Diagnosis of Shashi-Pena Syndrome Caused by Chromosomal Rearrangement Using Nanopore Sequencing

Ya Wang; Jianxin Tan; Yan Wang; An Liu; Fengchang Qiao; Mingtao Huang; Cuiping Zhang; Jing Zhou; Ping Hu; Zhengfeng Xu

doi:10.1212/NXG.0000000000000635

Diagnosis of Shashi-Pena Syndrome Caused by Chromosomal Rearrangement Using Nanopore Sequencing

Neurol Genet. 2021 Nov 23;7(6):e635. doi: 10.1212/NXG.0000000000000635. eCollection 2021 Dec.

Authors

Ya Wang¹, Jianxin Tan¹, Yan Wang¹, An Liu¹, Fengchang Qiao¹, Mingtao Huang¹, Cuiping Zhang¹, Jing Zhou¹, Ping Hu¹, Zhengfeng Xu¹

Affiliation

¹ Department of Prenatal Diagnosis, State Key Laboratory of Reproductive Medicine, Women's Hospital of Nanjing Medical University, Nanjing Maternity and Child Health Care Hospital, Nanjing, China.

Abstract

Background and objectives: The aim of this study was to uncover the genetic cause of delayed psychomotor development and variable intellectual disability in a proband whose previous genetic analyses, including chromosome microarray and whole exome sequencing, had been negative.

Methods: Long-read sequencing Oxford Nanopore Technology and RNA-seq analysis were performed on peripheral blood mononuclear cells. Genes with a fold change ≥ 1.5 and p ≤ 0.05 were identified as differentially expressed.

Results: Clinical examinations showed that the proband's features were similar to a rare autosomal-dominant neurodevelopmental syndrome, Shashi-Pena syndrome (MIM #617190). Karyotyping showed that a chromosomal balanced translocation t(2; 11) (p23; q23) was detected in the proband, her father, and her grandmother. Meanwhile, long-read sequencing identified 102 balanced translocations and 145 inversions affecting ASXL2 at an average of 15×. Combined with the family's RNA-seq results, the average mRNA expression of ASXL2 decreased in the patients.

Discussion: We identified a complex chromosomal rearrangement affecting ASXL2 as a pathogenic mechanism of Shashi-Pena syndrome in a Chinese family. This case study suggests that nanopore sequencing is suitable for pathogenic analysis of complex rearrangements, providing new avenues for the diagnosis of genetic diseases.