A rare case of dicentric ring chromosome and derivative ring chromosome Chimera / 中华医学遗传学杂志

OBJECTIVE@#Utilize high-resolution chromosome analysis and microarray detection to determine the genetic etiology of infertility of a 32-year old female patient.@*METHODS@#The peripheral blood of the patient was cultured for high-resolution chromosome G and C banding karyotype analysis, and then 750K SNP-Array chip detection was performed.@*RESULTS@#Karyotype analysis results showed that the patient's karyotype was 45,XX,-13 [7]/46,XX,r(13) (p13q34) [185]/46,XX,dic r(13;13)(p13q34;p13q34) [14]/ 47,XX,+der(13;13;13;13) (p13q34;p13q34;p13q34; p13q34), dic r(13;13) [1]/ 46,XX [3]. The microarray results showed that the patient had a 3.3 Mb deletion in the 13q34 segment of chromosome 13, which may be related to infertility.@*CONCLUSION@#Infertility of the patient reported in this article may be related to the deletion of chromosome segment (13q34-qter).

Significance and case analysis of FMR1 mutation screening during early and middle pregnancy / 中华医学遗传学杂志

OBJECTIVE@#To screen for mutations of fragile X mental retardation 1 (FMR1) gene during early and middle pregnancy and provide prenatal diagnosis for those carrying high-risk CGG trinucleotide expansions.@*METHODS@#Peripheral blood samples of 2316 pregnant women at 12 to 21(+6) gestational weeks were collected for the extraction of genomic DNA. CGG repeats of the FMR1 gene were detected by fluorescence PCR and capillary electrophoresis. Genetic counseling and prenatal diagnosis were provided for 3 women carrying the premutations.@*RESULTS@#The carrier rate of CGG repeats of the FMR1 gene was 1 in 178 for the intermediate type and 1 in 772 for the premutation types. The highest frequency allele of CGG was 29 repeats, which accounted for 49.29%, followed by 30 repeats (28.56%) and 36 repeats (8.83%). In case 1, the fetus had a karyotype of 45,X, in addition with premutation type of CGG expansion of the FMR1 gene. Following genetic counseling, the couple chose to terminate the pregnancy through induced labor. The numbers of CGG repeats were respectively 70/- and 29/30 for the husband and wife. In case 2, amniocentesis was performed at 20 weeks of gestation. The number of CGG repeats of the FMR1 gene was 29/-. No abnormality was found in the fetal karyotype and chromosomal copy number variations. The couple chose to continue with the pregnancy. Case 3 refused prenatal diagnosis after genetic counseling and gave birth to a girl at full term, who had a birth weight of 2440 g and no obvious abnormality found during follow-up.@*CONCLUSION@#Pregnant women should be screened for FMR1 gene mutations during early and middle pregnancy, and those with high-risk CGG expansions should undergo prenatal diagnosis, genetic counseling and family study.

Prenatal diagnosis and genetic counseling in two pedigrees affected with infantile polycystic kidney disease due to PKHD1 gene mutations / 中华医学遗传学杂志

OBJECTIVE@#To detect potential mutations of the PKHD1 gene in two pedigrees affected with infantile polycystic kidney disease.@*METHODS@#Clinical data and peripheral venous blood samples were collected from the probands and their parents as well as fetal amniotic fluid cells. Genome DNA was extracted from the peripheral blood samples and amniotic fluid cells. Exons 32 and 61 of the PKHD1 gene were amplified with PCR and subjected to direct sequencing.@*RESULTS@#The proband of pedigree 1 was found to carry c.4274T>G (p.Leu1425Arg) mutation in exon 32 and c.10445G>C (p.Arg3482Pro) mutation in exon 61 of the PKHD1 gene, which were inherited from her father and mother, respectively. The fetus has carried the c.4274T>G (p.Leu1425Arg) mutation. In pedigree 2, the wife and her husband had respectively carried a heterozygous c.5979_5981delTGG mutation and a c.9455delA mutation of the PKHD1 gene. No chromosomal aberration was found in the umbilical blood sample, but the genetic testing of their fetus was failed. Based on software prediction, all of the 4 mutations were predicted to be pathogenic.@*CONCLUSION@#PKHD1 c.4274T>G (p.Leu1425Arg), c.10445G>C (p.Arg3482Pro), c.5979_5981delTGG and c.9455delA were likely to be pathogenic mutations. The results have facilitated genetic counseling and prenatal diagnosis for the two pedigrees.