Genetic determinants of type 1 diabetes in individuals with weak evidence of islet autoimmunity at disease onset.

AIMS/HYPOTHESIS: Islet autoantibodies (AAbs) are detected in >90% of individuals with clinically suspected type 1 diabetes at disease onset. A single AAb, sometimes at low titre, is often detected in some individuals, making their diagnosis uncertain. Type 1 diabetes genetic risk scores (GRS) are a useful tool for discriminating polygenic autoimmune type 1 diabetes from other types of diabetes, particularly the monogenic forms, but testing is not routinely performed in the clinic. Here, we used a type 1 diabetes GRS to screen for monogenic diabetes in individuals with weak evidence of autoimmunity, i.e. with a single AAb at disease onset. METHODS: In a pilot study, we genetically screened 142 individuals with suspected type 1 diabetes, 42 of whom were AAb-negative, 27 of whom had a single AAb (single AAb-positive) and 73 of whom had multiple AAbs (multiple AAb-positive) at disease onset. Next-generation sequencing (NGS) was performed in 41 AAb-negative participants, 26 single AAb-positive participants and 60 multiple AAb-positive participants using an analysis pipeline of more than 200 diabetes-associated genes. RESULTS: The type 1 diabetes GRS was significantly lower in AAb-negative individuals than in those with a single and multiple AAbs. Pathogenetic class 4/5 variants in MODY or monogenic diabetes genes were identified in 15/41 (36.6%) AAb-negative individuals, while class 3 variants of unknown significance were identified in 17/41 (41.5%). Residual C-peptide levels at diagnosis were higher in individuals with mutations compared to those without pathogenetic variants. Class 3 variants of unknown significance were found in 11/26 (42.3%) single AAb-positive individuals, and pathogenetic class 4/5 variants were present in 2/26 (7.7%) single AAb-positive individuals. No pathogenetic class 4/5 variants were identified in multiple AAb-positive individuals, but class 3 variants of unknown significance were identified in 19/60 (31.7%) patients. Several patients across the three groups had more than one class 3 variant. CONCLUSIONS/INTERPRETATION: These findings provide insights into the genetic makeup of patients who show weak evidence of autoimmunity at disease onset. Absence of islet AAbs or the presence of a single AAb together with a low type 1 diabetes GRS may be indicative of a monogenic form of diabetes, and use of NGS may improve the accuracy of diagnosis.

A novel SPAST gene splicing variant (c.1617-2A>C) in a heterozygous carrier with hereditary spastic paraplegia.

Hereditary spastic paraplegia (HSP) is a group of genetically heterogenous neurodegenerative disorders characterized by progressive spasticity and weakness of lower limbs. We report a novel splicing variant (c.1617-2A>C) of the SPAST gene in a heterozygous carrier from an Italian family with autosomal dominant HSP. The case study describes a pure form of spastic paraparesis with the cardinal clinical features of SPG4. The novel variant affects a canonical splice site and is likely to disrupt RNA splicing. We conclude that the c.1617-2A>C substitution is a null variant, which could be classified as pathogenic; its penetrance should be further investigated.

Locally Performed HRD Testing for Ovarian Cancer? Yes, We Can!

Assessment of HRD status is now essential for ovarian cancer patient management. A relevant percentage of high-grade serous carcinoma (HGSC) is characterized by HRD, which is caused by genetic alterations in the homologous recombination repair (HRR) pathway. Recent trials have shown that not only patients with pathogenic/likely pathogenic BRCA variants, but also BRCAwt/HRD patients, are sensitive to PARPis and platinum therapy. The most common HRD test is Myriad MyChoice CDx, but there is a pressing need to offer an alternative to outsourcing analysis, which typically requires high costs and lengthy turnaround times. In order to set up a complete in-house workflow for HRD testing, we analyzed a small cohort of HGSC patients using the CE-IVD AmoyDx HRD Focus Panel and compared our results with Myriad's. In addition, to further deepen the mechanisms behind HRD, we analyzed the study cohort by using both a custom NGS panel that analyzed 21 HRR-related genes and FISH analysis to determine the copy numbers of PTEN and EMSY. We found complete concordance in HRD status detected by the Amoy and the Myriad assays, supporting the feasibility of internal HRD testing.

G41S SOD1 mutation: A common ancestor for six ALS Italian families with an aggressive phenotype.

More than 140 different mutations have been reported in the Cu/Zn superoxide dismutase-1 (SOD1) gene in patients with amyotrophic lateral sclerosis (ALS), some occurring as founder mutations. Occasionally, specific mutations are associated with a particular phenotype. We evaluated a possible genotype-phenotype correlation and looked for a founder effect in nine patients from six unrelated families with ALS, all carrying the G41S mutation, originating from north-west Tuscany in central Italy. Mutational analysis of the SOD1 gene was carried out by direct sequencing. A haplotype study was carried out using eight polymorphic markers flanking the SOD1 gene. The clinical pattern of the nine familial ALS (FALS) patients was characterized by spinal onset with early upper and lower motor neuron involvement, appearance of bulbar signs within one year, and death a few months later. Mean age at onset was 49.3 years and mean duration of disease was 0.9 years. Genotyping revealed a common haplotype for the G41S allele. We provide the first evidence that the G41S mutation in Italy originates from a common founder. In addition, our findings strengthen the data reported previously and indicate that the G41S mutation is consistently associated with a uniform and dramatic, fast-progressing phenotype.

Deciphering Variability of PKD1 and PKD2 in an Italian Cohort of 643 Patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD).

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common hereditary kidney disease. We analysed PKD1 and PKD2, in a large cohort of 440 unrelated Italian patients with ADPKD and 203 relatives by direct sequencing and MLPA. Molecular and detailed phenotypic data have been collected and submitted to the PKD1/PKD2 LOVD database. This is the first large retrospective study in Italian patients, describing 701 variants, 249 (35.5%) already associated with ADPKD and 452 (64.5%) novel. According to the criteria adopted, the overall detection rate was 80% (352/440). Novel variants with uncertain significance were found in 14% of patients. Among patients with pathogenic variants, in 301 (85.5%) the disease is associated with PKD1, 196 (55.7%) truncating, 81 (23%) non truncating, 24 (6.8%) IF indels, and in 51 (14.5%) with PKD2. Our results outline the high allelic heterogeneity of variants, complicated by the presence of variants of uncertain significance as well as of multiple variants in the same subject. Classification of novel variants may be particularly cumbersome having an important impact on the genetic counselling. Our study confirms the importance to improve the assessment of variant pathogenicity for ADPKD; to this point databasing of both clinical and molecular data is crucial.