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Biomedical subjects

Joy D A Delhanty

Publications and source records attributed to Joy D A Delhanty.

9 recordsLinked to original sources
PubMed2006

Complete cytogenetic investigation of oocytes from a young cancer patient with the use of comparative genomic hybridisation reveals meiotic errors.

OBJECTIVES: The complete cytogenetic investigation of human oocytes and the corresponding first polar bodies (PBs) derived from an 18-year old female cancer patient. METHODS: A whole-genome amplification method combined with comparative genomic hybridisation (CGH) was employed for the analysis of 14 oocytes and their corresponding first PBs. RESULTS: Chromosome abnormalities were detected in two oocyte-PB complexes. One oocyte had lost X-chromosome material (23,X,-Xcht), while its corresponding first PB showed the reciprocal gain (23,X,+Xcht). Double aneuploidy involving loss of chromatids for chromosomes X and 21 was identified in another first PB (23,X,-21cht,-Xcht). Aneuploidy was attributed to unbalanced pre-division of chromatids at meiosis I. CONCLUSIONS: Meiotic errors in chromosome segregation can occur even in oocytes derived from young women, confirming the existence of age-independent factors contributing to aneuploidy. Such factors are of relevance to fertility, miscarriage and preimplantation aneuploidy screening for the purposes of increasing IVF success rates. The reliability of CGH in examining the whole chromosome complement of a single cell and of being able to detect chromatid anomalies is confirmed by this study.

Adolescent↗
PubMed2004

Genetics of gametes and embryos.

Chromosome analysis of oocytes, sperm and embryos has mainly relied on fluorescent in situ hybridisation (FISH) and karyotyping. FISH studies have been performed on sperm from fertile and infertile men as well as men carrying known chromosomal translocations. Molecular DNA analyses has aided in the identification and treatment of men with Y chromosome deletions. In oocytes FISH and karyotyping have identified non-disjunction of univalents and predivision of chromatids. Analysis of the chromosomes from human embryos has shown that a high proportion of embryos are mosaic or chaotic, in addition to embryos beings uniformly and abnormal. FISH and PCR have also been used clinically for preimplantation genetic diagnosis (PGD). For patients at risk of transmitting a specific genetic or chromosomal abnormality, 1-2 blastomeres are biopsied from embryos and specific genes or chromosomes analysed. Normal embryos are then transferred to the uterus.

Chromosome Aberrations↗
PubMed2003

Cytogenetic and Y chromosome microdeletion screening of a random group of infertile males.

OBJECTIVE: To assess whether to perform routine cytogenetic and Y chromosome microdeletion screening on all infertile male patients. DESIGN: A cytogenetic and Y microdeletion study of a random group of infertile men. SETTING: University department. PATIENT(S): In total, 40 patients had azoospermia (21 nonidiopathic), 27 had severe oligozoospermia/oligoasthenozoospermia (<or=5 x 10(6)/mL) (5 nonidiopathic), 20 had oligozoospermia/oligoasthenozoospermia (5-20 x 10(6)/mL) (6 nonidiopathic), and 16 had asthenozoospermia (5 nonidiopathic). Many were candidates for intracytoplasmic sperm injection (ICSI). INTERVENTION(S): Collection of blood samples from all patients and buccal cells from one patient. MAIN OUTCOME MEASURE(S): Karyotype analysis, polymerase chain reaction (PCR) screening for Y chromosome microdeletions, and fluorescence in situ hybridization of abnormal chromosomes. RESULT(S): Ten (9.7%) subjects, including one nonidiopathic patient, were found to have an abnormal karyotype. Two idiopathic azoospermic patients were missing large portions of Y chromosome euchromatin, confirmed by PCR analysis and an additional idiopathic azoospermic patient had a Y chromosome microdeletion. CONCLUSION(S): Routine cytogenetic analysis of all infertile male patients is required but it may be advisable to limit routine Y chromosome microdeletion screening to patients with severe male factor infertility (<or=5 x 10(6)/mL).

Chromosome Deletion↗
PubMed2002

Preimplantation genetic diagnosis for single gene disorders: experience with five single gene disorders.

We report our experience of 14 preimplantation genetic diagnosis (PGD) cycles in eight couples carrying five different single gene disorders, during the last 18 months. Diagnoses were performed for myotonic dystrophy (DM), cystic fibrosis (CF) [Delta F508 and exon 4 (621+1 G>T)], fragile X and CF simultaneously, and two disorders for which PGD had not been previously attempted, namely neurofibromatosis type 2 (NF2) and Crouzon syndrome. Diagnoses for single gene disorders were carried out on ideally two blastomeres biopsied from Day 3 embryos. A highly polymorphic marker was included in each diagnosis to control against contamination. For the dominant disorders, where possible, linked polymorphisms provided an additional means of determining the genotype of the embryo hence reducing the risk of misdiagnosis due to allele dropout (ADO). Multiplex fluorescent polymerase chain reaction (F-PCR) was used in all cases, followed by fragment analysis and/or single-stranded conformation polymorphism (SSCP) for genotyping. Embryo transfer was performed in 13 cycles resulting in one biochemical pregnancy for CF, three normal deliveries (a twin and a singleton) and one early miscarriage for DM and a singleton for Crouzon syndrome. In each case the untransferred embryos were used to confirm the diagnoses performed on the biopsied cells. The results were concordant in all cases. The inclusion of a polymorphic marker allowed the detection of extraneous DNA contamination in two cells from one case. Knowing the genotype of the contaminating DNA allowed its origin to be traced. All five pregnancies were obtained from embryos in which two blastomeres were biopsied for the diagnosis. Our data demonstrate the successful strategy of using multiplex PCR to simultaneously amplify the mutation site and a polymorphic locus, fluorescent PCR technology to achieve greater sensitivity, and two-cell biopsy to increase the efficiency and success of diagnoses.

Adult↗
PubMed2002

First clinical application of comparative genomic hybridization and polar body testing for preimplantation genetic diagnosis of aneuploidy.

OBJECTIVE: To develop a preimplantation genetic diagnosis (PGD) protocol that allows any form of chromosome imbalance to be detected. DESIGN: Case report employing a method based on whole-genome amplification and comparative genomic hybridization (CGH). SETTING: Clinical IVF laboratory. PATIENT(S): A 40-year-old IVF patient. INTERVENTION(S): Polar body and blastomere biopsy. MAIN OUTCOME MEASURE(S): Detection of aneuploidy. RESULT(S): Chromosome imbalance was detected in 9 of 10 polar bodies. A variety of chromosomes were aneuploid, but chromosomal size was found to be an important predisposing factor. In three cases, the resulting embryos could be tested using fluorescence in situ hybridization, and in each case the CGH diagnosis was confirmed. A single embryo could be recommended for transfer on the basis of the CGH data, but no pregnancy ensued. CONCLUSION(S): Evidence suggests that preferential transfer of chromosomally normal embryos can improve IVF outcomes. However, current PGD protocols do not allow analysis of every chromosome, and therefore a proportion of abnormal embryos remains undetected. We describe a method that allows every chromosome to be assessed in polar bodies and oocytes. The technique was accurate and allowed identification of aneuploid embryos that would have been diagnosed as normal by standard PGD techniques. As well as comprehensive cytogenetic analysis, this protocol permits simultaneous testing for multiple single-gene disorders.

Adult↗
PubMed2002

A novel, de novo germline TP53 mutation in a rare presentation of the Li-Fraumeni syndrome in the maxilla.

We undertook the genetic analysis of a classic Li-Fraumeni syndrome (LFS) family with clustering of primary tumours including two maxillary sarcomas, a rare LFS site of tumour occurrence. Our aim was to investigate the presence of a specific type of TP53 mutation that could be associated with this unusual predilection of site for cancer occurrence. Mutational screening of the coding region of TP53 revealed an A>T transversion in codon 144 of exon 5 (CAG>CTG, Gln>Leu) in the germline of one of the three affected members, with loss of heterozygosity (LOH) in the tumour tissue. All other affected members were negative for germline or somatic TP53 mutations. TP53 immunohistochemistry was uninformative. The mutation we report is a de novo constitutional TP53 mutation that has not been previously described in the literature. It could explain the more burdened phenotype of the affected patient (died at 21 months). Alternative mechanisms to explain the overall family phenotype are discussed.

Adolescent↗