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Marchetti GB, Milani D, Pisciotta L, Pezzoli L, Marchisio P, Rinaldi B, Iascone M. The Phenotype-Based Approach Can Solve Cold Cases: The Paradigm of Mosaic Mutations of the CREBBP Gene. Genes (Basel) 2024; 15:654. [PMID: 38927590 PMCID: PMC11202993 DOI: 10.3390/genes15060654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 05/17/2024] [Accepted: 05/20/2024] [Indexed: 06/28/2024] Open
Abstract
Rubinstein-Taybi syndrome (RTS) is a rare genetic disorder characterized by intellectual disability, facial dysmorphisms, and enlarged thumbs and halluces. Approximately 55% of RTS cases result from pathogenic variants in the CREBBP gene, with an additional 8% linked to the EP300 gene. Given the close relationship between these two genes and their involvement in epigenomic modulation, RTS is grouped into chromatinopathies. The extensive clinical heterogeneity observed in RTS, coupled with the growing number of disorders involving the epigenetic machinery, poses a challenge to a phenotype-based diagnostic approach for these conditions. Here, we describe the first case of a patient clinically diagnosed with RTS with a CREBBP truncating variant in mosaic form. We also review previously described cases of mosaicism in CREBBP and apply clinical diagnostic guidelines to these patients, confirming the good specificity of the consensus. Nonetheless, these reports raise questions about the potential underdiagnosis of milder cases of RTS. The application of a targeted phenotype-based approach, coupled with high-depth NGS, may enhance the diagnostic yield of whole-exome sequencing (WES) in mild and mosaic conditions.
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Affiliation(s)
| | - Donatella Milani
- Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico di Milano, 20122 Milano, Italy
| | - Livia Pisciotta
- Università degli Studi di Milano Statale, 20122 Milano, Italy; (G.B.M.); (L.P.); (P.M.)
- Child Neuropsychiatry Unit, ASST Fatebenefratelli Sacco, 20100 Milano, Italy
| | - Laura Pezzoli
- Laboratorio di Genetica Medica, ASST Papa Giovanni XXIII, 24127 Bergamo, Italy; (L.P.); (M.I.)
| | - Paola Marchisio
- Università degli Studi di Milano Statale, 20122 Milano, Italy; (G.B.M.); (L.P.); (P.M.)
- Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico di Milano, 20122 Milano, Italy
| | - Berardo Rinaldi
- Medical Genetics Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, 20122 Milano, Italy;
| | - Maria Iascone
- Laboratorio di Genetica Medica, ASST Papa Giovanni XXIII, 24127 Bergamo, Italy; (L.P.); (M.I.)
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Hewat TI, Johnson MB, Flanagan SE. Congenital Hyperinsulinism: Current Laboratory-Based Approaches to the Genetic Diagnosis of a Heterogeneous Disease. Front Endocrinol (Lausanne) 2022; 13:873254. [PMID: 35872984 PMCID: PMC9302115 DOI: 10.3389/fendo.2022.873254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 06/14/2022] [Indexed: 11/17/2022] Open
Abstract
Congenital hyperinsulinism is characterised by the inappropriate release of insulin during hypoglycaemia. This potentially life-threatening disorder can occur in isolation, or present as a feature of syndromic disease. Establishing the underlying aetiology of the hyperinsulinism is critical for guiding medical management of this condition especially in children with diazoxide-unresponsive hyperinsulinism where the underlying genetics determines whether focal or diffuse pancreatic disease is present. Disease-causing single nucleotide variants affecting over 30 genes are known to cause persistent hyperinsulinism with mutations in the KATP channel genes (ABCC8 and KCNJ11) most commonly identified in children with severe persistent disease. Defects in methylation, changes in chromosome number, and large deletions and duplications disrupting multiple genes are also well described in congenital hyperinsulinism, further highlighting the genetic heterogeneity of this condition. Next-generation sequencing has revolutionised the approach to genetic testing for congenital hyperinsulinism with targeted gene panels, exome, and genome sequencing being highly sensitive methods for the analysis of multiple disease genes in a single reaction. It should though be recognised that limitations remain with next-generation sequencing with no single application able to detect all reported forms of genetic variation. This is an important consideration for hyperinsulinism genetic testing as comprehensive screening may require multiple investigations.
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Jin P, Gao X, Wang M, Qian Y, Yang J, Yang Y, Xu Y, Xu Y, Dong M. Case Report: Identification of Maternal Low-Level Mosaicism in the Dystrophin Gene by Droplet Digital Polymerase Chain Reaction. Front Genet 2021; 12:686993. [PMID: 34276787 PMCID: PMC8280780 DOI: 10.3389/fgene.2021.686993] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 04/27/2021] [Indexed: 01/12/2023] Open
Abstract
Germline mosaicism should be suspected when the same de novo mutations are identified in a second pregnancy with asymptomatic parents. Our study aims to find a feasible approach to reveal the existence of germline mosaicism. Multiplex Ligation-dependent Probe Amplification was performed on a Duchenne muscular dystrophy affected pedigree to detect deletion mutations. Then gap-polymerase chain reaction was performed to amplify the breakpoints junction sequence. Droplet digital polymerase chain reaction was utilized to identify the mutation frequencies in healthy parents. The same deletion in the exon 51 of the dystrophin gene, which was 50,035 bp in size, was detected in the proband and the fetus but not in their parents. Droplet digital polymerase chain reaction analysis of peripheral blood samples revealed mutant alleles of 3.53% in maternal blood cells. We here report a case of maternal low-level mosaicism confirmed by droplet digital polymerase chain reaction in peripheral blood samples, which reveals the existence of germline mosaicism. Gap-polymerase chain reaction combined with droplet digital polymerase chain reaction provide insights into the detection of germline mosaicism.
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Affiliation(s)
- Pengzhen Jin
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Xiaoyang Gao
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Miaomiao Wang
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Yeqing Qian
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Jingjin Yang
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Yanmei Yang
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Yuqing Xu
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Yanfei Xu
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
| | - Minyue Dong
- Women's Hospital, School of Medicine Zhejiang University, Hangzhou, China.,Key Laboratory of Reproductive Genetics, Ministry of Education, Zhejiang University, Hangzhou, China
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