Genetic analysis and reproductive intervention of 7 families with gonadal mosaicism for Duchenne muscular dystrophy / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for 7 families with gonadal mosaicism for Duchenne muscular dystrophy (DMD).@*METHODS@#For the 7 families presented at the CITIC Xiangya Reproductive and Genetic Hospital from September 2014 to March 2022, clinical data were collected. Preimplantation genetic testing for monogenic disorders (PGT-M) was carried out for the mother of the proband from family 6. Peripheral venous blood samples of the probands, their mothers and other patients from the families, amniotic fluid samples from families 1 ~ 4 and biopsied cells of embryos cultured in vitro from family 6 were collected for the extraction of genomic DNA. Multiplex ligation-dependent probe amplification (MLPA) was carried out for the DMD gene, and short tandem repeat (STR)/single nucleotide polymorphism (SNP)-based haplotypes were constructed for the probands, other patients, fetuses and embryos.@*RESULTS@#The results of MLPA showed that the probands and the fetuses/probands' brothers in families 1 ~ 4, 5, 7 had carried the same DMD gene variants, whilst the probands' mothers were all normal. The proband in family 6 carried the same DMD gene variant with only 1 embryo (9 in total) cultured in vitro, and the DMD gene of the proband's mother and the fetus obtained through the PGT-M were normal. STR-based haplotype analysis showed that the probands and the fetuses/probands' brothers in families 1 ~ 3 and 5 have inherited the same maternal X chromosome. SNP-based haplotype analysis showed that the proband from family 6 has inherited the same maternal X chromosome with only 1 embryo (9 in total) cultured in vitro. The fetuses in families 1 and 6 (via PGT-M) were both confirmed to be healthy by follow up, whilst the mothers from families 2 and 3 had chosen induced labor.@*CONCLUSION@#Haplotype analysis based on STR/SNP is an effective method for judging gonad mosaicism. Gonad mosaicisms should be suspected for women who have given births to children with DMD gene variants but with a normal peripheral blood genotype. Prenatal diagnosis and reproductive intervention may be adapted to reduce the births of further affected children in such families.

Identification and analysis of gene mutations of an neurofibromatosis type 1 patient / 中国医师杂志

Objective To explore mutation diagnosis and discuss the pathogenic and clinical characteristics of neurofibromatosis type 1 (NF1).Methods DNA sequencing combined with denaturing highperformance liquid chromatography (DHPLC) method was used to diagnose patients and parents.Results A new nonsense mutations c.503C ＞ G(p.S168 *) was identified.Conclusions NF1 is a rare autosomal dominant genetic disease.Most of them are caused by new mutations.Genetic diagnosis of sporadic cases is very important for treatment and the future generations.

Mutation screening of the TYR and P gene in three patients with oculocutaneous albinism / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify the mutations of the tyrosinase gene (TYR) and P gene in patients with oculocutaneous albinism (OCA).</p><p><b>METHODS</b>Polymerase chain reaction (PCR) and denaturing high performance liquid chromatography (DHPLC) were applied to detect the mutations in all exons of TYR gene and P gene. Then DNA sequencing and restriction endonuclease analysis were used to confirm the mutations detected by DHPLC. Novel mutations were screened in 100 unrelated persons with normal phenotypes to exclude the possibility of polymorphism.</p><p><b>RESULTS</b>Two mutations were detected in the P gene of the three patients and none in TYR gene. Heterozygous mutation of T450M in exon 13 of the P gene was detected in patient 1. Patient 2 had a heterozygous mutation of T450M in exon 13 and a heterozygous mutation of G775R in exon 23 of the P gene. Patient 3 had a heterozygous mutation of G775R as well. Restriction endonuclease analysis of the P gene exon 13 showed that the Oli I site had partly disappeared resulting from the heterozygous mutation T450M in patient 1 and patient 2, but not in 100 unrelated individuals. The heterozygous mutation T450M is a novel mutation.</p><p><b>CONCLUSION</b>Gene diagnosis of OCA can be carried out effectively by combining PCR, DHPLC, DNA sequencing and restriction endonuclease analysis.</p>

Mutation screening and prenatal diagnosis of Wilson's disease by denature high performance liquid chromatography / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To study the clinical application of denature high performance liquid chromatography (DHPLC) technique on mutation screening and prenatal diagnosis for Wilson's disease (WD).</p><p><b>METHODS</b>Genomic DNA of the probands with Wilson's disease and their parents from 6 families was subjected to polymerase chain reaction (PCR) for the 21 exons and the 5' untranslated region of ATP7B gene. Mutation screening of the PCR products was performed by DHPLC. The abnormal peaks were confirmed by further sequencing analysis. Based on the successful gene diagnosis for the patients, prenatal diagnosis was performed in 4 families, including 1 twin and 3 singletons.</p><p><b>RESULTS</b>Five disease-causing mutations and 8 polymorphisms were found in the 6 probands by DHPLC and sequencing. The parents were carriers with the same mutation as their affected children. Prenatal diagnosis showed that two pregnancies were abnormal, including a twin pregnancy with compound heterozygote for Arg778Leu and IVS4-1G>C mutation, and a single pregnancy with a compound heterozygote for Ser975Tyr and Pro992Leu mutations. These two pregnancies were terminated after genetic counseling. Another two pregnancies included a singleton carrier with Ser975Tyr mutation and a normal genotype fetus, respectively. These two pregnancies were continued and the babies were healthy.</p><p><b>CONCLUSION</b>DHPLC is a powerful tool in prenatal diagnosis as well as in postnatal diagnosis.</p>