ABSTRACT
Objective@#To evaluate the application value and significance of low-depth whole-genome sequencing for copy number variations (CNV-Seq) in the genetic diagnosis and prenatal diagnosis of X-linked ichthyosis (XLI) due to STS gene deletion.@*Methods@#Clinical data were collected from 3 616 subjects who received CNV-Seq, and single-gene test results were collected from 7 patients or pedigrees with ichthyosis in The First Affiliated Hospital of Zhengzhou University in 2018. The 3 616 samples included 2 891 prenatal samples from pregnant women (most were amniotic fluid samples, some fetal villus samples, very few umbilical blood samples) and 725 peripheral blood samples from other subjects. Genomic DNA was extracted from amniocytes or peripheral blood, and then subjected to CNV-Seq. Quantitative PCR (qPCR) and single nucleotide polymorphism (SNP) -comparative genomic hybridization (CGH) array were performed to verify the detected CNVs. Pathogenicity of the CNVs was analyzed according to the database of genomic variants (DGV) , database of genomic variation and phenotype in humans using ensembl resources (DECIPHER) , clinical genome resource (ClinGen) and online Mendelian inheritance in man (OMIM) .@*Results@#Of the 3 616 subjects receiving CNV-Seq, Xp22.31 deletion was identified in prenatal samples from 6 pregnant women, including 5 male and 1 female fetuses. The deleted fragment of Xp22.31 covered the XLI region containing the major gene STS. The parental CNV-Seq showed that the Xp22.31 deletion was spontaneous mutation in 2 of the 6 fetuses, and inherited from the parents in the other 4 fetuses. qPCR confirmed that the female fetus was a carrier of a complete heterozygous deletion of the STS gene, and there was a complete deletion of the STS gene in the other 5 male fetuses. SNP-CGH array also confirmed that the female fetus was heterozygous Xp22.31 deletion carrier, which was consistent with the CNV-Seq results. Ichthyosis gene panel sequencing in the 7 patients with ichthyosis showed 1 with harlequin ichthyosis, 2 with ichthyosis vulgaris, 3 with XLI, and no causative mutation in 1. CNV-Seq confirmed that Xp22.31 deletion existed in the above 2 patients with XLI due to STS gene deletion. Moreover, Xp22.31 duplication was found in 16 out of 3 616 subjects receiving CNV-Seq, but they were all individuals or fetuses with normal phenotype.@*Conclusions@#CNV-Seq is a stable and reliable method for screening whole-genome CNVs, and can be applied to genetic diagnosis and prenatal diagnosis of XLI due to STS gene deletion. The deletion of Xp22.31 fragment containing the STS gene can cause XLI, and the duplication of the same region is highly likely to be the polymorphic variation.
ABSTRACT
Objective To evaluate the application value and significance of low-depth whole-genome sequencing for copy number variations(CNV-Seq)in the genetic diagnosis and prenatal diagnosis of X-linked ichthyosis(XLI)due to STS gene deletion. Methods Clinical data were collected from 3616 subjects who received CNV-Seq, and single-gene test results were collected from 7 patients or pedigrees with ichthyosis in The First Affiliated Hospital of Zhengzhou University in 2018. The 3616 samples included 2891 prenatal samples from pregnant women(most were amniotic fluid samples, some fetal villus samples, very few umbilical blood samples)and 725 peripheral blood samples from other subjects. Genomic DNA was extracted from amniocytes or peripheral blood, and then subjected to CNV-Seq. Quantitative PCR(qPCR)and single nucleotide polymorphism(SNP)-comparative genomic hybridization(CGH)array were performed to verify the detected CNVs. Pathogenicity of the CNVs was analyzed according to the database of genomic variants(DGV), database of genomic variation and phenotype in humans using ensembl resources (DECIPHER), clinical genome resource (ClinGen) and online Mendelian inheritance in man (OMIM). Results Of the 3616 subjects receiving CNV-Seq, Xp22.31 deletion was identified in prenatal samples from 6 pregnant women, including 5 male and 1 female fetuses. The deleted fragment of Xp22.31 covered the XLI region containing the major gene STS. The parental CNV-Seq showed that the Xp22.31 deletion was spontaneous mutation in 2 of the 6 fetuses, and inherited from the parents in the other 4 fetuses. qPCR confirmed that the female fetus was a carrier of a complete heterozygous deletion of the STS gene, and there was a complete deletion of the STS gene in the other 5 male fetuses. SNP-CGH array also confirmed that the female fetus was heterozygous Xp22.31 deletion carrier, which was consistent with the CNV-Seq results. Ichthyosis gene panel sequencing in the 7 patients with ichthyosis showed 1 with harlequin ichthyosis, 2 with ichthyosis vulgaris, 3 with XLI, and no causative mutation in 1. CNV-Seq confirmed that Xp22.31 deletion existed in the above 2 patients with XLI due to STS gene deletion. Moreover, Xp22.31 duplication was found in 16 out of 3616 subjects receiving CNV-Seq, but they were all individuals or fetuses with normal phenotype. Conclusions CNV-Seq is a stable and reliable method for screening whole-genome CNVs, and can be applied to genetic diagnosis and prenatal diagnosis of XLI due to STS gene deletion. The deletion of Xp22.31 fragment containing the STS gene can cause XLI, and the duplication of the same region is highly likely to be the polymorphic variation.