R176X mutant homozygote in phenylketonuria firstly detected in Hui nationality in China: One case report / 中国组织工程研究

ABSTRACT

BACKGROUND: Phenylketonuria is caused by gene mutation of phenylalanine hydroxylasel (PAH), which is mainly induced by permutation, short segments and insertion of base.OBJECTIVE: To evaluate the gene mutation of phenylalanine hydroxylasel in phenylketonuria in Hui nationality.DESIGN: Open study.SETTING: Urumqi General Hospital of Lanzhou Military Area Command of Chinese PLA; Capital Pediatrics Institute.PARTICIPANTS: A boy of Hui nationality in China and aged 3.1 years was selected in this study. The boy had intellect hysteresis in his one year and received medical treatment in his three years, while he was diagnosed as cerebral paralysis. After repeatedly inefficient treatment, he was hospitalized in our hospital on December 13, 2004. Iron sesquichloride in urine was strongly positive and concentration of serum phenylalanine was 1 680 μmol/L; therefore, he was diagnosed as the typical phenylketonuria.METHODS: 5 mL venous blood was selected from the boy and his parents, respectively, and anticoagulated with EDTA-Na2. DNA in gene group was extracted by using typical phenol/chloroform method. In addition, polymerase chain reaction (PCR) primer sequence of extron 7, 6, 11, 3, 12 and 5 of PAH gene was designed based on references. And then, PCR products were detected with 2% agarose gel electrophoresis. 5 μL PCR products were mixed with the same volume of degenerated buffer solution, degenerated at 97 ℃ for 5 minutes, put in iced bath and performed with 80 g/Lnon-degenerated polyacrylamide gel electrophoresis. After that, the products were dealt with sliver staining routinely, and single strand DNA banding patterns were analyzed and recorded. ABI377 automatic sequenator (PE Company) was used to detect PCR sequence and purify PCR product in Shanghai Boya Biotechnology Company.MAIN OUTCOME MEASURES: Iron sesquichloride in urine, concentration of serum phenylalanine and mutant gene types of phenylalanine hydroxylase.RESULTS: Extron 7, 6, 11, 3, 12 and 5 of PAH gene were analyzed in the boy and his parents. The results demonstrated that SSCP electrophoresis in extron 6 was different from that in the normal control group. Site of electrophoresis strip of his father was coincident with that of his mother, but different from that of the boy. Sequencing results indicated that point mutation (cytosine replaced by thymine), which was a R176X mutant heterozygote, occurred at the 526th site of cDNA of phenylalanine hydroxylase gene in his parents; however, two chromosomes of the boy had mutation at the same site, which was R176X mutant homozygote.CONCLUSION: Mutation of R176X homozygote of phenylketonurea is firstly reported in Hui nationality in China.