Characterization of PAH Gene Mutations and Analysis of Genotype-Phenotype Correlation in Patients with Phenylalanine Hydroxylase Deficiency from Fujian Province, Southeastern China

Phenylalanine hydroxylase deficiency (PAHD) is the most prevalent inborn error of amino acid metabolism in China, has a complex phenotype with many variants and genotypes among different populations. Here, we analyzed the phenylalanine hydroxylase（ PAH ） gene mutations in a cohort of 93 PAHD patients from Fujian Province. And, the analysis of genotype and phenotype correlation in patients with PAHD was also determined. 44 different pathogenic variants were identified, including five novel variants. The three most prevalent mutations among all patents were p.Arg53His (18.03%), p.Arg241Cys (14.75%), and p.Arg243Gln (7.65%). The frequency of the p.Arg53His variant was the highest in patients with mild hyperphenylalaninemia (MHP), while the frequency of the p.Val399= and p.Arg111Ter variants was the highest in patients with classic phenylketonuria(cPKU). The most abundant genotypes observed in PAHD patients were p.Arg53His/p.Arg243Gln, p.Arg53His/p.IVS4-1G>A, and p.Arg53His/p.Arg241Cysp. As for the genotype-phenotype prediction, the APV/GPV system performed well in predicting the actual phenotype, as the overall consistency rate was 85.71% for PAHD patients. In conclusion, we established a PAH gene mutation spectrum in the PAHD patients in Southeastern China. A quantitative correlation analysis between genotype and phenotype severity is helpful for genetic counseling and management.

Blood phenylalanine reduction reverses gene expression changes observed in a mouse model of phenylketonuria

Phenylketonuria (PKU) is a genetic deficiency of phenylalanine hydroxylase (PAH) in liver resulting in blood phenylalanine (Phe) elevation and neurotoxicity. A pegylated phenylalanine ammonia lyase (PEG-PAL) metabolizing Phe into cinnamic acid was recently approved as treatment for PKU patients. A potentially one-time rAAV-based delivery of PAH gene into liver to convert Phe into tyrosine (Tyr), a normal way of Phe metabolism, has now also entered the clinic. To understand differences between these two Phe lowering strategies, we evaluated PAH and PAL expression in livers of PAHenu2 mice on brain and liver functions. Both lowered brain Phe and increased neurotransmitter levels and corrected animal behavior. However, PAL delivery required dose optimization, did not elevate brain Tyr levels and resulted in an immune response. The effect of hyperphenylalanemia on liver functions in PKU mice was assessed by transcriptome and proteomic analyses. We observed an elevation in Cyp4a10/14 proteins involved in lipid metabolism and upregulation of genes involved in cholesterol biosynthesis. Majority of the gene expression changes were corrected by PAH and PAL delivery though the role of these changes in PKU pathology is currently unclear. Taken together, here we show that blood Phe lowering strategy using PAH or PAL corrects both brain pathology as well as previously unknown lipid metabolism associated pathway changes in liver.

Telehealth and COVID-19: Empowering Standards of Management for Patients Affected by Phenylketonuria and Hyperphenylalaninemia

Phenylketonuria (PKU) and Hyperphenylalaninemia (HPA) are inborn errors of metabolism (IEM) due to mutations in the PAH gene resulting in increased blood phenylalanine (Phe) concentrations. Depending on the Phe levels, a lifelong dietary intervention may be needed. During the COVID-19 pandemic, finding new strategies to ensure follow-up and metabolic control for such patients became mandatory and telehealth was identified as the most eligible tool to provide care and assistance beyond barriers. The aim of this study was to evaluate how telehealth use may have impacted disease follow-ups. Seven hundred and fifty-five patients affected by PKU/HPA in follow-ups at the Clinical Department of Pediatrics (San Paolo Hospital, ASST Santi Paolo e Carlo, University of Milan, Italy) were included in this study. The data regarding the used telehealth model, type of performed consultations and patients’ perspectives were retrospectively collected and analyzed after a one-year experience of implemented follow-ups. The results demonstrated that telehealth seemed to be a useful tool to improve the adherence to treatment and that it could guarantee continuous assistance and care beyond the surrounding epidemiological status. Patients expressed great satisfaction with the offered services and requested that they were implemented in standards of care on a long-term basis. Our results suggested the implementation of telehealth in the management guidelines for PKU/HPA patients.

Clinical and Genetic Characteristics of Phenylketonuria in Ryazan Region

Aim. This investigation seeks to determine the incidence of phenylketonuria in the Ryazan region, assess the spectrum of mutations in the PAH gene (phenylalanine hydroxylase), investigate the interrelationship between the diseases clinical course, the phenylalanine blood level, and the patients genotype. Materials and Methods. The incidence of phenylketonuria was studied based on the data of massive neonatal screening for the period from 2000 to 2019. Molecular genetic examination of mutations was conducted in 39 patients using the allele-specific multiplex ligation method. The interrelationship between the phenylalanine blood level on the fifth day of life and retest, the diseases clinical course, and the patients genotype was assessed according to the medical record data of 33 patients under dispensary observation in a medico-genetic clinic. The patients were divided into two groups. The first group (n=21) had two severe mutations (residual activity of phenylalanine hydroxylase 10%). The second group (n=12) had one severe and one mild mutation (the residual activity of the enzyme 10%). Results. The incidence of phenylketonuria in the Ryazan region was one in 5054 newborns, exceeding the Russian Federations average parameters. Eighteen mutations were discovered in the PAH gene. The most frequent was the R408W mutation (56.4% alleles). The second most frequent mutations were the IVS10-11GA (6.4%) and P281L (5.1%). The R158Q and Y418C mutations occurred with a frequency of 4.1% and Е280К mutation of 2.7%. All the rest of the mutations occurred as single cases. Investigation of the interrelationship between the phenylalanine blood level, the diseases clinical course, and the patients genotype revealed a reliably higher content of amino acid in the first group on retest (32.11.7 mg/% vs. 17.71.5 mg/% in the second group, р0.001) and predomination of more severe forms of phenylketonuria (90.5% vs. 41.7%, respectively, р0.001). Disorders in neuropsychic and speech development were present in 28.6% of patients in the first group but were absent in the second group. Conclusion. By conducting the study, the incidence of phenylketonuria was determined in the Ryazan region. The spectrum of mutations in the PAH gene was defined. The interrelationship between the diseases clinical portrait, the phenylalanine blood level, and the patients PAH genotype was revealed.

PATHOGENETIC POTENTIAL OF THE MUTATIONS OF PAH GENE

Some associations were also observed in this study andone of them, including R243X mutation and V245V polymorphism. The mean quality value of surrounding nucleotides of these variants was higher than 50 which proved their accuracy. The R261Q mutation in exon 7 was observed in seven patients from 30 patient. Studies have shown that this mutation is most common in the Azerbaijani population. Being R261G (G-A) mutation we have found a substitution of guanine with adenine. The result of mutation was on protein level, and arginine amino acid was substituted with gluthamine amino acid.