Analysis of PAH gene variants and prenatal diagnosis for 43 Chinese pedigrees affected with Phenylketonuria

Abstract

To explore the characteristics of phenylalanine hydroxylase (PAH) gene variants and prenatal diagnosis for 43 Chinese pedigrees affected with Phenylketonuria (PKU). Forty three PKU pedigrees diagnosed at the First Affiliated Hospital of Zhengzhou University between 2019 and 2021 were selected as the study subjects. Variants of the PAH gene of the probands were screened by high-throughput sequencing, and candidate variants were verified by Sanger sequencing. Negative cases were further analyzed by multiplex ligation-dependent probe amplification (MLPA) to detect large fragment deletions and duplications of the PAH gene. For 43 women undergoing subsequent pregnancy, Sanger sequencing, MLPA, combined with short tandem repeats (STR) sequence-based linkage analysis, were carried out for prenatal diagnosis. Among the 86 alleles carried by the 43 probands, 78 nucleotide variants (90.70%) and 3 large deletions (3.49%) were found based on high-throughput sequencing and MLPA. The 81 mutant alleles had included 21 missense variants, 5 splice site variants, 4 nonsense variants, 2 microdeletions, 1 insertional variant and 2 large fragment deletions. Relatively common variants have included p.Arg243Gln (23.26%), p.Arg111Ter (8.14%), EX6-96A>G (6.98%), p.Val399Val (5.81%) and p.Arg413Pro (4.65%). Most of the variants were located in exons 7, 11, 3, 6 and 12. For the 43 families undergoing prenatal diagnosis, 9 fetuses (20.45%) were diagnosed with PKU, 20 (45.45%) were heterozygous carriers, and 15 (34.09%) did not carry the same pathogenic allele as the proband. All neonates were followed up till 6 months old, and the accuracy of prenatal diagnosis was 100%. The combination of high-throughput sequencing, Sanger sequencing, MLPA and linkage analysis can increase the diagnostic rate of PKU and attain accurate prenatal diagnosis.