Cytogenetic and molecular genetic analysis of three cases with small supernumerary marker chromosomes / 中华医学遗传学杂志

ABSTRACT

OBJECTIVE@#To delineate the origin and structure of 3 cases of small supernumerary marker chromosomes (sSMCs) through cytogenetic and molecular genetic analysis.@*METHODS@#Conventional G, C and N banding were carried out to analyze the chromosomal karyotypes. Chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH) were used to delineate the origin and structure of the sSMCs.@*RESULTS@#In case 1, chromosomal karyotype of peripheral blood sample was 47,XY,+mar. This de novo sSMC was a dual-satellited dicentric inverted duplicated marker chromosome, for which CMA yielded a normal result. It was predicted to not increase the risk of offspring. In case 2, the fetal chromosomal karyotype was 47,XY,+mar[17]/46,XY[33]. Chromosomal banding suggested that this de novo segment contained euchromatin, and the result of CMA was arr[hg19] 5p12q11.1(45 694 574-49 475 697) × 3. FISH showed the sSMC to be a fragment derived from 5p12 containing the HCN1 gene. Case 3 was found to have a fetal karyotype of 45,XY,-13[25]/46,XY,r(13)[18]/46,XY,-13,+mar[7]. Both parents had refused further examination.@*CONCLUSION@#Conventional chromosomal banding combined with molecular methods can delineate the origin and structure of the sSMCs, which can help with prediction of their pathogenicity and facilitate genetic counseling.