QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 30 November 2006
doi: 10.1242/dev.02709

This Article Summary Full Text Full Text (PDF) Supplementary Material Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Amin, N. M. Articles by Liu, J. Search for Related Content PubMed PubMed Citation Articles by Amin, N. M. Articles by Liu, J.

A Zn-finger/FH2-domain containing protein, FOZI-1, acts redundantly with CeMyoD to specify striated body wall muscle fates in the Caenorhabditis elegans postembryonic mesoderm

Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.

View larger version (23K): [in this window] [in a new window]   Fig. 1. The C. elegans hermaphrodite postembryonic M lineage. Times are indicated post-hatching at 25°C. (A) The M lineage showing all differentiated cell types that arise from M [modified from Sulston and Horvitz (Sulston and Horvitz, 1977)]. (B) A schematic lateral view of the M lineage through larval development. a, anterior; d, dorsal; l, left; p, posterior; r, right; v, ventral.

View larger version (51K): [in this window] [in a new window]   Fig. 2. The M lineage phenotypes of cc609 mutants. All images are ventral/lateral views with anterior to the left. (A-H) Wild-type (A,B,E,F) and cc609 mutant (C,D,G,H) animals at the late L2 stage (A-D) and adult stage (E-H). SMs are visualized using hlh-8::gfp and labeled with red arrows. CCs are visualized using intrinsic CC::gfp; embryonic CCs are labeled with white arrowheads and M-derived CCs with blue arrows. Type I vulval muscles are visualized using egl-15::gfp and labeled with green arrows. Note the presence of two SMs in the wild-type larva (A,B) and four SM-like cells in the cc609 larva (C,D). B and D show the SM-like cells at higher magnification. Also note the lack of M-derived CCs in cc609 larva (C,G) compared with wild-type animals (A,E). cc609 adults have extra type I vulval muscles (vm1-like cells) (G,H) compared with wild type (E,F). F and H show the vulval muscles in higher magnification. (I-L) Representations of the hermaphrodite M lineage in wild-type (I) and different cc609 mutant (J-L) animals. Unmarked cells refer to BWMs. (I) Wild-type animals always give rise to two CCs, two SMs and 14 BWMs. (J-L) cc609 mutant animals consistently have a loss of M-derived CCs and some BWMs, with the concomitant gain of SM-like cells.

View larger version (16K): [in this window] [in a new window]   Fig. 3. fozi-1 encodes a novel protein. (A) fozi-1 gene structure (not drawn to scale) showing molecular lesions of fozi-1 mutants. The first intron of fozi-1 spans 7 kb upstream of the translation start site. (B) The structural motifs of FOZI-1 include a Q-rich region (amino acids 88-133), two C2H2 zinc finger motifs (amino acids 177-201) and an FH2 formin homology domain (amino acids 369-732). (C) pNMA04, pNMA27 and pNMA28 are fozi-1 fusion constructs used to purify recombinant FOZI-1 fragments. pNMA36 and pNMA37 were used in transgenic assays.

View larger version (80K): [in this window] [in a new window]   Fig. 4. Expression pattern of FOZI-1 in wild-type, cc609 and cc610 hermaphrodites and embryos. All images are lateral views with anterior to the left and dorsal up (unless otherwise noted). (A-D) Wild-type (A,B) and cc609 (C,D) embryos stained with anti-FOZI-1 antibody (A,C) and DAPI (B,D). Nuclear FOZI-1 is seen in a subset of cells at the 2-fold stage of embryogenesis in wild-type (A) but not in cc609 (C) embryos. (E,F) FOZI-1 staining in a wild-type L1 larva on two different focal planes. FOZI-1 was observed in the nuclei of 7-12 head neurons (arrow, E) and 5-7 cells along the ventral nerve cord (arrowheads, E,F) and in cells derived from the M lineage (red box, E,F). (G-R) Double labeling with anti-FOZI-1 antibody and hlh-8::gfp at the 2-M (G-I), 16-M (J-L), 18-M (M-O) and 2-SM (P-R) stages in wild-type animals. Anti-FOZI-1 antibody staining is shown in panels G,J,M,P; hlh-8::gfp is shown in panels H, K,N,Q; the corresponding merged images are shown in panels I,L,O,R. FOZI-1 staining was first detected at the 2-M stage (G-I) and persisted through the 16-M (J-L) stages. At the 18-M stage (M-O) FOZI-1 is still present in all undifferentiated CC and BWM precursors but is absent in the SMs. Arrowheads in panel M denote cells in the ventral nerve cord. (P-R) FOZI-1 is not present in the 2-SM cells and the subsequent SM lineage (data not shown). (S) Summary of FOZI-1 expression in the M lineage. The wild-type M lineage is shown with overlay of FOZI-1 expression highlighted in red. (T,U) Staining of cc609 (T) and cc610 (U) animals at mid-L1 stage using anti-FOZI-1 antibodies. (T) No FOZI-1 was detected in cc609 animals. (U) Wild-type level and localization pattern of FOZI-1 are detected in cc610 mutant animals in head neurons (arrow), ventral nerve cord (arrowheads) and the M lineage (red box).

View larger version (103K): [in this window] [in a new window]   Fig. 5. Expression of FOZI-1 in different M lineage mutants. (A-C)A fozi-1(cc609); ayIs6(hlh-8::gfp) mutant animal at the 8-M stage stained with anti-HLH-1 antibody (red in A,B) and DAPI (C). White arrows represent M lineage as marked by hlh-8::gfp. Embryonically derived BWMs are denoted by open arrowheads. (D-F) Anti-FOZI-1 staining in hlh-1(cc561ts) (D), mab-5(e1239) (E) and mls-2(cc615) (F) animals. FOZI-1 is present in the M lineage of all three mutants. Arrowhead denotes a cell from the ventral nerve cord (F). (G) A ceh-20(n2513) animal stained with anti-FOZI-1 antibody. FOZI-1 is detected in the head neurons (arrow) and the ventral nerve cord (arrowheads), but not in the M lineage (red box).

View larger version (25K): [in this window] [in a new window]   Fig. 6. HLH-1 functions redundantly with FOZI-1 and MAB-5 to specify M-derived BWMs. (A,B) Quantification of the number of SM-like cells (expressing hlh-8::gfp) (A) and M-derived BWMs (expressing myo-3::gfp) (B). n values are given for each genotype scored. Mean values are shown with error bars representing standard deviation for each sample set. All animals showed normal proliferation in the early M lineage up to the 16-M stage. The number of SM-like cells and M-derived BWMs were also scored in the following animals: mab-5(RNAi), hlh-1(RNAi), hlh-1(RNAi); mab-5(e1239), hlh-1(RNAi); fozi-1(cc609), hlh-1(RNAi); fozi-1(cc609) mab-5(RNAi) and hlh-1(cc561ts+RNAi); fozi-1(cc609) mab-5(e1239). For each genotype, more than 50 animals were scored for the number of SMs and more than ten animals were scored for the number of M-derived BWMs. *A small percentage of these animals lacked all M-derived BWMs and had a total of 16-18 SM-like cells.

View larger version (9K): [in this window] [in a new window]   Fig. 7. A model for muscle fate specification in the postembryonic mesoderm. At least two redundant mechanisms functioning downstream of the Pbx/Exd homolog CEH-20 are involved in specifying myogenic fates in the postembryonic mesoderm (see Discussion). Solid lines in this model do not necessarily represent direct regulation. Dashed lines represent a hypothetical situation.