Title : Epigenetic modulation of human neurological disorders: Lesch-Nyhan disease as a model disorder
Abstract:
Epigenetics is the study of how cells control gene activity without changing the DNA sequence. Epigenetic changes affect how genes are turned on and off, or expressed, and thus help regulate how cells in different parts of the body use the same genetic code. Errors in epigenetic process can not only lead to abnormal gene activity or inactivity but also influence alternative splicing (AS) and could cause human diseases. Otherwise, there is also epistasis (gene-gene interactions) in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. So, the effects of a given gene on a biological trait are masked or enhanced by one or more other genes. This abstract concerns the Lesch-Nyhan disease, LND, a rare X-linked recessive neurogenetic disorder, MIM: 300322). Despite having been characterized since more than 60 years ago (from the first report of Lesch M, Nyhan WL in 1964), however, up to now, there is no satisfactory explanation of how the loss of the hypoxanthine-guanine phosphoribosyltrnasferase (HGprt) enzyme function affects the brain to cause the intellectual impairment, and self-mutilating behaviors in LND. This has made difficult for the development of an effective treatment for LND. Some findings reported that expression of the b-amyloid precursor protein (APP) gene from human skin fibroblasts from normal subject (control) as well as LND patients was (a) under epigenetic regulation of alternative APP pre-mRNA splicing; and (b) via epistasis between the hypoxanthine phosphoribosyltransferase 1 (HPRT1, encoded for HGprt) and APP genes affecting alternative APP pre-mRNA splicing leading to the production of alternative APP fragments that might be responsible for the differing severity in LND patients. Understanding of how epigenetic defects and epistasis affecting human health, especially for neurological disorders, could suggest targets for therapeutic interventions. For such a purpose, LND has been selected as a valuable model for studying genetic-epigenetic interplay as well as for exploring epistasis between HPRT1 and APP genes. And so, the construction of expression vectors for HGprt enzyme and APP via the glycosyl-phosphatidylinositol, GPI, anchor is performed (Figure 1). Information obtained from such expression vectors would be useful for future directions to design therapies. The present abstract is aimed at enhancing, for the fist time, the importance of an epigenetic modulation via epistasis between APP and HGprt in LND based on findings found from divers publications suggesting that the pathogenesis of this monogenic LND results from combinatorial and multigenic defects and could be considered as a model disorder for the research on other genetic diseases, especially human neurological disorders.
The mammalian expression vector pcDNATM 3.1 (+) is used as backbone in which all genes of interest are inserted in the right frame into the pcDNATM 3.1 (+) vector. The construct comprising the sequence encoding the C-terminal of the glycosyl-phosphatidylinositol, GPI, anchor derived from the human folate receptor 1 (FOLR1) protein; the entire coding sequence (CDS) of hypoxanthine phosphoribosyltransferase 1 (HPRT1) gene encoding HGprt enzyme or the CDS of APP gene encoding APP coupled with the CDS of the green fluorescent protein (GFP) gene.
