Abstract
BackgroundIn prenatal diagnosis, CMA has begun to emerge as a favorable alternative to karyotype analysis, but it could not identify balanced translocations, triploidies, inversion and heteromorphisms. Therefore, conventional cytogenetic and specific staining methods still play an important role in the work-up of chromosome anomaly. This study investigated the application of C-banding and AgNOR-staining techniques in prenatal diagnosis of chromosomal heteromorphisms and some structure abnormalities.ResultsAmong the 2970 samples, the incidence of chromosomal heteromorphisms was 8.79% (261/2970). The most frequent was found to be chromosome Y (2.93%, 87/2970), followed by chromosome 1 (1.65 %, 49/2970), 9 (1.52 %, 45/2970), 22 (0.77 %, 23/2970) and 15 (0.64 %, 19/2970). We compared the incidence of chromosomal heteromorphisms between recurrent spontaneous abortion (RSA) group and control group. The frequency of autosomal hetermorphisms in RSA group was 7.63% higher than that in control group (5.78%), while the frequency of Y chromosomal heteromorphisms was 4.76% lower than that in control group (5.71%). Here we summarized 4 representative cases, inv (1) (p12q24), psu dic (4;17) (p16.3;p13.3), r(X)(p11; q21) and an isodicentric bisatellited chromosome to illustrate the application of C-banding or AgNOR-staining, CMA or NGS was performed to detect CNVs if necessary.ConclusionsThis study indicated that C-banding and AgNOR-staining were still effective complementary methods to identify chromosomal heteromorphisms and marker chromosomes or some structural rearrangements involving the centromere or acrocentric chromosomes. Our results suggested that there was no evidence for an association between chromosomal heteromorphisms and infertility or recurrent spontaneous abortions. Undoubtedly, sometimes we needed to combine the results of CMA or CNV-seq to comprehensively reflect the structure and aberration of chromosome segments. Thus, accurate karyotype reports and genetic counseling could be provided.
Highlights
Currently, chromosomal microarray analysis (CMA) and copy number variation sequencing (CNV-Seq) are widely used in prenatal diagnosis due to the capability of identifying microdeletion and microduplication syndromes as well as de novo pathogenic CNVs which may be missed by conventional karyotyping [1]
Chromosome banding techniques are generally divided into two types: (1) bands are distributed along the entire chromosome, e.g. the most frequently used Giemsa-trypsin banding (G-banding), Q banding and R banding; (2) bands are located in specific chromosomal regions, including C-banding, AgNOR staining and T-banding
This study summarized the application of C-banding and Ag-Nucleolar Organizer Region (NOR) staining techniques for the prenatal diagnosis of fetal chromosome karyotype in our hospital, and explored the relationship between heteromorphisms and recurrent spontaneous abortion (RSA)
Summary
Chromosomal microarray analysis (CMA) and copy number variation sequencing (CNV-Seq) are widely used in prenatal diagnosis due to the capability of identifying microdeletion and microduplication syndromes as well as de novo pathogenic CNVs which may be missed by conventional karyotyping [1]. Their drawbacks are obvious including the incompetence of balanced translocations, triploidies, inversion and heteromorphisms identification. This study investigated the application of C-banding and AgNOR-staining techniques in prenatal diagnosis of chromosomal heteromorphisms and some structure abnormalities
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