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. 2017 Jul 25:10:28.
doi: 10.1186/s13039-017-0329-1. eCollection 2017.

Formation of upd(7)mat by trisomic rescue: SNP array typing provides new insights in chromosomal nondisjunction

Sandra Chantot-Bastaraud  1   2   3   4 , Svea Stratmann  5 , Frédéric Brioude  1   2   3 , Matthias Begemann  5 , Miriam Elbracht  5 , Luitgard Graul-Neumann  6 , Madeleine Harbison  7 , Irène Netchine  1   2   3 , Thomas Eggermann  5
Affiliations

Formation of upd(7)mat by trisomic rescue: SNP array typing provides new insights in chromosomal nondisjunction

Sandra Chantot-Bastaraud et al. Mol Cytogenet. .

Abstract

Background: Maternal uniparental disomy (UPD) of chromosome 7 (upd(7)mat) accounts for approximately 10% of patients with Silver-Russell syndrome (SRS). For upd(7)mat and trisomy 7, a significant number of mechanisms have been proposed to explain the postzygotic formation of these chromosomal compositions, but all have been based on as small number of cases. To obtain the ratio of isodisomy and heterodisomy in UPDs (hUPD, iUPD) and to determine the underlying formation mechanisms, we analysed a large cohort of upd(7)mat patients (n = 73) by SNP array typing. Based on these data, we discuss the UPDs and their underlying trisomy 7 formation mechanisms.

Results: A whole chromosome 7 maternal iUPD was confirmed in 28.8%, a mixture or complete maternal hUPD in 71.2% of patients.

Conclusions: We could demonstrate that nondisjunction mechanism affecting chromosome 7 are similar to that of the chromosomes more frequently involved in trisomy (and/or UPD), and that mechanisms other than trisomic rescue have a lower significance than previously suspected. Furthermore, we suggest SNP array typing for future parent- and cell-stage-of origin studies in human aneuploidies as they allow the definite classification of trisomies and UPDs, and provide information on recombinational events and their suggested association with aneuploidy formation.

Keywords: Chromosome 7; Formation mechanism; Maternal uniparental Disomy 7; Trisomic rescue.

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Conflict of interest statement

Ethics approval and consent to participate

The study was approved by the ethics review boards of the University Hospital of the RWTH Aachen (No. EK159–08) and the Hôpitaux de Paris (Assistance Publique—Hôpitaux de Paris authorization no. 682). Written informed consent for participation was received for all patients, either from the patients themselves or their parents.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Formation mechanisms of trisomy and UPD after meiotic and mitotic nondisjunction. iUPD formation by gamete complementation is not shown as it should be very rare, but the allelic patterns correspond to those of monosomic rescue. Possible typing results of four different molecular markers are shown to illustrate the role of their physical localization (close or far from the centromere on both arms) for the discrimination between hUPD and iUPD
Fig. 2
Fig. 2
Local Affymetrix GenomeWideSNP_6.0 Array signal distribution pattern (a) showing total upd(7)mat, segmental iUPD(7q)mat and mixed hUPD/iUPDiUPD. Note that only a differentiation between hUPD and iUPD is possible, whereas the parental origin as well as the identification of segmental UPD is only possible by including the results of microsatellite typing. b Distribution of SNP (light green) and oligo probes (dark green). c Physical map of chromosome 7
Fig. 3
Fig. 3
Analysis of the data from the array typing in hUPD carriers: Distribution of uniparental isodisomy stretches in the 20 hUPD cases analysed by the Affymetrix SNP6.0 arrays
See this image and copyright information in PMC

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