👤 Fernando Fabiani

Genetic testing is valuable to confirm molecular diagnosis in nearly 60% of cases suspected of hypertrophic cardiomyopathy (HCM). However, the interpretation of variants, especially those of uncertain significance (VUSs), remains challenging for laboratories and clinicians. In April 2024, the ClinGen Cardiomyopathy Variant Curation Expert Panel (VCEP) adapted the ACMG/AMP criteria for eight of the sarcomeric genes ( Here, two groups of curators reinterpreted variants with the most recent data using the Cardiomyopathy VCEP specifications until a consensus was reached. To streamline the process, we created a semiautomated decision support tool based on these gene-specific rules. The application of the Cardiomyopathy VCEP specifications resulted in the reclassification of 17.4% ( Using gene-specific ACMG/AMP criteria reduces the rate of VUS, increasing diagnostic yield, and informing clinical management in the context of HCM. Nonetheless, ongoing efforts to generate evidence and promote standardization remain essential to improve variant interpretation. Show less

MYBPC3 pathogenic variants are the most common cause of hypertrophic cardiomyopathy (HCM) and are associated with significant phenotypic heterogeneity. Despite their pathogenic potential, MYBPC3 founder variants persist within specific populations. This study investigates the MYBPC3 c.2309-2 A > G splice variant hypothesizing its founder origin in central Italy. The aim was to confirm the presence of a common haplotype, assess its molecular and clinical impact, and compare the phenotype with that of other MYBPC3 founder variants. Among the 5251 HCM patients recruited at eight Italian referral centers, 1108 probands (21.1%) were identified as carriers of pathogenic or likely pathogenic MYBPC3 variants, and among these, 11.6% carried the c.2309-2 A > G variant. Haplotype reconstruction using short tandem repeats and tag-SNPs revealed a unique 5.2 Mb haplotype segregating with the c.2309-2 A > G variant in all carriers. Age estimation suggested that the variant originated approximately 481 years ago, likely in the Lazio region with clustering in Rome. Clinically, carriers exhibited variable expressivity with age-and sex-dependent penetrance. Males showed earlier onset, higher penetrance and greater disease severity compared to females. RNA analysis showed the retention of both introns 23 and 24, and significantly reduced MYBPC3 expression consistent with haploinsufficiency. Comparative analysis with other MYBPC3 founder variants highlighted differences in phenotypic expression, particularly in left ventricular wall thickness and clinical outcomes. This study establishes c.2309-2 A > G as an Italian MYBPC3 founder mutation, enhancing the understanding of HCM genetics and regional founder effects. These findings emphasize the importance of targeted genetic screening and personalized management for MYBPC3 c.2309-2 A > G carriers. Show less

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac muscle disease characterized by clinical and genetic heterogeneity. Genetic testing can reveal the presence of disease-causing variants in genes encoding sarcomere proteins. However, it yields inconclusive or negative results in 40-60% of HCM cases, owing to, among other causes, technical limitations such as the inability to detect pathogenic intronic variants. Therefore, we aimed to increase the diagnostic yield of molecular analysis for HCM by improving the Show less

Most primary severe hypertriglyceridemias (HTGs) are diagnosed in adults, but their molecular foundations have not been completely elucidated. We aimed to identify rare dysfunctional mutations in genes encoding regulators of lipoprotein lipase (LPL) function in patients with familial and non-familial primary HTG. We sequenced promoters, exons, and exon-intron boundaries of LPL, APOA5, LMF1, and GPIHBP1 in 118 patients with severe primary HTG (triglycerides >500 mg/dL) and 53 normolipidemic controls. Variant functionality was analyzed using predictive software and functional assays for mutations in regulatory regions. We identified 29 rare variants, 10 of which had not been previously described: c.(-16A>G), c.(1018+2G>A), and p.(His80Arg) in LPL; p.(Arg143Alafs*57) in APOA5; p.(Val140Ile), p.(Leu235Ile), p.(Lys520*), and p.(Leu552Arg) in LMF1; and c.(-83G>A) and c.(-192A>G) in GPIHBP1. The c.(1018+2G>A) variant led to deletion of exon 6 in LPL cDNA, whereas the c.(-16A>G) analysis showed differences in the affinity for nuclear proteins. Overall, 20 (17.0%) of the patients carried at least one allele with a rare pathogenic variant in LPL, APOA5, LMF1, or GPIHBP1. The presence of a rare pathogenic variant was not associated with lipid values, family history of HTG, clinical diagnosis, or previous pancreatitis. Less than one in five subjects with triglycerides >500 mg/dL and no major secondary cause for HTG may carry a rare pathogenic mutation in LPL, APOA5, LMF1, or GPIHBP1. The presence of a rare pathogenic variant is not associated with a differential phenotype. Show less

Cholesterol is required in the brain for synaptogenesis and its turnover is critical for cerebral functions. Several proteins involved in cholesterol handling and metabolism are transcriptionally regulated by the nuclear liver X receptor (LXR) alpha and beta. Sterol 27-hydroxylase (CYP27) is a ubiquitously expressed enzyme involved in cholesterol metabolism. Notably, its deficiency causes a disease characterized by progressive neurologic impairment. With the final goal to understand the pathophysiological role of CYP27A1 in the CNS, we studied the expression pattern of Cyp27a1 and other related genes in primary cultures of rat glia and neurons. Secondly, given the pivotal role of LXR in the regulation of cholesterol homeostasis, we investigated the effects of its activation on the expression of Cyp27a1.We found that primary astrocytes express different sterol hydroxylases and are able to uptake exogenous 27-hydroxycholesterol. We found that both microglia and astrocytes express preferentially Lxrbeta. However, despite this similarity, we observed cell-specific responsiveness of known and novel (including Cyp27a1) target genes to LXR activation. The increase of mRNA and protein levels in treated astrocytes is paralleled by transactivation of the proximal Cyp27a1 promoter in transfected astrocytes. We suggest that the astrocyte-restricted up-regulation of Cyp27a1 may be ascribable to differential expression of transcriptional co-activators. Given the role of astrocytes in maintaining brain homeostasis, we hypothesize that impairment of CYP27 activity in these cells may alter critical features of the astrocytes, from the handling and delivery of cholesterol to neurons to the release of signaling molecules. Show less