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First published online 3 September 2003
doi: 10.1242/dev.00678

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Distinct roles of transcription factors EGL-46 and DAF-19 in specifying the functionality of a polycystin-expressing sensory neuron necessary for C. elegans male vulva location behavior

¹ HHMI and Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
² Division of Cell Biology, Biozentrum, University of Basel, Klingelbergstr. 50/70, CH-4056 Basel, Switzerland
³ Department of Biosciences at Novum, Karolinska Institutet, Alfred Nobels alle 7, Södertörns Högskola, SE-141 89 Huddinge, Sweden

View larger version (109K): [in a new window]   Fig. 1. HOB gene expression in wild-type and mutant males. Left lateral views (anterior leftwards, ventral downwards). Scale bar: 20 µm. (A1,A2) Expression of ceh-26::gfp in the HOB neuron of a wild-type adult male. Absence of fluorescence in an egl-46(sy628) mutant (A3), an egl-44(n1080) mutant (A4) and a daf-19(m86) mutant (A5). (B1,B2) HOB and ray expression of pkd-2::gfp was observed in a wild-type adult male. (B3) An egl-46(sy628) male with ray but not HOB expression. (B4) An egl-44(n1080) male with expression in both HOB and ray cells. (B5) No visible expression in both HOB and rays of a daf-19 mutant. (C1,C2) Normal osm-6::gfp expression in HOA and HOB at the L4 stage. Expression was not affected in egl-46(sy628) (C3) and egl-44(n1080) mutants (C4). (C5) No expression was observed in HOA and HOB cells of a daf-19(m86) mutant male. Cell positions of HOB in A3,A4,A5,B3,B5, and HOA and HOB in C5 were located by overlaying with the Nomarski pictures of the same animal. Hook structure autofluorescence is indicated by small arrows. The original osm-6::gfp strain has a ncl-1(-) background. ncl-1(-) was still present in the him-5 strain of osm-6::gfp integrant (C1,C2) and an egl-46(sy628) mutant background (C3), but was crossed out in egl-44(n1080) (C4) and daf-19(m86) mutants (C5). egl-46(sy628) mutant also had a dpy-11 mutation in the background (C3). No effect on osm-6::gfp expression was detected for ncl-1(-) and dpy-11 mutations.

View larger version (19K): [in a new window]   Fig. 2. Vulval location behavior. The x-axis represents the number of vulva encounters measured until a tested male stopped at the hermaphrodite vulva. The y-axis represents the distribution of males in the tested group that located the vulva at each vulva encounter. (A) egl-46(+) versus egl-46(sy628). Both strains have ceh-26::gfp III; him-5(e1490) V in the background. (B) egl-46(+) versus egl-46(n1127). Strains in B contain him-8(e1489) IV. (C) egl-44(+) vs. egl-44(n1080). Animals in C are all with him-5(e1490) V. In each assay, similar number of wild-type control males and mutant males were examined at same time using the same microscope.

View larger version (116K): [in a new window]   Fig. 3. egl-46::cfp expression in HOB and ray neurons of the male tail. Nomarski (A) and fluorescence (B) images of an L4 male with expression in HOB (arrows). Nomarski (C) and fluorescence (D) images of an adult male with CFP expression in HOB (arrows) and ray neurons (arrowheads). (E) Ventral view (left side upwards) of an adult male tail with CFP expression in some ray neurons of both sides (arrowheads). Not all the ray neurons are in the same focal plane. Scale bars: 20 µm. Left lateral views.

View larger version (153K): [in a new window]   Fig. 4. egl-44::yfp expression in the male tail. Left lateral view. Scale bars: 20 µm. (A,B) Different levels of YFP expression in PVX, PVY, HOA and HOB (arrows). In this particular animal, HOA has extremely faint YFP fluorescence (in most cases, YFP expression is undetectable in the HOA hook neuron; data not shown). (C,D) An L4 male with faint YFP expression in the PCB, PCC and PCh cells of the left postcloacal sensilla, in addition to cells from ray lineage in the background. (E,F) Bright expression in hypodermal R1.p, R2.p, R3.p, R4.p, and R5.p at the left side (arrowheads).

View larger version (56K): [in a new window]   Fig. 5. daf-19::gfp expression in the hook neurons. Left lateral view. Scale bars: 20 µm. Nomarski (A) and fluorescence (B) images of a wild-type male tail at the fourth larval lethargus. daf-19::gfp expression in HOB is significantly stronger than that in HOA, PVX and PVY. The same expression pattern was present in egl-46(sy628) (C) and egl-44(n1080) mutant males (D) (arrows).

View larger version (18K): [in a new window]   Fig. 6. Distinct pathways involved in HOB gene regulation. Transcriptional regulation by egl-44 and egl-46 directs a cell-specific pathway necessary for HOB function in vulva location behavior. In the general ciliogenic pathway, the RFX-transcription factor DAF-19 controls expression of cilium structural genes to provide functional compartment common for all ciliated sensory neurons. DAF-19 has an additional influence on HOB neuronal function by affecting expression of downstream genes in the HOB-specific pathway through some unknown factor(s), indicated by Y. Genes in the shadowed box are the ones in which the Lov phenotype were analyzed in mutants (Barr and Sternberg, 1999) (this work). There are no existing mutants for ceh-26 and nlp-8.