A de novo partial 5p deletion and cryptic 18p duplication detected by SNP-Array in a boy featuring Cri du Chat syndrome / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To determine the karyotype of a boy suspected to have Cri du Chat syndrome with severe clinical manifestations, and to assess the recurrence risk for his family.</p><p><b>METHODS</b>High-resolution GTG banding was performed to analyze the patient and his parents. Fluorescence in situ hybridization (FISH) with Cri du Chat syndrome region probe as well as subregional probes mapped to 5pter, 5qter, 18pter, 18qter, and whole chromosome painting probe 18 was performed to analyze the patient and his parents. In addition, single nucleotide polymorphism-based arrays (SNP-Array) analysis with Affymetrix GeneChip Genome-wide Human SNP Nsp/Sty 6.0 were also performed to analyze the patient.</p><p><b>RESULTS</b>Karyotype analysis indicated that the patient has carried a terminal deletion in 5p. FISH with Cri du Chat syndrome region probe confirmed that D5S23 and D5S721 loci are deleted. SNP-Array has detected a 15 Mb deletion at 5p and a 2 Mb duplication at 18p. FISH with 5p subtelomeric probes and 18p subtelomeric probe further confirmed that the derivative chromosome 5 has derived from a translocation between 5p and 18p, which has given rise to a 46,XY,der(5)t(5;18)(p15.1;p11.31)dn karyotype.</p><p><b>CONCLUSION</b>A de novo 5p partial deletion in conjunction with a cryptic 18p duplication has been detected in a boy featuring Cri-du-Chat syndrome. His parents, both with negative findings, have a low recurrence risk. For its ability to detect chromosomal imbalance, SNP-Array has a great value for counseling of similar patients and assessment of recurrence risks.</p>

Chromosome copy analysis by single-cell comparative genomic hybridization technique based on primer extension preamplification and degenerate oligonucleotide primed-PCR / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To establish a single-cell whole genome amplification (WGA) technique, in combination with comparative genomic hybridization (CGH), for analyzing chromosomal copy number changes, and to explore its clinical application in preimplantation genetic diagnosis (PGD).</p><p><b>METHODS</b>Twelve single-cell samples with known karyotypes, including 5 chorionic villus samples, 4 human embryonic stem cell (hESC) samples and 3 peripheral lymphocyte samples, and 4 single blastomere samples carrying chromosomal abnormalities detected by PGD, were collected for whole genome amplification by combining primer extension preamplification (PEP) with degenerate oligonucleotide primed-PCR (DOP-PCR) amplification. The amplified products labeled by red fluorescence were mixed with control DNA labeled by green fluorescence, and then the mixture was analyzed by CGH. As a comparison, 10 single cell samples were amplified by DOP-PCR only and then CGH analysis was performed.</p><p><b>RESULTS</b>The amplification using PEP-DOP-PCR was more stable than traditional DOP-PCR. The products of PEP-DOP-PCR range from 100 bp to 1000 bp, with the mean size being about 400 bp. The CGH results were consistent with analyses by other methods. However, only 6 out of 10 single cell samples were successfully amplified by DOP-PCR, and CGH analysis showed a high background and 2 samples showed inconsistent results from other methods.</p><p><b>CONCLUSION</b>PEP-DOP-PCR can effectively amplify the whole genome DNA of single cell. Combined with CGH, this WGA method can successfully detect single-cell chromosomal copy number changes, while DOP-PCR was easy to fail to amplify and amplify inhomogeneously, and CGH analysis using this PCR product usually showed high background. These results suggest that PEP-DOP-CGH is a promising method for preimplantation genetic diagnosis.</p>

Identification of a cryptic 1p36.3 microdeletion in a patient with Prader-Willi-like syndrome features / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To determine the karyotype of a patient with Prader-Willi-like syndrome features.</p><p><b>METHODS</b>Chromosomal high resolution banding was carried out to analyze the karyotype of the patient, and methylation-specific PCR was used to analyze the imprinting region of chromosome 15. Subtelomeric region was screened by multiplex ligation-dependent probe amplification (MLPA), and fluorescent in situ hybridization (FISH) and real-time quantitative PCR were further performed to identify the deleted region.</p><p><b>RESULTS</b>No abnormality was discovered by high resolution karyotype analysis and methylation-specific PCR studies. MLPA analysis showed that the patient had a deletion of 1p subtelomeric area, which was confirmed by FISH analysis. The deleted region was shown within a 4.2 Mb in the distal 1p by 3 BAC FISH probes of 1p36 combined with real-time PCR technique. Family pedigree investigation showed the chromosome abnormality was de novo. Therefore, partial monosomy 1p36 was likely responsible for the mental retardation of the patient.</p><p><b>CONCLUSION</b>Molecular cytogenetic techniques should be performed to those patients with Prader-Willi-like syndrome features, to determine their karyotypes.</p>

Delineating a supernumerary marker chromosome by combining several cytogenetic and molecular cytogenetic techniques / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To characterize a supernumerary marker chromosome (SMC) by comparative genomic hybridization (CGH), fluorescence in situ hybridization (FISH) and traditional cytogenetic techniques, and to explore the clinical application of these techniques in delineating de novo marker chromosomes.</p><p><b>METHODS</b>A mental retardation patient received chromosome test by ordinary G banding. CGH and FISH techniques were used to analyze the origin of the de novo SMC, and N banding technique and C banding techniques were used to analyze the SMC structure. The phenotypic effects of the SMC were analyzed after the karyotype was determined.</p><p><b>RESULTS</b>By G banding technique, the patient was showed to have a mosaic karyotype with SMC: mos.47, XX, +mar [31]/48, XX, +2mar[29]. CGH analysis showed a gain of 15q11 --> q14, and the result was confirmed by FISH with chromosome 15 painting probe. The further FISH analysis showed the SMC had two signals with UBE3A probe for detecting Prader-willi syndrome/Angelman syndrome (PWS/AS). N banding and C banding analysis showed the SMC had a double satellite and double centromere, respectively. Combined with the above results, the karyotype of the patient was: mos.47, XX, +der (15) (pter --> q14::q14 --> pter) [31]/48, XX, +2der (15) (pter --> q14::q14 --> pter) [29]. ish der(15)(WCP15+, UBE3A++, PML-).</p><p><b>CONCLUSION</b>CGH is a valuable method to detect imbalanced chromosomal rearrangement. Combined with FISH and the traditional cytogenetic technique, it provides a valuable technique platform for characterizing the structure of the de novo SMC, and a basis for exploring the relation between karyotype and phenotype, prognosis and recurrent risk.</p>

Identification and characterization of marker chromosome in Turner syndrome / 中华妇产科杂志

Objective To analyze the karyotypes of 11 cases of Turner syndrome with marker chromosome,and study the phenotypic effects resulting from the abnormal karyotype.Methods Eleven Turner syndrome patients had a mosaic karyotype and carried a marker chromosome,and 6 marker chromosomes were ring chromosomes.Their karyotypes were showed as mos.45,X/46,X,+mar or mos. 45,X/46,X,+r.Fluorescence in situ hybridization(FISH)technique with X/Y centromere probes was performed to determine the origin of the marker chromosome.Reverse chromosome painting technique was used to identify the breakpoints of two largest markers.Phenotype effects with different chromosome breakpoints were compared.Results All the 11 marker chromosomes were ring X chromosomes.The breakpoints of the r(X)were involved in Xp22,Xq22,Xq24 and Xq26,etc.Conclusions The marker chromosomes in Turner syndrome mainly originate from X chromosome and form ring chromosome X.Each r (X)in our patients was mosaic,indicating it was originated from mitosis error during early embryo development.To analyze the origin of the marker chromosome and the breakpoint of r(X)will provide guidance for the therapy and prognosis of the Turner syndrome patient.