Дрозофиланың Escargot гені және оның жасушалық процестердегі ролі

Type of gene

Escargot (esg) is a transcription factor expressed in Drosophila melanogaster. It is responsible for the maintenance of intestinal stem cells and is used as a marker for those types of cells in Drosophila. Apart from its expression in the gut, esg is also expressed in expressed in germline stem cells and cyst stem cells of the testis and, during development, in neural stem cells and imaginal disks.

In the year 1992, Mary Whiteley and coworkers identified a gene which is very similar to Drosophila Snail gene and named it escargot. They found that it encodes for zinc finger like snail related genes.

Esg is required for the maintenance of somatic cyst stem cells in their stem state. The testis in Drosophila has two types of stem cells i. e., the germline stem cells and the somatic cyst stem cells. Germline stem cells divide to generate a daughter gonialblast and a germline stem cell. The gonialblast undergoes mitotic transit amplifying divisions to produce spermatocytes which will eventually give rise to haploid spermatids. On the other hand, cyst stem cells generate cyst cells and cyst stem cells. Cyst stem cells/cyst cells encapsulate the gonialblast and differentiate with differentiating germline and act analogously to the mammalian sertoli cells. Drosophila insulin like peptide signaling pathway is required for the differentiation of dividing cyst stem cells. Esg overexpression enhances the activity of imaginal morphogenesis protein late 2 (ImpL2) (fly homolog of mammalian insulin like growth factor binding protein IGFBP7), which is required to prevent the differentiation of dividing cyst stem cells and there by maintains the cyst stem cells in stem cell state.

Fibroblast growth factor signaling is important for trachea development in insects. Branching morphogenesis of the tracheal system in Drosophila is governed by FGF signaling. The primordial tip cells expressing Branchless/Breathless will initiate the primary branching and migration. The tip cells get differentiated into fusion cells or terminal cells. Fusion cells will get differentiated into different type of cells while terminal cells form cytoplasmic extensions with intracellular lumen. Esg regulates the diversification of branching tip cells by inhibiting the FGF signaling.

The Snail related zinc finger transcription factor family has been implicated in stem cell maintenance in the model insect, the fly D. melanogaster. Besides snail, D. melanogaster encodes five snail paralogs including esg, worniu, scratch, scratch like 1, and scratch like 2. The Snail family members snail, esg and worniu are involved in forming variable structures in D. melanogaster by functioning in several cellular process like cell behavior, cell shape, cell asymmetric divisions, cell fate regulation and cell differentiation, Recently, esg orthologue was identified in the genome of the leipdopteran Chloridea virescens.

Intra Tumour Heterogeneity (ITH) is the altered and diverse morphological, genetic, epigenetic, transcriptomic and metabolomic states of cancerous cells. The somatic epithelial cells of the Drosophila ovary emerge from germline stem cells to form polarized follicle cells that establish the monolayered epithelia which surrounds the germline cells within an egg chamber. Drosophila ovarian follicle cell model was used to study the ITH. Heterogeneity was induced in the follicle cells in situ. It was discovered that loss of cell polarity induces heterogenous multilayering. Esg was upregulated in the heterogenous cell population down stream of Upd/Jak STAT signaling and maintains the non polar cells. This can be extrapolated to the cancer associated fibroblasts which communicate with tumour cells via IL 6/STAT3 and this regulates cancer stem cell maintenance via Snail .