Genetic analysis of a gonadal-mosaicism BMD family with prenatal diagnosis and PGT-M / 中华检验医学杂志

Objective:To identify the pathogenic characteristics of a suspected gonadal mosaicism Becker muscular dystrophy (BMD) family, and provide provide basis for pregnancy selection of similar families.Methods:A BMD family admitted to Hunan Jiahui Genetics Hospital from June 2012 to September 2019 was systematically reviewed. The medical history and family history of the proband were checked, and multiplex ligation-dependent probe amplification was used to detect the deletion/duplication of 79 exons of the Duchenne muscular dystrophy (DMD) gene in the proband, fetuses, and parents. Moreover, potential variants were verified by combining PCR amplification, short tandom repeat polymorphic linkage analysis, and real-time fluorescence quantitative PCR. High-quality embryos are screened for transplantation after preimplantation genetic testing for monogenic (PGT-M). And amniotic fluid was collected in the second trimester for prenatal diagnostic verification.Results:According to the phenotype analysis of the proband, the initial clinical diagnosis was BMD, and the exon 45-50 deletion in DMD gene was detected. The mutation was not detected in the mother′s peripheral blood, but when she was pregnant again, the prenatal diagnosis showed that the fetus had the same deletion mutation as the proband. Neither of two vitro embryos tested by PGT-M has the deletion mutation, then single embryo transfer was performed nor was pregnancy successful. After confirmation of prenatal diagnosis during pregnancy, a normal baby girl was born by full-term cesarean section.Conclusions:This BMD family was a family with two consecutive BMD homodeletion mutations, and the mutation of the DMD gene was not detected in the peripheral blood of the proband′s mother and two embryonic cells, suggesting that the mother may be a gonad chimeric carrier of this deletion mutation. The combined application of prenatal diagnosis and PGT-M provides a reference approach to effectively avoid the birth of similar children.

A typical Say-Barber-Biesecker/Young-Simpson syndrome caused by heterozygous mutation of KAT6B gene / 中华实用儿科临床杂志

A patient with global developmental delay and facial abnormality treated in Hunan Maternal and Child Health Care Hospital in September 2018 was diagnosed as a typical Say-Barber-Biesecker/Young-Simpson syndrome (SBBYSS)accompanied with comprehensive clinical manifestations and genetic testing was carried out.The patient carries a heterozygous synonymous mutation of KAT6B gene (NM_012330.3)c.3147G>A (p.P1049P), thus leading to the formation of a new cleavage site (receptor) and forming a new truncated protein.In Chinese, this is the second typical SBBYSS that has been identified and the first prenatal genetic diagnosis has been performed.This study has broadened the mutation spectrum of SBBYSS caused by the mutation of KAT6B gene in Chinese population.

Detection of Spinal Muscular Atrophy Using a Duplexed Real-Time PCR Approach With Locked Nucleic Acid-Modified Primers

Background@#Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder mainly caused by homozygous deletions that include exon 7 of the survival motor neuron 1 (SMN1) gene. A nearby paralog gene, SMN2, obstructs the specific detection of SMN1. We optimized a duplexed real-time PCR approach using locked nucleic acid (LNA)-modified primers to specifically detect SMN1. @*Methods@#An LNA-modified primer pair with 3´ ends targeting SMN1 specific sites c.835-44g and c.840C was designed, and its specificity was examined by real-time PCR and Sanger Sequencing. A duplexed real-time PCR approach for amplifying SMN1 and control gene albumin (ALB) was developed. A randomized double-blind trial with 97 fresh peripheral blood samples and 25 dried blood spots (DBS) was conducted to evaluate the clinical efficacy of the duplexed approach. This new approach was then used to screen 753 newborn DBS. @*Results@#The LNA-modified primers exhibited enhanced specificity and 6.8% increased efficiency for SMN1 amplification, compared with conventional primers. After stabilizing the SMN1 test by optimizing the duplexed real-time PCR approach, a clinical trial validated that the sensitivity and specificity of our new approach for detecting SMA patients and carriers was 100%. Using this new approach, 15 of the screened 753 newborns were identified as carriers via DBS, while the rest were identified as normal individuals. These data reveal a carrier rate of 1.99% in Hunan province, South Central China. @*Conclusions@#We have developed a novel, specific SMN1 detection approach utilizing real-time PCR with LNA-modified primers, which could be applied to both prenatal carrier and newborn screening.

Biochemical and genetic characteristics of 40 neonates with carnitine deficiency / 中南大学学报(医学版)

OBJECTIVES@#Primary carnitine deficiency (PCD) is a rare fatty acid metabolism disorder that can cause neonatal death. This study aims to analyze carnitine levels and detect SLC22A5 gene in newborns with carnitine deficiency, to provide a basis for early diagnosis of PCD, and to explore the relationship between carnitine in blood and SLC22A5 genotype.@*METHODS@#A total of 40 neonates with low free carnitine (C0G (p.Y251C), c.495 C>A (p.R165E), and c.1298T>C (p.M433T). We found 14 PCD patients including 2 homozygous mutations and 12 heterozygous mutations, 14 with 1 mutation, and 12 with no mutation among 40 children. The C0 concentration of children with SLC22A5 gene homozygous or complex heterozygous mutations was (4.95±1.62) μmol/L in the initial screening, and (3.90±1.33) μmol/L in the second screening. The C0 concentration of children with no mutation was (7.04±2.05) μmol/L in the initial screening, and (8.02±2.87) μmol/L in the second screening. There were significant differences between children with homozygous or compound heterozygous mutations and with no mutation in C0 concentration of the initial and the second screening (both @*CONCLUSIONS@#There are 5 new mutations which enriched the mutation spectrum of SLC22A5 gene. C0<5 μmol/L is highly correlated with SLC22A5 gene homozygous or compound heterozygous mutations. Children with truncated mutation may have lower C0 concentration than that with untruncated mutation in the initial screening.

Prenatal diagnosis for 30 women carrying a FMR1 mutation / 中华医学遗传学杂志

OBJECTIVE@#To determine the CGG repeat number and methylation status of FMR1 gene for fetuses whose mothers have carried a FMR1 mutation.@*METHODS@#For 30 pregnant women, the fetal CGG repeat number was determined with a GC-rich PCR system by using chorionic villus, amniotic fluid or umbilical blood samples. The methylation status of the FMR1 gene was confirmed with Southern blotting.@*RESULTS@#In total 30 prenatal diagnoses were performed for 29 carriers of FMR1 gene mutations and 1 with FMR1 gene deletion mosaicism. Three fetuses were found to carry premutations, 9 were with full mutations and 1 with mosaicism of premutation and full mutations. Eighteen fetuses were normal.@*CONCLUSION@#Considering the genetic complexity of Fragile X syndrome (FXS), single method may not suffice accurate determination of their genetic status. The pitfalls and technical limitations of protocols requires adoption of personalized strategy for its prenatal diagnosis.

Prenatal diagnosis for 30 women carrying a FMR1 mutation / 中华医学遗传学杂志

Objective@#To determine the CGG repeat number and methylation status of FMR1 gene for fetuses whose mothers have carried a FMR1 mutation.@*Methods@#For 30 pregnant women, the fetal CGG repeat number was determined with a GC-rich PCR system by using chorionic villus, amniotic fluid or umbilical blood samples. The methylation status of the FMR1 gene was confirmed with Southern blotting.@*Results@#In total 30 prenatal diagnoses were performed for 29 carriers of FMR1 gene mutations and 1 with FMR1 gene deletion mosaicism. Three fetuses were found to carry premutations, 9 were with full mutations and 1 with mosaicism of premutation and full mutations. Eighteen fetuses were normal.@*Conclusion@#Considering the genetic complexity of Fragile X syndrome (FXS), single method may not suffice accurate determination of their genetic status. The pitfalls and technical limitations of protocols requires adoption of personalized strategy for its prenatal diagnosis.