HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE ADVANCED SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Watanabe, N. Articles by Ohshima, Y. Search for Related Content PubMed Articles by Watanabe, N. Articles by Ohshima, Y.

Department of Biology, Faculty of Sciences, Kyushu University Graduate School, Hakozaki, Fukuoka 812-8581, Japan

	Abstract

Top Abstract Introduction Results Discussion Experimental procedures References

 
Body size determination is critical for multicellular organisms; however, the mechanisms remain largely unknown. Mutations that alter body size were studied to solve the mechanisms, for example, in mouse, fruit fly and the nematode Caenorhabditis elegans. In C. elegans, a large mutant and several small body size (sma) mutants are known. Of the latter, sma-2, sma-3, sma-4, sma-6, dbl-1 and daf-4 have a mutation in the components of the DBL-1/TGFß signal pathway, and sma-5 in a MAP kinase homologue. We have constructed double mutants carrying two of such small body size mutations, sma-5 and sma-4 or sma-2. They are much smaller than either of the parental single mutants, indicating that the sma-5 gene functions independently of the DBL-1/TGFß pathway. We show that their body volumes are as small as 1/10 of that of the wild-type, and that the sizes of major organs are much reduced, by the methods previously developed by us. But the numbers of cells are not changed, suggesting that the cells are very small. These results highlight surprising flexibility of body size and cell size in a multicellular organism, which will give a novel insight into the mechanisms of body size control.

	Introduction

Top Abstract Introduction Results Discussion Experimental procedures References

 
There are substantial studies on the size of an animal or a plant in the literature. For example, mice which over-expressed growth hormone became larger (Palmiter et al. 1982), while mutants in Pit-1 transcription factor or cGMP-dependent protein kinase II in mice were reported to be smaller (Li et al. 1990; Pfeifer et al. 1996). In Dictyostelium, smlA mutant cells over-secrete a factor to form very small fruiting bodies (Brock & Gomer 1999). In Drosophila, mutants in the components of the insulin/insulin-like growth factor 1 (IGF-1) signaling pathway were reported to be smaller (Leevers et al. 1996; Böhni et al. 1999). Many factors known to control body size or growth in various animals are involved in insulin/insulin-like growth factor signaling as described above, or TGFß signaling (Massague et al. 2000; Patterson & Padgett 2000), suggesting that they are major and conserved signal pathways controlling body size. However, the mechanisms of body size determination are largely unknown (Conlon & Raff 1999).

Caenorhabditis elegans is an excellent model animal for studies on body size control. The number of somatic nuclei is fixed at 959 in an adult hermaphrodite, and their entire cell lineages were elucidated (Sulston 1988). There are many mutants with an abnormal body size or shape. For example, several mutants in TGFß signaling factors such as DBL-1/CET-1 (ligand), DAF-4 and SMA-6 (receptor), SMA-2, SMA-3 and SMA-4 (Smad transcriptional factors) are small (Estevez et al. 1993; Savage et al. 1996; Krishna et al. 1999; Morita et al. 1999; Suzuki et al. 1999). We and others showed that egl-4 mutants have a larger body size (Daniels et al. 2000; Fujiwara et al. 2002; Hirose et al. 2003), and that the egl-4 gene encodes cyclic GMP-dependent protein kinases (Fujiwara et al. 2002; L’Etoile et al. 2002; Hirose et al. 2003). We also showed that another small mutant sma-5 has a mutation in the gene encoding a MAP kinase homologue (Watanabe et al. 2005). We previously developed methods to measure body volume, and those to analyze morphology and volume of major organs using a confocal microscope; cell size in the major organs is increased in the egl-4 mutants while cell numbers are not. Genetic interaction studies strongly suggest that the DBL1/TGFß pathway functions downstream of EGL-4 for body size control since the body size of a double mutant carrying egl-4 and sma-6 or dbl-1 mutations is close to that of the single small mutant (Hirose et al. 2003). In contrast to the egl-4 mutants, three small mutants in the DBL-1 pathway and the sma-5 mutant have much smaller cell size and indistinguishable cell numbers in major organs (Nagamatsu & Ohshima 2004; Watanabe et al. 2005). We also showed that cGMP down-regulates body size through EGL-4 (Nakano et al. 2004).

Here, we have constructed double mutants carrying two of such small body size mutations, in the sma-5 gene encoding a MAP kinase homologue, and sma-4 or sma-2 gene in the DBL1/TGFß pathway. They are much smaller than either of the parental single mutants, indicating that the sma-5 gene functions independently of the DBL-1 pathway. We also show that their body volumes are as small as 1/10 of that of the wild-type, and that the sizes of major organs are much reduced. But the numbers of cells are not changed, suggesting that the cells are very small. These results highlight surprising flexibility of body size and cell size in a multicellular organism, and provide novel insights into the mechanisms controlling body size.

	Results

Top Abstract Introduction Results Discussion Experimental procedures References

 
Construction and phenotypes of the double mutants

The sma-5 mutant differs from the DBL-1/TGFß pathway mutants as to the phenotypes other than the body size phenotype (Watanabe et al. 2005), suggesting that the sma-5 gene does not belong to this pathway. To verify this, we constructed double mutant lines carrying a mutation in both sma-5 and sma-4 or sma-2 genes. The double mutants are much smaller than the wild-type (Fig. 1), and also smaller than either of the parental single mutants (Table 1). Volume measurement shows that body sizes of the doubles are reduced down to around 10% of that of the wild-type (Table 1). These results confirm that the sma-5 gene functions independently of the DBL-1 pathway to which the other known sma genes belong.

View larger version (99K): [in this window] [in a new window]   Figure 1  DIC microphotographs of an L4 stage animal of wild-type N2 (A), sma-4 (e729) (B), sma-5 (n678) (C) and sma-4 (e729); sma-5 (n678) double mutant (D). The photographs were taken with Zeiss AxioPhotII microscope and AxioCam CCD camera after paralyzed with 50 mM NaN3.

View larger version (12K): [in this window] [in a new window]   Figure 2  Growth curves in terms of body volumes of wild-type (-•-), FK312 sma-5 (n678) (--), DR1369 sma-4 (e729) (--), and FK412 or FK413 sma-4 (e729); sma-5 (n678) (a) or (c) (--, --). Error bars indicate standard deviations. Number of worms examined for each time point was 10–15. The growth of worms was synchronized by allowing parents to lay eggs for 4 h. Body volumes were measured as described in Experimental procedures.

The volumes of the two major organs, intestine and hypodermis, were measured for the wild-type, the single sma mutants and the double mutants (Table 1). All the single mutants sma-5, sma-2 and sma-4 have distinctly smaller organs than those of the wild-type, as reported previously (Nagamatsu & Ohshima 2004; Watanabe et al. 2005). The double mutants have still smaller organs than the single mutants. However, the number of intestinal cells at L1 stage is not changed in the double mutant (Table 2). It is known that the intestine of the wild-type has 20 cells both at L1 larval and adult stages, and maximally 34 nuclei in adults in contrast to 20 nuclei at L1 stage (Hedgecock & White 1985). Although the number of intestinal cells in an adult is generally hard to determine, it should be 20 for all the double and single mutants as in the wild-type, since their intestine has more than 20 nuclei (Table 2). The total number of body wall muscle cells in the double mutant is hard to determine since they are too small and stacked together near the head or tail. However, it is probably similar to that of the wild-type (23 or 24/quadrant) because the number is similar to that of the wild-type along the major part of the body and because two parental single mutants sma-5 and sma-4 have the same number of body wall muscle cells as the wild-type (Nagamatsu & Ohshima 2004; Watanabe et al. 2005). Thus, the average cell size of these organs in the double mutant is probably much smaller. For the hypodermal cell volume, at least the single giant syncytium hyp7 should also be much smaller since it occupies most of the hypodermis (White 1988).

Chromosomal ploidy is the well known and universal regulator of cell size (Conlon & Raff 1999). In C. elegans, such cases suggesting the role of hypodermal chromosomal ploidy in body size control were reported (Morita et al. 2002; Lozano et al. 2006). On the other hand, we previously showed that chromosomal ploidy of intestinal cells, which is known to have the highest value of 32 in wild-type adults, was not reduced in sma-2, sma-4, sma-6 (Nagamatsu & Ohshima 2004) or sma-5 (Watanabe et al. 2005) mutants. The ploidy value of intestinal cells for the sma-4; sma-5 double mutant FK413 was determined to be 26 ± 3.2 (mean ± SEM; n = 17), which is slightly (about 20%) reduced from those of the wild-type or the parental single mutants. We also determined average protein content of a sma-4; sma-5 double mutant worm. It was 0.15 µg/worm, 14% of the wild-type value, and is further reduced from those of the sma-4 (30%) or sma-5 (22%).

	Discussion

Top Abstract Introduction Results Discussion Experimental procedures References

 
We have shown that the super small body size of the sma-5; sma-4 or sma-5; sma-2 double mutants is due to the small cell size, and not due to reduced cell number. In contrast, body size difference among mammals is likely to be mainly due to the difference in the cell number (Conlon & Raff 1999). In C. elegans, change in cell number may be more difficult than change in cell size because of the small total number of cells and the rather rigid cell lineage (Sulston 1988).

On the mechanisms of organ size control by sma-5 gene, we previously showed that expression in hypodermis or excretory cell increased intestinal volume as well as that of hypodermis itself (Watanabe et al. 2005). As to sma-2 or sma-4 genes, we have not done experiments corresponding to those for sma-5. However, importance of hypodermal expression of sma-3 or sma-6 in body length control was reported by other people (Yoshida et al. 2001; Wang et al. 2002). Also, we showed that expression of egl-4, which functions upstream of the TGFß sma genes, in hypodermis or neurons control sizes of other organs (in a cell or organ-nonautonomous manner) as well as its own size (Nakano et al. 2004). Taken together, these results strongly suggest that body size control by these genes include a diffusible factor, or that hypodermal size indirectly controls the size of other organs by controlling the size of the cuticle which is synthesized by hypodermis, as proposed by us (Nakano et al. 2004). This latter mechanism seems to be interesting and similar to the mechanism by which major tissue in mammalian bone, chondrocytes or cartilage growth plate, controls organ size through formation of skeleton (Kronenberg 2003).

Chromosomal ploidy is a universal control factor of cell size, as reviewed (Conlon & Raff 1999). In fact, intestinal cells in an adult C. elegans are known to have the highest chromosomal ploidy (32C) and are the largest cells (the average volume is 45 000 µm³ in adults based on our measurement), except for the giant syncytium hyp7 carrying many nuclei of 8C, 4C or 16C. However, among the diploid cells which are majority of the somatic cells, body wall muscle cells (average volume of about 7000 µm³) are much larger than neurons and most hypodermal cells. These results indicate that cell size is not always related to chromosomal ploidy. Evidently nutrition is another important factor for control of cell or body size. Also, as we showed in various mutants, cell volume in intestine, body wall muscle (and probably hyp7) varies much without any or much change in chromosomal ploidy (Nagamatsu & Ohshima 2004; Watanabe et al. 2005). Thus, although chromosomal ploidy is an important regulator of cell or body size in C. elegans as proposed (Morita et al. 2002; Lozano et al. 2006), clearly it is not the sole regulator. There should be many regulators.

Although there was slight reduction in the nuclear number or chromosomal ploidy of intestine, it is not likely a major reason for the drastic reduction of the intestinal volume in the double mutant (reduced to 16% of the wild-type value). In contrast, reduction of the total protein content of the double mutant (reduced to 14%) is well correlated to that of the whole body volume (12% of the wild-type value). These results further extend the results for sma-5, sma-2, sma-4 and sma-6 mutants (Nagamatsu & Ohshima 2004; Watanabe et al. 2005). The level of general protein expression or ribosome biogenesis was proposed to have an important relation to the cell size in C. elegans (Nagamatsu & Ohshima 2004; Watanabe et al. 2005), yeast (Jorgensen et al. 2002) and other organisms (Saucedo & Edgar 2002).

Total mass checkpoint mechanisms that keep constant organ size and body size were suggested based on experiments with transplantation, regeneration or alteration in chromosomal ploidy, as reviewed (Conlon & Raff 1999; Saucedo & Edgar 2002). In spite of these presumed mechanisms, mutations leading to a change in total body size exist as cited before. These mutations might break the possible link between control of cell size and that of cell proliferation (Potter & Xu 2001). It is noted that in C. elegans a large body size mutant (Fujiwara et al. 2002; Hirose et al. 2003) as well as small body size mutants (Estevez et al. 1993; Savage et al. 1996; Krishna et al. 1999; Morita et al. 1999; Suzuki et al. 1999; Watanabe et al. 2005) are known.

We have found no case of such drastic reduction of body or cell size as reported here, in the known small size mutants such as cited above. Furthermore, although cell size mutants were systematically isolated in the yeast S. cerevisiae (Jorgensen et al. 2002) or Drosophila S2 cell (Bjorklund et al. 2006), none look much smaller than 1/2 of the size of the wild-type. Although dogs may vary 50-fold in body mass among subspecies (Neff & Rine 2006), their size variation is presumed to originate through several or more mutations and through variations in cell number, not in cell size. The results presented here have shown remarkable flexibility of body size and cell size in the adult of C. elegans through only two mutations. This could be due to the flexibility of a multicellular organism, and should give a novel insight into the mechanisms of body size control.

	Experimental procedures

Top Abstract Introduction Results Discussion Experimental procedures References

 
Strains and culture of C. elegans

Bristol strains of C. elegans wild-type strain N2, CB502 sma-2 (e502) and DR1369 sma-4 (e729) were obtained from Caenorhabditis Genetics Center, Minneapolis, MN. FK312 sma-5 (n678) was previously described (Watanabe et al. 2005). FK410 sma-2; sma-5, FK412 and FK413 sma-4; sma-5 double mutants were produced by crossing the parental single mutants, and the two mutations in the doubles were confirmed by DNA sequencing. The handling of C. elegans strains was performed as described (Brenner 1974; Sulston & Hodgkin 1988).

Measurement of body sizes

Total body volume, body length and diameters of a worm were measured essentially as described using the automated device Senchu Gazo Kaiseki Sochi SVK-3 A (Showa Denki Co. Ltd) described by Hirose et al. (2003), but only body volumes are shown here.

Measurement of organ sizes

Volumes of hypodermis or intestine shown in Table 1 were obtained with analysis of transgenic worms expressing GFP specifically in each organ, using Zeiss LSM-510 (NLO) laserscanning fluorescent microscope equipped with Zeiss Axiovert 200 M microscope, as described (Watanabe et al. 2005). To express GFP in hypodermis or intestine, col-19p::gfp or dss-1p::gfp was introduced into sma-2, sma-4 sma-2; sma-5 and sma-4; sma-5 mutants in this study, as was done for N2, egl-4 and sma-5 mutants previously (Hirose et al. 2003; Watanabe et al. 2005).

Transgenic animals

Of the transgenic lines shown in Table 1, FK290, FK340, FK336 and FK383 were previously described (Watanabe et al. 2005). The other transgenic lines expressing dss-1p::gfp in intestine or col-19p::gfp in hypodermis were obtained by mating respective transgenic lines in the wild-type background and sma-2 or sma-4 to get transgenic lines in the single mutant background, and then mating their males with sma-5 hermaphrodites to get transgenic lines in the double mutant background.

Measurement of nuclear or cell numbers and analysis of DNA contents

The procedures for measurement of intestinal nuclei, body wall muscle cells, intestinal cell numbers and intestinal chromosomal ploidy were previously described (Nagamatsu & Ohshima 2004; Watanabe et al. 2005).

Analysis of protein contents

Total protein contents of 2-day-old animals were measured as described (Nagamatsu & Ohshima 2004).

	Acknowledgements

 
Some nematode strains were obtained from the Caenorhabditis Genetic Center, which is funded by a grant from the National Institute of Health for Research Resources. We thank A. Fire for vectors, M. Fujiwara, K. Miyahara and other members of our laboratories for discussion and help. This work was supported by a grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan to YO.

	Footnotes

 
Communicated by: Yuji Kohara

^aPresent address: Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, 4-22-1, Ikeda, Kumamoto 860-0082, Japan.

^* Correspondence: E-mail: ohshima{at}life.sojo-u.ac.jp

	References

Top Abstract Introduction Results Discussion Experimental procedures References

 
Bjorklund, M., Taipale, M., Varjosalo, M., Saharinen, J., Lahdenpera, J. & Taipale, J. (2006) Identification of pathways regulating cell size ane cell-cycle progression by RNAi. Nature 439, 1003–1009.

Böhni, R., Riesgo-Escovar, J., Oldham, S., Brogiolo, W., Stocker, H., Andruss, B.F., Beckingham, K. & Hafen, E. (1999) Autonomous control of cell and organ size by CHICO, a Drosophila homolog of vertebrate IRS1-4. Cell 97, 865–875.[CrossRef][Medline]

Brenner, S. (1974) The genetics of Caenorhabditis elegans. Genetics 77, 71–94.[Abstract/Free Full Text]

Brock, D.A. & Gomer, R.H. (1999) A cell-counting factor regulating structure size in Dictyostelium. Genes Dev. 13, 1960–1969.[Abstract/Free Full Text]

Conlon, I. & Raff, M. (1999) Size control in animal development. Cell 96, 235–244.[CrossRef][Medline]

Daniels, S.A., Ailion, M., Thomas, J.H. & Sengupta, P. (2000) egl-4 acts through a transforming growth factor-ß/SMAD pathway in Caenorhabditis elegans to regulate multiple neuronal circuits in response to sensory cues. Genetics 156, 123–141.[Abstract/Free Full Text]

Estevez, M., Attisano, L., Wrana, J.L., Albert, P.S., Massague, J. & Riddle, D.L. (1993) The daf-4 gene encodes a bone morphogenetic protein receptor controlling C. elegans dauer larva development. Nature 365, 644–649.[CrossRef][Medline]

Fujiwara, M., Sengupta, P. & McIntire, S.L. (2002) Regulation of body size and behavioral state of C. elegans by sensory perception and EGL-4 cGMP-dependent protein kinase. Neuron 36, 1091–1102.[CrossRef][Medline]

Hedgecock, E.M. & White, J.G. (1985) Polyploid tissues in the nematode Caenorhabditis elegans. Dev. Biol. 107, 128–133.[CrossRef][Medline]

Hirose, T., Nakano, Y., Nagamatsu, Y., Misumi, T., Ohta, H. & Ohshima, Y. (2003) Cyclic GMP-dependent protein kinase EGL-4 controls body size and lifespan in C. elegans. Development 130, 1089–1099.[Abstract/Free Full Text]

Jorgensen, P., Nishikawa, J.L., Breitkreutz, B.J. & Tyers, M. (2002) Systematic identification of pathways that couple cell growth and division in yeast. Science 294, 395–400.[CrossRef]

Krishna, S., Maduzia, L.L. & Padgett, R.W. (1999) Specificity of TGFß signaling is conferred by distinct type I receptors and their associated SMAD proteins in Caenorhabditis elegans. Development 126, 251–260.[Abstract]

Kronenberg, H.M. (2003) Developmental regulation of the growth plate. Nature 423, 332–336.[CrossRef][Medline]

Leevers, S.J., Weinkove, D., MacDougall, L.K., Hafen, E. & Waterfield, M.D. (1996) The Drosophila phosphoinositide 3-kinase Dp110 promotes cell growth. EMBO J. 15, 6584–6594.[Medline]

L’Etoile, N.D., Coburn, C.M., Eastham, J., Kistler, A., Gallegos, G. & Bargmann, C.I. (2002) The cyclic GMP-dependent protein kinase EGL-4 directs olfactory adaptation in C. elegans. Neuron 36, 1079–1089.[CrossRef][Medline]

Li, S., Crenshaw, E.B. III, Rawson, E.J., Simmons, D.M., Swanson, L.W. & Rosenfeld, M.G. (1990) Dwarf locus mutants lacking three pituitary cell types result from mutations in the POU-domain gene pit-1. Nature 347, 528–533.[CrossRef][Medline]

Lozano, E., Saez, A.G., Flemming, A.J., Cunha, A. & Leroi, A.M. (2006) Regulation of growth by ploidy in Caenorhabditis elegans. Curr. Biol. 16, 493–498.[CrossRef][Medline]

Massague, J., Blain, S.W. & Lo, R.S. (2000) TGF-ß signaling in growth control, cancer, and heritable disorders. Cell 103, 295–309.[CrossRef][Medline]

Morita, K., Chow, K.L. & Ueno, N. (1999) Regulation of body length and male tail ray pattern formation of Caenorhabditis elegans by a member of TGF-ß family. Development 126, 1337–1347.[Abstract]

Morita, K., Flemming, A.J., Sugihara, Y., Mochii, M., Suzuki, Y., Yoshida, S., Wood, W.B., Kohara, Y., Leroi, A.M. & Ueno, N. (2002) A Caenorhabditis elegans TGF-ß, DBL-1, controls the expression of LON-1, a PR-related protein, that regulates polyploidization and body length. EMBO J. 21, 1063–1073.[CrossRef][Medline]

Nagamatsu, Y. & Ohshima, Y. (2004) Mechanisms for the control of body size by a G-kinase and a downstream TGFß signal pathway in Caenorhabditis elegans. Genes Cells 9, 39–47.[Abstract/Free Full Text]

Nakano, Y., Nagamatsu, Y. & Ohshima, Y. (2004) cGMP and a germ-line signal control body size in C. elegans through cGMP-dependent protein kinase EGL-4. Genes Cells 9, 773–779.[Abstract/Free Full Text]

Neff, M.W. & Rine, J. (2006) A fetching model organism. Cell 124, 229–231.[CrossRef][Medline]

Palmiter, R.D., Brinster, R.L., Hammer, R.E., Trumbauer, M.E., Rosenfeld, M.G., Birnberg, N.C. & Evans, R.M. (1982) Dramatic growth of mice that develop from eggs microinjected with metallothionein-growth hormone fusion genes. Nature 300, 611–615.[CrossRef][Medline]

Patterson, G.I. & Padgett, R.W. (2000) TGF ß-related pathways. Roles in Caenorhabditis elegans development. Trends Genet. 16, 27–33.[CrossRef][Medline]

Pfeifer, A., Aszodi, A., Seidler, U., Ruth, P., Hofmann, F. & Fässler, R. (1996) Intestinal secretory defects and dwarfism in mice lacking cGMP-dependent protein kinase II. Science 274, 2082–2086.[Abstract/Free Full Text]

Potter, C.J. & Xu, T. (2001) Mechanisms of size control. Curr. Opin. Genet. Dev. 3, 279–286.

Saucedo, L.J. & Edgar, B.A. (2002) Why size matters: altering cell size. Curr. Opin. Genet. Dev. 12, 565–571.[CrossRef][Medline]

Savage, C., Das, P., Finelli, A.L., Townsend, S.R., Sun, C.Y., Baird, S.E. & Padgett, R.W. (1996) Caenorhabditis elegans genes sma-2, sma-3, and sma-4 define a conserved family of transforming growth factor ß pathway components. Proc. Natl. Acad. Sci. USA 93, 790–794.[Abstract/Free Full Text]

Sulston, J. (1988) Cell lineage. In: The Nematode Caenorhabditis elegans (eds W.B. Wood & the Community of C. elegans Researchers), pp. 123–155. Cold Spring Harbor, New York, NY: Cold Spring Harbor Laboratory.

Sulston, J. & Hodgkin, J. (1988) Methods. In: The Nematode Caenorhabditis elegans (eds W.B. Wood & the Community of C. elegans Researchers), pp. 587–606. Cold Spring Harbor, New York, NY: Cold Spring Harbor Laboratory.

Suzuki, Y., Yandell, M.D., Roy, P.J., Krishna, S., Savage-Dunn, C., Ross, R.M., Padgett, R.W. & Wood, W.B. (1999) A BMP homolog acts as a dose-dependent regulator of body size and male tail patterning in Caenorhabditis elegans. Development 126, 241–250.[Abstract]

Wang, J., Tokarz, R. & Savage-Dunn, C. (2002) The expression of TGFß signal transducers in the hypodermis regulates body size in C. elegans. Development 129, 4989–4998.[Abstract/Free Full Text]

Watanabe, N., Nagamatsu, Y., Gengyo-Ando, K., Mitani, S. & Ohshima, Y. (2005) Control of body size by SMA-5, a homolog of MAP kinase BMK1/ERK5, in C. elegans. Development 132, 3175–3184.[Abstract/Free Full Text]

White, J. (1988) The anatomy. In. The Nematode Caenorhabditis elegans (eds W. B. Wood & the Community of C. elegans Researchers), pp. 81–122. Cold Spring Harbor, New York, NY: Cold Spring Harbor Laboratory.

Yoshida, S., Morita, K., Mochii, M. & Ueno, N. (2001) Hypodermal expression of Caenohabditis elegans TGF-ß type-I receptor SMA-6 is essential for the growth and maintenance of body length. Dev. Biol. 240, 32–45.[CrossRef][Medline]

Received: 2 November 2006
Accepted: 4 February 2007

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Watanabe, N. Articles by Ohshima, Y. Search for Related Content PubMed Articles by Watanabe, N. Articles by Ohshima, Y.