Cytogenetic and molecular genetic analysis of small supernumerary marker chromosomes in fetal amniotic fluid / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the origin and mechanism of small supernumerary marker chromosomes (sSMC) in order to facilitate genetic counseling.</p><p><b>METHODS</b>Chromosome karyotypes of two fetuses and their immediate family members were analyzed by conventional G banding. High-throughput whole genome sequencing was used to determine the origin of sSMCs.</p><p><b>RESULTS</b>Fetus 1 was shown to have a karyotype of 47,XY,+mar but with normal FISH and B ultrasound findings. Its father also had a 47,XY,+mar karyotype with normal FISH results and clinical phenotype. High-throughput genome sequencing revealed that fetus 1 and its father were both 46,XY,dup(21)(q11.2;q21.1) with a 6.2 Mb duplication of the long arm of chromosome 21. The fetus was born with normal phenotype and developed well. Its grandmother also had a karyotype of 46,XX,t(15;21)(q13;p13) with normal FISH result and clinical phenotype. The karyotypes of its mother and grandfather were both normal. Analysis of fetus 2 showed a 47,XY,+mar karyotype with normal FISH results. High-throughput genome sequencing suggested a molecular karyotype of 46,XX. The fetus was born with normal phenotype and developed well. The karyotypes of its parents were both normal.</p><p><b>CONCLUSION</b>Considering their variable origins, identification of sSMC should combine conventional G banding analyses with high-throughput whole genome sequencing for precise delineation of the chromosomes.</p>

Genetic analysis and counseling for two fetal cases with large de novo Yq deletions / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze the deletion region for two fetal cases with large Yq deletions in order to provide genetic counseling and prenatal diagnosis.</p><p><b>METHODS</b>For both cases, amniotic fluid samples were cultured and analyzed with G banding and fluorescence in situ hybridization (FISH). Multiplex polymerase chain reaction was also carried out to amplify 15 sequence tagged sites (STS) of azoospermia factor (AZF) on the Y chromosome.</p><p><b>RESULTS</b>For both samples, the karyotypes were determined as 46,X,del(Y)(pter→q11:). No heterochromatin was found in C band. The karyotypes of their fathers were 46,XY, and heterochromatin was found in C band. STS analyses suggested that only sY82, sY84 and sY86 in AZFa were amplifiable while the other 12 STS were negative in amniotic fluid for the first case, which indicated deletions of AZFb, AZFd and AZFc. No AZF deletion was found in its father. For the second case, all 15 STS were amplifiable in the amniotic fluid, suggesting no AZF deletion. No AZF deletion was found in its father too.</p><p><b>CONCLUSION</b>Conventional karyotyping combined with FISH and molecular genetics techniques can enable characterization of AZF microdeletions and facilitate genetic counseling and prenatal diagnosis.</p>

Analysis of two false positive cases from noninvasive prenatal testing / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To track and analyze two false positive cases from non-invasive prenatal testing for potential fetal aneuploidy.</p><p><b>METHODS</b>The two cases, respectively reported to have XO (+++) and T18 (1/20) XO(+), were analyzed with conventional karyotyping, fluorescence in situ hybridization (FISH) and massively parallel genomic sequencing (MPS).</p><p><b>RESULTS</b>The first fetus, who was suspected for XO(+++), was verified to have super female syndrome (47,XXX/46,XX) due to confined placental mosaicism by karyotyping of amniotic fluid cells, FISH analysis of placenta and massively parallel sequencing (MPS) of fetal tissue. The second fetus, suspected to have trisomy 18 (1/20) XO(+), was verified to have Turner syndrome by karyotyping, FISH and MPS analyses of umbilical cord blood cells. And the karyotype was 45,X[48]/46, X, der(X) del(X) (p11.21) del(X) (q13.3)[62].</p><p><b>CONCLUSION</b>Non-invasive prenatal testing carries a risk for false positive diagnosis of fetal sex chromosome and trisomy 18. Combined cytogenetic and molecular techniques are required to ensure an accurate diagnosis.</p>

Gel immobilization of human genome / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To develop a solid phase PCR method by covalent single point immobilization for recycle utilization of human genome.</p><p><b>METHODS</b>Polymethacrylamide gel was selected as a solid PCR carrier based on DNA-hydrogel copolymer chemistry presented by Mirzabekov. (CH2)6NH2 amino-modified PCR product and randomly fractured formic acid-modified plasmid pGEM-T-HLA-G were used as templates. The specificity of the attachment chemistry was characterized by acrylamide gel electrophoresis, and the thermal stability of method was demonstrated by PCR. This method was applied for the recycle utilization of human genome. Sequencing was used to exclude the possibility of introduced mutations during modification and immobilization procedures.</p><p><b>RESULTS</b>The PCR detections of plasmid DNA and human genome DNA immobilized by polymethacrylamide gel was successful. The thermal stability of method was successfully demonstrated by performing PCR after 16 rounds of standard 36 PCR cycles. And the sequencing was found no mutation.</p><p><b>CONCLUSION</b>The DNA immobilization method with polymethacrylamide gel as a solid phase carrier is stable and specific, which can be a possible approach for realizing recycle utilization of human genome for whole-genome sequencing and SNP detection.</p>

Whole-genome sequencing: a new approach for understanding of pathogenesis and individualized treatment of cancer / 浙江大学学报·医学版

With the development of sequencing technology, the cost of whole-genome sequencing was significantly declined.Meanwhile, with the application of combined whole-genome sequencing with epigenetic analysis on methylation and histone acetylation, the comprehensive and systematic analysis of numerous samples became a reality and we are able to re-understand the genesis and development of cancer. New ideas are emerging in comparative genomics research methods, from comparison of genomes among different individuals to horizontal self-comparison of different tissues and vertical self-comparison of genomes recently.Individualized diagnosis and treatment of cancer has shown a bright future.