Multicolor-FISH Characterization of a Prenatal Mosaicism for a Chromosomal Rearrangement Undetected by Molecular Cytogenetics

Laura Mary (1, 2) , Philippe Loget (1) , Sylvie Odent (1) , Dominique Aussel (3) , Gwenaëlle Le Bouar (1) , Erika Launay (1) , Catherine Henry (1) , Marc-Antoine Belaud-Rotureau (1, 2) , Sylvie Jaillard (1, 2)

1 Centre Hospitalier Universitaire de Rennes [CHU Rennes] = Rennes University Hospital [Ponchaillou]
2 Irset - Institut de recherche en santé, environnement et travail
3 Clinique mutualiste La Sagesse

Fetal mosaicism for chromosomal rearrangements remains a challenge to diagnose, even in the era of whole-genome sequencing. We present here a case of fetal mosaicism for a chromosomal rearrangement explored in amniocytes and fetal muscle, consisting of a major cell population (95%) with partial monosomy 4q and a minor population (5%) with additional material replacing the 4qter deleted segment. Molecular techniques (MLPA, array-CGH) failed to assess the origin of this material. Only multicolor-FISH identified the additional segment on chromosome 4 as derived from chromosome 17. Due to the poor prognosis, the couple chose to terminate the pregnancy. Because of low-level mosaicism, chromosomal microarray analysis (CMA), now considered as first-tier prenatal genetic analysis, did not allow the identification of the minor cell line. In case of large CNVs (>5 Mb) detected by CMA, karyotyping may be considered to elucidate the mechanism of the underlying rearrangement and eliminate mosaicism.

Mots clés: Multicolor-FISH; Prenatal diagnosis; Mosaicism; aCGH; Chromosome rearrangement

Domaines: Sciences du Vivant [q-bio]

Laura Mary, Philippe Loget, Sylvie Odent, Dominique Aussel, Gwenaëlle Le Bouar, et al.. Multicolor-FISH Characterization of a Prenatal Mosaicism for a Chromosomal Rearrangement Undetected by Molecular Cytogenetics. Cytogenetic and Genome Research, 2021, 161 (3-4), pp.143-152. ⟨10.1159/000514592⟩. ⟨hal-03215883⟩