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Gene. 2019 Jul 30;707:239-245. doi: 10.1016/j.gene.2019.05.029. Epub 2019 May 15.

In vitro residual activities in 20 variants of phenylalanine hydroxylase and genotype-phenotype correlation in phenylketonuria patients.

Author information

1
Department of Pediatric Endocrinology/Genetics, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Institute for Pediatric Research, Shanghai 200092, China.
2
Department of Rehabilitation, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China.
3
The Laboratory of Pediatric Infectious Diseases, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai 200127, China.
4
Department of Laboratory Medicine, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai 200127, China.
5
The Laboratory of Pediatric Infectious Diseases, Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai 200127, China. Electronic address: xi.mo@shsmu.edu.cn.
6
Department of Pediatric Endocrinology/Genetics, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Institute for Pediatric Research, Shanghai 200092, China. Electronic address: guxuefan@xinhuamed.com.cn.
7
Department of Pediatric Endocrinology/Genetics, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Institute for Pediatric Research, Shanghai 200092, China. Electronic address: yuyongguo@shsmu.edu.cn.

Abstract

Phenylketonuria (PKU), caused by phenylalanine hydroxylase (PAH) gene variants, is a common autosomal inherited metabolic disease. So far, 1111 PAH variants have been revealed. The residual activity of the PAH variants is the key determinant of the metabolic phenotype and BH4 responsiveness in PKU patients. In this study, the spectrum of PAH variants in 1083 Chinese PKU patients was analyzed. Then 20 variants (p.L52F, p.R86P, p.L128P, p.L142P, p.D163N, p.C203G, p.E214G, p.F260L, p.M276T, p.L311R, p.P314A, p.L364F, p.Q375H, p.F382I, p.A395S, p.V412D, p.E108*, p.C203*, p.C284* and p.E353*) were expressed in COS-7 cells. The residual activities and protein expression levels were detected by isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and Western blotting, respectively. We compared the results of the phenotypic prediction based on APV and PAH activity respectively, and further explored the relationship between residual activity and phenotype in PKU patients. We reported 9 newly discovered PAH variants for the first time, thereby expanding the spectrum of PAH variants. Among the 20 variants in our assay, 8 variants showed mild impaired residual activities (48-92%) and approximately normal protein expression levels compared to the wild-type PAH. In contrast, 9 variants showed severely impaired residual activities (0-34%) and reduced protein expression. However, three variants (p.L52F, p.F260L and p.P314A) showed impaired residual activities (5%, 32% and 29%), although the proteins were well expressed. We assigned APV scores for 14 variants, in which the results of the phenotypic prediction were consistent for 12/14 (86%) variants based on APV and residual activity respectively, and the residual activity correctly predicted 17/22 (77%) of the patients. Our study helped to further understand the genotype-phenotype correlation in PKU patients.

KEYWORDS:

Allelic phenotype values; In vitro expression; Phenylalanine hydroxylase; Phenylketonuria; Residual activity

PMID:
31102715
DOI:
10.1016/j.gene.2019.05.029
[Indexed for MEDLINE]

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