The role of yan in mediating the choice between cell division and differentiation

Abstract

An allele of the yan locus was isolated as an enhancer of the Ellipse mutation of the Drosophila epidermal growth factor receptor (Egfr) gene. This yan allele is an embryonic lethal and also fails to complement the lethality of anterior open (aop) mutations. Phenotypic and complementation analysis revealed that aop is allelic to yan and genetically the lethal alleles act as null mutations for the yan gene. Analysis of the lethal alleles in the embryo and in mitotic clones showed that loss of yan function causes cells to overproliferate in the dorsal neuroectoderm of the embryo and in the developing eye disc. Our studies suggest that the role of yan is defined by the developmental context of the cells in which it functions. An important role of this gene is in allowing a cell to choose between cell division and differentiation. The relationship of the Egfr and Notch pathways to this developmental role of yan is discussed.

Yan, an ETS‐domain transcription factor, negatively modulates the Wingless pathway in the Drosophila eye

“…On the basis of our in vivo and in vitro characterization of the antagonistic interaction between Yan and the Wingless pathway, we propose that yan has a dual role at the moving anterior/posterior boundary defined by the morphogenetic furrow (Fig 5D). In addition to the previously defined function of Yan in inhibiting premature photoreceptor recruitment (O'Neill et al , 1994; Rogge et al , 1995), we suggest that Yan blocks Wingless signalling at the morphogenetic furrow, probably by regulating the activity of Armadillo protein (Fig 5D). By maintaining low Wingless signalling activity, we propose that Yan maintains the competence of these cells to adopt a retinal fate.…”

“…In 5-10% of the adult eyes, we also observed aberrant structures from yan À/À clones, including tube-like overgrowths (Fig 2D-D 0 ). Loss of photoreceptor differentiation in yan À/À clones was previously reported, which indicated an early, cell-autonomous requirement of yan for neuronal fate (Rogge et al, 1995). Moreover, we were intrigued by the similarity between the adult phenotypes shown by the yan À/À clones with those of axin À/À clones or Flip-Out clones expressing Armadillo* (Baonza & Freeman, 2002;Fig 2B,C).…”

Ratiometric sensing of Pnt and Yan transcription factor levels confers ultrasensitivity to photoreceptor fate transitions in Drosophila

“…We focused our study on two ETS-family transcription factors, the activator Pointed (Pnt) and the repressor Yan (also known as Anterior Open, or Aop), that compete for the same DNA binding sites across the genome (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). This activator/repressor pair functions downstream of receptor tyrosine kinase (RTK) signaling to regulate cell state transitions in many developing Drosophila tissues, including progenitor to photoreceptor transitions in the eye (10)(11)(12)(21)(22)(23)(24)(25)(26)(27)(28). During eye development, eight distinct photoreceptor (R) neurons, R1-R8, are specified from a specific pool of multipotent progenitor (P) cells that co-express Pnt and Yan and are poised to differentiate (Figures 1A and S1A) (28).…”

“…In Drosophila , two ETS-domain transcription factors, Pointed (Pnt) and Yan (also known as Aop, Anterior open), act downstream of signals mediated by receptor tyrosine kinases (RTKs) to regulate cell fate transitions in a wide variety of tissues across the body and across the life cycle (Flores et al, 2000; Gabay et al, 1996a; Gabay et al, 1997; Halfon et al, 2000; Lachance et al, 2014; Melen et al, 2005a; O’Neill et al, 1994; Rebay and Rubin, 1995; Rogge et al, 1995; Shwartz et al, 2013; Xu et al, 2000). Consistently across many different developmental transitions, loss of yan results in too many progenitors transitioning to a particular fate, while loss of pnt prevents fate transitions (Brunner et al, 1994; Flores et al, 2000; Gabay et al, 1996a; Halfon et al, 2000; O’Neill et al, 1994; Xu et al, 2000).…”

“…In Drosophila, two ETS-domain transcription factors, Pointed (Pnt) and Yan (also known as Aop, Anterior open), act downstream of signals mediated by receptor tyrosine kinases (RTKs) to regulate cell fate transitions in a wide variety of tissues across the body and across the life cycle (Flores et al, 2000;Gabay et al, 1996a;Gabay et al, 1997;Halfon et al, 2000;Lachance et al, 2014;Melen et al, 2005a;O'Neill et al, 1994;Rebay and Rubin, 1995;Rogge et al, 1995;Shwartz et al, 2013;Xu et al, 2000).…”