Identification of a novel TBR1 gene variant in a Chinese pedigree affected with intellectual developmental disorder with autism and speech delay

Abstract

To describe a family with intellectual developmental disorder with autism and speech delay (IDDAS) caused by a splice variant of TBR1 gene. A pregnant women with mental retardation, who also had a family history of mental retardation, was admitted to Prenatal Diagnosis Center of WanBei Coal and Electricity Group General Hospital Corporation in April 2019. Molecular genetic tests were performed on the pregnant women and ten other family members to analyze the pathogenic genotype. Functional assays of the pathogenic variant was carried out by minigene technology. With the determination of the genotype, prenatal diagnosis was carried out by amniotic fluid sampling. Through whole exome sequencing, a novel splicing variant (c.1129-1G>C) was identified in the TBR1 gene of the proband, which has co-segregated with the disease phenotype in the family. The results of minigene assay showed abnormal splicing of exon 5. The variant was not detected in the fetal amniotic fluid. Fetal growth and development were normal one year after the birth. The c.1129-1G>C variant of the TBR1 probably underlay the disease in of the pedigree. Timely prenatal genetic diagnosis and consultation can help to stop the transmission of the pathogenic variant.