Assessment of Pathogenic Variants in the PAH Gene and Genotype-Phenotype Correlation in Phenylketonuria Patients from Turkey.

This study aims to determine the allele and genotype frequency, evaluate genotype-phenotype correlation and contribute to the spectrum of pathogenic variants in the PAH gene. Ninety-three individuals diagnosed with PKU were included in the study. Next-generation sequencing was utilized for detecting variants in the PAH gene. Copy Number Variations in patients without biallelic pathogenic variant were investigated by Multiplex Ligation-dependent Probe Amplification method. Genotype-phenotype correlations and genotype-based phenotype predictions were examined by comparing molecular test results with BIOPKUdb database. The clinical distributions of the patients were as follows: classic PKU 21% (n = 19), mild PKU 3% (n = 3), and mild hyperphenylalaninemia 76% (n = 71), respectively. Thirty-nine distinct variants and 70 distinct genotypes were found in patients. The most frequently observed variant was p.(Ala300Ser) (13.9%) and the most frequently observed genotype was p.[Ala300Ser];[Ala300Ser] (5.6%). Compound heterozygous genotypes (%69) were more prevalent than homozygous genotypes. A novel variant, c.441+4A>C, was observed. Predicted metabolic phenotypes in the database showed consistency with patient phenotypes (n = 33/41). BH4 responsiveness showed partial consistency with database predictions (n = 13/25). Establishing genotype-phenotype correlations can facilitate personalized management approaches. Overall, this study contributes to understanding the genetic basis and clinical course of PKU.

Genetic Landscape and Clinical Features of Hyperphenylalaninemia in North Ossetia-Alania: High Frequency of P281L and P211T Genetic Variants in the PAH Gene.

This study, conducted in the Republic of North Ossetia-Alania (RNOA), aimed to explore the genetic landscape of hyperphenylalaninemia (HPA) and phenylketonuria (PKU) in the Ossetian population using data from newborn screening (NBS). Through comprehensive molecular genetic analysis of 29 patients with HPA from diverse ethnic backgrounds, two major genetic variants in the PAH gene, P281L and P211T, were identified, constituting 50% of all detected pathogenic alleles in Ossetian patients. Remarkably, these variants exhibited an exceptionally high frequency in the Ossetian population, surpassing global prevalence rates. This study unveiled a notable prevalence of mild forms of HPA (78%), underscoring the importance of genetic counseling for carriers of pathogenic variants in the PAH gene. Moreover, the findings emphasized the necessity for ongoing monitoring of patients with mild forms, as they may lack significant symptoms for diagnosis, potentially impacting offspring. Overall, this research offers valuable insights into the genetic landscape of HPA and PKU in the Ossetian population.

Variants of the phenylalanine hydroxylase gene in neonates with phenylketonuria in Hainan, China.

OBJECTIVE: To investigate the incidence of phenylalanine hydroxylase (PAH) deficiency and PAH genotypes in neonates in Hainan, China. Methods: We performed heal stick to collect blood and obtain dry blood spot specimens from newborns in Hainan from January 2007 to December 2016. Phenylalanine (Phe) concentration in these dry blood spots was measured by the fluorescence method to screen phenylketonuria (PKU). For suspicious samples, the genotypes of the PAH gene were amplified by biotin labeled oligonucleotide primers. Polymerase chain reaction (PCR) products were then analyzed by flow-through hybridization to detect genotypes. At the same time, peripheral blood samples of children suspicious of PKU and their parents were used to perform gene sequencing. Results: Of the 914,520 newborns screened, 29 of them had PAH deficiency. The incidence of PAH deficiency in Hainan was 3.17/100,000. A total of 58 mutant alleles belonging to 15 different types were identified in the 29 patients. In terms of genotypes frequency, the top 4 were: c.611A > G 20.7% (12/58) , c.728G > A 17.2%, c.158G > A 15.2% (9/58) and c.721C > T 13.8% (8/58). The frequencies of other genotypes were all below 10%. Conclusion: The incidence of PAH deficiency in Hainan is relatively high among all provinces in southern China. With a total frequency of 67.2%, c.611A > G, c.728G > A, c.158G > A and c.721C > T, and are the most common PAH gene genotypes.

Spectrum of PAH gene variants among a population of Han Chinese patients with phenylketonuria from northern China.

BACKGROUND: Phenylketonuria (PKU), which primarily results from a deficiency of phenylalanine hydroxylase (PAH), is one of the most common inherited inborn errors of metabolism that impairs postnatal cognitive development. The incidence of various PAH variations differs by race and ethnicity. The aim of the present study was to characterize the PAH gene variants of a Han population from Northern China. METHODS: In total, 655 PKU patients and their families were recruited for this study; each proband was diagnosed both clinically and biochemically with phenylketonuria. Subjects were sequentially screened for single-base variants and exon deletions or duplications within PAH via direct Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). RESULTS: A spectrum of 174 distinct PAH variants was identified: 152 previously documented variants and 22 novel variants. While single-base variants were distributed throughout the 13 exons, they were particularly concentrated in exons 7 (33.3%), 11 (14.2%), 6 (13.2%), 12 (11.0%), 3 (10.4%), and 5 (4.4%). The predominant variant was p.Arg243Gln (17.7%), followed by Ex6-96A > G (8.3%), p.Val399 = (6.4%), p.Arg53His (4.7%), p.Tyr356* (4.7%), p.Arg241Cys (4.6%), p.Arg413Pro (4.6%), p.Arg111* (4.4%), and c.442-1G > A (3.4%). Notably, two patients were also identified as carrying de novo variants. CONCLUSION: The composition of PAH gene variants in this Han population from Northern China was distinct from those of other ethnic groups. As such, the construction of a PAH gene variant database for Northern China is necessary to lay a foundation for genetic-based diagnoses, prenatal diagnoses, and population screening.

Mutation analysis of the PAH gene in phenylketonuria patients from Rio de Janeiro, Southeast Brazil.

BACKGROUND: Phenylketonuria (PKU) is an autosomal recessive disease resulting from mutations in the PAH gene. Most of the patients are compound heterozygotes, and genotype is a major factor in determining the phenotypic variability of PKU. More than 1,000 variants have been described in the PAH gene. Rio de Janeiro's population has a predominance of Iberian, followed by African and Amerindian ancestries. It is expected that most PKU variants in this Brazilian state have originated in the Iberian Peninsula. However, rare European, African or pathogenic variants that are characteristic of the admixed population of the state might also be found. METHODS: A total of 102 patients were included in this study. Genomic DNA was isolated from dried blood spots. Sanger sequencing was used for PAH gene variant identification. Deletions and duplications were also screened using MLPA analysis. Haplotypes were also determined. RESULTS: Nine (8.8%) homozygous and 93 (91.2%) compound heterozygous patients were found. The spectrum included 37 causative mutations. Missense, nonsense, and splicing pathogenic variants corresponded to 63.7%, 2.9%, and 22.6% of the mutant alleles, respectively. Large (1.5%), and small deletions, inframe (5.4%) and with frameshift (3.9%), comprised the remainder. The most frequent pathogenic variants were: p.V388M (12.7%), p.R261Q (11.8%), IVS10-11G>A (10.3%), IVS2+5G>C (6.4%), p.S349P (6.4%), p.R252W (5.4%), p.I65T (4.4%), p.T323del (4.4%), and p.P281L (3.4%). One novel variant was detected: c.934G>T (p.G312C) [rs763115697]. CONCLUSION: The three most frequent pathogenic variants in our study (34.8% of the alleles) were also the most common in other Brazilian states, Portugal, and Spain (p.V388M, p.R261Q, IVS10-11G>A), corroborating that the Iberian Peninsula is the major source of PAH mutations in Rio de Janeiro. Pathogenic variants that have other geographical origins, such IVS2+5G>C, p.G352Vfs*48, and IVS12+1G>A were also detected. Genetic drift and founder effect may have also played a role in the mutation spectrum we observed.

Mutations of the phenylalanine hydroxylase gene in Iranian patients with phenylketonuria.

Phenylketonuria (PKU) is an autosomal recessive disease which results from mutations in the phenylalanine hydroxylase (PAH) gene. The aim of this study was the identification of sixteen different mutations in Iranian patients with hyperphenylalaninemia. The mutations were detected during the characterization of PAH genotypes of 39 PKU patients from Qazvin and Zanjan provinces of Iran. PAH mutations have been analyzed by PCR and direct sequencing of PCR products of the promoter region and all 13 exons of PAH gene, including the splicing sites. A mutation detection rate of 74.3 % was realized. Two mutations were found at high frequencies: R176X (10.25 %) and p.P281L (10.25 %). The frequencies of the other mutations were: IVS2+5G>A (2.56 %), IVS2+5G>C (2.56 %), p.L48S (2.56 %), p.R243Q (2.56 %), p.R252Q (5.12 %), p.R261Q (7.69 %), p.R261X (5.12 %), p.E280K (2.56 %), p.I283N (2.56 %), IVS9+5G>A (2.56 %), IVS9+1G>A (1.28 %), IVS11+1G>C (1.28 %), p.C357R (1.28 %), c.632delC (2.56 %). The present results confirm the high heterogeneity of the PAH locus and contribute to information about the distribution and frequency of PKU mutations in the Iranian population.

Association Between PAH Mutations and VNTR Alleles in the West Azerbaijani PKU Patients.

INTRODUCTION: We report the frequency of IVS10nt546, R261Q, S67P, R252W, and R408W mutations linked to PAH VNTR alleles in the west Azerbaijani PKU patients. MATERIAL AND METHODS: VNTR alleles and IVS10nt546, R261Q, S67P, R252W, R408W mutations were studied in a total of 20 PKU patients by PCR and RFLP-PCR. OUTCOMES: Our analysis showed that 95% of cases were homozygote for an allele containing eight-repeat VNTR (VNTR8); while 5% were homozygote for an allele containing three-repeat VNTR (VNTR3). The IVS10nt546, R252W, and R261Q mutations were associated with VNTR8 allele, and also, R252W and S67P mutations were associated with VNTR3 allele. VNTR8 was common among mutant alleles as were IVS10nt546-VNTR8 (50%), R252W-VNTR8 (2.5%), and R261Q-VNTR8 (22.5%). The association of VNTR3 was found as R252W-VNTR3 (2.5%) and S67P-VNTR3 (2.5%) among studied cases. The frequency of IVS10nt546-VNTR8/IVS10nt546-VNTR8, IVS10nt546-VNTR8/ND-VNTR8, IVS10nt546-VNTR8/R252W-VNTR8, R261Q-VNTR8/R261Q-VNTR8, R261Q-VNTR8/ND-VNTR8, and S67P-VNTR3/ R252W-VNTR3 were 30%, 35%, 5%, 20%, 5%, and 5%, respectively. R408W mutation was not found in this study. CONCLUSIONS: The present report is the first in its own kind in the west Azerbaijani population (Iran) and implies that the most common PKU mutation in this population, IVS10nt546, is exclusively associated with VNTR8 allele, and IVS10nt546-VNTR8 alleles testing should be considered for routine carrier screening and prenatal diagnostic setting.