Our body contains more than two hundred different cell types which are responsible for development of complex organs like heart, kidney, liver, eyes, brain etc. All these cell types originate form single cell i.e. a fertilized egg which contains same genetic material (DNA) contributed by mother and father. Although each cell type contains same basic genetic information (DNA) inherited from fertilized egg, yet their identity is different from one another when they contribute to development of different tissues/organs. How identity of different cell types is established and how cell fates established early during development are maintained (cell memory) in subsequent development are questions which are being investigated in our lab using fruit fly (Drosophila melanogaster). In Drosophila melanogaster, genetic analyses have uncovered two groups of genes, the Polycomb Group (PcG) and the Trithorax Group (TrxG), responsible for maintaining gene expression patterns in OFF and ON states, respectively. Both PcG and TrxG proteins affect gene activity (ON or OFF) without causing any change in primary DNA sequence of a gene and this mode of action is stable and heritable generations after generations of cells. Such heritable changes in gene expression which do not involve any alteration in the basic genetic information (i.e. DNA sequence) are referred to as epigenetics which is hallmark of cell memory. This also explains how cells with same DNA sequence (i.e. genes) can acquire different identity which is maintained through epigenetic inheritance with the help of PcG and TrxG system. Importantly, PcG and trxG proteins are evolutionary conserved and most of our knowledge about their function was pioneered from studies in Drosophila. Molecular analysis showed that many of the proteins encoded by the PcG and trxG act in large protein complexes, and modify the local properties of chromatin (DNA + proteins that package DNA) to maintain repression i.e. OFF (PcG) or activation i.e. ON (TrxG) of their target genes. Maintenance of gene expression patterns by PcG and TrxG proteins is hallmark of cell memory which ensures maintenance of cell identity throughout our life. Although, epigenetic regulation of gene expression by PcG protein complexes have been well characterized with respect to their biochemical activity, however, little is known about their dynamic behavior during development in different cell types.With the help of molecular biology and computational approaches Tariq’s Epigenetic lab has identified novel factors potentially involved in maintenance of cell memory and these factors are currently being characterized at molecular and cellular level using genomic and proteomic approaches.
Our lab is located on 3rd floor of Syed Babar Ali School of Science and Engineering (SBASSE) in Department of Biology.
Epigenetics, Cell Signaling, Drosophila, PcG, TrxG, Gene regulation
9-315 A, SBA School of Science and Engineering,
Lahore University of Management Sciences (LUMS), DHA 54792, Lahore, Pakistan.
Tel: +92 (42) 3560 8218, Fax: +92 (42) 3572 5048