A De Novo CaSR Missense Variant in Combination with Two Inherited Missense Variants in CFTR and SPINK1 Detected in a Patient with Chronic Pancreatitis.

Chronic pancreatitis is often secondary to alcohol abuse, but pancreatitis with no other aetiology is frequently associated with variants in genes encoding proteins related to zymogen granule activation. Our goal was to identify genomic variants in a patient by analyzing an extended panel of genes associated with the intra-pancreatic activation of the trypsin pathway. A 23-year-old woman was addressed at our institution because of chronic pancreatitis of unknown aetiology presenting recurrent episodes since she was the age of four. Next Generation Sequencing was performed to analyze a panel of nine genes associated with pancreatitis (CaSR, CFTR, CPA1, CTRC, CTSB, KRT8, PRSS1, PRSS2, and SPINK1). Three missense variants were found: p.Leu997Phe, maternally inherited, in the CFTR gene; p.Ile73Phe, paternally inherited, in the SPINK1 gene; and p.Phe790Ser, a de novo variant, in the CaSR gene. They were classified, respectively as probably benign, a Variant of Uncertain Significance, and the last one, which has never been described in the literature, as likely being pathogenic following American College of Medical Genetics and Genomics standard guidelines. Extensive intra-pancreatic activation of trypsin pathway gene sequencing detected rare variants that were not found with other gene screening and showed that variants in different genes may interact in contributing to the onset of the pancreatitis phenotype.

Genome-Wide DNA Methylation Profiling Solves Uncertainty in Classifying NSD1 Variants.

BACKGROUND: Inactivating NSD1 mutations causing Sotos syndrome have been previously associated with a specific genome-wide DNA methylation (DNAm) pattern. Sotos syndrome is characterized by phenotypic overlap with other overgrowth syndromes, and a definite diagnosis might not be easily reached due to the high prevalence of variants of unknown significance (VoUS) that are identified in patients with a suggestive phenotype. OBJECTIVE: we performed microarray DNAm profiling in a set of 11 individuals with a clinical suspicion of Sotos syndrome and carrying an NSD1 VoUS or previously unreported variants to solve uncertainty in defining pathogenicity of the observed variants. The impact of the training cohort size on sensitivity and prediction confidence of the classifier was assessed. RESULTS: The Sotos syndrome-specific DNAm signature was validated in six individuals with a clinical diagnosis of Sotos syndrome and carrying bona fide pathogenic NSD1 variants. Applying this approach to the remaining 11 individuals with NSD1 variants, we succeeded in confirming pathogenicity in eight subjects and excluding the diagnosis of Sotos syndrome in three. The sensitivity and prediction confidence of the classifier based on the different sizes of the training sets did not show substantial differences, though the overall performance was improved by using a data balancing strategy. CONCLUSIONS: The present approach solved uncertainty in cases with NDS1 VoUS, further demonstrating the clinical utility of DNAm profiling.

A novel CDKN2A in-frame deletion associated with pancreatic cancer-melanoma syndrome.

Pancreatic cancer-melanoma syndrome (PCMS) is an inherited condition in which mutation carriers have an increased risk of malignant melanoma and/or pancreatic cancer. About 30% of PCMS cases carry mutations in CDKN2A. This gene encodes several protein isoforms, one of which, known as p16, regulates the cell-cycle by interacting with CDK4/CDK6 kinases and with several non-CDK proteins. Herein, we report on a novel CDKN2A germline in-frame deletion (c.52_57delACGGCC) found in an Italian family with PCMS. By segregation analysis, the c.52_57delACGGCC was proven to segregate in kindred with cutaneous melanoma (CM), in kindred with CM and pancreatic cancer, and in a single case presenting only with pancreatic cancer. In the literature, duplication mapping in the same genic region has been already reported at the germline level in several unrelated CM cases as a variant of unknown clinical significance. A computational approach for studying the effect of mutational changes over p16 protein structure showed that both the deletion and the duplication of the c.52_57 nucleotides result in protein misfolding and loss of interactors' binding. In conclusion, the present results argue that the quantitative alteration of nucleotides c.52_57 has a pathogenic role in p16 function and that the c.52_57delACGGCC is associated with PCMS.