bearing the HSP27 R127W mutation. METHODS: Twenty-one members of a five generation Sardinian family have been studied, including thirteen members affected by peroneal muscular atrophy and proved heterozygous for the known HSP27 R127W mutation. Twelve patients and eight unaffected relatives were subjected to clinical examination. A standardised electrophysiological study was performed in eleven patients and six unaffected relatives. RESULTS: Mean age at onset (+/-SD) was 31.2+/-7.2 years. Mean age at investigation was 45.2+/-12.9 years and mean disease duration at the time of investigation was 14+/-12.9 years. According to current criteria for CMT2 and dHMN, of the 10 patients who had undergone both clinical and neurophysiological examination, five were diagnosed as CMT2, two as dHMN and a further two patients were labelled as an intermediate type. Finally, due to the presence of spastic paraplegia, the index patient did not meet established criteria for the diagnosis of CMT or dHMN. DISCUSSION: Findings obtained in the present study, broadening the spectrum of clinical manifestations of disorders associated with HSP27 mutations, support the hypothesis of a continuum between CMT2 and dHMN forms and suggest a possible common spectrum between these entities and several forms of CMT plus pyramidal features (HMSN V), providing important implications for molecular genetic testing.

Genetic loci linked to type 1 diabetes and multiple sclerosis families in Sardinia.

BACKGROUND: The Mediterranean island of Sardinia has a strikingly high incidence of the autoimmune disorders Type 1 Diabetes (T1D) and Multiple Sclerosis (MS). Furthermore, the two diseases tend to be co-inherited in the same individuals and in the same families. These observations suggest that some unknown autoimmunity variant with relevant effect size could be fairly common in this founder population and could be detected using linkage analysis. METHODS: To search for T1D and MS loci as well as any that predispose to both diseases, we performed a whole genome linkage scan, sequentially genotyping 593 microsatellite marker loci in 954 individuals distributed in 175 Sardinian families. In total, 413 patients were studied; 285 with T1D, 116 with MS and 12 with both disorders. Model-free linkage analysis was performed on the genotyped samples using the Kong and Cox logarithm of odds (LOD) score statistic. RESULTS: In T1D, aside from the HLA locus, we found four regions showing a lod-score > or =1; 1p31.1, 6q26, 10q21.2 and 22q11.22. In MS we found three regions showing a lod-score > or =1; 1q42.2, 18p11.21 and 20p12.3. In the combined T1D-MS scan for shared autoimmunity loci, four regions showed a LOD >1, including 6q26, 10q21.2, 20p12.3 and 22q11.22. When we typed more markers in these intervals we obtained suggestive evidence of linkage in the T1D scan at 10q21.2 (LOD = 2.1), in the MS scan at 1q42.2 (LOD = 2.5) and at 18p11.22 (LOD = 2.6). When all T1D and MS families were analysed jointly we obtained suggestive evidence in two regions: at 10q21.1 (LOD score = 2.3) and at 20p12.3 (LOD score = 2.5). CONCLUSION: This suggestive evidence of linkage with T1D, MS and both diseases indicates critical chromosome intervals to be followed up in downstream association studies.

Phenotypic variability related to C9orf72 mutation in a large Sardinian kindred.

We investigated intrafamilial phenotypic variability in carriers of the C9orf72 mutation, analysing clinical, neuropsychological and imaging characteristics of various members from a large Sardinian kindred with FTD or ALS. We compared these with those of C9 + patients in our ALS and FTD cohorts. Results showed that three patients carried the C9orf72 mutation: two with ALS and one with FTD and Parkinsonism. C9 + patients in our bvFTD Sardinian cohort had a higher frequency of Parkinsonism than non-mutated patients (75% vs. 36.3%, p <0.02). Parkinsonism was present in 2.7% of our ALS cohort and 3.3% of the C9 + patients. The prevalence of Parkinsonism in C9 + patients in the bvFTD and ALS cohorts showed a statistically significant difference (p <0.006). In conclusion, Parkinsonism was frequently associated with FTD but not ALS in a large Sardinian family, a finding reflected in the wider C9orf72 associated Sardinian ALS and FTD populations.

Constructional apraxia in frontotemporal dementia associated with the C9orf72 mutation: broadening the clinical and neuropsychological phenotype.

In our study we analysed clinical and neuropsychological data in a cohort of 57 Sardinian patients with FTD (55 apparently unrelated and two belonging to the same family), who underwent genetic screening for the C9orf72 mutation. Eight out of 56 patients were found positive for the C9orf72 mutation representing 14% of the entire cohort and 31.6% of the familial cases (6/19). C9orf72 mutated patients differed from the other FTD cases of the cohort for a younger age of onset, higher frequency of familial history for FTD and higher prevalence of delusional psychotic symptoms and hallucinations. In the neuropsychological assessment, C9orf72 mutated patients differed from non-mutated for the high frequency of visuospatial dysfunction regarding constructional apraxia (p = 0.02). In conclusion, our study confirms that Sardinian FTD patients have peculiar genetic characteristics and that C9orf72 mutated patients have a distinctive clinical and neuropsychological profile that could help differentiate them from other FTD patients. In our cohort we found that constructional apraxia, rarely reported in FTD, can properly discriminate between C9orf72 mutated and non-mutated patients and contribute to broaden the neuropsychological profile in frontotemporal dementia associated with this mutation.

Clinical phenotypes and radiological findings in frontotemporal dementia related to TARDBP mutations.

It has been shown that different genes could be associated with distinctive clinical and radiological phenotypes of FTD. TARDBP gene has been described worldwide in few cases of FTD so its phenotype is still unclear. The objective is to study the clinical and radiological characteristics of TARDBP-related FTD. In the present study, we report clinical, neuropsychological and radiological features of five new Sardinian non-related cases of FTD carriers of the p.A382T TARDBP mutation. Furthermore, we reviewed non-related FTD cases with TARDBP mutations previously described in literature. The p.A382T missense mutation of TARDBP was present in the 21.7 % of familial cases of our FTD cohort (5/23) and in no one of the sporadic patients. 3 of 5 patients showed a temporal variant FTD and 4/5 a predominant temporal involvement at MRI. The review of the literature of FTD cases with TARDBP mutations showed that in 5 of 16 cases, the clinical phenotype was consistent with temporal variant of FTD or semantic dementia (31 %) and in 7 of 16 cases neuroimaging showed predominant temporal lobe involvement (43.7 %). Our study further supports the pathogenetic role of TARDBP mutations in pure FTD and in the full spectrum of FTD/ALS. The presence of a predominant temporal lobe involvement in a high percentage of FTD mutated patients with a peculiar clinical pattern could be useful in the differential diagnosis with other forms of dementia/FTD both sporadic and familial.

C9ORF72 intermediate repeat expansion in patients affected by atypical parkinsonian syndromes or Parkinson's disease complicated by psychosis or dementia in a Sardinian population.

The hexanucleotide repeat expansion GGGGCC in the C9ORF72 gene larger than 30 repeats has been identified as a major genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Recent papers investigated the possible pathogenic role and associated clinical phenotypes of intermediate C9ORF72 repeat expansion ranging between 20 and 30 repeats. Some studies suggested its pathogenicity for typical Parkinson's disease (PD), atypical parkinsonian syndromes, FTD with/without parkinsonism, and ALS with/without parkinsonism or with/without dementia. In our study, we aimed to screen patients affected by atypical parkinsonian syndromes or PD complicated by psychosis or dementia for the presence of C9ORF72 repeat expansions, and in unrelated age- and sex-matched healthy controls. Consecutive unrelated patients with atypical parkinsonian syndromes and patients with PD complicated by psychosis or dementia were included in this study. Atypical parkinsonian syndromes were further divided into two groups: one with patients who met the criteria for the classic forms of atypical parkinsonism [multiple system atrophy (MSA), Lewy body disease (LBD), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD)] ;and patients who did not meet the above criteria, named non-classical atypical parkinsonism with or without dementia. Ninety-two unrelated patients (48 men, 44 women) were enrolled. None of the patients was found to be carriers of C9ORF72 repeat expansions with more than 30 repeats. Intermediate 20-30 repeat expansions were detected in four female patients (4.3 %). Three of them presented clinical features of atypical parkinsonian syndromes, two with non-classical atypical parkinsonism and dementia FTD-like, and one with non-classical atypical parkinsonism without dementia. The other patient presented clinical features of typical PD complicated by psychosis. Among 121 control subjects, none presented long or short expansion for the C9ORF72 gene. Our findings seem to support the hypothesis that the hexanucleotide expansions of C9ORF72 gene with intermediate repetitions between 20 and 29 repetitions could be associated with typical PD with psychosis or dementia and atypical parkinsonisms with dementia (non-classical atypical parkinsonism with dementia FTD-like) or without dementia (non-classical atypical parkinsonism upper MND-like), although the causal relationship is still unclear. In these latter patients, parkinsonism, more or less levodopa responsive, constituted the symptomatological central core at onset.

Vitamin D responsive elements within the HLA-DRB1 promoter region in Sardinian multiple sclerosis associated alleles.

Vitamin D response elements (VDREs) have been found in the promoter region of the MS-associated allele HLA-DRB1*15:01, suggesting that with low vitamin D availability VDREs are incapable of inducing *15:01 expression allowing in early life autoreactive T-cells to escape central thymic deletion. The Italian island of Sardinia exhibits a very high frequency of MS and high solar radiation exposure. We test the contribution of VDREs analysing the promoter region of the MS-associated DRB1 *04:05, *03:01, *13:01 and *15:01 and non-MS-associated *16:01, *01, *11, *07:01 alleles in a cohort of Sardinians (44 MS patients and 112 healthy subjects). Sequencing of the DRB1 promoter region revealed a homozygous canonical VDRE in all *15:01, *16:01, *11 and in 45/73 *03:01 and in heterozygous state in 28/73 *03:01 and all *01 alleles. A new mutated homozygous VDRE was found in all *13:03, *04:05 and *07:01 alleles. Functionality of mutated and canonical VDREs was assessed for its potential to modulate levels of DRB1 gene expression using an in vitro transactivation assay after stimulation with active vitamin D metabolite. Vitamin D failed to increase promoter activity of the *04:05 and *03:01 alleles carrying the new mutated VDRE, while the *16:01 and *03:01 alleles carrying the canonical VDRE sequence showed significantly increased transcriptional activity. The ability of VDR to bind the mutant VDRE in the DRB1 promoter was evaluated by EMSA. Efficient binding of VDR to the VDRE sequence found in the *16:01 and in the *15:01 allele reduced electrophoretic mobility when either an anti-VDR or an anti-RXR monoclonal antibody was added. Conversely, the Sardinian mutated VDRE sample showed very low affinity for the RXR/VDR heterodimer. These data seem to exclude a role of VDREs in the promoter region of the DRB1 gene in susceptibility to MS carried by DRB1* alleles in Sardinian patients.

Parkin Exon Rearrangements and Sequence Variants in LRRK2 Mutations Carriers: Analysis on a Possible Modifier Effect on LRRK2 Penetrance.

Mutations in LRRK2 represent the most common causes of Parkinson's disease (PD) identified to date, but their penetrance is incomplete and probably due to the presence of other genetic or environmental factors required for development of the disease. We analyzed the presence of parkin sequence variants (mutations or polymorphisms) and exon rearrangements in LRRK2 mutations carriers (both PD patients and unaffected relatives) in order to detect a possible modifier effect on penetrance. Eight families with nine PD patients with heterozygous LRRK2 mutations (identified within 380 Sardinian PD patients screened for the presence of the five most common LRRK2 mutations) and sixteen additional relatives were genetically investigated for the presence of LRRK2 and parkin mutations. No evidence was found for the presence of pathological parkin mutations or exon rearrangements in patients or not affected family members. Three single-nucleotide polymorphisms (SNPs) were identified both in patients and unaffected relatives but did not significantly differ between the two groups. These data provide no support to the hypothesis whereby such parkin gene mutations may be commonly implicated in possible effect on penetrance in LRRK2 mutation carriers.

Genetic analysis for five LRRK2 mutations in a Sardinian parkinsonian population: importance of G2019S and R1441C mutations in sporadic Parkinson's disease patients.

Mutations in the LRRK2 gene are the most common known cause of familial and sporadic Parkinson's disease (PD). Few studies performed to date to assess frequency of these mutations are actually only representative of specific areas. Here we study the frequency and clinical phenotype of LRRK2 G2019S, I2020T and R1441C/G/H mutations in 356 Sardinian patients with idiopathic PD and 208 controls. Seventeen additional subjects, relatives of PD mutated probands, were enrolled. Eight patients were mutated in heterozygosis for LRRK2 gene (2.3%): six carried the G2019S (1.7%) and two the R1441C (0.6%) mutation. Three PD patients G2019S carriers (50%) were detected in two contiguous villages comprising 3921 inhabitants while the other three (50%) were identified in the remaining population of 796,079 inhabitants. Only one mutated proband had a family history of PD. LRRK2 G2019S and R1441C mutations associated with PD were not an uncommon mutation in a Sardinian population, especially in sporadic PD patients. The detection of the G2019S variant in ten unaffected relatives confirms a reduced penetrance of the underlying mutation and might explain its prevalence among patients with sporadic PD. These findings may provide new insights into the importance of studies of frequency of LRKK2 mutations in PD patients originating from small ethnically homogeneous populations.

mtDNA nt13708A variant increases the risk of multiple sclerosis.

BACKGROUND: Mitochondrial DNA (mtDNA) polymorphism is a possible factor contributing to the maternal parent-of-origin effect in multiple sclerosis (MS) susceptibility. METHODS AND FINDINGS: In order to investigate the role of mtDNA variations in MS, we investigated six European MS case-control cohorts comprising >5,000 individuals. Three well matched cohorts were genotyped with seven common, potentially functional mtDNA single nucleotide polymorphisms (SNPs). A SNP, nt13708 G/A, was significantly associated with MS susceptibility in all three cohorts. The nt13708A allele was associated with an increased risk of MS (OR = 1.71, 95% CI 1.28-2.26, P = 0.0002). Subsequent sequencing of the mtDNA of 50 individuals revealed that the nt13708 itself, rather than SNPs linked to it, was responsible for the association. However, the association of nt13708 G/A with MS was not significant in MS cohorts which were not well case-control matched, indicating that the significance of association was affected by the population structure of controls. CONCLUSIONS: Taken together, our finding identified the nt13708A variant as a susceptibility allele to MS, which could contribute to defining the role of the mitochondrial genome in MS pathogenesis.