Analysis of D4Z4 mutation in a child with facioscapulohumeral muscular dystrophy presented initially as mental retardation / 中华医学遗传学杂志

OBJECTIVE@#To identify pathological mutation of D4Z4 in a child with facioscapulohumeral muscular dystrophy (FSHD) presented initially as mental retardation.@*METHODS@#Wechsler Intelligence Scale for Children Revised in China (WISC-IV) was used to assess the patient's IQ. Other clinical data was also collected. With genomic DNA extracted from peripheral blood samples, the child and his parents were subjected to medical exome sequencing and copy number variation analysis by next generation sequencing (NGS). The D4Z4 repeats and their origin source were determined by molecular combing.@*RESULTS@#By the WISC-IV test, the child was found to have a total IQ of 41, with a speech comprehension IQ of 45, and perceptual inference index IQ of 52. No pathological mutation was detected by NGS. By molecular combing method, the child was found to carry a D4Z4 spanning 5.2 kb with a copy number of 2. Analysis of his parents indicate that the mutation was de novo.@*CONCLUSION@#The D4Z4 copy number variation may account for the FSHD and mental retardation in the child. The molecular combing method can be used to identify the number of repeat units and facilitate the diagnosis of FSHD.

Prenatal diagnosis of two families with megalencephalic leukoencephalopathy with subcortical cysts / 中华围产医学杂志

Objectives To provide genetic counseling and prenatal molecular diagnosis for two families with megalencephalic leukoencephalopathy with subcortical cysts (MLC).Methods Two MLC patients (probands 1 and 2) were admitted to the Department of Pediatrics of Peking University First Hospital in June 2011 and June 2009,respectively.Peripheral blood was collected and DNA sequencing was performed for genetic analysis for the two MLC patients and their parents.Amniotic fluid and villus of two fetuses (fetus 1 and 2) were collected at 21+4 and 12+3 weeks of gestational age from their mothers when they were pregnant again.The genomic DNA of the two fetuses was extracted and corresponding sites of MLC1 gene were sequenced.Haplotype analysis using a combination of 3 microsatellite markers (AR,DXS6807 and DXS6797) on chromosome X and sex determining region of Y chromosome was performed to detect maternal cell contamination.Verification of the prenatal molecular diagnosis and follow up study after birth were conducted for both fetuses.Results Macrocephaly,motor development delay and typical findings on brain MRI were identified in the two probands,and were clinically diagnosed with MLC.Compound heterozygous mutations were detected in proband 1 [c.353C＞T (p.T118M) and c.803C＞G (p.T268R)] and proband 2 [c.353C＞T (p.T118M) and c.836T＞C(p.L279P)],respectively.MLC was genetically diagnosed.Heterozygous variation in c.353[c.353C＞T (p.T118M)] and wild c.803C were identified in fetus 1,and both wild c.353C and c.836T were found in fetus 2.No maternal cell contamination was detected in both fetuses.Sequencing the corresponding sites after birth confirmed the prenatal diagnosis,and the head circumference and motor development were normal in fetus 1 at 5 months old.No macrocephaly was found and no DNA sequencing was done in fetus 2 at one month old.Conclusions Genetic counseling and prenatal molecular diagnosis for MLC families combined with clinical and genetic diagnosis are important in preventing MLC.Haplotype analysis with a combination of three microsatellite markers on chromosome X and sex determining region of Y chromosome is useful in detecting maternal cell contamination and avoiding its influence on prenatal diagnosis,and confirming the reliability of prenatal diagnosis.