Genetic analysis of three fetuses with small supernumerary marker chromosome derived from chromosome 15
10.3760/cma.j.cn113903-20240328-00225
- VernacularTitle:携带15号染色体来源小标记染色体胎儿3例遗传学分析
- Author:
Xiaoxian SUN
1
;
Xiaohan ZHAO
1
;
Jing TAO
1
;
Ting LU
1
;
Bowen ZHAO
1
;
Hua JIN
1
Author Information
1. 山东第一医科大学附属济南妇幼保健院产前诊断中心，济南 250000
- Publication Type:Journal Article
- Keywords:
Marker chromosomes;
Pseudodicentric chromosomes;
Chromosome duplication;
Genetics;
Prenatal diagnosis
- From:
Chinese Journal of Perinatal Medicine
2025;28(5):408-413
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the genetic characteristics of fetuses carrying a small supernumerary marker chromosome (sSMC) derived from chromosome 15.Methods:This was a retrospective study involving three fetuses who were diagnosed with microdeletions or microduplications by non-invasive prenatal testing (NIPT) and confirmed to carry sSMC derived from chromosome 15 through prenatal diagnosis at the Center of Prenatal Diagnosis, Jinan Maternity and Child Care Hospital Affiliated to Shandong First Medical University from June to October 2023. Clinical data, including NIPT results and ultrasound findings, were collected. Genetic tests for the fetuses and their parents were performed using genetic karyotype analysis, fluorescence in situ hybridization (FISH), and single nucleotide polymorphisms array (SNP-array). All data were analyzed using descriptive statistics. Results:(1) The mothers of the three fetuses were aged 36, 37, and 41 years, and all of them were multiparous with no family history of genetic disorders. The fetuses exhibited duplications of 8.80, 8.17, and 8.80 Mb in the 15q11.2q13.3 region, respectively. Amniotic fluid karyotyping revealed a 47,XN,+mar karyotype in all three cases. The abnormal sSMC contained two centromeres. One of them was pycnotic, deeply stained, but remained active, while the other was enlarged and formed a band, losing its activity. Both were pseudo-dicentric structures. (2) FISH was not performed on Fetus 1. FISH results for both Fetus 2 and Fetus 3 were ish idic(15)( D15Z1++, SNRPN++, PML-), indicating the presence of two copies of the D15Z1 and SNRPN probes on the sSMC, with no PML probe signal. The D15Z1 probe was located at both ends of the sSMC, while the SNRPN probe was near the center. (3) SNP-array results were arr[GRCh37] 15q11.2q13.2(22 770 422-31 098 691)×4 for Fetus 1, covering 29 OMIM genes including UBE3A and 38 protein-coding genes; arr[GRCh37] 15q11.2q13.3(22 770 422-32 915 723)×4 for Fetus 2, covering 36 OMIM genes including UBE3A and 50 protein-coding genes; and arr[GRCh37] 15q11.2q13.1 (22 770 422-28 560 664)×4 and arr[GRCh37] 15q13.1q13.3(29 009 041-32 444 043)×3 for Fetus 3, covering 24 OMIM genes including UBE3A and 20 protein-coding genes. Additionally, Fetus 3 had a 3.435 Mb duplication in 15q13.1q13.3, covering 11 OMIM genes including CHRNA7 and 20 protein-coding genes. (4) No significant abnormalities were found in the peripheral blood karyotyping for the parents of Fetus 1 or in the SNP-array analysis for the parents of Fetus 3. (5) All three families opted for pregnancy termination. There were no obvious abnormalities in the appearance of Fetus 1 and Fetus 3 after induction, while details of Fetus 2 were unavailable. Conclusion:The three fetuses carried a psu idic(15)(q13)-derived sSMC, leading to increased copy numbers in the 15q11q13 region.
