Copy number variation analysis and outcomes of 1 658 fetuses with increased nuchal translucency / 中华围产医学杂志

Objective:To analyze the genetic etiology and prognosis in fetuses with increased nuchal translucency (NT) in order to assist in the clinical prenatal genetic counseling and diagnosis.Methods:This study retrospectively enrolled 1 658 cases of singleton pregnancy (<35 years old) receiving invasive prenatal diagnosis, including karyotype analysis and/or chromosome microarray analysis or copy number variation (CNV) sequencing, due to NT value ≥2.5 mm in the first trimester in Henan Provincial People's Hospital from August 2014 to December 2021. They were divided into different groups according to the thickness of NT (≥2.5-<3.0, ≥3.0-<3.5, ≥3.5-<4.5, ≥4.5-<5.5, ≥5.5-<6.5 and ≥6.5 mm groups) and abnormal ultrasound findings (isolated increased NT group, increased NT complicated by soft markers/non-severe structural abnormality group and increased NT complicated by severe structural abnormality group). The results of invasive prenatal diagnosis and pregnancy outcomes were compared between different groups using Chi-square test and trend Chi-square test. Results:The detection rates of numerical abnormalities of chromosomes were 15.8% (262/1 658) and 17.6% (252/1 431) when the NT thickness cut-off value were 2.5 mm or 3.0 mm, respectively. Overall, the detection rate of numerical abnormalities of chromosomes increased with thickness of NT ( χ2trend=180.75, P<0.001), ranging from 6.6% (44/671) in the NT≥2.5-<3.5 mm group to 45.6% (113/248) in the NT≥5.5 mm group. The incidence of pathogenic/likely pathogenic CNV(P/LP CNV) did not increased with NT thickness ( χ2trend=3.26, P=0.071), and the highest detection rate was observed in the NT≥4.5-<5.5 mm group (9.0%, 19/211). The detection rate of numerical abnormalities of chromosomes plus P/LP CNV in the isolated NT≥2.5-<3.0 mm group and NT≥3.0-<3.5 mm group were 5.3% (10/188) and 9.6% (36/375), respectively, however, the difference was not statistically significant ( χ2=3.06, P=0.080). The detection rates of numerical abnormalities of chromosomes plus P/LP CNV in the isolated NT≥3.5-<4.5 mm group and NT≥2.5-<3.0 mm complicated by soft markers/ non-severe structural abnormality group were 12.7% (52/410) and 24.1% (7/29), respectively, and the risk were 2.6 times (95% CI: 1.3-5.2) and 5.7 times (95% CI: 2.0-16.4) of the isolated NT≥2.5-<3.0 mm group, respectively. The pregnancy termination rate increased with the NT thickness ( χ2trend=304.42, P<0.001), ranging from 10.8% (23/212) in the NT≥2.5-<3.0 mm group to 90.7% (117/129) in the NT≥6.5 mm group. After exclusion of the pregnancies terminated due to numerical abnormalities of chromosomes and P/LP CNV, 87.6% (862/984) of the fetus with increased NT were born alive. Conclusions:The detection rate of numerical abnormalities of chromosomes increases with the thickness of NT. Invasive prenatal diagnosis is required for non-advance aged singleton pregnant women when fetuses present with isolated NT≥2.5 mm with or without soft markers/structural abnormalities.

Analysis of GNAS gene variant in a Chinese pedigree affected with pseudohypoparathyroidism / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic etiology of a Chinese pedigree affected with pseudohypoparathyroidism.@*METHODS@#Peripheral blood samples of the proband and his parents were collected and subjected to trio-whole exome sequencing (trio-WES). Candidate variants were verified among the pedigree and 50 randomly selected healthy individuals through analysis of restriction fragment length polymorphism. Short tandem repeat (STR) linkage analysis was used to verify the parental origin of the pathogenic variants.@*RESULTS@#Trio-WES and Sanger sequencing showed that the proband and his mother had both harbored a c.121C>G (p.His41Asp) variant of the GNAS gene, which was not found in other family members and the 50 healthy controls. The variant was not found in international databases. Based on guidelines from the American College of Medical Genetics and Genomics, the variant was predicted to be likely pathogenic.@*CONCLUSION@#The novel c.121C>G variant of the GNAS gene probably underlay the disease in this pedigree. Above finding has enriched the spectrum of GNAS gene variants.

Application of genomic copy number variation detection technology in prenatal diagnosis of 7617 pregnant women with serological screening abnormalities during the second trimester of pregnancy / 中华医学遗传学杂志

OBJECTIVE@#To analyze the genomic variation characteristics of fetal with abnormal serological screening, and to further explore the value of copy number variation (CNV) detection technology in prenatal diagnosis of fetal with abnormal serological screening.@*METHODS@#7617 singleton pregnant women who underwent amniocentesis for prenatal diagnosis solely due to abnormal Down's serological screening were selected. According to the results of serological screening, the patients were divided into high risk group, borderline risk group and single abnormal multiple of median (MOM) group. CMA and CNV-Seq were used to detect the copy number variation of amniotic fluid cell genomic DNA and combined with amniotic fluid cell karyotype analysis for prenatal diagnosis. Outpatient revisit combined with telephone inquiry was used for postnatal follow-up.@*RESULTS@#Among 7617 amniotic fluid samples, aneuploidy was detected in 138cases (1.81%) by CMA and CNV-Seq, 9 cases of aneuploid chimerism were detected by amniotic fluid cell karyotype analysis, and 203 cases of fetus carrying pathogenic and likely pathogenic CNV (P/LP CNV) were detected, the variant of uncertain significance (VUS) was detected in 437 cases (5.7%), the overall abnormal detection rate was 10.33%. The detection rate of aneuploidy by CMA and CNV-Seq in three group were 123 cases (2.9%), 13 cases (1.3%) and 2 cases (0.4%), respectively,and showing no significant difference (χ 2=7.469, P=0.024). The detection rate of pathogenic and likely pathogenic CNV in three group were 163cases (2.6%); 24 cases (2.6%) and 16 cases (3.3%), respectively, and showing no significant difference (χ 2=0.764, P=0.682). The CMA reported 2.9% (108/3729)P/LP CNV, and CNV-seq reported 2.4% (95/3888)P/LP CNV, both tests showed similar detective capabilities (χ 2=1.504, P=0.22).The most popular P/LP CNV in this cohort were Xp22.31 microdeletion, 16p13.11 microduplication /microdeletion, 22q11.21 microduplication /microdeletion. In fetuses with P/LP CNV CNV, 59 fetuses were terminated pregnancy, and 32 of 112 fetuses born had abnormal clinical manifestations. Non-medically necessary termination of pregnancy occurred in 11 fetuses carrying VUS CNV, 322 fetuses carrying VUS CNV were born, 4 of them presented abnormal clinical manifestations.@*CONCLUSION@#Compared with the traditional chromosome karyotype, CMA and CNV-Seq can improve the detection rate of pathogenic and likely pathogenic CNV. CMA and CNV-seq can be used for first tier diagnosis of pregnant women in the general population with abnormal Down's serological screening.

Pedigree analysis and prenatal diagnosis of intellectual disability caused by synonymous mutations of p.S434S in DLG3 gene / 中华围产医学杂志

Objective:To analyze the pathogenic gene and prenatal diagnosis of a family with intellectual disability.Methods:Out of this family consisting of 17 members in three generations, four males had intellectual disability. The proband's elder sister (Ⅱ-7) visited Henan Provincial People's Hospital in Oct 2019 for genetic counseling at 8 weeks of gestation. After informed consent was obtained, peripheral blood samples of the family members were collected. The whole exome sequencing was performed on the genome DNA of the proband (Ⅱ-9, male) and his parents to screen the candidate variants for phenotype co-segregated analysis by Sanger sequencing. The expression vectors were constructed by homologous recombination and the splicing experiments were performed in vitro. Reverse transcription polymerase chain reaction, Sanger sequencing, and TA clone sequencing were used to analyze the effect of candidate variants on splicing. After the pathogenic variant was determined the proband's elder sister underwent prenatal diagnosis (Ⅲ-7) using goldeneyeTM20A genotyping system and Sanger sequencing. Results:A hemizygous synonymous variant of c.1302G>A (p. S434S) in DLG3 gene was found in the proband by whole exome sequencing, which was carried by his mother (Ⅰ-1) and co-segregated with the phenotype in other family patients. In vitro splicing experiment showed that c.1302G>A variant led to abnormal splicing of 88.24% transcripts, which further resulted in the reading frame shift and protein function impairment. The mutation was not detected in the fetus (Ⅲ-7), who was born alive later and showed no abnormal mental or behavioral development at the age of one and a half year and is still being followed up. Conclusions:The synonymous mutation c.1302G>A in DLG3 gene was the etiopathogenesis of X-linked intellectual disability in this family.

Early warning of low maternal unconjugated estriol level by prenatal screening for fetus with X-linked ichthyosis / 中华妇产科杂志

Objective:To analyze the characteristic of prenatal serological screening in fetus with X-linked ichthyosis (XLI), and to explore the relationship between unconjugated estriol (uE 3) levels and XLI. Methods:A total of 56 fetuses with Xp22.31 microdeletion indicated by prenatal diagnosis and 70 fetuses diagnosed with trisomy 21 and 26 fetuses with trisomy 18 in Henan Provincial People's Hospital and Affiliated Hospital of Weifang Medical College from September 2016 to June 2021 were collected. The multiples of median (MoM) values of uE 3, alpha-fetoprotein (AFP), and human chorionic gonadotropin (hCG) during the second trimester of pregnancy were retrospectively analyzed. Prenatal diagnosis was made by amniotic fluid karyotype analysis and genome copy number variant analysis, parent genetic verification and pathogenicity analysis were performed, and maternal and infant outcomes were followed up. Results:Of 56 pregnant women with fetal Xp22.31 microdeletion, 43 underwent serological screening during the second trimester of pregnancy, of which 42 were abnormal (39 male fetuses and 3 female fetuses). The median uE 3 MoM value of 39 male fetuses [0.06 (0.00-0.21)] was lower than the normal value and significantly lower than that of fetuses with trisomy 21 [0.71 (0.26-1.27)] and fetuses with trisomy 18 [0.36 (0.15-0.84)], the difference was statistically significant ( Z=99.96, P<0.001). While the MoM values of AFP and hCG were all within the normal range. Among the 56 fetuses carrying Xp22.31 microdeletion, 45 were male fetuses and 11 were female fetuses, and the deletion fragments all involved STS gene. Eighty-nine percent (50/56) were inherited from mother (49 cases) or father (1 case), and 11% (6/56) were de novo mutations. Follow-up showed 48 live births (38 males and 10 females) and 8 chose to terminate pregnancy (7 males and 1 female). Among the 38 male newborns, 37 presented with scaly skin changes from 1 to 3 months of age, and one had no clinical manifestations until 4 months after birth. Ten female newborns had no obvious clinical manifestations. Conclusions:The decrease levels of uE 3 MoM on maternal serological screening is closely related to the higher risk of XLI in male fetuses. For pregnant women with low uE 3 in serological screening or with family history of ichthyosis, in addition to chromosomal karyotype analysis, joint detection of genomic copy number variant analysis should be recommended.

Identification of pathogenic variant in a Chinese pedigree affected with non-syndromic cleft lip and palate / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for a Chinese pedigree affected with non-syndromic cleft lip and cleft palate (NSCLP).@*METHODS@#With informed consent obtained, members of the pedigree were subjected to clinical examination and history taking to exclude syndromic cleft lip and palate. One affected member was subjected to whole-exome sequencing and bioinformatics analysis. Candidate variant was verified by Sanger sequencing and co-segregation analysis of her family members and 100 unrelated healthy individuals.@*RESULTS@#Whole-exome sequencing and co-segregation analysis showed that all affected members of this pedigree have carried a heterozygous missense c.253A>G (p.Cys85Arg) variant in exon 4 of the IRF6 gene, which has co-segregated with the phenotype and was not found among the 100 unrelated healthy individuals.@*CONCLUSION@#The missense c.253A>G variant in exon 4 of the IRF6 gene probably underlay the NSCLP in this pedigree.

Genetic mutation analysis in three pedigrees with hereditary multiple exostosis / 中华检验医学杂志

Objective:To detect the pathogenic gene of the three pedigrees with hereditary multiple exostosis, and to provide evidences for genetic counselling and prenatal diagnosis.Methods:The three families were admitted to the Institute of Medical Genetics of Henan Provincial People′s Hospital due to hereditary multiple exostosis from January 2018 to December 2020. Detail medical history and the blood samples of the family members were collected after they signed the informed consent forms. The pathological mutations were selected from the proband using whole exome sequencing (WES). Sanger sequencing was used to conduct the co-segregation analysis of the family members. The pathogenicity of the mutation was analyzed in combination with ACMG guidelines.Results:The EXT1 gene c.1056+2T>C mutation, c.369dupA (p.G124fs) mutation and the EXT2 gene c.1171C>T (p.Q391*) mutation were detected in the probands through whole exome sequencing. The same mutations were found in the patients from these three families, while the mutation was not detected among the healthy family members. These variations have co-segregated with the disease phenotype. According to ACMG guidelines, all mutations in these three families meet the criteria of pathogenic variations. Conclusion:The EXT1 gene c.1056+2T>C mutation, c.369dupA (p.G124fs) mutation and the EXT2 gene c.1171C>T (p.Q391*) mutation were identified to be responsible for hereditary multiple exostosis in these families.