One of the most important roles of the skin is the formation of an effective barrier to prevent desiccation as well as to keep out foreign pathogens and allergens. This is a tightly regulated process and involves many structural proteins, lipids, enzymes and biochemical components. One of the proteins that has an indispensable role in barrier formation is filaggrin, which is encoded by the filaggrin gene (FLG) that lies within a cluster of epidermal genes known as the epidermal differentiation complex (EDC) on chromosome 1q21. Recent studies in Europe have shown that null mutations in FLG lead to the loss of the filaggrin protein; this is the underlying genetic cause of ichthyosis vulgaris (IV) and is a significant predisposing factor for atopic dermatitis (AD) and other atopic conditions such as asthma, allergic rhinitis and food allergy. In this thesis, the critical role of FLG-null mutations was examined and confirmed as a strong predisposing factor for AD in Singaporean Chinese patients. In addition, AD patients with FLG mutations also showed an increased susceptibility for recurrent skin infections. Interestingly, a diverse and wide spectrum of FLG-null mutations was identified in the Singaporean Chinese population, as opposed to the dominance of a few common FLG mutations in Europe. This result highlighted discrete genetic variations between different ethnic groups. FLG-null mutations were also shown to have significant gene modifying effects on other skin barrier genes such as steroid sulphatase gene (STS) to exacerbate the phenotype of X-linked ichthyosis (XLI). Next, the effect of FLG¬-null mutations on other complex conditions such as acne vulgaris and childhood peanut sensitisation was investigated but no significant association of FLG mutations with these diseases were observed in the Singaporean Chinese population. Lastly, a study was attempted to search for a candidate gene for psoriasis within the EDC, through the use of fine mapping techniques. With the advent of faster and cheaper next generation sequencing (NGS) in the near future, the quest for susceptibility factors in complex traits will increase in effectiveness and speed.
|Date of Award||2011|
|Sponsors||Agency for Science, Technology and Research|
|Supervisor||Ellen Lane (Supervisor) & Irwin McLean (Supervisor)|
- Genetic disorder