Clinical value of different genetic testing methods for detection of true fetal chromosome mosaicism / 中华围产医学杂志

Objective:To investigate the performance of chromosome karyotype, chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH) in prenatal diagnosis of true fetal chromosome mosaicism. Methods:This retrospective study enrolled 40 women with true fetal chromosome mosaicism from 4 071 singleton pregnant women who were indicated for and underwent amniocentesis or/and cordocentesis in the the First Affiliated Hospital of Sun Yat-sen University from April 2018 to August 2021. The results of chromosome karyotyping, CMA and FISH, the types of chromosomal mosaicism, mosaicism ratio and pregnancy outcomes were analyzed using Chi-square test. Results:(1) The detection rate of true fetal mosaicism was 0.98% (40/4 071). (2) Sex chromosome mosaicism accounted for 42.5% (17/40). Other chromosomal mosaicism involved chromosomes 21, 22, 18, 16, 7, 12, 15, 17 and 20, as well as balanced chromosomal translocation. (3) The detection rate of true fetal mosaicism by chromosome karyotyping was 77.4% (24/31) from amniotic fluid samples and 10/19 from umbilical cord blood samples, while that data by CMA was 76.7% (23/30) and 7/11,respectively. (4) Of the 40 pregnant women with fetal chromosome mosaicism, FISH test was performed on 20 cases (14 cases were verified with both amniotic fluid and umbilical cord blood samples, five with amniotic fluid samples and one with umbilical cord blood sample), and all of the diagnosis of mosaicism were confirmed. For those with mosaicism ratio <30%, the detection rate by FISH was higher than that by CMA among amniotic fluid samples [14/19 vs 43.5% (10/23), χ2=3.88, P=0.049]. (5) Among the 40 pregnant women, five were lost to follow-up; 18 chose to terminate the pregnancy; and 17 continued the pregnancy to delivery. No abnormalities in mental or physical development were reported in the 17 neonates after birth or during on-line follow-up between 6 to 24 months old. Of the 14 pregnant women with mosaicism ratio <30% which confirmed by FISH, eight chose to continue the pregnancy, and no abnormalities in mental development or growth were found in the neonates. Conclusions:In prenatal diagnosis of true fetal choromosome mosaicism, the incidence of sex chromosome mosaicism is the highest. FISH may improve the prenatal diagnosis rate of mosaicism and is more accurate in determining the mosaicism ratio. The combination of FISH, CMA and chromosome karyotyping would significantly improve the detection rate of chromosomal mosaicism and assess the mosaicism ratio more accurately, which is of great value in clinical consultation and evaluation of fetal prognosis.

Prenatal genetic analysis of two fetuses with Miller-Dieker syndrome / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To perform molecular cytogenetic study on two fetuses with abnormal ultrasound findings and analyze their genotype-phenotype correlation.</p><p><b>METHODS</b>G-banded karyotyping, single nucleotide polymorphism array (SNP array) and fluorescence in situ hybridization (FISH) were performed on amniotic fluid cells from both fetuses and peripheral blood samples from their parents. Results of SNP array were analyzed with bioinformatics software.</p><p><b>RESULTS</b>G-banded karyotyping failed to detect any abnormalities in both fetuses and their parents. SNP array detected a 2.484 Mb terminal deletion at 17p13.3 [arr[hg19] 17p13.3 (83 035-2 567 405)×1] in fetus 1 and a 3.295 Mb terminal deletion at 17p13.3p13.2 [arr[hg19] 17p13.3p13.2 (83 035- 3 377 560)×1] in fetus 2. Both deletions have overlapped with the critical region of Miller-Dieker syndrome (MDS) and involved candidate genes such as PAFAH1B1, YWHAE and CRK. In addition, SNP array and FISH analyses on the parental peripheral blood samples demonstrated that both 17p13.3 and 17p13.3p13.2 deletions were of de novo origin. Metaphase FISH performed on amniotic fluid cells confirmed the presence of 17p13.3 and 17p13.3p13.2 deletions detected by the SNP array, while metaphase FISH performed on the parents excluded any potential chromosome rearrangements.</p><p><b>CONCLUSION</b>Abnormal ultrasound features for fetuses with MDS mainly include central nervous system anomalies. SNP array can efficiently detect 17p13.3 microdeletions underlying MDS, and accurately map the breakpoints and involved genes, which may facilitate understanding of the genotype and phenotype correlations for MDS.</p>

Application of single nucleotide polymorphism-based array analysis for prenatal diagnosis of a fetus with de novo derivative chromosome / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze a fetus with increased nuchal translucency and nuchal fold, and to assess the recurrence risk for her family and provide a basis for prenatal diagnosis.</p><p><b>METHODS</b>G-banded karyotyping and single nucleotide polymorphism-based array (SNP-Array) analysis were used to analyze the fetus and her parents.</p><p><b>RESULTS</b>SNP-Array analysis has detected a 41.04 Mb duplication at Xp22.33p11.4 and a 30.51 Mb duplication at 13q31.3q34 in the fetus. G-banding karyotyping indicated that the fetus had a karyotype of 46,X,der(X)(13qter-13q31::Xp11.4-Xp22.3::Xp22.3-Xqter). Her parents had normal results for both G-banding karyotyping and SNP-Array analysis, suggesting that the fetus has carried a de novo derivative chromosome X.</p><p><b>CONCLUSION</b>SNP-Array combined with G-banding karyotyping is helpful to confirm the composition and connection type of de novo derivative chromosome, which can improve the accuracy of diagnosis and is valuable for the evaluation of recurrence risk.</p>

Prenatal genetic diagnosis for a fetus with atypical neurofibromatosis type 1 microdeletion / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze the correlation between atypical neurofibromatosis type 1(NF1) microdeletion and fetal phenotype.</p><p><b>METHODS</b>Fetal blood sampling was carried out for a woman bearing a fetus with talipes equinovarus. G-banded karyotyping and single nucleotide polymorphism array (SNP-array) were performed on the fetal blood sample. Fluorescence in situ hybridization (FISH) was used to confirm the result of SNP array analysis. FISH assay was also carried out on peripheral blood specimens from the parents to ascertain the origin of mutation.</p><p><b>RESULTS</b>The karyotype of fetus was found to be 46, XY by G-banding analysis. However, a 3.132 Mb microdeletion was detected in chromosome region 17q11.2 by SNP array, which overlaped with the region of NF1 microdeletion syndrome. Analyzing of the specimens from the fetus and its parents with FISH has confirmed it to be a de novo deletion.</p><p><b>CONCLUSION</b>Talipes equinovarus may be an abnormal sonographic feature of fetus with atypical NF1 microdeletion which can be accurately diagnosed with SNP array.</p>

Genetic analysis of a fetus with partial 1q monosomy and partial 17q trisomy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze a fetus with abnormal sonographic features and correlated its genotype with phenotype.</p><p><b>METHODS</b>G-banding analysis, single nucleotide polymorphism array (SNP array) and fluorescence in situ hybridization (FISH) were performed for the fetus. Karyotyping and FISH were also carried out for the parents.</p><p><b>RESULTS</b>SNP array detected a 4.4 Mb deletion at 1q44 and a 10.4 Mb duplication at 17q24.3q25.3 in the fetus. Based on the results of SNP array and FISH analysis, the father was diagnosed with a cryptic t(1;17)(q44;q24.3) translocation. The fetus has inherited a der(1)t(1;17)(q44;q24.3) from its father.</p><p><b>CONCLUSION</b>The 1q44 deletion and 17q24.3q25.3 duplication may have contributed to the abnormal sonographic features presented by the fetus.</p>

Prenatal diagnosis of 1p36.3 microdeletion in a fetus with complex heart defect / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze a fetus presenting with complex heart defect and assess the recurrence risk.</p><p><b>METHODS</b>Conventional karyotyping, fluorescence in situ hybridization (FISH) and single nucleotide polymorphism-based array (SNP-array) were used to analyze the fetus and his parents.</p><p><b>RESULTS</b>SNP-array has detected a 6.9 Mb microdeletion at 1p36.33-p36.23 in the fetus. Chromosomal and FISH analyses indicated that the father of the fetus had a karyotype of 46,XY,t(1;14)(p36.3;p12), and that the fetus has inherited an abnormal chromosome 1 derived from the paternal translocation.</p><p><b>CONCLUSION</b>SNP-array combined with GTG banding and FISH can help to detect cryptic translocation, microdeletion or microduplication of chromosomes and is valuable to assess the recurrence risk for the affected family.</p>

Prenatal diagnosis of five cases of monochorionic-diamniotic twins discordant for karyotype analysis / 中华医学遗传学杂志

OBJECTIVE To explore the mechanism and diagnostic method for monochorionic-diamniotic twins discordant for karyotype analysis. METHODS Dual amniocentesis was performed on five pairs of monochorionic-diamniotic twins, which all consisted of a normal twin and one with multiple malformations revealed by ultrasound. Karyotype analysis was performed on amniocytes derived from each of the twins. Zygosity was also determined with DNA extracted from amniocytes with 16 polymorphic microsatellite markers. RESULTS Three cases of 45,X, one case of 47,XX,+9 and one case of 47,XY,+18 were detected among the abnormal twins, while the normal fetuses all had a normal karyotype. DNA analysis suggested that, in all cases, the twins have shared the 16 polymorphic microsatellite markers, which confirmed their monozygosity. CONCLUSION Monochorionic-diamniotic twins may be discordant for karyotyping, for which anaphase lagging, chromosomal non-disjunction and trisomy rescue may be the underlying reasons. As a simple method, dual amniocentesis can be used to obtain amniotic fluid samples for karyotype analysis and determination of zygosity for such twins.

Chromosomal microarray analysis for lateral ventriculomegaly in fetus / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the relationship between fetal lateral ventriculomegaly and chromosomal microarray analysis (CMA) abnormalities.</p><p><b>METHODS</b>Fifty fetuses with lateral ventriculomegaly detected by ultrasound and a normal karyotype were included. Forty four fetuses were classified as mild ventriculomegaly (MVM), in which the lateral ventricular atrium was 10-15 mm. Six had severe ventriculomegaly (SVM), with the lateral ventricularatrium being ≥ 15 mm. The fetuses were also divided into isolated (n= 21) and non-isolated groups (n= 29) based on whether they are associated with other anomalies.</p><p><b>RESULTS</b>Thirteen (26%) of the fetuses were found to be abnormal by CMA. For the 44 cases with MVM, 9 (20.9% ) were found to be abnormal, while for the 6 cases with SMV, 4 (66.7%) were found to be abnormal (P>0.05). CMA abnormalities were found in 2 (9.5%) of the 21 fetuses with isolated ventriculomegaly group and 11 (37.9%) of the 29 fetuses with non-isolated ventriculomegaly group (P<0.05).</p><p><b>CONCLUSION</b>Chromosome microdeletions and microduplications are the most common abnormalities found in fetal lateral ventriculomegaly. When ventriculomegaly is associated with other anomalies, the incidence of CMA abnormally is much higher. Prenatal diagnosis is necessary for fetuses with lateral ventriculomegaly.</p>

Misdiagnosis of mosaic tetrasomy 9p in a fetus by single nucleotide polymorphism-based array / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the reason for discordant results of karyotyping and microarray analysis in a fetus with mosaic tetrasomy 9p.</p><p><b>METHODS</b>Amniocentesis was carried out for a pregnant woman with advanced age for whom ultrasound scan has indicated fetal ventricular expansion, intrauterine growth retardation and persistent upper venous cavity. G-banded karyotyping and single nucleotide polymorphism-based arrays (SNP-array) analysis were performed at the same time.</p><p><b>RESULTS</b>Analysis of amniocytic chromosome has suggested mosaic tetrasomy 9p (47,XX,+psu idic(9)(q21)[23]/46,XX[27]). While SNP-array has detected a non-mosaic trisomy 9p with a 68.7 Mb duplication at 9p24.3q21.11. The results of the two methods were therefore discordant.</p><p><b>CONCLUSION</b>SNP-array will analyze genetic material in the form of numbers rather than morphology. For chimeras containing two types of cell lines, when the mosaic rate was close to 50% and the average amount of genetic material of the chimeras was equivalent to the amount of genetic material of non-chimeras, microarray analysis may come to the conclusion of a non-mosaic heteroploidy. Therefore, microarray results for large segment chromosome abnormalities should be combined with the results of G-banded karyotyping for genetic counseling.</p>

Confirmation of a maternal cryptal balanced translocation through analysis of a fetus using microarray / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze a fetus with heart defects and to assess the recurrence risk for her family.</p><p><b>METHODS</b>Single nucleotide polymorphism-based arrays (SNP-Array) analysis using Affymetrix Genome Wide Human SNP CytoHD was performed to analyze the fetus and her parents. Karyotype analysis was also carried out.</p><p><b>RESULTS</b>SNP-Array has detected a 14.5 Mb duplication at 9p and a 14.7 Mb deletion at 11q. Karyotype analysis indicated that the fetus' mother has a karyotype of 46, XX, t(9;11) (p23;q24). Therefore, the fetus has inherited a derivative chromosome 11 derived from the maternal translocation, and her karyotype was 46, XX, der(11) t(9;11) (p23;q24) mat.</p><p><b>CONCLUSION</b>SNP-Array combined with high resolution GTG banding has confirmed that the fetus has a derivative chromosome 11 derived from her mother's balanced translocation, resulting in partial 9p trisomy and partial 11q monosomy. This couple therefore have a high recurrence risk. SNP-Array is capable of detecting small chromosomal imbalance in abnormal fetuses and can pinpoint the breakpoints. It therefore has the advantage for the detection of unbalanced translocation which is difficult to detect with GTG banding, which is important for assessment the recurrence risk for cryptic balanced translocation carriers.</p>

Cytogenetic and molecular genetic study of fetal supernumerary marker chromosomes and derivative chromosomes / 中华围产医学杂志

Objective To investigate the prenatal diagnosis and phenotypic assessment strategies for fetal supernumerary marker chromosomes and derivative chromosomes. Methods Five cases of fetal supernumerary marker chromosomes and one case of fetal derivative chromosomes were diagnosed in the First Affiliated Hospital of Sun Yat-Sen University from March 12, 2010 to November 9, 2012 by conventional chromosome banding, fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY). These cases were retrospectively reviewed. Combined with the results of ultrasonography, abnormal phenotypes and pregnancy outcomes were evaluated in these cases. Results All of the five supernumerary marker chromosomes were de novo, in which two were mosaic and the remaining three cases were non-mosaic. Of these five cases, two were type 47, XX+mar and ultrasound indicated abnormal phenotypes. FISH and SKY confirmed that they were derived from chromosome 4 and 22, respectively. The other three cases were marker chromosome with Turner syndrome karyotype (abnormal phenotypes were not found by ultrasound), in which two cases were derived from chromosome Y (by FISH) and one case was identified as ring chromosome X (by FISH and SKY). One de novo derivative chromosome was verified as a product of reciprocal translocation between chromosome 2 and 6 (by FISH and SKY). Induced abortion was performed in all cases between 25 and 32 gestational weeks. Conclusions By combining conventional chromosome banding, FISH and SKY, the origin and content of supernumerary marker chromosomes and derivative chromosomes can be identified. On this basis, clinical phenotype evaluation and genetic counseling may be offered with the ultrasonographic result.

Cytogenetic and molecular study of a patient with severe oligozoospermia and asthenozoospermia / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore genetic etiologies of a patient with severe oligozoospermia and asthenozoospermia.</p><p><b>METHODS</b>G-banded karyotyping and fluorescence in situ hybridization (FISH) were used to characterize the origin and structure of the abnormal chromosome discovered in this patient. Multiplex polymerase chain reaction (PCR) was used to detect microdeletion of azoospermia factor (AZF).</p><p><b>RESULTS</b>G-banding revealed a karyotype of 45,X,der(15) (?::p11.2→ qter)dn for the patient. Dual-color FISH confirmed that SRY gene was present in a segment attached to the short arm of chromosome 15. Sex chromosome mosaicism and numerical abnormality therefore were both present. Dual-color FISH revealed karyotype of nuc ish(DXZ1× 1, SRY× 1)[390/400]/(DXZ1× 2, SRY× 1) [10/400]. Four-color FISH showed that the abnormal chromosome 15 has derived from a pseudodicentric (Y;15) translocation, and that the breakpoint on Y chromosome was located at Yq12. G-banding and FISH results confirmed that the karyotype was 45,X,der(15)(?::p11.2→ qter)dn.ish psu dic(15;Y)(p11.2;q12)(D15Z1+ , SNRPN+ , PML+ ; SRY+ , DYZ3+ , DYZ1+ ). Microdeletion of AZFc combined with sY254 deletion was detected by multiplex PCR.</p><p><b>CONCLUSION</b>Cytogenetic and molecular genetic analysis of the patient has indicated meiotic disturbances with spermatogenetic arrest resulting from a pseudodicentric chromosome derived from Y;15 translocation and spermatogenesis dysfunction resulting from partial deletion of AZFc region.</p>

Investigation of ultrasound markers in screening fetal trisomy 21 / 中华妇产科杂志

Objective To investigate the clinical value of ultrasound markers in screening fetal trisomy 21.Methods From Jan.2001 to Dec.2011,a retrospective study about sonographic information of 138 fetuses diagnosed as trisomy 21 was taken in the First Affiliated Hospital of Sun Yat-sen University.All fetuses were divided into 3 groups:isolated ultrasound markers,non-isolated ultrasound markers,and isolated structural malformations or other abnormalities.The relationship between trisomy 21 and ultrasound markers as well as structural anomalies or other abnormalities was analyzed.Results Sonographic anomalies were detected in 132 fetuses(95.7％,132/138),including ultrasound markers and structural malformations or other abnormalities.One hundred and twenty cases(87.0％,120/138)had ultrasound markers,38(31.7％,38/120)had one marker and 82(68.3％,82/120)had more than one marker (P ＜ 0.01).Fifty-one fetuses(37.0％,51/138)had isolated ultrasound markers and non-isolated markers were found in 69 fetuses(50.0％,69/138).Only 12 fetuses(8.7％,12/138)had isolated structural malformations or other abnormalities.In 20 fetuses on whom the first-trimester ultrasound screening were performed,all had ultrasound markers,95％(19/20)had thickened nuchal translucency and 55％ (11/20)had nasal bone hypoplasia.The most common ultrasound markers on the second-trimester screening were nasal bone hypoplasia,which accounted for 41.9％(52/124)cases,followed by thickened nuchal fold (25.0％,31/124),short fenurs and humerus(24.2％,30/124),echogenic intracardiac focus(16.1％,20/124),mild ventriculomegaly(15.3％,19/124),hyperechoic bowel(12.9％,16/124),mild renal pyelectasis(12.1％,15/124).Furthermore,thc common structural malformations or other abnormalities were as follows:cardiac defects(33.1％,41/124),digestive system(26.6％,33/124).Condusions Ultrasound markers are valuable for screening fetal trisomy 21.The fetuses of trisomy 21 usually had more than one ultrasound markers or associated with other abnormalities.Combinations of ultrasound markers with the results of serum screening and maternal age are necessary for evaluation.