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Biomedical subjects

G Tachdjian

Publications and source records attributed to G Tachdjian.

At least 37 records · Page 2Linked to original sources
PubMed2003

[Contribution of genotyping for fetal sex determination in maternal serum for preimplantation genetic diagnosis of X-linked diseases].

OBJECTIVE: Couples with a risk of transmitting X-linked diseases included in a preimplantation genetic diagnosis (PGD) center need early and rapid fetal sex determination during pregnancy in two situations. The first situation corresponds to control of embryo sexing after PGD, the second one being that of couples in PGD program having a spontaneous pregnancy. Determination of fetal sex can be achieved by karyotyping using invasive procedures such as chorionic villus sampling (CVS), amniocentesis or cordocentesis and by non-invasive procedures such as ultrasound (US) examination. CVS is the earliest invasive procedure for fetal sex determination and molecular analysis of X-linked genetic disorders during the first trimester but it is associated with a risk of fetal loss. US allows reliable fetal sex determination only during the second trimester. Recently, reliable non-invasive fetal sex determination was realized by using SRY gene amplification in maternal serum. PATIENTS AND METHODS: We report the prospective use of fetal sex determination in maternal serum in our PGD center. Management of pregnancies was performed using this non-invasive procedure in four cases of embryo sexing control and nine cases of spontaneous pregnancies in couples included in PGD program for X-linked diseases. RESULTS: Fetal sex results using SRY gene amplification on maternal serum were in complete concordance with fetal sex observed by cytogenetic analysis or US examination, as well as at birth. DISCUSSION AND CONCLUSION: This new strategy allowed rapid sex determination during the first trimester and permitted to avoid performing invasive procedures in nine pregnancies.

Adult↗
PubMed2003

[First birth after preimplantation genetic diagnosis performed on thawed embryos].

OBJECTIVE: To report the birth of the first infant conceived after preimplantation genetic diagnosis (PGD) performed on frozen-thawed embryos in our PGD center. PATIENTS AND METHODS: Three couples (C1, C2 and C3) who had frozen embryos from a previous in vitro fertilization attempt were enrolled in our PGD program. Embryos were thawed one day before the biopsy procedure for the couples C1 and C3 and the day of the biopsy for the couple C2. The single cell genetic analysis was performed by a multiplex PCR for the couple C1 and by fluorescent in situ hybridization for the couples C2 and C3. The embryos transfers were carried out on the third or fourth day. RESULTS: Out of ten thawed embryos, eight were biopsied and five were transferred during three embryos transfers. Two biochemical and one ongoing pregnancy were obtained yielded one birth. CONCLUSIONS: PGD may be offered to couples at risk of transmission of a serious and incurable genetic disease and having frozen embryos.

Biopsy↗
PubMed2002

De novo interstitial direct duplication 1(q23.1q31.1) in a fetus with Pierre Robin sequence and camptodactyly.

Interstitial duplications of chromosomal region 1q are rarely seen. We report the first prenatal diagnosis of pure partial trisomy 1q. The fetus was karyotyped for polyhydramnios, micrognathia, and flexion of fingers of both hands. Conventional and molecular cytogenetics showed a de novo direct duplication of the chromosomal region 1q23.1q31.1 leading to a partial trisomy 1q. At autopsy, the fetus showed Pierre Robin sequence (PRS) and camptodactyly. The main histological finding was a decreased number of motoneurons with apoptotic features in the anterior horn of the spinal cord. A literature review and our observations suggest that genetic material mapping to chromosome 1q25 could be responsible for PRS with distal arthrogryposis when this is in triple dose.

Chromosome Aberrations↗
PubMed2002

Female pseudohermaphroditism in a fetus with a deletion 9(q22.2q31.1).

Interstitial deletions of chromosomal region 9q are rarely seen. We report the first prenatal diagnosis of a de novo interstitial deletion 9q. The fetus was karyotyped for intrauterine growth retardation (IUGR). Conventional and molecular cytogenetics showed female karyotype with a de novo deletion of the chromosomal region 9(q22.2q31.1) leading to a partial monosomy 9q. At autopsy, the fetus showed growth retardation, dysmorphy, and a female pseudohermaphroditism. These results suggest that a gene(s) for genital development reside in chromosomal region 9q22.2q31.1.

Adult↗
PubMed2002

[Preimplantation genetic diagnosis experience in Paris: evaluation of first births].

OBJECTIVE: To report the birth of the first fourteen infants conceived after preimplantation genetic diagnosis (PGD) in our unit. PATIENTS AND METHODS: Fifty-nine couples were enrolled between January 2000 and July 2001. They had a total of 71 oocyte pick-up cycles. The collected oocytes were inseminated by intracytoplasmic sperm injection. The resulting embryos were biopsied on the third day of development and the genetic analysis was performed on the same day. Most of the embryo transfers were carried out on the fourth day. RESULTS: The 71 oocyte pick-up cycles yielded 872 oocytes of which 731 were suitable for intacytoplasmic sperm injection. Among the 505 embryos obtained, 421 embryos were biopsied and genetic diagnosis was performed for 312 (74%) of these. 127 embryos were transferred during the course of 58 transfer procedures. There were 18 biochemical and 12 ongoing (7 singles, 4 twins and 1 triple) pregnancies. Fourteen infants have been born and 2 are expected. CONCLUSION: PGD has gained a place among the choices offered to couples at risk of transmission of a serious and incurable genetic disease.

Adult↗
PubMed2001

Cytogenetic analysis of trophoblasts by comparative genomic hybridization in embryo-fetal development anomalies.

Cytogenetic studies of spontaneous abortions or intrauterine fetal death depend on conventional tissue culturing and karyotyping. This technique has limitations such as culture failure and selective growth of maternal cells. Fluorescent in situ hybridization (FISH) using specific probes permits diagnosis of aneuploidies but is limited to one or a few chromosomal regions. Comparative genomic hybridization (CGH) provides an overview of chromosomal gains and losses in a single hybridization directly from DNA samples. In a prospective study, we analyzed by CGH trophoblast cells from 21 fetuses in cases of spontaneous abortions, intrauterine fetal death or polymalformed syndrome. Six numerical chromosomal abnormalities including one trisomy 7, one trisomy 10, three trisomies 18, one trisomy 21 and one monosomy X have been correctly identified by CGH. One structural abnormality of the long arm of chromosome 1 has been characterized by CGH. One triploidy and two balanced pericentromeric inversions of chromosome 9 have not been identified by CGH. Sexual chromosomal constitutions were concordant by both classical cytogenetic technique and CGH. Contribution of trophoblast analysis by CGH in embryo-fetal development anomalies is discussed.

Abortion, Spontaneous↗
PubMed2001

Assisting reproduction of infertile men carrying a Robertsonian translocation.

BACKGROUND: In order to provide better genetic counselling for Robertsonian translocation carriers, the meiotic segregation of chromosomes 13, 14 and 21 from six infertile (13;14) and (14;21) Robertsonian translocation carriers was examined. METHODS: Dual-colour fluorescence in-situ hybridization analysis using locus-specific probes was carried out on spermatozoa of translocation carriers. Spermatozoa from six proven fertile subjects were analysed using the same probes as controls. RESULTS: We observed that the frequencies of unbalanced spermatozoa were similar in the (13;14) translocation carriers (9.0, 10.0 and 12.9%) and in the (14;21) translocation carriers (8.7, 7.2 and 7.0%). These frequencies were significantly increased compared with the control population (P < 0.05). CONCLUSIONS: This high frequency might justify the use of preimplantation genetic diagnosis in these patients where the translocation is usually associated with infertility, requiring intracytoplasmic sperm injection, as it might improve the outcome of the assisted reproduction technique.

Adult↗
PubMed2000

Analysis of uncultured amniocytes by comparative genomic hybridization: a prospective prenatal study.

Comparative genomic hybridization (CGH) is a new molecular cytogenetic technique which can detect and map whole and partial aneuploidies throughout a genomic specimen DNA without culturing specimen cells. Thus, CGH may be used as a comprehensive and rapid screening test in prenatal unbalanced chromosomal abnormalities detection. We report the results of the first prospective study to evaluate the use of the CGH technique on uncultured amniocytes. Seventy-one amniotic fluid samples, obtained by transabdominal amniocentesis between the 14th and 35th weeks of gestation, were simultaneously investigated using CGH and conventional cytogenetics. Amniocentesis were done for advanced maternal age (21.1%), fetal ultrasound anomalies (73.3%) and high level of biochemical markers in maternal serum (5.6%). Sixty-six (93%) informative results were generated on a total of 71 analysed specimens. Fifty-nine samples were reported as disomic for all autosomes with a normal sex chromosome constitution using CGH and conventional cytogenetics. Among them, three pericentromeric chromosomal inversions were undetected by CGH analysis. Seven numerical aberrations were characterized, including one case of trisomy 13, one case of trisomy 18 and five cases of trisomy 21. Advantages and limitations of CGH for a rapid prenatal screening of unbalanced chromosomal aberrations are discussed.

Amniocentesis↗
PubMed1999

De novo inverted duplication 9p21pter involving telomeric repeated sequences.

We report on clinical and cytogenetic findings in a boy with partial 9p duplication, dup(9)(p21pter). Clinical manifestations included facial and hand anomalies and mental retardation. Fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH) were used to characterize further and confirm the conventional banding data. Investigation by FISH using whole chromosome 9 paint probe showed that the additional material was derived from chromosome 9. Using CGH, a region of gain was found in the chromosome segment 9p21pter. YACs and telomeric probes confirmed the duplicated region. Using the all-human telomeric sequences probe, intrachromosomal telomeric signal was noted on the short arm of the abnormal chromosome 9. Mechanism of formation of the duplication, including intrachromosomal telomeric sequences, is discussed.

Abnormalities, Multiple↗
PubMed1999

[Contribution of molecular cytogenetics to the diagnosis of chromosome anomalies].

UNLABELLED: MOLECULAR CYTOGENETICS: New fluorescent in situ hybridization (FISH) techniques have been developed using fluorescent non-radioactive DNA probes. FISH: Based on the complementary of nucleotides FISH enables visualization and localization of a DNA fragment on chromosomes by hybridizing the complementary DNA sequence, the probe. Many types of tissues can be analyzed, for example hematopoietic cells in blood or bone marrow, amniotic cells, trophoblasts, fibroblasts, gamete or tumoral cells. APPLICATIONS: Molecular cytogenetics can be used to characterize chromosome anomalies in many fields of cytogenetics (constitutional studies, prenatal diagnosis, hematology, oncology).

Chromosome Aberrations↗
PubMed1998

[Genomic imprinting].

UNLABELLED: AN EXCEPTION TO THE RULE: For certain genes, alleles are expressed differently depending on whether they originate from the maternal or paternal genome. This is called the parental imprinting. The parental imprinting plays an important role in development and a dysregulation can lead to various disease states. Loss of the parental imprinting or its alteration is implicated in certain genetic diseases and cancers. When the process is altered, two homologous chromosomes may come from the same parent, a situation termed uniparental disomy. GENETIC DISEASE IN MAN: Several genetic diseases in man are known to be related to the parental imprinting. Willi-Prader disease, Angelman disease and Beckwith-Wiedemann disease are the most extensively studied. MECHANISMS: Some of the underlying mechanisms are known, but several points concerning the parental imprinting remain to be elucidated, particularly the precise nature of the molecular mechanisms and the identification of the genes controlling this genetic process.

Angelman Syndrome↗
PubMed1998

Altered patterns of DNA methylation on chromosomes from leukemia cell lines: identification of 5-methylcytosines by indirect immunodetection.

An immunodetection technique has been developed to map with high resolution the methylated sites of human chromosomes. We have used this method to define the methylated areas of chromosomes from normal donors and from leukemia cell lines. The chromosomes were exposed for a short time to UV light to induce mild denaturation. The methylated sites were detected in situ by using monoclonal antibodies against 5-methylcytosine (prepared in mouse), and fluorescein-conjugated antimouse immunoglobulins. The chromosomes from normal cells exhibited a fluorescent pattern with RCT banding, although some differences from previously reported patterns could be detected. With this method we have been able to show the presence of two types of R-bands: High fluorescence R-band (HFR) and low fluorescence R-band (LFR). Chromosomes from leukemia cell lines exhibited low global staining with disrupted RCT banding of the chromosomes. The decreased level of the methylation status of the chromosomes from leukemia cells was confirmed by detection of 5-methylcytosines on total immobilized DNA. Thus, we have shown that this method can be used to determine the methylated status of chromosomes and, in turn, to map not only the structural (banding) but also the functional (methylation status) properties of the different chromosome domains in normal and pathologic human cells.

5-Methylcytosine↗
PubMed1998

Identification and characterization of a de novo partial trisomy 10p by comparative genomic hybridization (CGH).

We report the characterization of a de novo unbalanced chromosome rearrangement by comparative genomic hybridization (CGH) in a 15-day-old child with hypotonia and dysmorphia. We describe the combined use of CGH and fluorescence in situ hybridization (FISH) to identify the origin of the additional chromosomal material on the short arm of chromosome 6. Investigation with FISH revealed that the excess material was not derived from chromosome 6. Identification of unknown unbalanced aberrations that could not be identified by traditional cytogenetics procedures is possible by CGH analysis. Visual analysis of digital images from CGH-metaphase spreads revealed a predominantly green signal on the telomeric region of chromosome 10p. After quantitative digital ratio imaging of 10 CGH-metaphase spreads, a region of gain was found in the chromosome band 10p14-pter. The CGH finding was confirmed by FISH analysis, using a whole chromosome 10 paint probe. These results show the usefulness of CGH for a rapid characterization of de novo unbalanced translocation, unidentifiable by karyotype alone.

Adolescent↗
PubMed1998

Comparative genomic hybridization: technical development and cytogenetic aspects for routine use in clinical laboratories.

Comparative genomic hybridization (CGH) offers a new global approach for detection of chromosomal material imbalances of the entire genome in a single experiment without cell culture. In this paper, we discuss the technical development and the cytogenetic aspects of CGH in a clinical laboratory. Based only on the visual inspection of CGH metaphase spreads, the correct identification of numerical and structural anomalies are reported. No commercial image analysis software was required in these experiments. We have demonstrated that this new technology can be set up easily for routine use in a clinical cytogenetics laboratory.

Aneuploidy↗
PubMed1998

Comparison of comparative genomic hybridization with conventional karyotype and classical fluorescence in situ hybridization for prenatal and postnatal diagnosis of unbalanced chromosome abnormalities.

The comparative genomic hybridization (CGH) technique was initially used for detection of chromosomal imbalances in tumor cells. CGH can also be used as a supplementary method to karyotypic analysis in clinical cytogenetic cases. In order to evaluate CGH usefulness in prenatal and postnatal analysis of whole chromosome and segmental aneusomies, we investigated 13 clinical samples from blood, cultured chorionic villi, cultured amniotic fluids and uncultured amniotic fluids. These specimens, initially analyzed by conventional cytogenetics, included 5p monosomy, 9p duplication, add 6p, unbalanced translocation between chromosomes 5 and 10, mosaic tetrasomy 12p (50%), unbalanced (X;X) translocation and Prader-Willi deletion (15q11-13). In addition, six numerical chromosome aberrations (tetrasomy X, trisomies 13, 18, 21 and monosomy X) were analysed. All the chromosomal abnormalities, except the Prader-Willi deletion, were correctly detected by CGH. Here, we have demonstrated that the CGH technique is an alternative to classical fluorescence in situ hybridization using specific probes for detection of the unbalanced chromosomal aberrations in prenatal and postnatal diagnosis and could be used for rapid prenatal screening for unbalanced aberrations.

Amniotic Fluid↗