The Hox genes play a role in anteroposterior axis specification of bilaterian animals that has been conserved for more than 600 million years. However, some of these genes have occasionally changed their roles in evolution. For example, the insect gene fushi tarazu (ftz), although localised in the Hox cluster, no longer acts as a Hox gene, but is involved in segmentation and nervous system development. Recent data of Mouchel‐Vielh et al.,1 and Hughes and Kaufman2 on ftz homologues in (...) a crustacean and a myriapod, respectively, shed new light onto the evolution of this gene. BioEssays 24:992–995, 2002. © 2002 Wiley‐Periodicals, Inc. (shrink)

Abstractftz is one of the ‘pair rule’ segmentation genes of Drosophila melanogaster, and is an important component of the segmentation process in the fruit fly. We discuss the transcriptional mechanism which causes ftz to be expressed in a seven stripe pattern during embryogenesis.

In a recent paper, Merabet and Hudry discuss models explaining the functional evolution of fushi tarazu (ftz) from an ancestral homeotic to a pair‐rule segmentation gene in Drosophila. As most of the experimental work underlying these models comes from our research, we wish to reply to Merabet and Hudry providing an explanation of the experimental approaches and logical framework underlying them. We review experimental data that support our hypotheses and discuss misconceptions in the literature. We emphasize that the (...) change in ftz function required changes in both expression pattern and protein function and review the evidence that these functional changes involved a switch in cofactor‐interaction motifs during arthropod radiations. While agreeing with Merabet and Hudry that protein context likely contributes to Ftz function, we argue that until supporting evidence for alternative mechanisms is obtained, the role of cofactor‐interaction motifs in driving a functional switch remains compelling. (shrink)

Retinoids play an important role in development and differentiation(1,2). Their effect is mediated through nuclear receptors, RAR (α, β and γ) and RXR (α, β and γ),Abbreviations. RAR: retinoic acid receptor; RXR: retinoid X receptor; T3:thyroid hormone receptor; VD3R: vitamin D3 receptor; PPAR: peroxisome proliferator activated receptor; EcR ecdycsone receptor; USP, ultraspiracle; NGFI‐B: also referred to as nur77a; ELP: embryonal long terminal repeat‐binding protein; FTZ‐F1: positive regulator of the fushi tarazu gene in blastodermstage embryos of Drosophila melanogaster; GR: (...) glucocorticoid receptor; ER: estrogen receptor; RARE, retinoic acid response element; PR: progesterone receptor; DR+x: direct repeat with a spacing of x nucleotides; DBD: DNA‐binding domain; CRABP I and II: cellular retinoic acid binding protein type I and II, respectively; MoMLV: Moloney Murine Leukemia Virus; TBP: TATA‐binding protein; TAF: TBP associated factor. which are members of a distinct subclass (hereafter referred to as type II) of the nuclear receptor superfamily that includes the thyroid hormone receptor (T3R), the vitamin D3 receptor (VD3R) and the peroxisome proliferator activated receptor (PPAR). Type II receptors transactivate through binding sites composed of closely related half‐sites (consensus sequence AGG/T TCA) arranged as direct repeats and, with the possible exception of RXR, do not bind to their cognate binding sites as homodimers but require RXR for high affinity binding. RXR thus provides a link between biologically distinct ligand induced pathways and is a potential target for cross‐regulation. In addition, RAR can utilize alternative routes to enhance transcription initiation mediated through transcriptional co‐activators which are expressed in a cell‐type specific manner. (shrink)

This essay explores whether ontology is internal to traditional Chinese culture from the perspective of the view from above. Ancient Chinese philosophy, poetry, and art abound with all kinds of descriptions of viewing from above. Such views from on high, as illustrated by famous works discussed in this essay, usually admit of no fixed focus; that is, there is no ontic being, concealed or disclosed, controlling the perceiving eyes. The gaze from above, which is either fluid or decentered, in some (...) cases does not even focus on any real object. It merely reveals an abstract historical review or an attitudinal stance. As such, the fushi gaze, devoid of any concrete object of perception or any central point of reference, always points to the absence of ontology. (shrink)