https://www.cell.com/cell/pdf/S0092-8674(00)80582-6.pdf

A spatial map of olfactory receptor expression in the Drosophila antenna.

https://www.cell.com/cell/pdf/S0092-8674(00)00021-0.pdf

An olfactory sensory map in the fly brain

http://www.columbia.edu/cu/biology/courses/g4008x/readings03/genomics/Carlson%20Drosophila.pdf

A novel family of divergent seven-transmembrane proteins: candidate odorant receptors in Drosophila.

Cell division is commonly thought to involve the equal distribution of cellular components into the two daughter cells. During many cell divisions, however, proteins, membrane compartments, organelles, or even DNA are asymmetrically distributed between the two daughter cells. Here, we review the various types of asymmetries that have been described in yeast and in animal cells. Asymmetric segregation of protein determinants is particularly relevant for stem cell biology. We summarize the relevance of asymmetric cell divisions in various stem cell systems and discuss why defects in asymmetric cell division can lead to the formation of tumors.

/pdf/dividing-cellular-asymmetry-asymmetric-cell-division-and-its-24monk1adr.pdf

Dividing cellular asymmetry: asymmetric cell division and its implications for stem cells and cancer

We have identified Math5, a mouse basic helix-loop-helix (bHLH) gene that is closely related to Drosophila atonal and Xenopus Xath5 and is largely restricted to the developing eye. Math5 retinal expression precedes differentiation of the first neurons and persists within progenitor cells until after birth. To position Math5 in a hierarchy of retinal development, we compared Math5 and Hes1 expression in wild-type and Pax6-deficient (Sey) embryos. Math5 expression is downregulated in Sey/+ eyes and abolished in Sey/Sey eye rudiments, whereas the bHLH gene Hes1 is upregulated in a similar dose-dependent manner. These results link Pax6 to the process of retinal neurogenesis and provide the first molecular correlate for the dosage-sensitivity of the Pax6 phenotype. During retinogenesis, Math5 is expressed significantly before NeuroD, Ngn2 or Mash1. To test whether these bHLH genes influence the fates of distinct classes of retinal neurons, we ectopically expressed Math5 and Mash1 in Xenopus retinal progenitors. Unexpectedly, lipofection of either mouse gene into the frog retina caused an increase in differentiated bipolar cells. Directed expression of Math5, but not Xath5, in Xenopus blastomeres produced an expanded retinal phenotype. We propose that Math5 acts as a proneural gene, but has properties different from its most closely related vertebrate family member, Xath5.

Math5 encodes a murine basic helix-loop-helix transcription factor expressed during early stages of retinal neurogenesis

Specification of cell fate in the adult sensory organs is known to be dependent on intrinsic and extrinsic signals. We show that the homeodomain transcription factor Prospero (Pros) acts as an intrinsic signal for the specification of cell fates within the mechanosensory lineage. The sensory organ precursors divide to give rise to two secondary progenitors - PIIa and PIIb. Pros is expressed in PIIb, which gives rise to the neuron and thecogen cells. Loss of Pros function affects the identity of PIIb and neurons fail to differentiate. Pros misexpression is sufficient for the transformation of PIIa to PIIb fate. The expression of Pros in the normal PIIb cell appears to be regulated by Notch signaling.

Sibling cell fate in the Drosophila adult external sense organ lineage is specified by prospero function, which is regulated by Numb and Notch

We have examined the mechanisms underlying the development of the olfactory sense organs on the third segment of the antenna of Drosophila. Our studies suggest that a novel developmental strategy is employed. Specification of the founder or precursor cell is not governed by the genes of the achaete-scute complex. Another basic helix-loop-helix encoding gene, atonal, is essential for determination of only a subset of the sensilla types--the sensilla coeloconica. Therefore, we predict the existence of additional proneural genes for the selection of sensilla trichoidea and sensilla basiconica. The choice of a founder cell from the presumed proneural domain is regulated by Notch activity. Soon after delamination of the founder cell, two to three additional neighboring cells also take on a sensory fate and these cells together form a presensillum cluster. The selection of neighbors does not occur when endocytosis is blocked using a temperature sensitive allele of shibire, thus suggesting that cell-cell communication is required for this step. The cells of the cluster divide once before terminal differentiation which is influenced by Notch activity. The final cell number within each sensillum is controlled by programmed cell death.

G.V. Reddy

Papers

Sibling cell fate in the Drosophila adult external sense organ lineage is specified by prospero function, which is regulated by Numb and Notch

Development of the Drosophila olfactory sense organs utilizes cell-cell interactions as well as lineage