title: Molecular characterization of a mosaic NIPBL deletion in a Cornelia de Lange patient with severe phenotype.
abstract: Cornelia de Lange syndrome (CdLS, OMIM #122470, #300590, #610759, #614701, #300882) is a rare neurodevelopmental syndrome characterized by growth retardation, intellectual disability, dysmorphic facial features, multisystem malformations, and limb reduction defects. Wide variability of phenotypes is common among CdLS patients. Mutations in genes encoding either regulators (NIPBL, HDAC8) or subunits (SMC1A, SMC3, RAD21) of the cohesin complex, are altogether found in approximately 65% of CdLS patients. We describe a CdLS patient with classic severe phenotype who was found negative to mutations in the NIPBL and SMC1A genes by DHPLC and direct sequencing. MLPA analysis performed to disclose potential intragenic NIPBL deletions/duplications, suggested a partial deletion which was confirmed by FISH with a BAC clone encompassing the NIPBL region that highlighted asymmetric signals in a fraction of cells (72%). The occurrence of a genomic deletion in mosaic condition was validated by array-CGH analysis. Long-range PCR and sequencing of the junction fragment mapped the telomeric and the centromeric breakpoint within NIPBL IVS1 and IVS32, respectively. Both deletion breakpoints were embedded in a microsatellite region that might be the motif directly mediating this large deletion by an intrachromatid recombination mechanism. Consistent with the molecular analyses, the patient displayed a severe phenotype that was characterized by drastic CdLS clinical signs including premature death. This case provides a second example of mosaicism in CdLS. Despite mitigated by mosaicism, the large intragenic deletion identified in the present case was poorly tolerated due to the high mosaicism level. Based on these data, overlooked cases of mosaicism may lead to underestimated mutation rates of known genes and may also contribute to the clinical heterogeneity of CdLS.
authors: Medical Genetics, Department of Health Sciences, Università degli Studi di Milano, Via A. di Rudinì 8, 20142 Milan, Italy. cristina.gervasini@unimi.it
authors: Cristina
authors: C
authors: Gervasini
authors: Ilaria
authors: I
authors: Parenti
authors: Chiara
authors: C
authors: Picinelli
authors: Jacopo
authors: J
authors: Azzollini
authors: Maura
authors: M
authors: Masciadri
authors: Anna
authors: A
authors: Cereda
authors: Angelo
authors: A
authors: Selicorni
authors: Silvia
authors: S
authors: Russo
authors: Palma
authors: P
authors: Finelli
authors: Lidia
authors: L
authors: Larizza
mesh_terms: D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D003635:De Lange Syndrome / Q000175:diagnosis / Q000235:genetics*; D017353:Gene Deletion; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008214:Lymphocytes / Q000166:cytology; D008297:Male; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D009030:Mosaicism; D010641:Phenotype; D011506:Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D000098550:Structural Maintenance of Chromosome Protein 1
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; C487465:NIPBL protein, human; D011506:Proteins; D000098550:Structural Maintenance of Chromosome Protein 1