Non-neural phenotype of spinal and bulbar muscular atrophy: Results from a large cohort of Italian patients

Objective: To carry out a deep characterisation of the main androgen-responsive tissues involved in spinal and bulbar muscular atrophy (SBMA). Methods: 73 consecutive Italian patients underwent a full clinical protocol including biochemical and hormonal analyses, genitourinary examination, bone metabolism and densitometry, cardiological evaluation and muscle pathology. Results: Creatine kinase levels were slightly to markedly elevated in almost all cases (68 of the 73; 94%). 30 (41%) patients had fasting glucose above the reference limit, and many patients had total cholesterol (40; 54.7%), low-density lipoproteins cholesterol (29; 39.7%) and triglyceride (35; 48%) levels above the recommended values. Although testosterone, luteinising hormone and follicle-stimulating hormone values were generally normal, in one-third of cases we calculated an increased Androgen Sensitivity Index reflecting the presence of androgen resistance in these patients. According to the International Prostate Symptom Score (IPSS), 7/70 (10%) patients reported severe lower urinal tract symptoms (IPSS score >19), and 21/73 (30%) patients were moderately symptomatic (IPSS score from 8 to 19). In addition, 3 patients were carriers of an indwelling bladder catheter. Videourodynamic evaluation indicated that 4 of the 7 patients reporting severe urinary symptoms had an overt prostate-unrelated bladder outlet obstruction. Dual-energy X-ray absorptiometry scan data were consistent with low bone mass in 25/61 (41%) patients. Low bone mass was more frequent at the femoral than at the lumbar level. Skeletal muscle biopsy was carried out in 20 patients and myogenic changes in addition to the neurogenic atrophy were mostly observed. Conclusions: Our study provides evidence of a wide non-neural clinical phenotype in SBMA, suggesting the need for comprehensive multidisciplinary protocols for these patients. \ua9 2016 Published by the BMJ Publishing Group Limited

Exome-wide Rare Variant Analysis Identifies TUBA4A Mutations Associated with Familial ALS

Exome sequencing is an effective strategy for identifying human disease genes. However, this methodology is difficult in late-onset diseases where limited availability of DNA from informative family members prohibits comprehensive segregation analysis. To overcome this limitation, we performed an exome-wide rare variant burden analysis of 363 index cases with familial ALS (FALS). The results revealed an excess of patient variants within TUBA4A, the gene encoding the Tubulin, Alpha 4A protein. Analysis of a further 272 FALS cases and 5,510 internal controls confirmed the overrepresentation as statistically significant and replicable. Functional analyses revealed that TUBA4A mutants destabilize the microtubule network, diminishing its repolymerization capability. These results further emphasize the role of cytoskeletal defects in ALS and demonstrate the power of gene-based rare variant analyses in situations where causal genes cannot be identified through traditional segregation analysis

Analysis of shared common genetic risk between amyotrophic lateral sclerosis and epilepsy

Because hyper-excitability has been shown to be a shared pathophysiological mechanism, we used the latest and largest genome-wide studies in amyotrophic lateral sclerosis (n = 36,052) and epilepsy (n = 38,349) to determine genetic overlap between these conditions. First, we showed no significant genetic correlation, also when binned on minor allele frequency. Second, we confirmed the absence of polygenic overlap using genomic risk score analysis. Finally, we did not identify pleiotropic variants in meta-analyses of the 2 diseases. Our findings indicate that amyotrophic lateral sclerosis and epilepsy do not share common genetic risk, showing that hyper-excitability in both disorders has distinct origins

Genome-wide Analyses Identify KIF5A as a Novel ALS Gene

To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.Peer reviewe

Genetic correlation between amyotrophic lateral sclerosis and schizophrenia

A. Palotie on työryhmän Schizophrenia Working Grp Psychiat jäsen.We have previously shown higher-than-expected rates of schizophrenia in relatives of patients with amyotrophic lateral sclerosis (ALS), suggesting an aetiological relationship between the diseases. Here, we investigate the genetic relationship between ALS and schizophrenia using genome-wide association study data from over 100,000 unique individuals. Using linkage disequilibrium score regression, we estimate the genetic correlation between ALS and schizophrenia to be 14.3% (7.05-21.6; P = 1 x 10(-4)) with schizophrenia polygenic risk scores explaining up to 0.12% of the variance in ALS (P = 8.4 x 10(-7)). A modest increase in comorbidity of ALS and schizophrenia is expected given these findings (odds ratio 1.08-1.26) but this would require very large studies to observe epidemiologically. We identify five potential novel ALS-associated loci using conditional false discovery rate analysis. It is likely that shared neurobiological mechanisms between these two disorders will engender novel hypotheses in future preclinical and clinical studies.Peer reviewe

Caratterizzazione genetico-molecolare di un campione di soggetti affetti da disturbi dello spettro schizofrenico/bipolare provenienti da Chioggia

In order to identify susceptibility loci for schizophrenia (SZ) and bipolar disorder (BPD), we collected clinical informations and biological sample of patients affected by SZ, BPD and schizoaffective disorder (SA), in collaboration with Mental Health Centre of Chioggia. Recent findings, emerging from genetic studies, support the evidence that these diseases share a number of susceptibility genes. Accordig to this theory, we carried out genetic and molecular analysis to better undestand schizophrenia and its associated disorders in their genetic context. By performing these analysis we were able to: 1) Collect clinical and anagraphical informations about the 40 pedigrees with high loading for schizophrenia and bipolar disorder. For each family, pedigree structure was traced back to tree generations using both church registers and demographical records. Additionally, we genotyped microsatellite markers on chromosome Y to evaluate the possibility of common male ancestor. 2) Assess the weight of genetic component and the mode of inheritance of SZ/BPD, in the pedigrees. We performed a complex segregation analysis (in collaboration with Prof. Scapoli); the results suggest that a main additive gene, plus a residual polygenic component is the best fitting hereditary model for the collected sample (Scapoli et al., 2006). 3) Find susceptibility loci with a genome wide search (GWS) in 16 multigenerational pedigrees with a high loading of the diseases (57 subjects). We genotyped 489 microsatellite markers (465 in the first scan and 24 in the fine-mapping analysis) and we calculated, using a multipoint approach, LOD score parametric and non parametric (NPL). The higher LOD score was obtained on chromosome 15q26, with a peak on marker D15S1014 (NPL=3.05), that reaches the statistical criteria for suggestive linkage (genomic P value of 0.07). In this region (15q26) mapped the gene ST8SIA2. Recently, two SNPs located in the promoter of the gene were reported in association with schizophrenia in a Japanese and Chinese sample. In order to test the frequencies of these polimorfisms, we performed a preliminary analysis in a sample of 156 Italian subjects: 56 patients and 100 healthy subjects (50 from Chioggia and 50 from other Italian regions). The SNPs analyzed resulted to be rare or not polymorphic at all, both in Chioggia and in the general Italian population, so they are unlikely to be directly involved in schizophrenia in our population. In order to test the possibility that some families share minor susceptibility loci not identified in the previous analysis, we evaluated linkage data for each single family separately. We found that 2 of the 16 pedigrees showed high LOD score values in 3q24-27 and 18q23, therefore in these regions a further investigations, increasing the marker density and analysing the haplotypes, were carried out. In this way, we were able to reveal on chromosome 3q24-27 a putative common haplotype shared between a subset of families. With a similar approach on chromosome 18q23 we were not able to identify a good segregation shared among other pedigrees. 4) Evaluate a possible involvement of mitochondrial polymorphisms in the pathogenesis of psychiatric disease. We characterized the mt haplogroups (Hg) and haplotypes (HVI region) of 86 index cases; the distribution of the Hg were similar to those reported for a large sample of the general Italian population so we were not able to find any significant differecies in the distribution of the haplogrups. Interestingly, we identified 12 lineages that seem to be shared between different families. These data suggest that: - families that share the same mtDNA could have a same maternal ancestor; - the shared mitochondria could carry a particular set of polymorphisms that influence the genetic predisposition to SZ and BPD

A novel 9-bp insertion in the GJB1 gene causing a mild form of X-linked CMT with late onset

X-linked Charcot-Marie-Tooth disease is the second most common variant of CMT. CMTX1 is caused by mutations in the GJB1 gene encoding for connexin 32. We describe an Italian family with an intermediate CMTX phenotype with late onset. Mutation screening of the GJB1 gene revealed a 9-bp duplication leading to the insertion of three aminoacids (Thr-Val-Phe) between the end of the second extracellular domain and the beginning of the fourth transmembrane domain. This is the third in-frame insertion in the GJB1 gene identified so far and, like the previous ones, it consists in the duplication of the flanking sequence which is repeated in tandem in the wild-type gene

Novel mutations in the L1CAM gene support the complexity of L1 syndrome

X-linked hydrocephalus, MASA syndrome, X-linked complicated Spastic Paraplegia Type I and X-linked partial agenesis of the corpus callosum are the four rare diseases usually referred to L1 syndrome, caused by mutations in the L1CAM gene. By direct sequencing of L1CAM in 16 patients, we were able to identify seven mutations, five of which were never described before. Patients' phenotype evaluation revealed a correlation between the number of clinical features typical of L1 syndrome and the chance to find causative mutation. Our findings support that L1CAM mutations are associated with widely heterogeneous phenotypes, however the occurrence of several clinical features remains the best criterion for planning molecular testing both in familial and apparently sporadic cases

A novel KRT1 c.1433A>G p.(Glu478Gly) mutation in a newborn with epidermolytic ichthyosis.

Abstract Epidermolytic Ichthyosis is a rare genodermatosis related to point mutations affecting the genes encoding for keratin 1 or keratin 10. We report a case of Epidermolytic Ichthyosis in a newborn with a novel mutation (c.1433A>G) of KRT1 gene