Genetic analysis by targeted next-generation sequencing and novel variation identification of maple syrup urine disease in Chinese Han population

Xiaohua Fang,Ying Bai,Yin Feng,Xiangdong Kong,Xiaofan Zhu,Xuechao Zhao,Ning Liu

doi:10.1038/s41598-021-98357-2

Xiaohua Fang, Ying Bai + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-98357-2

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Abstract

Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder that affects the degradation of branched chain amino acids (BCAAs). Only a few cases of MSUD have been documented in Mainland China. In this report, 8 patients (4 females and 4 males) with MSUD from 8 unrelated Chinese Han families were diagnosed at the age of 6 days to 4 months. All the coding regions and exon/intron boundaries of BCKDHA, BCDKHB, DBT and DLD genes were analyzed by targeted NGS in the 8 MSUD pedigrees. Targeted NGS revealed 2 pedigrees with MSUD Ia, 5 pedigrees with Ib, 1 pedigree with MSUD II. Totally, 13 variants were detected, including 2 variants (p.Ala216Val and p.Gly281Arg) in BCKDHA gene, 10 variants (p.Gly95Ala, p.Ser171Pro, p.Phe175Leu, p.Arg183Trp, p.Lys222Thr, p.Arg285Ter, p.Arg111Ter, p.S184Pfs*46, p.Arg170Cys, p.I160Ffs*25) in BCKDHB gene, 1 variant (p.Arg431Ter) in DBT gene. In addition, 4 previously unidentified variants (p.Gly281Arg in BCKDHA gene, p.Ser171Pro, p.Gly95Ala and p.Lys222Thr in BCKDHB gene) were identified. NGS plus Sanger sequencing detection is effective and accurate for gene diagnosis. Computational structural modeling indicated that these novel variations probably affect structural stability and considered as likely pathogenic variants.

Highlights

The suspected variants found by NGS were confirmed by Sanger sequencing
The results of blood tandem mass spectrometry in all families showed that both leucine and valine were significantly higher, accompanied by amino acid ratio changes, consistent with MSUD biochemical findings
There are 26 (32.1%) gene variants located in the BCKDHA gene, 45 (55.6%) gene variants in the BCKDHB gene, 10 (12.3%) gene variants in the DBT gene, no variants in the DLD gene

Summary

Introduction

The suspected variants found by NGS were confirmed by Sanger sequencing. The patient in family 3 carried BCKDHB gene c.511T>C(p.Ser171Pro) and c. C.508C>T(p.Arg170Cys) compound heterozygous variants, and the child in pedigree 7 carried c.523T>C(p.Phe175Leu) and c.478-552del(p. Their parents were heterozygous carriers of the respective variant. Heterozygous variants in the same causative gene of MSUD were detected in both couples in the remaining six families. Gene sequences of four novel variant in BCKDHA and BCKDHB genes were shown in Fig

Methods

Results

Conclusion