Gallegos, Maria et al. (2015) International Worm Meeting "Cellular and Molecular Mechanisms Underlying Neurite Termination and Refinement in C. elegans."

Avina, Monika, Gallegos, Maria, Azevedo, Joshua, Das, Pranti, Ndungu-Case, Catherine, Serra, Lorrayne, Tara, Boshika, Flores, Alejandro

[International Worm Meeting, 2015]

In the posterior half of the worm, gentle touch is first detected by the mechanosensory neuron PLM. As expected for a spatially restricted function, the PLM dendrite occupies the posterior half of the animal. How is the termination point of the PLM dendrite established? Exuberant outgrowth followed by stereotyped pruning is a common feature in the development of neural circuits in vertebrates. In C. elegans, PLM also follows this pattern of growth (Gallegos and Bargmann 2004). Initially, the PLM dendrite extends rapidly, bypassing its target site then undergoes regulated shortening to terminate just posterior to the anterior mechanosensory neuron, ALM. My lab is interested in both molecular and cellular factors that contribute to this process. To date we have identified worm orthologs of the yeast RAM pathway that function during the regulated shortening step of PLM development: SAX-1 (an NDR kinase), F09A5.4 (an NDR kinase cofactor) and SAX-2 (a scaffold protein). More recently, genetic evidence suggests that vesicle trafficking may regulate PLM length both within and in parallel to RAM pathway signaling. For example, rab-10, a GTPase involved in polarized secretion leads to PLM overextension, a defect not enhanced in the absence of sax-2. We are also interested in identifying the cell or tissue that might initiate PLM dendrite termination. One candidate, BDU, is an interneuron that makes both gap junction and synaptic connections with mechanosensory circuit neurons. Interestingly, BDU extends a posterior neurite that makes contact with the PLM neurite tip at the right time and place to promote PLM termination (Gallegos unpublished data and Zhang et al 2013). To test the role that BDU might play in PLM termination, we created unc-86 mosaic animals that allow PLM development in the absence of ALM and BDU. Our preliminary data indicates that the PLM dendrite extends significantly longer on average in mosaic animals that lack ALM and BDU in comparison to non-mosaic controls suggesting that BDU is required to confine the PLM dendrite to the posterior half of the animal in a contact-dependent mechanism. In our initial experiments, however, BDU was not visible. We are redoing these experiments using GFP markers that light up both BDU and PLM to ensure that their development is normal in nonmosaic controls. We are also attempting to use the free Duplication qDp3 to confirm our findings.

Zucker-Aprison E et al. (1986) Worm Breeder's Gazette "the heptamers in the vitellogenin promoters: an update."

Blumenthal TE, Zucker-Aprison E, Cane J

[Worm Breeder's Gazette, 1986]

There are two heptamers repeated multiple times upstream of the C. enin genes. In order to obtain evidence for or against the functional importance of these heptamers we have investigated their evolutionary stability. We sequenced the homologous promoters from C. briggsae and the only C. enin promoter remaining unsequenced vit-3. This brings the total number of nematode vitellogenin promoters sequenced to eleven. The data are shown schematically in the Figure. Box 1 TGTCAAT, is shown as rectangles; Box 2 CTGATAA is shown as ovals. In general the heptamers have beer very highly conserved while the sequences between them have diverged considerably. In particular there has been strong conservation of the Box 1 heptamers centered at -45 ( just upstream of the TArA box)those at -180 (which we have suggested may be at the 5' border of the promoter regions) and at least one Box 1 between -45 and -180. In each case the locations and sequences of at least these Box 1 heptamers and at least one Box 2 heptamer per promoter have been conserved. This data strongly supports the hypothesis that Box 1 and Box 2 are involved in vit promoter function. We are initiating experiments to determine the relationship between the two heptamers and the three modes of regulation: sex stage and tissue. {Figure 1} We have noted previously the presence of Box 2 in the vertebrate vitellogenin promoters. Klein-Hitpass et al. (Cell 46 1053) have tested the idea that this heptamer plays a role in Xenopus vitellogenin gene induction by estrogen in a transient expression assay using a human mammary cell line. They present evidence that it is a binding site for an activator protein required for estrogen induction but not the site for estrogen receptor itself. They name it the 'elegans box'. Does this mean that the regulatory protein that binds to this sequence in the C. e is also present in human mammary cells?