mosaic marker chromosome in prenatal diagnosis
EVANGELIDOU Paola
I would like to request what is the Group's experience with the presence of mosaic marker chromosome identified in prenatal diagnosis, (originally on CVS, then confirmed on Amnio), identified to have chromosome 16 origin by array CGH. The copy number gain from the array analysis (Oligo array 2x105K used) is from 16p11.1 to 16p11.2 and it is approximately 5.27Mb in size. The marker is de novo in origin and it was confirmed by FISH analysis with whole chromosome paint probes. With the means available it cannot be determined whether this is actually a marker or ring chromosome. The literature on such marker chromosomes is poor and in my 16 year experience in prenatal diagnosis this is the first time we come across a marker with chromosome 16 origin. The presence of the marker is 66% in CVS and 56% in amnio and there were no ultrasound findings on the First trimester screening. Cytogenetic prenatal diagnosis was requested by the physician following prenatal diagnosis for the B- Thalassemia national screening program.
Any experience shared on this will be greatly appreciated.
Thanks
Paola
Mark Pertile
Paola,
Do you have the genomic co-ordinates of duplicated region of 16p from
the aCGH experiment? This should allow you to make a very accurate
assessment of the likely clinical significance of this marker.
Proximal 16p is full of low copy repeats (LCRs) and duplication within
this region is likely to be benign. However, the size of the duplicated
region you describe (5.27 Mb) is likely to extend to the edge of (and
perhaps include) the 16p11.2 DD/ASD susceptibility locus at
chr16:29.56-30.11 Mb (NCBI 36/hg18). Duplication of this region is
variably penetrant, and would be expected to be even less penetrant in
mosaic form. Nonetheless it would be valuable to know whether it is
included in the marker. Assessment of the actual genomic region
duplicated should allow for the most informed genetic counselling.
Regards
Mark.
Hello all,
Thanks
Paola
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EVANGELIDOU Paola
Thank you for the reply. The genomic co-ordinates of the duplicated region are in fact 29.73-35Mb NCBI36/Hg18 and fall within the region you describe.
CALLIER Patrick
For my experience we have been performed array-CGH on an sSMC on chr16 de novo, ultrasound finding showed fetus hygroma. We used 4*44K agilent and the array-cgh profil showed 3Mb duplication of euchromatin material. arr 16p11.2p11.1 (31,675,728-34,847,226)x3 hg18
This region is known to be benign variant in DGV (http://projects.tcag.ca/cgi-bin/variation/gbrowse/hg18/#search) and in Liehr Webpages the references of sSMC markers (http://www.fish.uniklinikum-jena.de/sSMC.html)
The family decided to continue the pregnancy to term and the baby born normaly and normal after one years
For your sSMC you need to see DGV and Liehr Webpage with coordinate...
Best regards
Patrick
Dr Callier Patrick
Laboratoire de Cytogénétique
Plateau technique de Biologie
2 rue Angélique Ducoudray
21070 Dijon
Tel: 03.80.29.34.89
Fax: 03.80.29.50.79
________________________________________
De : cytogenetics-methods...@googlegroups.com [cytogenetics-methods...@googlegroups.com] de la part de EVANGELIDOU Paola [pa...@cing.ac.cy]
Date d'envoi : samedi 11 février 2012 10:02
À : cytogenetics-methods...@googlegroups.com
Objet : mosaic marker chromosome in prenatal diagnosis
Hello all,
Thanks
Paola
--
Mark Pertile
Yes your marker does encompases this region. This makes counselling more difficult than if the 16p breakpoint was more proximal. Cooper GM et al. Nat Genet. 2011 43(9):838-846 estimated penetrance at 0.93 (P=0.0004) based on case:control comparisons. However, the fact that the marker is mosaic must further lower the risk.
A recent useful review paper is:
Rosenfeld JA et al. Speech delays and behavioral problems are the predominant features in individuals with developmental delays and 16p11.2 microdeletions and microduplications. <https://mx1.mcri.edu.au/pubmed/21731881> J Neurodev Disord. 2010 Mar;2(1):26-38. The free full text article can be accessed through PubMed (PMID: 21731881). You can link directly to the pdf from here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3125720/pdf/11689_2009_Article_9037.pdf <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3125720/pdf/11689_2009_Article_9037.pdf>
Regards
Mark
________________________________
Dear Mark,
Paola,
Regards
Mark.
Hello all,
Thanks
Paola
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