Analysis of ARID1B gene variants in two Chinese pedigrees with Coffin-Siris syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for two Chinese pedigrees affected with Coffin-Siris syndrome (CSS).@*METHODS@#Whole exome sequencing (WES) was carried out for the probands. Candidate variants were verified by Sanger sequencing of the probands and their family members.@*RESULTS@#The two probands were respectively found to harbor a heterozygous c.5467delG (p.Gly1823fs) variant and a heterozygous c.5584delA (p.Lys1862fs) variant of the ARID1B gene, which were both of de novo in origin and unreported previously. Based on the guidelines of American College of Medical Genetics and Genomics, both variants were predicted to be pathogenic (PVS1+PS2+PM2).@*CONCLUSION@#The c.5467delG (p.Gly1823fs) and c.5545delA (p.Lys1849fs) variants of the ARID1B genes probably underlay the CSS in the two probands. Above results have enabled genetic counselling and prenatal diagnosis for the pedigrees.

Mutation analysis and prenatal diagnosis for 50 pedigrees affected with Duchenne/Becker muscular dystrophy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To establish individualized prenatal diagnosis program for families affected with Duchenne/Becker muscular dystrophy (DMD/BMD) and different clinical background using a variety of methods.</p><p><b>METHODS</b>Multiplex ligation-dependent probe amplification (MLPA) was performed on 50 patients suspected for DMD/BMD. For single exon deletions of the DMD gene, PCR was used for validating the results. For those without any deletion or duplication, Sanger sequencing was used to screen for DMD gene mutations in the children and their mothers. Prenatal genetic testing was provided to female carriers using chorionic villus, amniocentesis or cord blood samples. To ensure the accuracy of diagnosis, all prenatal specimens were also subjected to linkage analysis.</p><p><b>RESULTS</b>Among the 50 patients with DMD/BMD, 23 harbored large deletions, 11 only had single exon deletions, 10 harbored duplications, and 5 had small scare mutations. No mutation was detected in one family. For 37 women undergoing prenatal diagnosis, 10 fetuses were identified as affected males, 6 were female carriers, while 21 were not found to carry any mutation. Testing of creatine kinase was consistent with the results of prenatal diagnosis. For a patient harboring exon 51 deletion, the same mutation was found in a fetus but not in their mother. The proband and fetus had inherited the same haplotype, which suggested that the mother probably has germline mosaicism for the mutation.</p><p><b>CONCLUSION</b>Application of individualized methods for analyzing pregnant women with different clinical background can minimize the risk for giving birth to further children affected with DMD/BMD.</p>

Mutation analysis and prenatal diagnosis for 12 families affected with hereditary hearing loss and enlarged vestibular aqueduct / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To carry out mutation analysis and prenatal diagnosis for 12 families affected with hearing loss and enlarged vestibular aqueduct from southern Zhejiang province.</p><p><b>METHODS</b>Clinical data and peripheral venous blood samples of 38 members from the 12 families were obtained. Mutations of 4 genes, namely SLC26A4, GJB2, c.538C to T and c.547G to A of GJB3, m.1555A to G and m.1494C to T of 12S rRNA, were detected by PCR and Sanger sequencing. Maternal contamination was excluded by application of STR detection during prenatal diagnosis.</p><p><b>RESULTS</b>Among the probands from the 12 families, 11 were found to be compound heterozygotes or homozygotes and 25 were heterozygotes. All of the families were detected with IVS7-2A to G mutations, and 4 had a second heterozygous mutation (c.2168A to G of the SLC26A4 gene). Four rare pathogenic mutations, namely IVS5-1G to A, c.946G to T, c.1607A to G and c.2167C to G, were detected in another four families. In addition, the partner of proband from pedigree 3 was identified with compound heterozygous mutations of c.235delC and c.299-300delAT, and proband of pedigree 5 has carried a mutation of c.109G to A in GJB2. For SLC26A4 gene, prenatal diagnostic testing has revealed heterozygous mutations in 6 fetuses and compound heterozygous mutations in 2 fetuses.</p><p><b>CONCLUSION</b>IVS7-2A to G and c.2168A to G of the SLC26A4 gene were the most common mutations in southern Zhejiang. Such mutations can be found in most families affected with hearing loss and enlarged vestibular aqueduct, which may facilitate genetic counseling and prenatal diagnosis for such families.</p>

Analysis of clinical phenotypes and GJB2 gene mutations in families affected with hearing loss from southern Zhejiang / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze the clinical features and pathological mutations in 44 families affected with hearing loss from southern Zhejiang, and to provide genetic counseling and prenatal diagnosis for 6 of the families.</p><p><b>METHODS</b>Microarray was employed to detect c.35delG, c.176del16, c.235delC and c.299-300delAT mutations of the GJB2 gene among 228 patients. For those carrying a single heterozygous mutation, the whole coding region of the GJB2 gene was analyzed by Sanger sequencing. For prenatal diagnosis, maternal DNA contamination was excluded by application of STR analysis.</p><p><b>RESULTS</b>The microarray assay has detected 49 patients with GJB2 mutations, which included 24 homozygous c.235delC mutations, 5 compound heterozygous c.235delC/c.176del16 mutations, 2 compound heterozygous c.235delC/c.299-300delAT mutations. Respectively, 16, 1 and 1 patients have carried single heterozygous c.235delC, c.176del16, and c.299-300delAT mutation. For the 16 patients, 7, 1, 1, 2, and 3 were detected by Sanger sequencing with a second heterozygous mutation of c.109G>A (2 of which were in conjunction with heterozygous c.176del16 and c.299-300delAT mutations), c.230G>A, c.427C>T, c.508-511 dupAACG, 79G>A+341A>G, respectively. Prenatal diagnosis revealed a compound heterozygous mutation in a fetus, heterozygous mutations in 4 fetuses, and no mutation of the GJB2 gene in 1 fetus.</p><p><b>CONCLUSION</b>The proportion of carriers for GJB2 gene mutations in patients with hearing loss from southern Zhejiang has reached 21.5%. The c.235delC, c.176del16, and compound c.299-300delAT and c.109G>A mutations can cause moderate to severe hearing loss. In most affected families, Heterozygous mutations may be identified by sequencing the whole coding region of the GJB2 gene. Genetic analysis and prenatal diagnosis can prevent birth of further affected children.</p>

Mutational analysis and prenatal diagnosis in a family affected with hypophosphatemic rickets / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the clinical characteristics and genetic mutation in a family affected with hypophosphatemic rickets.</p><p><b>METHODS</b>Whole exome sequencing (WES) was used to screen potential mutations in genomic DNA extracted from peripheral venous blood sample from the proband. Suspected mutation was confirmed with Sanger sequencing. Amniotic fluid was sampled from the proband for prenatal diagnosis. Potential maternal contamination was excluded by analysis of short tandem repeat (STR) markers.</p><p><b>RESULTS</b>WES has identified a heterozygous c.2058_2059insAGTT (p.L686fs) mutation of the PHEX gene in the proband, which was confirmed by Sanger sequencing in other affected individuals from the family. The mutation was detected in the amniotic fluid sample from the fetus but not among healthy members from the family.</p><p><b>CONCLUSION</b>Identification of the PHEX mutation by WES has facilitated genetic counseling and prenatal diagnosis for the family affected with hypophosphatemic rickets.</p>

SNP array analysis of three cases with partial 21q trisomy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze three cases with partial 21q trisomy, and correlate their genotypes with phenotypes.</p><p><b>METHODS</b>G-banding chromosomal analysis and single nucleotide polymorphism (SNP array) were performed for the three cases and their parents.</p><p><b>RESULTS</b>SNP array has detected partial 21q trisomy in three cases and one mother, with variable size and location of the duplications. Case 1 harbored a 12.35 Mb duplication at 21q22.11q22.3, which spanned the Down syndrome critical region. Case 2 harbored a 35.32 Mb duplication at 9p24.3p13.3 and a 14.42 Mb duplication at 21q11.2q21.3, with the former spanning the partial 9p trisomy syndrome critical region excluding the Down syndrome critical region, and was inherited from his mother. Case 3 harbored a 4.17 Mb tetraploidy at 21q11.2q21.1 in the form of mosaicism, which spared the Down syndrome critical region. His mother carried a 4.17 Mb triploidy at 21q11.2q21.1, which was also a mosaicism.</p><p><b>CONCLUSION</b>Partial 21q trisomy may occur in various forms and its clinical phenotypes are heterogeneous. Combined use of genetic techniques, particularly SNP array, is crucial for diagnosing partial 21q trisomy and delineating its genotype-phenotype correlation.</p>

Analysis of PKHD1 gene mutation in a family affected with infantile polycystic kidney disease / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze PKHD1 gene mutation in a family affected with autosomal recessive polycystic kidney disease (ARPKD).</p><p><b>METHODS</b>Genomic DNA was extracted from peripheral and cord blood samples obtained from the parents and the fetus. Potential mutations were identified using targeted exome sequencing and confirmed by Sanger sequencing. Pathogenicity of the mutation was analyzed using PolyPhen-2 and SIFT software.</p><p><b>RESULTS</b>Compound heterozygous mutations of c.11314C>T (p.Arg3772*) and a novel missense c.889T>A (p.Cys297Ser) of the PKHD1 gene were identified in the fetus. The mother was found to have carried the c.11314C>T mutation, while the father was found to have carried the c.889T>A mutation. PolyPhen-2 and SIFT predicted that the c.889T>A mutation is probably damaging.</p><p><b>CONCLUSION</b>A novel mutation in PKHD1 gene was detected in our ARPKD family. Compound heterozygous PKHD1 mutations were elucidated to be the molecular basis for the fetus affected with ARPKD, which has facilitated genetic counseling and implement of prenatal diagnosis for the family.</p>