Inferring biallelism of two FSH receptor mutations associated with spontaneous ovarian hyperstimulation syndrome by evaluating FSH, LH and HCG cross-activity.

RESEARCH QUESTION: What is the cumulative effect of two follicle-stimulating hormone receptor (FSHR) mutations in spontaneous ovarian hyperstimulation syndrome (sOHSS) pathogenesis? Are these mutations in the mono- or biallelic state? DESIGN: Two FSHR mutations were found in a pregnant patient affected by sOHSS with no predisposing conditions. While the p.Asn106His mutation is novel, the p.Ser128Tyr mutation has been associated with sOHSS previously. The patient's FSHR gene was analysed by Sanger sequencing, and FSHR cDNAs carrying a single or both point mutations were created by mutagenesis in vitro. cAMP activation by recombinant FSH, luteinizing hormone (LH), human chorionic gonadotropin (HCG) and thyroid-stimulating hormone (TSH) was evaluated in transfected HEK293 cells by bioluminescence resonance energy transfer. RESULTS: All mutations decreased the 50% effective concentration of FSH calculated for cAMP (P < 0.05, n = 6), resulting in two- to 10-fold lower ligand potency. TSH failed to induce an FSHR-mediated increase in intracellular cAMP, while LH was approximately four-fold more potent than HCG in p.Ser128Tyr FSHR-expressing HEK293 cells despite lower cAMP plateau levels (P < 0.05, n = 5). The p.Ser128Tyr FSHR mutation was found to be responsible for an LH-/HCG-induced increase in cAMP when it was in the biallelic heterozygous state with p.Asn106His, but no increase in cAMP was induced in the monoallelic state. CONCLUSION: In-vitro data support that, in pregnant patients with sOHSS, the two FSHR mutations have an opposing effect on the pathogenesis of sOHSS and are in the biallelic heterozygous form, allowing HCG to induce a p.Ser128Tyr FSHR-mediated increase in cAMP.

A case of Feingold type 2 syndrome associated with keratoconus refines keratoconus type 7 locus on chromosome 13q.

We report on a 58-year old woman with microcephaly, mild dysmorphic features, bilateral keratoconus, digital abnormalities, short stature and mild cognitive delay. Except for keratoconus, the phenotype was suggestive for Feingold syndrome type 2 (FGLDS2, MIM 614326), a rare autosomal dominant disorder described in six patients worldwide, due to the haploinsufficiency of MIR17HG, a micro RNA encoding gene. Karyotype showed a de novo deletion on chromosome 13q, further defined by array-Comparative Genomic Hybridization (a-CGH) to a 17.2-Mb region. The deletion included MIR17HG, as expected by the FGLDS2 phenotype, and twelve genes from the keratoconus type 7 locus. Because our patient presented with keratoconus, we propose she further refines disease genes at this locus. Among previously suggested candidates, we exclude DOCK9 and STK24, and propose as best candidates IPO5, DNAJC3, MBNL2 and RAP2A. In conclusion, we report a novel phenotypic association of Feingold syndrome type 2 and keratoconus, a likely contiguous gene syndrome due to a large genomic deletion on 13q spanning MIR17HG and a still to be identified gene for keratoconus.

ATNX2 is not a regulatory gene in Italian amyotrophic lateral sclerosis patients with C9ORF72 GGGGCC expansion.

There are indications that both familial amyotrophic lateral sclerosis (ALS) and sporadic ALS phenotype and prognosis are partly regulated by genetic and environmental factors, supporting the theory that ALS is a multifactorial disease. The aim of this article was to assess the role of ATXN2 intermediate length repeats in a large series of Italian and Sardinian ALS patients and controls carrying a pathogenetic C9ORF72 GGGGCC hexanucleotide repeat. A total of 1972 ALS cases were identified through the database of the Italian ALS Genetic consortium, a collaborative effort including 18 ALS centers throughout Italy. The study population included: (1) 276 Italian and 57 Sardinian ALS cases who carried the C9ORF72 expansion; (2) 1340 Italian and 299 Sardinian ALS cases not carrying the C9ORF72 expansion. A total of healthy 1043 controls were also assessed. Most Italian and Sardinian cases and controls were homozygous for 22/22 or 23/23 repeats or heterozygous for 22/23 repeats of the ATXN2 gene. ATXN2 intermediate length repeats alleles (≥28) were detected in 3 (0.6%) Italian ALS cases carrying the C9ORF72 expansion, in none of the Sardinian ALS cases carrying the expansion, in 60 (4.3%) Italian cases not carrying the expansion, and in 6 (2.0%) Sardinian ALS cases without C9ORF72 expansion. Intermediate length repeat alleles were found in 12 (1.5%) Italian controls and 1 (0.84%) Sardinian controls. Therefore, ALS patients with C9ORF72 expansion showed a lower frequency of ATXN2 polyQ intermediate length repeats than both controls (Italian cases, p = 0.137; Sardinian cases, p = 0.0001) and ALS patients without C9ORF72 expansion (Italian cases, p = 0.005; Sardinian cases, p = 0.178). In our large study on Italian and Sardinian ALS patients with C9ORF72 GGGGCC hexanucleotide repeat expansion, compared to age-, gender- and ethnic-matched controls, ATXN2 polyQ intermediate length does not represent a modifier of ALS risk, differently from non-C9ORF72 mutated patients.

Array-Comparative Genomic Hybridization Analysis in Fetuses with Major Congenital Malformations Reveals that 24% of Cases Have Pathogenic Deletions/Duplications.

Karyotyping and aCGH are routinely used to identify genetic determinants of major congenital malformations (MCMs) in fetal deaths or terminations of pregnancy after prenatal diagnosis. Pathogenic rearrangements are found with a variable rate of 9-39% for aCGH. We collected 33 fetuses, 9 with a single MCM and 24 with MCMs involving 2-4 organ systems. aCGH revealed copy number variants in 14 out of 33 cases (42%). Eight were classified as pathogenic which account for a detection rate of 24% (8/33) considering fetuses with 1 or more MCMs and 33% (8/24) taking into account fetuses with multiple malformations only. Three of the pathogenic variants were known microdeletion syndromes (22q11.21 deletion, central chromosome 22q11.21 deletion, and TAR syndrome) and 5 were large rearrangements, adding up to >11 Mb per subject and comprising strong phenotype-related genes. One of those was a de novo complex rearrangement, and the remaining 4 duplications and 2 deletions were 130-900 kb in size, containing 1-7 genes, and were classified as variants of unknown clinical significance. Our study confirms aCGH as a powerful technique to ascertain the genetic etiology of fetal major congenital malformations.

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.

ATXN2 is a modifier of phenotype in ALS patients of Sardinian ancestry.

Intermediate-length CAG expansions (encoding 27-33 glutamines, polyQ) of the Ataxin2 (ATXN2) gene represent a risk factor for amyotrophic lateral sclerosis (ALS). Recently, it has been proposed that ≥31 CAG expansions may influence ALS phenotype. We assessed whether ATXN2 intermediate-length polyQ expansions influence ALS phenotype in a series of 375 patients of Sardinian ancestry. Controls were 247 neurologically healthy subjects, resident in the study area, age- and gender-matched to cases. The frequency of ≥31 polyQ ATNX2 repeats was significantly more common in ALS cases (4 patients vs. no control, p = 0.0001). All patients with ≥31 polyQ repeats had a spinal onset versus 73.3% of patients with <31 polyQ repeats. Patients with an increased number of polyQ repeats have a shorter survival than those with <31 repeats (1.2 vs. 4.2 years, p = 0.035). In this large series of ALS patients of Sardinian ancestry, we have found that ≥31 polyQ repeats of the ATXN2 gene influenced patients' phenotype, being associated to a spinal onset and a significantly shorter survival.

HFE p.H63D polymorphism does not influence ALS phenotype and survival.

It has been recently reported that the p.His63Asp polymorphism of the HFE gene accelerates disease progression both in the SOD1 transgenic mouse and in amyotrophic lateral sclerosis (ALS) patients. We have evaluated the effect of HFE p.His63Asp polymorphism on the phenotype in 1351 Italian ALS patients (232 of Sardinian ancestry). Patients were genotyped for the HFE p.His63Asp polymorphism (CC, GC, and GG). All patients were also assessed for C9ORF72, TARDBP, SOD1, and FUS mutations. Of the 1351 ALS patients, 363 (29.2%) were heterozygous (GC) for the p.His63Asp polymorphism and 30 (2.2%) were homozygous for the minor allele (GG). Patients with CC, GC, and GG polymorphisms did not significantly differ by age at onset, site of onset of symptoms, and survival; however, in SOD1 patients with CG or GG polymorphism had a significantly longer survival than those with a CC polymorphism. Differently from what observed in the mouse model of ALS, the HFE p.His63Asp polymorphism has no effect on ALS phenotype in this large series of Italian ALS patients.

The role of TREM2 R47H as a risk factor for Alzheimer's disease, frontotemporal lobar degeneration, amyotrophic lateral sclerosis, and Parkinson's disease.

A rare variant in TREM2 (p.R47H, rs75932628) was recently reported to increase the risk of Alzheimer's disease (AD) and, subsequently, other neurodegenerative diseases, i.e. frontotemporal lobar degeneration (FTLD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Here we comprehensively assessed TREM2 rs75932628 for association with these diseases in a total of 19,940 previously untyped subjects of European descent. These data were combined with those from 28 published data sets by meta-analysis. Furthermore, we tested whether rs75932628 shows association with amyloid beta (Aß42) and total-tau protein levels in the cerebrospinal fluid (CSF) of 828 individuals with AD or mild cognitive impairment. Our data show that rs75932628 is highly significantly associated with the risk of AD across 24,086 AD cases and 148,993 controls of European descent (odds ratio or OR = 2.71, P = 4.67 × 10(-25)). No consistent evidence for association was found between this marker and the risk of FTLD (OR = 2.24, P = .0113 across 2673 cases/9283 controls), PD (OR = 1.36, P = .0767 across 8311 cases/79,938 controls) and ALS (OR = 1.41, P = .198 across 5544 cases/7072 controls). Furthermore, carriers of the rs75932628 risk allele showed significantly increased levels of CSF-total-tau (P = .0110) but not Aß42 suggesting that TREM2's role in AD may involve tau dysfunction.

CHCH10 mutations in an Italian cohort of familial and sporadic amyotrophic lateral sclerosis patients.

Mutations in CHCHD10 have recently been described as a cause of frontotemporal dementia (FTD) comorbid with amyotrophic lateral sclerosis (ALS). The aim of this study was to assess the frequency and clinical characteristics of CHCHD10 mutations in Italian patients diagnosed with familial (n = 64) and apparently sporadic ALS (n = 224). Three apparently sporadic patients were found to carry c.100C>T (p.Pro34Ser) heterozygous variant in the exon 2 of CHCHD10. This mutation had been previously described in 2 unrelated French patients with FTD-ALS. However, our patients had a typical ALS, without evidence of FTD, cerebellar or extrapyramidal signs, or sensorineural deficits. We confirm that CHCHD10 mutations account for ∼ 1% of Italian ALS patients and are a cause of disease in subjects without dementia or other atypical clinical signs.

A genome-wide association study of myasthenia gravis.

IMPORTANCE: Myasthenia gravis is a chronic, autoimmune, neuromuscular disease characterized by fluctuating weakness of voluntary muscle groups. Although genetic factors are known to play a role in this neuroimmunological condition, the genetic etiology underlying myasthenia gravis is not well understood. OBJECTIVE: To identify genetic variants that alter susceptibility to myasthenia gravis, we performed a genome-wide association study. DESIGN, SETTING, AND PARTICIPANTS: DNA was obtained from 1032 white individuals from North America diagnosed as having acetylcholine receptor antibody-positive myasthenia gravis and 1998 race/ethnicity-matched control individuals from January 2010 to January 2011. These samples were genotyped on Illumina OmniExpress single-nucleotide polymorphism arrays. An independent cohort of 423 Italian cases and 467 Italian control individuals were used for replication. MAIN OUTCOMES AND MEASURES: We calculated P values for association between 8,114,394 genotyped and imputed variants across the genome and risk for developing myasthenia gravis using logistic regression modeling. A threshold P value of 5.0×10(-8) was set for genome-wide significance after Bonferroni correction for multiple testing. RESULTS: In the overall case-control cohort, we identified association signals at CTLA4 (rs231770; P=3.98×10(-8); odds ratio, 1.37; 95% CI, 1.25-1.49), HLA-DQA1 (rs9271871; P=1.08×10(-8); odds ratio, 2.31; 95% CI, 2.02-2.60), and TNFRSF11A (rs4263037; P=1.60×10(-9); odds ratio, 1.41; 95% CI, 1.29-1.53). These findings replicated for CTLA4 and HLA-DQA1 in an independent cohort of Italian cases and control individuals. Further analysis revealed distinct, but overlapping, disease-associated loci for early- and late-onset forms of myasthenia gravis. In the late-onset cases, we identified 2 association peaks: one was located in TNFRSF11A (rs4263037; P=1.32×10(-12); odds ratio, 1.56; 95% CI, 1.44-1.68) and the other was detected in the major histocompatibility complex on chromosome 6p21 (HLA-DQA1; rs9271871; P=7.02×10(-18); odds ratio, 4.27; 95% CI, 3.92-4.62). Association within the major histocompatibility complex region was also observed in early-onset cases (HLA-DQA1; rs601006; P=2.52×10(-11); odds ratio, 4.0; 95% CI, 3.57-4.43), although the set of single-nucleotide polymorphisms was different from that implicated among late-onset cases. CONCLUSIONS AND RELEVANCE: Our genetic data provide insights into aberrant cellular mechanisms responsible for this prototypical autoimmune disorder. They also suggest that clinical trials of immunomodulatory drugs related to CTLA4 and that are already Food and Drug Administration approved as therapies for other autoimmune diseases could be considered for patients with refractory disease.

A novel p.E121G heterozygous missense mutation of SOD1 in an apparently sporadic ALS case with a 14-year course.

The frequency of SOD1 mutations differs among populations: in Italy they account for 13.6% of familial ALS and 0.7% of sporadic cases. We describe an apparently sporadic Italian ALS patient, carrying a novel p.E121G heterozygous missense mutation of SOD1, with a 14-year disease course and a prevalent lower motor neuron phenotype, which are not uncommon among SOD1 mutations carriers. To our knowledge, no other mutation of codon 121 of SOD1 has ever been reported. Three in silico models suggest a deleterious effect of the p.E121G mutation. Nevertheless, further studies are necessary to confirm its pathogenic role and to evaluate eventual genotype-phenotype correlations.

Cognitive correlates in amyotrophic lateral sclerosis: a population-based study in Italy.

BACKGROUND: There is less data available regarding the characteristics of cognitive impairment in patients with amyotrophic lateral sclerosis (ALS) in a population-based series. METHODOLOGY: Patients with ALS incident in Piemonte, Italy, between 2009 and 2011 underwent an extensive neuropsychological battery. Cognitive status was classified as follows: normal cognition, frontotemporal dementia (ALS-FTD), executive cognitive impairment (ALS-ECI), non-executive cognitive impairment (ALS-NECI), behavioural impairment (ALS-Bi), non-classifiable cognitive impairment. We also assessed 127 age-matched and gender-matched controls identified through patients' general practitioners. RESULTS: Out of the 281 incident patients, 207 (71.9%) underwent the neuropsychological testing; of these, 19 were excluded from the analysis due previous conditions affecting cognition. Ninety-one (49.7%) patients were cognitively normal, 23 (12.6%) had ALS-FTD, 36 (19.7%) ALS-ECI, 10 (5.5%) ALS-NECI, 11 (6.0%) ALS-Bi and 11 (6.0%) non-classifiable cognitive impairment, 1 had comorbid Alzheimer's disease. Patients with ALS-FTD were older, had a lower education level, and had a shorter survival than any other cognitive group. Of the nine cases with C9ORF72 mutation, six had ALS-FTD, two ALS-ECI and one was cognitively normal; one of the five patients with SOD1 mutations and one of the five patients with TARBDP mutations had ALS-Bi. CONCLUSIONS: About 50% of Italian patients with ALS had some degree of cognitive impairment, in keeping with a previous Irish study, despite the largely different genetic background of the two populations. The lower educational attainment in patients with ALS-FTD indicated a possible role of cognitive reserve in ALS-related cognitive impairment. ALS-ECI and ALS-NECI may represent discrete cognitive syndromes in the continuum of ALS and FTD.

ATXN2 polyQ intermediate repeats are a modifier of ALS survival.

OBJECTIVE: To analyze the frequency and clinical characteristics of patients with amyotrophic lateral sclerosis (ALS) with intermediate-length (CAG) expansion (encoding 27-33 glutamines, polyQ) in the ATXN2 gene, in a population-based cohort of Italian patients with ALS (discovery cohort), and to replicate the findings in an independent cohort of consecutive patients from an ALS tertiary center (validation cohort). METHODS: PolyQ repeats were assessed in 672 patients with incident ALS in Piemonte and Valle d'Aosta regions, Italy, in the 2007-2012 period (discovery cohort); controls were 509 neurologically healthy age- and sex-matched subjects resident in the study area. The validation cohort included 661 patients with ALS consecutively seen between 2001 and 2013 in the ALS Clinic Center of the Catholic University in Rome, Italy. RESULTS: In the discovery cohort, the frequency of ≥31 polyQ ATNX2 repeats was significantly more common in ALS cases (19 patients vs 1 control, p = 0.0001; odds ratio 14.8, 95% confidence interval 1.9-110.8). Patients with an increased number of polyQ repeats had a shorter survival than those with <31 repeats (median survival, polyQ ≥31, 1.8 years, interquartile range [IQR] 1.3-2.2; polyQ <31, 2.7 years, IQR 1.6-5.1; p = 0.001). An increased number of polyQ repeats remained independently significant at multivariable analysis. In the validation cohort, patients with ≥31 polyQ repeats had a shorter survival than those with <31 repeats (median survival, polyQ ≥31, 2.0 years, IQR 1.5-3.4; polyQ <31, 3.2 years, IQR 2.0-6.4; p = 0.007). CONCLUSIONS: ATXN2 polyQ intermediate-length repeat is a modifier of ALS survival. Disease-modifying therapies targeted to ATXN2 represent a promising therapeutic approach for ALS.

Large cryptic genomic rearrangements with apparently normal karyotypes detected by array-CGH.

BACKGROUND: Conventional karyotyping (550 bands resolution) is able to identify chromosomal aberrations >5-10 Mb, which represent a known cause of intellectual disability/developmental delay (ID/DD) and/or multiple congenital anomalies (MCA). Array-Comparative Genomic Hybridization (array-CGH) has increased the diagnostic yield of 15-20%. RESULTS: In a cohort of 700 ID/DD cases with or without MCA, including 15 prenatal diagnoses, we identified a subgroup of seven patients with a normal karyotype and a large complex rearrangement detected by array-CGH (at least 6, and up to 18 Mb). FISH analysis could be performed on six cases and showed that rearrangements were translocation derivatives, indistinguishable from a normal karyotype as they involved a similar band pattern and size. Five were inherited from a parent with a balanced translocation, whereas two were apparently de novo. Genes spanning the rearrangements could be associated with some phenotypic features in three cases (case 3: DOCK8; case 4: GATA3, AKR1C4; case 6: AS/PWS deletion, CHRNA7), and in two, likely disease genes were present (case 5: NR2F2, TP63, IGF1R; case 7: CDON). Three of our cases were prenatal diagnoses with an apparently normal karyotype. CONCLUSIONS: Large complex rearrangements of up to 18 Mb, involving chromosomal regions with similar size and band appearance may be overlooked by conventional karyotyping. Array-CGH allows a precise chromosomal diagnosis and recurrence risk definition, further confirming this analysis as a first tier approach to clarify molecular bases of ID/DD and/or MCA. In prenatal tests, array-CGH is confirmed as an important tool to avoid false negative results due to karyotype intrinsic limit of detection.

NADPH oxidase (NOX2) activity is a modifier of survival in ALS.

NADPH-oxidases (NOX) catalyze the formation of reactive oxygen species (ROS), which play a role in the development of neurological diseases, particularly those generated by the phagocytic isoform NOX2. Increased ROS has been observed in the amyotrophic lateral sclerosis (ALS) SOD1 transgenic mouse, and in this preclinical model the inactivation of NOX2 decreases ROS production and extends survival. Our aim was to evaluate NOX2 activity measuring neutrophil oxidative burst in a cohort of 83 ALS patients, and age- and gender-matched healthy controls. Oxidative burst was measured directly in fresh blood using Phagoburst™ assay by flow cytometry. Mean fluorescence intensity (MFI), emitted in response to different stimuli, leads to produce ROS and corresponds to the percentage of oxidizing cells and their enzymatic activity (GeoMean). No difference was found between the MFI values in cases and controls. NOX2 activity was independent from gender and age, and in patients was not related to disease duration, site of onset (bulbar vs. spinal), or ALSFRS-R score. However, patients with a NOX2 activity lower than the median value showed a 1-year increase of survival from onset (p = 0.011). The effect of NOX2 was independent from other known prognostic factors. These findings are in keeping with the observations in the mouse model of ALS, and demonstrate the strong role of NOX2 in modifying progression in ALS patients. A proper modulation of NOX2 activity might hold therapeutic potential for ALS.

Genetic architecture of ALS in Sardinia.

Conserved populations, such as Sardinians, displaying elevated rates of familial or sporadic amyotrophic lateral sclerosis (ALS) provide unique information on the genetics of the disease. Our aim was to describe the genetic profile of a consecutive series of ALS patients of Sardinian ancestry. All ALS patients of Sardinian ancestry, identified between 2008 and 2013 through the Italian ALS Genetic Consortium, were eligible to be included in the study. Patients and controls underwent the analysis of TARDBP, C9ORF72, SOD1, and FUS genes. Genetic mutations were identified in 155 out of 375 Sardinian ALS cases (41.3%), more commonly the p.A382T and p.G295S mutations of TARDBP and the GGGGCC hexanucleotide repeat expansion of C9ORF72. One patient had both p.G295S and p.A382T mutations of TARDBP and 8 carried both the heterozygous p.A382T mutation of TARDBP and a repeat expansion of C9ORF72. Patients carrying the p.A382T and the p.G295S mutations of TARDBP and the C9ORF72 repeat expansion shared distinct haplotypes across these loci. Patients with cooccurrence of C9ORF72 and TARDBP p.A382T missense mutation had a significantly lower age at onset and shorter survival. More than 40% of all cases on the island of Sardinia carry a mutation of an ALS-related gene, representing the highest percentage of ALS cases genetically explained outside of Scandinavia. Clinical phenotypes associated with different genetic mutations show some distinctive characteristics, but the heterogeneity between and among families carrying the same mutations implies that ALS manifestation is influenced by other genetic and nongenetic factors.

Genome-wide analysis of the heritability of amyotrophic lateral sclerosis.

IMPORTANCE: Considerable advances have been made in our understanding of the genetics underlying amyotrophic lateral sclerosis (ALS). Nevertheless, for the majority of patients who receive a diagnosis of ALS, the role played by genetics is unclear. Further elucidation of the genetic architecture of this disease will help clarify the role of genetic variation in ALS populations. OBJECTIVE: To estimate the relative importance of genetic factors in a complex disease such as ALS by accurately quantifying heritability using genome-wide data derived from genome-wide association studies. DESIGN, SETTING, AND PARTICIPANTS: We applied the genome-wide complex trait analysis algorithm to 3 genome-wide association study data sets that were generated from ALS case-control cohorts of European ancestry to estimate the heritability of ALS. Cumulatively, these data sets contained genotype data from 1223 cases and 1591 controls that had been previously generated and are publically available on the National Center for Biotechnology Information database of genotypes and phenotypes website (http://www.ncbi.nlm.nih.gov/gap). The cohorts genotyped as part of these genome-wide association study efforts include the InCHIANTI (aging in the Chianti area) Study, the Piemonte and Valle d'Aosta Register for Amyotrophic Lateral Sclerosis, the National Institute of Neurological Disorders and Stroke Repository, and an ALS specialty clinic in Helsinki, Finland. MAIN OUTCOMES AND MEASURES: A linear mixed model was used to account for all known single-nucleotide polymorphisms simultaneously and to quantify the phenotypic variance present in ostensibly outbred individuals. Variance measures were used to estimate heritability. RESULTS: With our meta-analysis, which is based on genome-wide genotyping data, we estimated the overall heritability of ALS to be approximately 21.0% (95% CI, 17.1-24.9) (SE = 2.0%), indicating that additional genetic variation influencing risk of ALS loci remains to be identified. Furthermore, we identified 17 regions of the genome that display significantly high heritability estimates. Eleven of these regions represent novel candidate regions for ALS risk. CONCLUSIONS AND RELEVANCE: We found the heritability of ALS to be significantly higher than previously reported. We also identified multiple, novel genomic regions that we hypothesize may contain causative risk variants that influence susceptibility to ALS.

Analysis of the KIFAP3 gene in amyotrophic lateral sclerosis: a multicenter survival study.

Sporadic amyotrophic lateral sclerosis is a multifactorial disease of environmental and genetic origin. In a previous large multicenter genome wide study, common genetic variation in the Kinesin-Associated Protein 3 (KIFAP3) gene (rs1541160) was reported to have a significant effect on survival in amyotrophic lateral sclerosis patients. However, this could not be replicated in 3 smaller independent cohorts. We conducted a large multicenter multivariate survival analysis (n = 2362) on the effect of genetic variation in rs1541160. The previously reported beneficial genotype did not show a significant improvement in survival in this patient group.