Application of whole exome sequencing in fetal cases with skeletal abnormalities

OBJECTIVES: To investigate the role of whole exome sequencing (WES) technology in fetuses with skeletal abnormalities (SKA) for establishing an appropriate clinical diagnosis and treatment path. METHODS: From April 2019 to August 2020, eight special families were enrolled into the study. Their fetuses showed abnormal SKA by ultrasonic testing during pregnancy, but it is inconsistent with the normal results identified by chromosomal microarray analysis (CMA) of amniotic fluid or abortion. For further diagnosis, WES was performed to detect the causative genes mutations followed by Sanger sequencing. RESULTS: Among of these eight fetuses with SKA, we found more than half of pathogenic mutations were in COL1A1/2 gene, except for a known hotspot mutation in FGFR3 gene (c.1138G>A). Three heterozygous mutations of COL1A1 gene, c.2885G>A p (Gly962Asp), c.994G>A p (Gly332Arg) and c.1002 + 5G>T, were de novo mutations. The c.1002 + 5G>T mutation in COL1A1 was firstly reported. In addition, one fetus carried a novel heterozygous mutation of COL1A1 c.644G>A p (Gly215Asp), which was inherited from the mother. Another novel heterozygous mutation c.2482G>T p (Val828Phe) in the COL1A2 gene was identified in another fetus and was inherited from the father. Among of these COL1A1 mutations, these results might involve in two novel splicing mutations. CONCLUSION: Our study reported several novel heterozygous mutations which expands the COL1A1/2 mutation spectrum for prenatal diagnosis of SKA. Most importantly, WES technology is necessary as a routine step of the SKA diagnosis before or during pregnancy, combining with the detection of chromosome level.