Application of array comparative genomic hybridization for clinical diagnosis of small supernumerary marker chromosome

In general, normal human cells have 46 chromosomes. But there are about 300 million people in the world have one or more smaller structural abnormalities of chromosomes. These chromosomes are unrecognized by traditional cytogenetic staining method. We call this the extra chromosome marker chromosome. When the marker chromosome is smaller than the size of the chromosome 20. It is called small supernumerary marker chromosome (sSMC)
Early marker chromosome was found in 1961. But it may come from any part of any one chromosome. Therefore the characteristics of this chromosome research has always been lack of. Marker chromosome effects on the phenotype. have very large variation. Resulting difficulties in clinical diagnosis and genetic counseling.
Due to the lack of good diagnostic tools for marker chromosome in clinical genetic counseling. Therefore, the criterion of whether to continue pregnancy is depend on whether the marker chromosome is inherited from parents. But this criterion can not really meet the needs of parents, Therefore, this study collected clinical cytogenetic chromosome analysis of amniotic fluid of patients with marker chromosomes or blood samples. Use the analysis technique “array comparative genomic hybridization “which can detect genome-wide changes in gene dose by higher-resolution to explore the origin of the chromosome marker chromosomes, gene composition and with the relationship between clinical manifestations of cases to assess the clinical application of array comparative genomic hybridization to analyze the marker chromosomes feasibility.
Collection of 13 clinical cytogenetic chromosome analysis at the marker chromosome with the cell samples of patients. Using array comparative genomic hybridization analysis and the results was found, 7 cases of genes could significantly increase, of which four cases of birth have clear clinical symptoms, we analyze the genetic composition of marker chromosomes, disease gene were found. The other three are prenatal cases. After the array comparative genomic hybridization analysis and case consultation, the composition of two case’s marker chromosomes have euchromatin so they choose to terminate the pregnancy. Another case has increased chromosome segment is copy number variation, which is normal, so continue her pregnancy, child birth has no abnormal presentation.
6 cases no change in gene dosage, we speculated that the marker chromosome maybe from the centromere or heterochromatin. Of which five cases have been born, so far have no obvious abnormalities. One case of prenatal exam choose to terminate pregnancy due to personal reasons, however observation and appearance fetus is normal.
This study showed that the use of array comparative genomic hybridization to analyze the marker chromosome. In some cases that have been born. The results may explain the clinical symptoms of the case.
In the prenatal diagnosis, with appropriate interpretation and genetic counseling, Can provide useful information to reduce the risk of pregnant women give birth to abnormal fetuses and improve the wish of pregnant women to continue pregnancy. Is also a good clinical diagnostic tool for marker chromosome.