A study of biochemical genetic abnormalities associated with purine and pteridine metabolism

Purines and pteridines (more commonly referred to as 'folates') are fundamental components in a number of reactions involved in DNA and RNA synthesis and are inextricably linked to the basic metabolic pathways of the normal functioning cell. The aim of this project was to examine the ways in which existing biochemical and molecular techniques could be used to better effect in the diagnosis of a number of genetic disorders associated with purine and pteridine metabolism. The disorders under study covered a spectrum of inheritance patterns, notably Lesch-Nyhan Syndrome (LNS) and gout (X-linked); adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) deficiency (autosomal) and neural tube defects (multifactorial). Phase 1: Purines Lesch-Nyhan Syndrome The first phase of the project was an investigation of purine metabolism and as a first step, reliable reference ranges in various tissues were established which could be utilised in the diagnosis of patients with specific enzyme deficiencies. Control samples taken from subjects with no known history of metabolic disorders were analysed for the purine enzymes; hypoxanthine-guanine phosphoribosyl transferase (HGPRT); adenine phosphoribosyl transferase (APRT); ADA; PNP and phosphoribosyl pyrophosphate synthetase (PRPP-S) in various tissues, notably adult, fetal and cord red cells; cultured and fresh chorionic villi (CV); fibroblasts and cultured amniotic fluid cells. A critical analysis of the distribution parameters (Kolmogorov-Smirnov (KS) test) confirmed that all enzymes exhibited Gaussian distributions after log10 transformation of the data and this was carried out for ail reference ranges. Phase 2: Pteridines The second phase of the project involved a case-control study to examine the role played by the thermolabile mutation of the enzyme 5,10 methylene tetrahydrofolate reductase (MTHFR), in the development of neural tube defects (NTD) in a Scottish population. Assessment of the allelic frequency of the thermolabile variant, and the lymphocyte MTHFR enzyme activity was related to the folate and vitamin B12 status in both controls and in populations with a family history of NTD. (Abstract shortened by ProQuest.)