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Eur J Hum Genet. 2019 Jan 30. doi: 10.1038/s41431-019-0341-5. [Epub ahead of print]

Breakpoint mapping at nucleotide resolution in X-autosome balanced translocations associated with clinical phenotypes.

Author information

1
Genetics Division, Department of Morphology and Genetics, Universidade Federal de São Paulo, 04023-900, São Paulo, Brazil.
2
Human Reproduction and Genetics Center, Department of Collective Health, Faculdade de Medicina do ABC, Santo André/SP, Santo André, Brazil.
3
Department of Medical Genetics, School of Medical Sciences, University of Campinas (UNICAMP), Campinas, Brazil.
4
Institute of Human Genetics, Jena University Hospital, Friedrich Schiller University, D-07747, Jena, Germany.
5
Center for Integrative Genomics, University of Lausanne, 1015, Lausanne, Switzerland.
6
Genetics Division, Department of Morphology and Genetics, Universidade Federal de São Paulo, 04023-900, São Paulo, Brazil. melaragno.maria@unifesp.br.

Abstract

Precise breakpoint mapping of balanced chromosomal rearrangements is crucial to identify disease etiology. Ten female patients with X-autosome balanced translocations associated with phenotypic alterations were evaluated, by mapping and sequencing their breakpoints. The rearrangements' impact on the expression of disrupted genes, and inferred mechanisms of formation in each case were assessed. For four patients that presented one of the chromosomal breaks in heterochromatic and highly repetitive segments, we combined cytogenomic methods and short-read sequencing to characterize, at nucleotide resolution, breakpoints that occurred in reference genome gaps. Most of rearrangements were possibly formed by non-homologous end joining and have breakpoints at repeat elements. Seven genes were found to be disrupted in six patients. Six of the affected genes showed altered expression, and the functional impairment of three of them were considered pathogenic. One gene disruption was considered potentially pathogenic, and three had uncertain clinical significance. Four patients presented no gene disruptions, suggesting other pathogenic mechanisms. Four genes were considered potentially affected by position effect and the expression abrogation of one of them was confirmed. This study emphasizes the importance of breakpoint-junction characterization at nucleotide resolution in balanced rearrangements to reveal genetic mechanisms associated with the patients' phenotypes, mechanisms of formation that originated the rearrangements, and genomic nature of disrupted DNA sequences.

PMID:
30700833
DOI:
10.1038/s41431-019-0341-5

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