Biomedical subjects

Sara Nouri

Publications and source records attributed to Sara Nouri.

6 recordsLinked to original sources

PubMed2006

High-throughput analysis of chromosome abnormality in spontaneous miscarriage using an MLPA subtelomere assay with an ancillary FISH test for polyploidy.

Chromosome analysis of spontaneous miscarriages is clinically important but is hampered by frequent tissue culture failure and relatively low-resolution analysis. We have investigated replacement of conventional karyotype analysis with a quantitative subtelomere assay performed on uncultured tissue samples, which is based on Multiplex Ligation-Dependent Probe Amplification. This assay is suitable for this purpose as approximately 98% of all observed karyotype abnormalities in spontaneous miscarriages involve copy-number change to one or more subtelomere regions. A pilot study has compared karyotyping and subtelomere analysis on 78 samples. Extensive tissue necrosis accounted for failure of both karyotyping and subtelomere testing in four (5.1%) samples. Excluding these, there were no (0/74) subtelomere test failures compared to 9.5% (7/74) karyotype failures. Twenty-two (30%) whole chromosome aneuploidies and five (6.8%) structural abnormalities were detected using the subtelomere assay. With the exception of three cases of triploidy, all karyotype abnormalities were detected by the subtelomere assay. Following on from this study, a further 100 samples were tested using the subtelomere assay in conjunction with a simple ancillary FISH test using uncultured cells to exclude polyploidy in the event of a normal subtelomere assay result. Except for three necrotic samples, tests results were obtained for all cases revealing 18 abnormalities including one case of triploidy. Taking into consideration the high success rate for the combined MLPA and FISH test results, and the very significant additional advantages of cost-effective, high-throughput batching, and automated, objective analysis, this approach greatly facilitates routine investigation of chromosome abnormalities in spontaneous miscarriage.

Abortion, Spontaneous↗

PubMed2005

Unstable Robertsonian translocations der(13;15)(q10;q10): heritable chromosome fission without phenotypic effect in two kindreds.

Robertsonian translocations (RTs) are amongst the most common chromosome abnormalities, but being essentially balanced are not usually associated with phenotypic abnormality. Despite being dicentric, RTs are almost always transmitted stably through cell division without chromosome breakage. We have investigated spontaneous fission of der(13;15)(q10;q10) chromosomes in eight individuals from two unrelated kindreds with a view to assessing clinical significance and to seek an explanation for the peculiar heritable instability displayed by these chromosomes. In Family 1, fission products were observed in five members in three generations. The instability was observed in cells derived from chorionic villus and lymphocytes. In Family 2, the same phenomenon was observed in amniocytes from two separate pregnancies and maternal blood lymphocytes. Detailed FISH analysis of these RTs showed them to be dicentric with an unremarkable pericentromeric structure. Notably, combined immunofluoresence and FISH analysis showed the presence of the centromere-specific proteins CENP-A and CENP-E, consistent with functional dicentricity in >75% of cells analyzed. The fission products are, therefore, presumed to be the result of sporadic, bipolar kinetochore attachment, anaphase bridging with resultant inter-centromeric breakage in a small proportion of mitoses. None of the eight carriers shows phenotypic abnormality and therefore, for prenatal counseling purposes, there appears to be no increased specific risk associated with this phenomenon.

Autoantigens↗

PubMed2005

Molecular distinction between true centric fission and pericentric duplication-fission.

Centromere (centric) fission, also known as transverse or lateral centric misdivision, has been defined as the splitting of one functional centromere of a metacentric or submetacentric chromosome to produce two derivative centric chromosomes. It has been observed in a range of organisms and has been ascribed an important role in karyotype evolution; however, the underlying mechanisms remain unknown. We have investigated four cases of apparent centric fission in humans. Two cases show a missing chromosome 22 or 18 that is replaced by two centric ring products, a third case shows two chromosome-10-derived telocentric chromosomes, whereas a fourth case involves the formation of two chromosome-18-derived isochromosomes. In all four cases, results of gross cytogenetic and fluorescence in situ hybridisation analyses were consistent with a simple centric fission event. However, detailed molecular analyses provided evidence in support of centromere duplication as a predisposing mechanism for the observed chromosomal breakage in two of the cases. Results for the third case are consistent with direct centric fission not involving centromere pre-duplication as the likely mechanism. Insufficient material has precluded the further study of the fourth case. The data provide the first molecular evidence for centromere pre-duplication as a possible mechanism to explain the classically assumed simple "centric fission" events in clinical cytogenetics, karyotype evolution and speciation.

Fluorescent Antibody Technique↗

PubMed2004

Improved testing for CMT1A and HNPP using multiplex ligation-dependent probe amplification (MLPA) with rapid DNA preparations: comparison with the interphase FISH method.

Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are the two most common peripheral neuropathies, with incidences of about 1 in 2,500. Several techniques can be used to detect the typical 1.5-Mb duplication or deletion associated with these respective conditions, but none combines simplicity with high sensitivity. MLPA is a new technique for measuring sequence dosage. We have assessed its performance for the detection of the specific 1.5-Mb duplication/deletion by prospectively testing 50 patients referred with differential diagnoses of CMT or HNPP. Probes were designed to evaluate the TEKT3, PMP22, and COX10 genes within the CMT1A/HNPP region. We have compared the results with our existing fluorescence in situ hybridization (FISH) assay, which was performed in parallel. There was concordance of results for 49 patients. Of note, one patient showed an intermediate multiplex ligation-dependent probe amplification (MLPA) result with an abnormal FISH result, which is consistent with mosaicism. The assay works equally well with either purified DNA or rapid DNA preparations made by direct cell lysis. The use of the latter significantly reduces the cost of the assay. MLPA is a sensitive, specific, robust, and cost-effective technique suitable for fast, high-throughput testing and offers distinct advantages over other testing methods.

Charcot-Marie-Tooth Disease↗

PubMed2003

Pericentromeric euchromatin is conserved in minute human supernumerary chromosomes: a study using cross-species colour segmenting (RxFISH).

Investigation of marker chromosomes is one of the most challenging areas of clinical cytogenetics, especially in the prenatal scenario. A range of techniques including microdissection/reverse painting, SKY and M-FISH are available for the investigation of larger markers (>3 Mb). All these techniques rely on hybridization of unique, homologous sequences with simultaneous suppression of repeat sequences. In contrast, RxFISH is based on hybridization of cross-species syntenic sequences; repeat sequences do not hybridize due to species divergence. We have used RxFISH to analyse a group of the smallest, i.e. minute, supernumerary marker chromosomes. Our results suggest that even the smallest marker chromosomes often contain conserved pericentric euchromatin. More detailed characterization of pericentric genetic content is needed to assess the clinical significance of minute supernumerary markers.

Chromosome Aberrations↗

PubMed2002

Increased gene dosage at Xq26-q27 is associated with X-linked hypopituitarism.

We have identified a novel interstitial duplication at Xq26.1-q27.3 in a previously reported family with X-linked recessive hypopituitarism [1]. Mapping of the duplication was carried out using interphase FISH analysis of over 60 bacterial genomic clones from Xq25-q28. The proximal and distal breakpoints of the duplication are contained within the 432N13 and 91O18 clones, respectively, and are separated by approximately 9 Mb. Comparison with a recently published 13-Mb duplication in another XH family [2] indicated that the duplication break-points in these families were different. Therefore, we conclude that X-linked hypopituitarism is caused by increased dosage of a gene that is critical for pituitary development and that the causative gene is located within the 9-Mb duplicated region that we have defined.

Dosage Compensation, Genetic↗