Rapid genotyping of inversion variants in Mucopolysaccharidosis type II using long-range PCR: A case report

Abstract

Mucopolysaccharidosis II (MPS II) is a lysosomal storage disease caused by a deficiency in iduronate-2-sulfatase (IDS), leading to the accumulation of dermatan sulfate and heparan sulfate in lysosomes. Traditionally, genotyping of the IDS gene has been conducted through exome sequencing, which fails to detect inversion variants. Consequently, when no pathogenic variants are detected in exons, additional PCR-based analysis is required. Herein, we introduce a rapid genotyping technique method using long-range PCR for MPS II patients. We successfully identified an inversion variant and confirmed the sequences of the inversion regions. We also confirmed that the pathogenic variant in the patient originated de novo. These findings suggest that long-range PCR genotyping can identify inversion variants more rapidly compared to the previous PCR-based methods, making it a valuable tool for newborn screening (NBS) and genetic diagnosis.

Keywords: IDS gene; Iduronate-2-sulfatase; Inversion variant; Long-range PCR; Mucopolysaccharidosis type II.

Fig. 1

Long-range PCR of IDS. The top panel displays the gene structures of IDS and IDSP1 in a healthy control. The second top panel shows the gene structure of a patient with inversion variants between IDS and IDSP1. The striped box marks the genomic region of intron 7 in IDS and its homologous region in IDSP1. The wavy pattern box marks the genomic region of intron 2 in IDS and its homologous region in IDSP1. Insert A presents the results of long-range PCR: in the healthy control, PCR products A-1, −2, and A-3 were obtained; however, A-2 was not amplified in the patient. Insert B illustrates the PCR results for the inversion region: in the patient, the PCR products containing the inversion region, B-2 and B-4, indicated by red arrows and circles, were amplified. These products were not amplified in the health control.