[Rapid genetic prenatal diagnosis for achondroplasia].

OBJECTIVE: To explore the genetic prenatal diagnosis method for achondroplasia (ACH).

METHODS: During May to November 2007, three ACH pedigrees were diagnosed at the Prenatal Diagnosis Center, Department of Obstetrics and Gynecology, Affiliated Drum Tower Hospital of Medical College, Nanjing University. In family 1, there was a 6-month-old male ACH infant. In family 2, the expectant mother, with 18 weeks of pregnancy, was an ACH patient. Amniocentesis was performed for prenatal diagnosis. The fetus of family 3 was diagnosed as ACH by ultrasound examination on the 39th week of gestation. Umbilical cord blood of this fetus was collected for examination. Totally, three methods, restriction enzyme (SfcI and MspI) digestion analysis, denaturing high performance liquid chromatography (DHPLC) and sequencing analysis were performed simultaneously to detect the pathogenic mutation of fibroblastic growth factor receptor 3 (FGFR3) for the three ACH families.

RESULTS: (1) The DHPLC detection: heteroduplex was detected in the patient of family 1; both the patient and the fetus of family 2 showed heteroduplex results; the result of the fetus of family 3 was also heteroduplex. (2) The enzyme digestion analysis for the PCR products of 10 exon of FGFR3: after SfcI digestion, the PCR products of patients and the fetus of family 1 and 2 showed not only the band of 247 bp, but also bands of 162 bp and 85 bp. But their PCR products could not be digested by MspI, and it only showed the band of 247 bp. For the fetus of family 3, the PCR products could not be digested by SfcI, while after digestion by MspI, bands of 162 bp and 85 bp were shown up. The PCR products of the normal control could be digested by neither SfcI nor MspI. (3) The sequencing results: the heterozygote mutation of 1138 G-->A was confirmed in the patient of family 1. The pregnant woman and her fetus in family 2 showed the same result. The heterozygote mutation of G-->C was confirmed in the fetus of family 3. The site of 1138 was G homozygote in the normal control. The three detection results of the fetus in family 2 were the same as that of the mother, which means that the fetus inherited the same pathogenic mutation from his or her mother.

CONCLUSIONS: Both DHPLC and restriction enzyme digestion analysis could detect the mutation of FGFR3 gene, but DHPLC is more rapid, convenient and sensitive. So DHPLC can be applied to genetic diagnosis and prenatal diagnosis for ACH patients.