PRENATAL MOLECULAR KARYOTYPE( A-CGH)

Prenatal Chromosomal Microarray Analysis with Molecular Karyotype is a new application in the field of Molecular Cytogenetics that comes to enhance and even replace in many cases conventional cytogenetic testing.

Prenatal chromosomal analysis has been carried out over the last decades in order to avoid the birth of embryos bearing chromosomal abnormalities associated with known syndromes (e.g., Down Syndrome), and traditionally involved conventional karyotyping for the detection of numerical and structural abnormalities of embryonic chromosomes.

Molecular Karyotype is based on DNA microarrays and provides a resolution of 100 to 1000 times greater than conventional karyotype. This means that in addition to gross chromosomal aneuploidy, a number of other genetic disorders, caused by microdeletions and microduplications and are not detected by conventional cytogenetic analysis, can be simultaneously tested. These have been implicated in cases with mental retardation, congenital abnormalities, developmental delay and autism spectrum disorders and were impossible to detect until a few years ago.

Our laboratory utilizes the integrated microarray system of Agilent Technologies, one of the most sophisticated microarray platforms available. The oligonucleotide microarrays used provide coverage of the entire genome with an average resolution of 200kb, while offering increased resolution in 500 genomic regions that are associated with genetic diseases, in accordance with the International Standards for Cytogenomic Arrays Consortium, through the placement of an increased concentration of probes in regions which contain important genes (gene oriented arrangement).

Prenatal chromosomal analysis with molecular karyotype can be preventively performed in all pregnancies, as many of the genetic diseases it is able to detect are not accompanied by ultrasound findings. At the same time it must be performed in high-risk pregnancies, namely: • When there is family history of a specific genetic disease• When there are pathological ultrasound findings in pregnancy• In the case of women with multiple miscarriages• When the mother is at an advanced age

In all cases a meeting with a qualified geneticist precedes to provide the couple with sufficient information about the possibilities and limitations of the method.For Prenatal Molecular Karyotype analysis a sample of chorionic villi or amniotic fluid must first be obtained. The genetic material of the fetus is then isolated and analyzed by array comparative genomic hybridization (aCGH). In some cases it might be necessary to analyze the parental samples with the same technique.

 

Method: array Comparative Genomic Hybridization (aCGH) platform with ~60,000 oligonucleotide probes covering the entire genome while specifically targeting about 500 genome regions known to be associated with genetic syndromes

Sample Type: Chorionic villi or amniotic fluid sample and maternal blood sample in EDTA container

Time to result: 10 business days from the date of sample receipt

aCGH can not detect triploidy / polyploidy, point mutations, balanced translocations and low level mosaicism

The department of Molecular Biology participates successfully to the external quality sheme organised by GenQA for Prenatal Molecular Karyotype analysis.