Date of Award

1994

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Bachelor of Applied Sciences Honours

Faculty

Faculty of Science and Technology

First Supervisor

Professor Alan Bittles

Second Supervisor

Dr Ashleigh Murch

Third Supervisor

Anne Mitchell

Abstract

This honours project is based on the advancement of in situ hybridisation to metaphase chromosome spreads. The technique was carried out using cosmid probes which are specific for microdeleted regions on chromosome 22q11 associated with Di George syndrome (DGS) and related disorders. Disorders similar to DGS include partial Di George syndrome, III-IV pharyngeal pouch syndrome, velucardiofacial syndrome (VCFS), conotruncal facial anomaly and the CHARGE association. Recently the group of disorders with this microdeletion and comparable symptoms has been summarised by the acronym CATCh 22. Large deletions, translocations, monosomies, and trisomies of chromosomes are apparent under the light microscope, when prepared as metaphase chromosome spreads for karyotyping. Subtle microdeletions, however, are seldom detected by this method, even when high resolution banding techniques are undertaken. A more suitable technique for the detection of such microdeletions is in situ hybridisation. In situ hybridisation (ISH) has successfully been employed to identify chromosomes, to detect chromosomal abnormalities, and to determine chromosomal locations of specific gene sequences. The aim of the present study is to apply in situ hybridisation to the detection of suspected microdeletions of chromosome 22q11. Fluorescent in situ hybridisation (FISH) and other forms of non-isotopic in situ hybridisation (NISH) were carried out with cosmid probes specific for chromosome region 22q11, on peripheral blood samples of patients displaying DGS-like symptoms and controls. Patients suspected of having Di George syndrome were surveyed by Dr. S. Worthington at Princess Margaret Hospital for Children (Western Australia) as part of a clinical study into familial congenital heart disease (CHD). All patients tested have CHD, and display some DGS-like symptoms. The advancement of the FISH technique will assist clinicians in the identification of patients with the CATCH 22 sequence, and will further serve to demonstrate the ability of a cosmid probe to detect a microdeletion associated with a clinical disorder. The effectiveness of the method will also be compared to results obtained by routine cytogenetic analysis. The study shows that although in situ hybridisation is technically difficult to establish, it holds great promise as a sensitive and specific diagnostic test and research tool.

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