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Lisha An
Public Documents
1
Identification of novel deep intronic PAH gene variants in patients with phenylketonu...
Xiaohua Jin
and 10 more
January 03, 2021
Phenylketonuria (PKU) is caused by phenylalanine hydroxylase (PAH) gene variants. Previously, 94.21% of variants were identified using Sanger sequencing and multiplex ligation-dependent probe amplification. To investigate the remaining variants, whole-genome sequencing (WGS) was performed in four patients with PKU with unknown genotype to identify deep intronic or structural variants. Three novel heterozygous variants (c.706+368T>C; c.1065+241C>A; and c.1199+502A>T) were identified in a deep PAH gene intron. The c.1199+502A>T variant was detected in 60% (6/10) PKU patients. In silico prediction showed that the three deep variants may impact splice site selection and result in inclusion of a pseudo-exon. The c.1199+502A>T PAH minigene and reverse transcription PCR of blood RNA in a patient with PKU and compound heterozygous variants (c.1199+502A>T/ c.1199G>A) confirmed that the c.1199+502A>T variant creates a novel branch point and leads to the inclusion of a 25 bp in PAH mRNA (r.1199_2000ins1199+538_1199+562). Furthermore, the c.1199G>A mutation leads to the retention of an additional 17 nt in the PAH mRNA transcript (r.1199_2000ins1199+1_1199+17). These results expand the PAH genotypic spectrum and highlight that deep intronic analysis of PAH can improve genetic diagnosis in undiagnostic patients.