Ho F et al. (1992) Worm Breeder's Gazette "The Second Approach to Aligning the Genetic and Physical Maps on Chromosome I: PCR mapping of Potential Deletions"

Ho F, Janmaat A, Ha TT, Melathopoulos A, Liu T, Rose AM, Salmon R

[Worm Breeder's Gazette, 1992]

For the right portion of the chromosome, where we don't have a high density of mapped mutants, we are using the PCR mapping protocol of Barstead and Waterston (in 1991 C Mot Cyto 20:69) to position gamma-induced lethals (potential deletions). Using hIn1 as a balancer (Zetka and Rose, 1992 Genetics), we recovered several lethals linked to unc-101 and lev-11 which were induced with 1500 rads of gamma radiation. Primers were kindly provided by Junho Lee in Paul Sternberg's lab and Yuko Kozono in Bob Waterstons's lab. As controls for the PCR reactions, we are using a deletion outside the hIn1 region, hDf8 ,and primers from bli-4 (Ken Peters, unpublished) and AHH sequences (Prasad, Starr and Rose, in press). hDf8 deletes AHH, but not bli-4 .We have tested nine of our gamma induced lethals to date and one of these hDf14 (h1277 )is lacking DNA for the primer set INT 7-10 from unc-101 sequences provided by Junho Lee.

Miller LM et al. (1986) Worm Breeder's Gazette "y9: an XO-specific lethal mutation that suppresses the known XX-specific lethal mutations."

Miller LM, Meyer BJ

[Worm Breeder's Gazette, 1986]

y9 suppresses the XX-specific lethality of mutations in dpy-26. solated as a spontaneous revertant of dpy-28(yl) III, a temperature-sensitive, maternal-effect mutation preferentially lethal to XX animals. A dpy-28(yl); 90) strain produces 69% dead eggs, 4% Dpy adult hermaphrodites and 27% adult wild-type males at 20 C. By contrast, a dpy-28(yl); 90); y9 strain produces 57% dead eggs, 25% non-Dpy Egl hermaphrodites, and 18% males. Approximately 20% of the non-Dpy hermaphrodites have a small blip in the pre-anal region of the tail. Similar suppression is also seen when y9 is placed in combination with dpy-26(n199), 18), and dpy-28(s939) . All three strains produce non-Dpy Egl hermaphrodites (some sterile, some with pre-anal tail blips) and males. The percentage of XX animals rescued by the y9 mutation in these strains has not yet been determined; however, it is clear that these animals are dramatically healthier than without the y9 mutation. The ability of one mutation to suppress several XX-specific lethal mutations is extremely interesting and implies the involvement of these mutations in a common pathway for dosage compensation. y9 is an X-linked. XO-specific lethal mutation. When y9 was separated from dpy-28(yl), the resulting him-5(e1490); y9 strain produced phenotypically wild-type hermaphrodites but no males. Both the inability to produce XO males and the suppression of the XX- specific lethality of yl mapped to the X chromosome. Threefactor crosses place y9 between dpy-7 X and unc-9 X. We have eliminated the possibility that y9 simply suppresses the ability of the him-S mutation to produce nullo-X oocytes. This was demonstrated by showing the patroclinous inheritance of the lin-14( n179) X marker in the male progeny of the cross unc-32(e189); 90); y9 hermaphrodites mated by him-5; 79) males. Appropriate genetic tests have demonstrated that y9 does not transform XO animals into hermaphrodites. Moreover, in progeny counts of the him-S; y9 strain, the following results were obtained: 51% of the eggs laid developed into adult hermaphrodites and 49% of the eggs were dead. In a him-5(e1490) strain 55% of the eggs laid developed into adult hermaphrodites, 27% developed into adult males, and 18% of the eggs were dead. The lethality of y9 is XO-specific rather than male-specific because XX tra-1(e1488); 90); y9 pseudomales are healthy. ( No XO wild-type males are produced). Mutations in dpy-26 the XO lethality of y9. The dpy-28(yl); 90); y9 strain produces approximately 27% males, which is very close to the number expected from an e1490 strain. Although some of the males in this strain are sick, most are healthy and mate well. Similar results have been obtained with dpy-26(n199), 18), and dpy-28(s939). Thus, the mutual suppression exhibited between y9 and the XX-specific lethal mutations is neither allele-specific nor gene-specific. Another extragenic suppressor of Y9 is located on the X chromosome. The XO-specific lethality of y9 can be used in a powerful reversion scheme. Thus far, several revertants of y9 have been isolated by EMS mutagenesis of him-S(e1490); y9. One extragenic mutation, y16, is located on the X chromosome between y9 and unc-3 and restores males to the him-5(e1490); y9 strain. The males look completely wild-type and mate very well. Hermaphrodites homozygous for the y9y16 double, however, are dead. The phenotype of yl6 by itself is not yet known. Future experiments will reveal if either y9 or yl6 alter X-linked gene expression and/or interfere with proper sex determination.

Yandell MD et al. (1994) Worm Breeder's Gazette "ceg-1 is Very Similar to decapentaplegic."

Wood WB, Yandell MD

[Worm Breeder's Gazette, 1994]

CEG-I IS VERY SIMILAR TO DECAPENTAPLEGIC Mark Yandell and Bill Wood Department of MCD Biology, University of Colorado, Boulder We have cloned a TGF-beta homolog which we have provisionally called ceg-l for C. elegans growth factor-l. ceg-l is a member of the dpp/bmp2-4 subclassl of TGF-beta proteins (see PILEUP diagram) and is very similar to the Drosophila gene decapentaplegic (dpp) and the mouse gene GDF-5, the product of the brachypodism locus, alleles of which cause defects in limb morphologyv.2 We previously reported (WBG 12(5): 82) that ceg-l maps to chromosome V just to the left of the cluster. We have now mapped ceg-l to the genetic map by PCR from single dead embryos homozygous for either the deficiency sDf30 or the deficiency sDf20 and find that it maps to the cluster of lethals near dpy-l l which lie under both deficiencies. Developmental Northern blots show that ceg-l encodes a moderately rare transcript that is present in late embryos and L1 larvae. Sequencing of genomic and cDNA clones reveal that the ceg-l gene has eight introns and encodes a 1.7kb message which is trans-spliced to SL1. We are now preparing to inject heat-shock and LacZ contructs. We are also collaborating with Ronald Plasterk to obtain a Tc1 insertion in ceg-l. Kingsley, D. M., Genes and Development 8: 133-146, 1994. 2 Storm, E. E., Huynh, T. V., Copland, N. G., Jenkins, N. A., Kingsley, D. M., and Lee, S. Nature 368: 639-643. 1994.

Siddiqui SS et al. (1990) Worm Breeder's Gazette "Scanning Tunneling Microscopy (STM) of C. elegans Microtubules"

McKuskey B, Hameroff S, Siddiqui SS, Ward S, Sarid D

[Worm Breeder's Gazette, 1990]

We have been studying C. elegans microtubules from cellular and genetic aspects. Since scanning tunneling microscopy (STM) can provide atomic resolution of metals and semiconductive surfaces; our objective is to obtain images of C. elegans microtubules resolved at the atomic level. However, application of STM to biomolecules is faced with a variety of problems, including poor electrical conductivity, flexible stability under STM imaging conditions. In spite of limitations, recently, impressive images of DNA biomolecules have been obtained at atomic resolution. Microtubules (MT) were isolated from 30g of freshly grown N2 worms according to the procedure of Aamdot and Culotti 1986, and Siddiqui et al 1989, using cycles of temperature dependent assembly and disassembly (Shelanski, et al. 1973). Assembled MT were taken in MT isolation buffer (containing 0.1mM GTP, 20 M taxol, and 2.0 mM DTE), diluted tenfold and fixed in glutaraldehyde (0.1%). The samples were kept frozen at -20 C, for 4-5 days. The STM imaging samples were thawed, and a drop was smeared onto a chip of freshly cleaved HOPG ( highly oriented pyrolitic graphite, Union Carbide), and allowed to air dry at room temperature. The STM images were obtained using 'Nanascope II Digital Instruments, California (Sam Howell and C. Lee, kindly helped with the STM settings). All STM imaging was conducted at atmospheric pressure and at room temperature (22 C). Two different STM images of C. elegans MT are shown here. [See Figure 1] Most of our STM scans of MT correspond to one or two microtubules, but they appear flattened and bent along the seams of the protofilaments. The dimensions of alpha and -tubulin dimer subunits are about 8 nm, and each protofilament has a width of 4.6 nm. The flattening and buckeling of protofilaments along the seams could arise due to the fixation conditions, or caused by the STM current flow through the specimen. At present, we are unable to attribute this observation to any single factor, and the images of MT do not provide any higher resolution than conventional electron microscopy using negative staining. But it is increasingly possible that one may be able to resolve individual amino acids or even atoms using STM. We plan to continue looking for improved conditions for better STM or AFM images of C. elegans MT. Brief description of STM: Scanning tunneling microscopy (STM) traces three dimensional images of surfaces - even at the level of individual atoms. Gerd Binnig & Heinrich Rohrer of IBM Zurich received the Nobel Prize in 1986 for STM (Refer, e.g.: Scientific American, August,1985). Briefly in STM, the 'aperture' is a small tungston probe, its tip extremely fine (about 0. 2 nm in width, and may consist of a single atom). Piezoelectric controls move the tip within a nanometer or two of the surface of the conducting sample, allowing an overlap between the electron clouds of the atom at the probe tip and the closest atom of the sample placed on the surface. As a small voltage is applied to the tip, electrons 'tunnel' across this gap, creating a tiny tunneling current. The strength of the tunneling current is exponentially sensitive to the width of the gap (about an order of magnitude per angstrom). Depending on the substrate, typical currents and voltages are in the range of nanoamperes and millivolts. A servo system uses a feedback control that keeps the tip to substrate gap constant, by modulating the voltage across a piezoelectric positioning system (Piezoceramic materials expand or shrink extremely small distances (i.e. angstroms ) in response to the applied voltage. As the tip scans the surface, variations in this voltage, when plotted correspond to surface structure. I wish to thank members of Ward lab (Alicia, Andrea, Bill, Bonnie, Bruce, Jacob, John and Paul); Hameroff Lab (Dolly, Larry, Mohammad, and Richard); and Sarid Lab (Sam and Lee).

Heschl MFP et al. (1988) Worm Breeder's Gazette "an hsp70 gene subfamily encoding two grp78-like proteins."

Baillie DL, Heschl MFP

[Worm Breeder's Gazette, 1988]

We have been characterizing some of the genes from the hsp70 multigene family. We have recently sequenced two additional members of this family. The hsp70C gene is non-heat inducible and constitutively expressed, its mRNA is most abundant at the L1 larval stage. The hsp70C protein shares a high degree of identity with the rat grp78 protein (77% at the amino acid level). The rat grp78 protein is related to the hsp70 family and is found within the endoplasmic reticulum (Munro and Pelham, 1986, Cell 46, 291). The expression of the grp78 gene is enhanced when the cell or organism is starved of glucose. The hsp70C protein has a long, hydrophobic leader sequence and the COOH-terminal ER-retention signal sequence KDEL characteristic of the rat grp78 protein. Therefore, we conclude that the hsp70C gene is the grp78 equivalent in C. elegans.In a comparison with the hsp70C gene from C. briggsae, a high degree of homology in the coding and noncoding regions is observed. The 5' regulatory region of the two genes share several conserved blocks of sequences encompassing a heat shock element and copies of mammalian virus core enhancer sequences. One of these regions is highly conserved ( approximately 80%) with a sequence in the rat grp78 regulatory region. This region in the rat grp78 regulatory region is protected during nuclease footprinting studies (A. S. Lee, personal communication). We propose that this region may be involved in the glucose-mediated response. Another member of the hsp70 family characterized is the highly heat inducible gene hsp70D. We find that the hsp70D gene is closely related to both the hsp70C and grp78 genes (76% and 71% at the amino acid level respectively). As such, we identify the hsp70D gene as the first highly heat inducible variety of the grp78 subfamily. The COOH- terminal sequence is HDEL and not KDEL found in the hsp70C protein. Histidine is a conservative substitution of lysine and may function as an ER-retention signal. Only the last half of the hsp70D gene has been sequenced so we are unable to determine if the hsp70D gene, like the hsp70C gene, has a long, hydrophobic leader sequence.

Lee JH et al. (1994) Worm Breeder's Gazette "Molecular Genetics of SNAP-25 in C. elegans."

Meyer BJ, Lee JH

[Worm Breeder's Gazette, 1994]

Molecular genetics of SNAP-25 in C. elegans Junho Lee and Barbara Meyer Department of Molecular and Cell Biology 401 Barker Hall, University of California at Berkeley Berkeley, CA 94720 leejh@mendel.berkeley.edu Recent discoveries of components used in various types of membrane fusion events, from neurotransmitter release in mammalian neuronal cells to protein secretion in yeast cells, have led to a unified hypothesis. In order to extend our understanding of the biology of vesicle trafficking and membrane fusion events, it is important to study the roles of all the components of the fusion machinery. SNAP 25 is one of the components of the membrane fusion apparatus, and its molecular and biological functions have not been fully determined. It has been proposed that SNAP-25 is important in axonal growth during neural development and that it acts as a plasma membrane receptor in vesicle docking and fusion. Because this protein was shown to be conserved during evolution, it would be useful to investigate the molecular and biological functions of the SNAP-25 protein in a simpler model system such as the nematode C. elegans in order to test these hypotheses. We cloned a homolog of SNAP-25 by PCR using a set of degenerate primers that had been successfully used by C. Risinger and D. Larhammer to clone Drosopl2ila SNAP-25 homologs. They kindly provided the primers to us. We subcloned PCR-amplified products in a pBluescript vector, and determined the DNA sequence of the clones. The preliminary sequence comparison shows that C. elegans SNAP-25 is about 57% identical to the fly homolog, and 52% to the human homolog. The C. elegans SNAP-25 also shows a limited similarity to the yeast Sec9 protein (36% identity in a stretch of 50 amino acids). We screened the Barstead and Waterston cDNA library to identify full length cDNA clones. One of the cDNA clones contained 7 nucleotides identical to the 3' end of the SL-1 leader sequence, indicating that this clone contains a full length transcript. Sequencing of the clone is under way. We performed a YAC grid filter hybridization experiment using the PCR clone as a probe and identified three apparently positive YACs on chromosome V. Further physical mapping of the gene is under way.

Yanase S et al. (1998) Worm Breeder's Gazette "One tube RT-PCR assay from single worms"

Ishii N, Okano M, Yanase S

[Worm Breeder's Gazette, 1998]

In case of weakly expressed genes, Northern blot analysis may not be sensitive enough to detect transcription unless poly(A)+ RNA is prepared. We would like to report a simple method of RT-PCR assay from single animals that does not require poly(A)+ RNA preparation. Washed with M9 buffer, each single animal is transferred in 2 ul of TE (pH 8.0) in a 0.5 ml tube and frozen (-80oC, 20 min). 1 ul of lysis buffer [0.5 mg/ml proteinase K in 10 mM Tris (pH 8.0), 50 mM KCl, 2.5 mM MgCl2, 0.45% Tween 20 and 0.05% gelatin] is added and mixed well. After the addition of a mineral oil overlay, the tube is heated at 65oC for 1 hour and the reaction is stopped by the boil for 15 min. After cooling to 4oC, 1 ul of DNase I (7.5 units/ul, Pharmacia Biotech) is added and incubated at 37oC for 30 min. The reaction is stopped by boiling for 15 min. 46 ul of a master mix is then pipetted on top of the mineral oil overlay. The mix is formulated to bring the reaction volume to 50 ul using DEPC H2O with these final conditions: each 10 pmol of sense and anti-sense primers, 25 ul of 2x reaction mix and 1ul of SuperScript II RT/Taq DNA polymerase mix (GIBCO BRL). After a brief microfuge spin, the sample is incubated at 45-55oC for 30 min for cDNA synthesis. Then, 94oC for 2 min followed by amplification of 45 cycles of 94oC for 30 sec, 50-65oC (depending on the primer set) for 30 sec and 72oCo for 0.5-3 min (1 kb/min), followed by 72oC for 5 min. The PCR product (10 ul) is analyzed on 0.8-1.5% agarose gels. Using this method, we have been able to detect a typical sod-3 RT-PCR product of which the expression is lower than that of other genes. To avoid error in different stages, we recommend using some animals at the same developmental stage and duplicate with each primer set. This system is also useful for late-stage embryos. References: 1. Williams, B., D. et al. (1992) Genetics 131: 609-624 2. Andachi, Y. et al. (1993) WM'93: 33 3. Lee, E. H. et al. (1997) Focus 19 (2): 39-42 4. Sitaraman, K. et al. (1997) Focus 19 (2): 43-44

Alex Hajnal et al. (2002) Worm Breeder's Gazette "The MAP kinase phosphatase LIP-1 is required for the meiotic cell-cycle arrest in developing oocytes"

Erika Frohli Hoier, ALEX HAJNAL, Thomas Berset

[Worm Breeder's Gazette, 2002]

The RAS/MAP kinase signaling pathway plays an essential role at two steps during hermaphrodite germline development. First, RAS/MAP kinase (MPK-1) signaling is required for the progression of germ cells through the pachytene stage of meiotic prophase I (Lee et al. 2001, IWM abstract 991). After pachytene exit, MPK-1 is rapidly inactivated and the developing oocytes arrest in the diakinesis stage of meiotic prophase I. As the oocytes approach the spermatheca, the secreted sperm signal MSP causes the re-activation of MPK-1, which induces oocyte maturation and allows the meiotic cell cycle to progress (Miller et al. 2001). We have previously shown that the dual specificity phosphatase LIP-1 acts as a negative regulator of MPK-1 during vulval induction (Berset et al. 2001). Here, we report an important role for LIP-1 in regulating MPK-1 activity during germline development. A lip-1 loss-of function-mutation ( zh15 ) suppresses the pachytene arrest caused by reduction-of-function mutations in mpk-1 ( oz140 or ga111 ). Consistent with this genetic interaction, we detected anti-LIP-1 antibody staining in pachytene stage germ cells but no staining at other stages of germline development. Furthermore, the proximal gonads of lip-1(zh15) mutants contain more but smaller oocytes than wild-type gonads (12.3+/-4.1 oocytes in lip-1(zh15) as opposed to 7.9+/-1.6 in wild-type gonads). The rate of oocyte maturation, on the other hand, is unchanged. Thus, germ cells in lip-1(zh15) mutants exit the pachytene stage at an increased rate, resulting in an overall acceleration of oocyte development. Moreover, by staining gonads with an antibody specific for the diphosphorylated, activated form of MAP kinase (anti-DP-ERK) we found that MPK-1 fails to be inactivated after germ cells exit the pachytene stage in lip-1(zh15) mutants. The increased levels of activated MPK-1 persist throughout the diakinesis stage until fertilization occurs. Interestingly, in 9% of lip-1(zh15) single mutants a few (< 5) unfertilized oocytes per gonad arm display an endomitotic (Emo) phenotype, they start multiple mitotic cell cycles without undergoing cytokinesis. This Emo phenotype is more penetrant (>80%) and stronger (usually >20 mitotic nuclei per gonad arm) in feminized ( fem-2 or fog-1 ) lip-1(zh15) mutants that produce no sperm. Thus, unfertilized oocytes in lip-1(zh15) mutants often fail to arrest the meiotic cell-cycle. Taken together, our results indicate that LIP-1 is responsible for the inactivation of MPK-1 after germ cells exit the pachytene stage. The inactivation of MPK-1 by LIP-1 is critical to allow the developing oocytes to arrest the meiotic cell cycle in the diakinesis stage until oocyte maturation is induced.

Lee RYN et al. (1996) Worm Breeder's Gazette "egl-19(n2368sd) may cause myotonia by affecting voltage-dependent inactivation of L-type Ca2+ channels"

Lee RYN, Avery L

[Worm Breeder's Gazette, 1996]

We have shown previously that egl-19 (aka. eat-12, pat-5) plays a key role in controlling muscle contraction and depolarization (Lee et al., WBG 13(1): 45). Putative null mutations of egl-19 lead to a Pat phenotype, suggesting that embryonic muscles are unable to contract. Partial loss-of-function alleles show feeble contraction of pharyngeal, body, and egg-laying muscles while gain-of-function alleles lead to muscle hypercontraction. Based on the electrophysiological analysis of the pharyngeal phenotype, we argue that these contraction defects can be explained at least in part by defects in muscle excitation (loss-of-function) and repolarization (gain-of-function). We have cloned egl-19 (Lobel et al., WBG 13(2): 71). It encodes a polypeptide of 1,787 amino acids and shares more than 60% sequence identity with the alpha1 subunit of L-type voltage-activated Ca2+ channels. To address the question of how egl-19 affects muscle excitation, we localized its expression by constructing an egl-19::GFP translational fusion. EGL-19::GFP was first detected in body muscles in 1-1/2-fold embryos, before the onset of embryonic rolling. This result is consistent with the Pat phenotype seen in null mutants, suggesting a cell-autonomous muscle defect. By hatching, GFP fluorescence is found in pharyngeal muscles pm3, pm4, pm5, and pm7; in body muscles; and in the anal depressor muscle. The muscle expression pattern is again consistent with a muscle cell-autonomous defect caused by mutations. Interestingly, however, we also found expression in the nervous system including the pharyngeal neuron M4 and many neurons in the nerve ring, the ventral nerve cord, and the pre-anal ganglion. We do not know the significance of the apparent nervous system expression since most of the phenotypes of egl-19 mutants are consistent with defects of muscle function. (This is not surprising, as failure of muscle would hide most nervous system phenotypes.) One exception is that two gain-of-function alleles have a Daf-d phenotype. Although some dauers do form, their modification appears incomplete as they are less resistant to SDS treatment. We could not detect expression in egg-laying muscles. It may be that the level is too low, or that the promoter fragment we used lacks elements for vulval muscle expression. In order to learn at a molecular level how gain-of-function mutations of egl-19 affect muscle repolarization, we sequenced the coding regions of ad695sd and n2368sd. We did not find any mutation in the ORF of ad695sd. One possiblity is that ad695sd may affect gene expression. In egl-19(n2368sd), however, we found a G->A mutation in the putative 6th transmembrane domain of repeat I (IS6). This mutation would change a conserved glycine residue to an arginine. The IS6 region has previously been shown to determine the rate of voltage-dependent inactivation of L-type channels expressed in Xenopus oocytes (Zhang et al., Nature 372: 97). The myotonic phenotype (delayed relaxation/repolarization) of n2368sd can be reasonably explained by slower inactivation of muscle Ca2+ channels.

Park M et al. (1995) Worm Breeder's Gazette "CeMEF-2 Is Expressed in Muscle and Nerve."

Krause MW, Park M, Lee-Llacer R, Littlejohn R, Dichoso D

[Worm Breeder's Gazette, 1995]

CeMEF-2 is expressed in muscle and nerve Morgan Park, Daryl Dichoso*, Rey Lee-Llacer, Robert Littlejohn, and Michael Krause. Laboratory of Molecular Biology, NIDDK, NIH. *Dept. of Biology, University of Houston. The vertebrate Mef-2 family of genes encodes sequence specific transcription factors of the MADS box class that are related to the serum response factors (SRFs). Mef-2 genes are expressed in a variety of tissues, however, their expression in muscle has received the most attention. In vertebrates, MEF-2 isoforms play a critical role in activating a variety of muscle specific proteins during skeletal muscle differentiation, including a positive feedback regulation of MyoD family members such as MyoD and myogenin. In addition, certain MEF-2 isoforms are expressed in differentiating cardiac tissue and can activate cardiac-specific genes. In Drosophila, there appears to be only a single Mef-2-like gene that is expressed in precursors of all muscle types, with expression in striated muscle preceding that of the MyoD family member, nautilus; essentially no neuronal expression has been observed in flies. We have cloned a C. elegans member of the Mef-2 family by degenerate RT-PCR. PCR results were previously interpreted to suggest as many as five Mef-2-like genes might exist in the worm. However, genomic and cDNA library screens continue to pull out only a single gene. A careful re-examination of the PCR data has allowed us to eliminate (due to suspected PCR errors or contamination) all but a single product from C. elegans, consistent with a single gene. Genomic Southern blots also suggest a single gene, although there is a faintly hybridizing secondary band that can not be explained by the genomic locus we have cloned. We have looked at a single line of animals transformed with a CeMEF-2::beta-galactosidase reporter construct that includes ~7kb of sequence upstream of the ATG in addition to a large (2337bp) first intron. During embryogenesis, weak expression is seen at the tailbud stage in a few unidentified cells in the head region. Subsequently, other cells begin to express the reporter gene and by the three-fold stage, there is very strong expression in what appears to be all muscle cells (bwm, pharyngeal, others?) and all neurons. The large number of staining cells makes it difficult to determine if all minor muscle cell groups (intestinal, uterine, etc.) are expressing. Expression continues in both muscle and nerve to adulthood. The expression pattern of this mef-2::1acZ construct is similar to what is seen in vertebrates, suggesting that this transcription factor is playing a role in the differentiation of muscle and nerve in C. elegans. If the onset of expression during embryogenesis is correctly reflected by our reporter construct, it is unlikely that CeMEF-2 initiates the commitment of precursor blastomeres to these different cell types (eg. in body wall muscle cells, myosin heavy chain is activated prior to our reporter construct). Instead, CeMEF-2 might interact with other tissue-specific factors to enhance, or maintain, the expression of activated genes and help drive terminal differentiation.