Altieri V, Capozzi O, Marzano MC, Catapano O, Di Biase I, Rocchi M, De Tollis G. Molecular characterization of an analphoid supernumerary marker chromosome derived from 18q22.1➔qter in prenatal diagnosis: a case report.
Mol Cytogenet 2014;
7:69. [PMID:
25360155 PMCID:
PMC4213471 DOI:
10.1186/s13039-014-0069-4]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 10/06/2014] [Indexed: 11/30/2022] Open
Abstract
Background
Small supernumerary marker chromosomes (sSMC) occur in 0.072% of unselected cases of prenatal diagnoses, and their molecular cytogenetic characterization is required to establish a reliable karyotype-phenotype correlation. A small group of sSMC are C-band-negative and devoid of alpha-satellite DNA. We report the molecular cytogenetic characterization of a de novo analphoid sSMC derived from 18q22.1→qter in cultured amniocytes.
Results
We identified an analphoid sSMC in cultured amniocytes during a prenatal diagnosis performed because of advanced maternal age. GTG-banding revealed an sSMC in all metaphases. FISH experiments with a probe specific for the chromosome 18 centromere, and C-banding revealed neither alphoid sequences nor C-banding-positive satellite DNA thereby suggesting the presence of a neocentromere. To characterize the marker in greater detail, we carried out additional FISH experiments with a set of appropriate BAC clones. The pattern of the FISH signals indicated a symmetrical organization of the marker, the breakpoint likely representing the centromere of an inverted duplicated chromosome that results in tetrasomy of 18q22.1→qter. The karyotype after molecular cytogenetic investigations was interpreted as follows:
47,XY,+inv dup(18)(qter→q22.1::q22.1→neo→qter)
Conclusion
Our case is the first report, in the prenatal diagnosis setting, of a de novo analphoid marker chromosome originating from the long arm of chromosome 18, and the second report of a neocentromere formation at 18q22.1.
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