Wu Lq

[Mutational screening of the SLC26A4 gene in patients with nonsyndromic hearing loss by denaturing high-performance liquid chromatography].

OBJECTIVE To study the SLC26A4 gene mutations in patients with nonsyndromic hearing loss (NSHL) and provide the clinical guidance of gene diagnosis. METHODS PCR and denaturing high-performance liquid chromatography (DHPLC) were used to screen the 21 exons and their flanking regions of the SLC26A4 gene. Samples with abnormal DHPLC wave patterns were sequenced to identify the variations. RESULTS Among the 30 unrelated NSHL patients in whom no deafness-causing mutations of the GJB2 gene were identified, 10 types of variations were detected, including 7 known mutations, 2 novel mutations (F572L and D87Y), and 1 known polymorphism (Ivs11+47T>C). The Ivs7-2A>G is the most common type of variation, accounting for 40% of all the mutations. CONCLUSION SLC26A4 mutation is a major cause of NSHL, just next to the GJB2 mutations. For NSHL patients without deafness-causing GJB2 mutations, the SLC26A4 mutation rate was 23.3%, and the Ivs7-2A>G was the most common mutation.

[Rapid detection of the hot spot gene mutations in Chinese patients with nonsyndromic hearing loss by polymerase chain reaction-restrictive fragment length polymorphism].

OBJECTIVE To develop a rapid genetic diagnosis technique for the patients with hereditary hearing loss by screening hot spots of mutations, namely 235delC of the GJB2 gene, IVS7-2A>G of the SLC26A4 gene, and 1555A>G of mitochondrial 12S rRNA. METHODS Multiple PCR amplification of the three fragments covering the expected mutations in GJB2, SLC26A4 and 12S were carried out and the amplified products were analyzed by restriction fragment length polymorphism (RFLP). RESULTS Eighteen homozygous and 18 heterozygous 235delC, 2 homozygous and 13 heterozygous IVS7-2A>G, and 8 homogeneous 1555A>G were detected in the 200 patients with hearing loss. All the results were confirmed by sequencing. The detection rate of the three mutant alleles was 21.7% (71/400 + 8/200 = 0.217) and the genetic diagnosis rate was 14% [(18+2+8)/200 = 0.14]. CONCLUSION It is a convenient, efficient and economical method to screen the hot spots of mutation in the patient with hereditary hearing loss by using PCR-RFLP.

Genetic diagnosis and analysis for two cases of ring chromosome 22

OBJECTIVE To confirm the genetic diagnosis of two patients with ring chromosome 22 syndrome and investigate the mechanism underlying the formation of r(22) and potential genetic causes for the clinical phenotypes. METHODS Cytogenetic and molecular analyses using standard G-banding, fluorescence in situ hybridization and single nucleotide polymorphism array (SNP array) were performed. RESULTS For case 1, the karyotype was 46,XY,r(22)(p11q13). SNP array has identified a 7.0 Mb heterozygous deletion at 22q13.2q13.33. For case 2, the karyotype was 46,XY,r(22)(p11q13)[84]/45,XY,-22[6]; SNP array has detected a heterozygous microdeletion of 1.6 Mb at 22q13.33. CONCLUSION With combined application of genetic testing, 2 cases of r(22) syndrome were diagnosed, which has improved the understanding of the genotype-phenotype correlation of r(22).

[Phenotype-genotype correlation analysis of 12 cases with Angelman/Prader-Willi syndrome].

OBJECTIVE To investigate the genotype-phenotype correlation in patients with Angelman syndrome/Prader-Willi syndrome (AS/PWS) and assess the application value of high-resolution single nucleotide polymorphism microarrays (SNP array) for such diseases. METHODS Twelve AS/PWS patients were diagnosed through SNP array, fluorescence in situ hybridization (FISH) and karyotype analysis. Clinical characteristics were analyzed. RESULTS Deletions ranging from 4.8 Mb to 7.0 Mb on chromosome 15q11.2-13 were detected in 11 patients. Uniparental disomy (UPD) was detected in only 1 patient. Patients with deletions could be divided into 2 groups, including 7 cases with class I and 4 with class II. The two groups however had no significant phenotypic difference. The UPD patient had relatively better development and language ability. Deletions of 6 patients were confirmed by FISH to be of de novo in origin. The risk to their sibs was determined to be less than 1%. CONCLUSION The phenotypic differences between AS/PWS patients with class I and class II deletion need to be further studied. SNP array is useful in detecting and distinguishing of patients with deletion or UPD. This method may be applied for studying the genotype-phenotype association and the mechanism underlying AS/PWS.

Identification of the small supernumerary marker chromosomes in two patients with Turner syndrome

OBJECTIVE To identify the small supernumerary marker chromosomes (sSMC) and guide the genetic counseling and medical treatment in two patients with Turner syndrome. METHODS High resolution GTG and C banding, SRY amplification by PCR and fluorescence in situ hybridization (FISH) on metaphase chromosomes were performed to the two patients. RESULTS The karyotypes of the two patients were 45, X [29]/46,X, +mar[31] and 45,X[71]/46,X, +mar[29] respectively. SRY test indicated SRY-positive for patient 1, whose sSMC was originated from chromosome Y. The karyotype was confirmed as 45,X[29]/46,X,idic(Y)(q10)[31]. ish idic(Y)(q10)(RP11-115H13x2) (SRY+) by FISH. While in patient 2, the sSMC was originated from chromosome X, whose karyotype was determined as 45, X[71]/46,X, r(X)(p11.23q21)[29]. ish r(X) (p11.23q21)(AL591394.11xAC092268.3). CONCLUSION Using cytogenetic and molecular cytogenetic analyses, we have identified the sSMCs in two patients with Turner syndrome, which was helpful to the clinical diagnosis and treatment.

Genetic diagnosis and prenatal diagnosis of Angelman syndrome

OBJECTIVE To evaluate the conventional cytogenetic methods in genetic diagnosis and prenatal diagnosis in the family with a proband of Angelman syndrome (AS). METHODS High-resolution G-banding karyotyping and fluorescence in situ hybridization (FISH) on metaphase chromosomes were performed. RESULTS Two AS patients and 1 normal fetus in the family were successfully detected by FISH. CONCLUSION Our result demonstrated that patient with type I AS could be detected by combining the techniques of high-resolution G-banding and FISH with clinical observation, which would offer accurate genetic counseling information to the geneticists and provide the prenatal diagnosis for the AS family.