1,721,001 research outputs found
Molecular investigations of structural and numerical chromosome abnormalities in man
No full textThis thesis concerns two areas of investigation. (1) The chromosomal origins and in some cases the molecular composition of 76 autosomal supernumerary marker chromosomes (SMC) were identified using fluorescence in situ hybridisation (FISH) and polymerase chain reaction (PCR) techniques. Forty seven were de novo, 9 maternally and 7 paternally transmitted and in 13 cases the parental origin is not known. Thirty four cases were non-mosaic and 42 mosaics, with 26 cases ascertained prenatally and 50 postnatally. Thirty two of the SMCs were shown to be derived from chromosome 15. Sixteen de novo SMC(15)s were maternal in origin, contained proximal 15q euchromatin and were invariably ascertained in patients with moderate to severe mental retardation. By contrast, the majority of SMC(15) without 15q euchromatin were found in normal individuals. Three out of 6 patients with SMC(22) were shown to contain proximal 22q euchromatin but no straightforward correlation between the extent of additional material in the SMC(22) and phenotypic effects were observed. Of the 38 SMCs derived from other autosomes, euchromatin was detected in 9 out of 18 tested with paints and/or PCR; abnormal phenotypes were most commonly observed in patients with small ring shaped SMCs containing euchromatic sequences. Uniparental disomy for chromosomes 6 and 15 respectively were detected amongst the 47 cases examined.(2) Twenty six patients, with either isolated aniridia, with one or more of the WAGR (Wilms' tumour, aniridia, genital anomalies and mental retardation) syndrome or other anomalies were analysed by FISH with selected 11p13 markers including cosmids, FO2121, PAX6 (aniridia), D11S324 and WT1 (Wilms' tumour predisposition). Overall 8/26 (�30%) had abnormalities resolvable with FISH. Three patients with isolated aniridia were abnormal; the first with an apparently balanced reciprocal 7;11 translocation and an 11p13 breakpoint which by FISH was shown to be �30kb distal to the aniridia (PAX6) gene.</p
Frequent chromosome aberrations revealed by molecular cytogenetic studies in patients with aniridia
No full textSeventy-seven patients with aniridia, referred for cytogenetic analysis predominantly to assess Wilms tumor risk, were studied by fluorescence in situ hybridization (FISH), through use of a panel of cosmids encompassing the aniridia-associated PAX6 gene, the Wilms tumor predisposition gene WT1, and flanking markers, in distal chromosome 11p13. Thirty patients were found to be chromosomally abnormal. Cytogenetically visible interstitial deletions involving 11p13 were found in 13 patients, 11 of which included WT1. A further 13 patients had cryptic deletions detectable only by FISH, 3 of which included WT1. Six of these, with deletions <500 kb, share a similar proximal breakpoint within a cosmid containing the last 10 exons of PAX6 and part of the neighboring gene, ELP4. Two of these six patients were mosaic for the deletion. The remaining four had chromosomal rearrangements: an unbalanced translocation, t(11;13), with a deletion including the WAGR (Wilms' tumor, aniridia, genitourinary abnormalities, and mental retardation) region, and three balanced rearrangements with what appear to be position effect breakpoints 3' of PAX6: (a) a t(7;11) with the 11p13 breakpoint ~30 kb downstream of PAX6, (b) a dir ins(12;11) with a breakpoint >50 kb from PAX6, and (c) an inv(11)(p13q13) with a breakpoint >75 kb downstream of PAX6. The proportion and spectrum of chromosome anomalies in familial (4/14, or 28.5%) and sporadic (26/63, or 41%) cases are not significantly different. An unexpectedly high frequency of chromosomal rearrangements is associated with both sporadic and familial aniridia in this cohort
Perspective on the technical challenges involved in the implementation of array-CGH in prenatal diagnostic testing
No full textOur aim was to construct a streamlined technical workflow to facilitate a prospective, multi-centre evaluation of array comparative genomic hybridisation (array-CGH) in the prenatal diagnostic context. A collection of commercially available DNA extraction and quantification techniques were evaluated and compared using minimal quantities of amniotic fluid, chorionic villi and cultured cells. When prenatal DNA of suitable quality and quantity was obtained, array-CGH was performed using Oxford Gene Technology’s (OGT, Oxford, UK) CytoSure™ ISCA 8 × 60 K oligo array platform. With starting quantities of 2–4 ml amniotic fluid, 2–5 mg chorionic villi or under 150,000 cultured cells the following optimised technical workflow was identified: DNA extraction using the iGENatal™ kit (igenbiotech, Madrid, Spain) and quantification by the Qubit® 2.0 Fluorometer with the Qubit® dsDNA BR assay kit (Invitrogen™, Eugene, OR, USA). In addition, it was elucidated that array-CGH can be successfully performed with as little as 125 ng DNA in the experiment using the OGT CytoSure™ ISCA 8 × 60 K oligo array platform. Amidst an on-going debate on whether array-CGH should be applied in the prenatal diagnostic setting, by following the technical recommendations described here genetics laboratories can now gain exposure to prenatal array-CGH testing without compromising the conventional karyotype resul
A novel 2.43 Mb deletion of 7q11.22-q11.23
No full textWe present a patient with a novel heterozygous deletion of 7q11.22-q11.23. Standard cytogenetic analysis using the ELN cosmid 82C and the ELN/ LIMK1 cosmid 34B FISH probes suggested a diagnosis of Williams syndrome. Although he has supravalvular aortic stenosis and peripheral pulmonary artery stenosis, which are common in this condition, he does not have the clinical gestalt of Williams syndrome. 44k oligo array CGH analysis showed a 2.43 Mb deletion, encompassing the proximal 1.43 kb of the Williams syndrome critical region and extending approximately 1 Mb beyond it. The deletion of further genes outside the Williams syndrome critical region does not appear to be having a phenotypic effect at presen
The use of mouth brushings for screening girls who present with inguinal hernia for complete androgen insensitivity syndrome
No full textIntroduction: published guidance recommends that all girls with inguinal hernia should be screened for complete androgen insensitivity syndrome (CAIS). We report a novel, noninvasive screening technique.Methods: retrospective review of all girls undergoing inguinal herniotomy from April 2009 to October 2010. Those screened using the novel technique of extraction of Y chromosome specific DNA from a buccal mucosal sample obtained by mouth brushing are reported.Results: a total of 29 girls were screened by mouth brushing at median age 2.9 years (range 29 days to 9.3 years). Of the 29 samples, 25 were adequate for DNA extraction; 4 were inadequate and screening was repeated (3 repeat mouth brushing, 1 perioperative blood test). Mouth brushing was well tolerated by children and acceptable to parents. A preoperative blood test was avoided in all girls who had a mouth brushing. None of the girls in this study had CAIS. Turn-around time for mouth brushing was mean 4.9 days compared with a minimum of 10 days for a karyotype. This technique is cheaper than a karyotype (£87 vs. £205).Conclusion: extraction of Y chromosome specific DNA from a mouth brushing sample is effective for screening girls with inguinal hernia for CAIS. It is acceptable, cheaper, and quicker than alternative
Controversies in prenatal diagnosis 3: should everyone undergoing invasive testing have a microarray?
No full textChromosomal microarrays (CMA) are routinely used in postnatal genetic diagnosis. CMA is technically applicable in prenatal diagnosis. Pros and cons of routine use are discussed; technical aspects and dseign of array, yield, interpretation of CNV and variances of unknown significance (VOUS), quality control regimens. <br/
A 2.3Mb deletion of 17q24.2-q24.3 associated with ‘Carney Complex plus’
No full textWe present a 12-year-old with a de novo interstitial deletion of approximately 2.3 Mb in chromosome band 17q24-2eq24.3, which was identified by array CGH. The most characteristic features in this case are posterior laryngeal cleft and the presence of numerous freckles and lentigines in childhood. Growth restriction, microcephaly and moderate mental retardation are also prominent features but are frequently
seen with other chromosomal anomalies. The microdeletion causes haploinsufficiency of PRKAR1A (protein kinase, cAMP-dependent, regulatory 1?), which is known to cause Carney Complex but this diagnosis alone does not account for all of her problems and she therefore has ‘Carney Complex plus’.
This report illustrates the practical benefits associated with a clear cytogenetic diagnosis, as regular endocrinological and cardiac screening is required
The clinical utility of microarray technologies applied to prenatal cytogenetics in the presence of a normal conventional karyotype: a review of the literature
No full textThe clinical utility of microarray technologies when used in the context of prenatal diagnosis lies in the technology's ability to detect submicroscopic copy number changes that are associated with clinically significant outcomes. We have carried out a systematic review of the literature to calculate the utility of prenatal microarrays in the presence of a normal conventional karyotype. Amongst 12?362 cases in studies that recruited cases from all prenatal ascertainment groups, 295/12?362 (2.4%) overall were reported to have copy number changes with associated clinical significance (pCNC), 201/3090 (6.5%) when ascertained with an abnormal ultrasound, 50/5108 (1.0%) when ascertained because of increased maternal age and 44/4164 (1.1%) for all other ascertainment groups (e.g. parental anxiety and abnormal serum screening result). When additional prenatal microarray studies are included in which ascertainment was restricted to fetuses with abnormal ultrasound scans, 262/3730 (7.0%) were reported to have pCNCs
- …
