Samuel Ward

The University of Arizona | UA

FER-1 is required for fusion of specialized vesicles, called membranous organelles, with the sperm plasma membrane during Caenorhabditis elegans spermiogenesis. To investigate its role in membranous organelle fusion, we examined ten fer-1 mutations and found that they all cause the same defect in membrane fusion. FER-1 and the ferlin protein family...

Dissection of the phenotypic and molecular details of development and differentiation is a centuries-old topic in evolutionary biology. However, an adequate understanding is missing for the molecular evolution of genes that are expressed differentially throughout development-across time, tissues, and the sexes. In this study, we investigate the dyn...

Upon starvation or overcrowding, Caenorhabditis elegans interrupts its reproductive cycle and forms a specialised larva called dauer (enduring). This process is regulated by TGF-beta and insulin-signalling pathways and is connected with the control of life span through the insulin pathway components DAF-2 and DAF-16. We found that replacing cholest...

Comparison of Cholesterol Metabolism in Wild-Type, daf-12, and Double Mutant daf-9 daf-12 Worms (3.8 MB PDF).

Regio- and Stereospecific Synthesis of 4α-Substituted 5α-Cholestan-3β-ols (114 KB DOC).

Defining the forces that sculpt genome organization is fundamental for understanding the origin, persistence, and diversification of species. The genomic sequences of the nematodes Caenorhabditis elegans and Caenorhabditis briggsae provide an excellent opportunity to explore the dynamics of chromosome evolution. Extensive chromosomal rearrangement...

We performed a genome-wide analysis of gene expression in C. elegans to identify germline- and sex-regulated genes. Using mutants that cause defects in germ cell proliferation or gametogenesis, we identified sets of genes with germline-enriched expression in either hermaphrodites or males, or in both sexes. Additionally, we compared gene expression...

Cholesterol is a structural component of animal membranes that influences fluidity, permeability and formation of lipid microdomains. It is also a precursor to signalling molecules, including mammalian steroid hormones and insect ecdysones. The nematode Caenorhabditis elegans requires too little cholesterol for it to have a major role in membrane s...

The soil nematode Caenorhabditis elegans is an example of a species in which self-fertilizing hermaphrodites predominate, but functional males continue to persist--allowing outcrossing to persevere at low levels. Hermaphrodites can produce male progeny as a consequence of sex chromosome non-disjunction or via outcrossing with males. Consequently, t...

Sperm morphology evolves rapidly, resulting in an exceptional diversity of sperm size and shape across animal phyla. This swift evolution has been thought to prevent fertilizations between closely related species. Alternatively, recent correlative analyses suggest that competition among sperm from more than one male may cause sperm diversity, but t...

Immature spermatids from Caenorhabditis elegans are stimulated by an external activation signal to reorganize their membranes and cytoskeleton to form crawling spermatozoa. This rapid maturation, termed spermiogenesis, occurs without any new gene expression. To better understand this signal transduction pathway, we isolated suppressors of a mutatio...

Caenorhabditis elegans spermatids complete a dramatic morphogenesis to crawling spermatozoa in the absence of an actin- or tubulin-based cytoskeleton and without synthesizing new gene products. Mutations in three genes (spe-8, spe-12, and spe-27) prevent the initiation of this morphogenesis, termed activation. Males with mutations in any of these g...

We used DNA microarrays to profile gene expression patterns in the C. elegans germline and identified 1416 germline-enriched transcripts that define three groups. The sperm-enriched group contains an unusually large number of protein kinases and phosphatases. The oocyte-enriched group includes potentially new components of embryonic signaling pathw...

Genes expressed during C. elegans germline development have been identified using DNA microarrays.

This study examined the effects of oxygen tensions ranging from 0 to 90 kPa on the metabolic rate (rate of carbon dioxide production), movement and survivorship of the free-living soil nematode Caenorhabditis elegans. C. elegans requires oxygen to develop and survive. However, it can maintain a normal metabolic rate at oxygen levels of 3.6 kPa and...

Mutations that increase the longevity of the soil nematode Caenorhabditis elegans could define genes involved in a process specific for aging. Alternatively, these mutations could reduce animal metabolic rate and increase longevity as a consequence. In ectotherms, longevity is often negatively correlated with metabolic rate. Consistent with these o...

During spermiogenesis, Caenorhabditis elegans spermatids activate and mature into crawling spermatozoa without synthesizing new proteins. Mutations in the spe-12 gene block spermatid activation, rendering normally self-fertile hermaphrodites sterile. Mutant males, however, are fertile. Surprisingly, when mutant hermaphrodites mate with a male, thei...

In the free-living rhabditid nematode Caenorhabditis elegans, sperm size is a determinant of sperm competitiveness. Larger sperm crawl faster and physically displace smaller sperm to take fertilization priority, but not without a cost: larger sperm are produced at a slower rate. Here, we investigate the evolution of sperm size in the family Rhabdit...

Sperm competition is generally thought to drive the evolution of sperm miniaturization. Males gain advantage by transferring more sperm, which they produce by dividing limited resources into ever smaller cells. Here, we describe the opposite effect of size on the competitiveness of amoeboid sperm in the hermaphroditic nematode Caenorhabditis elegan...

In nematodes, sperm are amoeboid cells that crawl via an extended pseudopod. Unlike those in other crawling cells, this pseudopod contains little or no actin; instead, it utilizes the major sperm protein (MSP). In vivo and in vitro studies of Ascaris suum MSP have demonstrated that motility occurs via the regulated assembly and disassembly of MSP f...

Sperm competition is generally thought to drive the evolution of sperm miniaturization. Males gain advantage by transferring more sperm, which they produce by dividing limited resources into ever smaller cells. Here, we describe the opposite effect of size on the competitiveness of amoeboid sperm in the hermaphroditic nematode Caenorhabditis elegan...

During maturation of spermatids to motile spermatozoa in Caenorhabditis elegans, large vesicles called membranous organelles (MOs) fuse with the spermatid plasma membrane. Mutations in the gene fer-1 cause abnormal spermatozoa in which the MOs do not fuse, although they abut the plasma membrane normally. Here we describe the fer-1 gene, which we fo...

Male offspring, which cannot reproduce independently, represent a cost of sexual reproduction. This cost is eliminated by the production of hermaphroditic offspring in the self-fertilizing nematode Caenorhabditis briggsae. However, these hermaphrodites can outcross by mating with males. Half the sperm received from males contain no sex chromosome a...

Hermaphrodites with mutations in the spe-27 gene are self-sterile, laying only unfertilized eggs; mutant males are fertile. Hermaphrodites make spermatids that fail to activate to crawling spermatozoa so passing oocytes sweep them out of the spermatheca. These spermatids do activate and produce self-progeny if young mutant hermaphrodites are mated...

When male and hermaphrodite Caenorhabditis elegans mate, the male's sperm outcompete the hermaphrodite's own sperm and fertilize a majority of the offspring. Here, we investigate the mechanism of male sperm precedence. We rule out the possibility that male sperm are stronger and more competitive because they are activated later than hermaphrodite s...

When male and hermaphroditeCaenorhabditis elegans mate, the male's sperm outcompete the hermaphrodite's own sperm and fertilize a majority of the offspring. Here, we investigate the mechanism of male sperm precedence. We rule out the possibility that male sperm are stronger and more competitive because they are activated later than hermaphrodite sp...

Six independent mutations in the Caenorhabditis elegans spe-26 gene cause sterility in males and hermaphrodites by disrupting spermatogenesis. Spermatocytes in mutants with the most severe alleles fail to complete meiosis and do not form haploid spermatids. Instead, these spermatocytes arrest with missegregated chromosomes and mislocalized actin fi...

We describe a protocol for artificial insemination of Caenorhabditis elegans which we used to evaluate the viability of sperm from different strains and of sperm activated in vitro. Worms can be artificially inseminated with almost 100% success. Both male and hermaphrodite sperm can be used for insemination. Sperm from a sterile hermaphrodite [fem-...

Caenorhabditis elegans spermatozoa move by crawling. Their motility requires thin cytoskeletal filaments assembled from a unique cytoskeletal protein, the major sperm protein (MSP). During normal sperm development the MSP is segregated to developing sperm by assembly into filaments that form a paracrystalline array in a transient organelle, the fib...

The isolation and properties of a gene encoding a histone H1 protein of Caenorhabditis elegans, his-24, are described. The predicted protein sequence is similar to histone H1 proteins of other eukaryotes. However, the gene structure of his-24 is atypical for a histone H1 gene; it contains an intron and encodes a polyadenylated mRNA. A family of app...

Loss-of-function mutations in the spe-11 gene in Caenorhabditis elegans result in a paternal-effect embryonic-lethal phenotype: fertilization of wild-type oocytes by sperm from homozygous spe-11 mutant males leads to abnormal zygotic development, whereas oocytes from homozygous spe-11 hermaphrodites when fertilized by wild-type sperm develop normal...

Nematode spermatozoa, unlike their mammalian counterparts, are nonflagellated crawling cells. The pseudopod of these cells contains the major sperm protein (MSP) which comprises more than 15% of the protein in the sperm. MSP is presumed to function as a cytoskeletal element involved in motility. An Ascaris MSP cDNA sequence was used as a probe to i...

Nematode sperm contain unusual organelles, membranous organelles, which undergo dramatic morphological changes during spermatogenesis. Early in spermatogenesis, the membranous organelle functions to transport sperm specific components to the spermatids; later, during the formation of the crawling spermatozoa, it adds new components to the cell surf...

Spermiogenesis in Caenorhabditis elegans involves the conversion of spherical, sessile spermatids into bipolar, crawling spermatozoa. In males, spermiogenesis is induced by mating, while in hermaphrodites, spermiogenesis occurs before the first oocytes are fertilized. Alternatively, spermiogenesis can be induced in vitro by treatment with monensin...

The DNA from a number of free-living and parasitic nematode species was examined to determine the genomic number and distribution of DNA sequences encoding two evolutionarily conserved proteins; the major sperm protein (MSP) and nematode actin. Ascaris and Caenorhabditis MSP cDNA sequences and Ascaris genomic actin sequences were used to probe Sout...

Mutations affecting Caenorhabditis elegans spermatogenesis can be used to dissect the processes of meiosis and spermatozoan morphological maturation. We have obtained 23 new chromosome I mutations that affect spermatogenesis (spe mutations). These mutations, together with six previously described mutations, identify 11 complementation groups, of wh...

The major sperm proteins (MSPs) are encoded in the Caenorhabditis genome by a multigene family with more than 50 genes dispersed in small clusters at three chromosomal loci. In spite of their dispersed locations, all of the MSP genes appear to be expressed at the same time exclusively in the testis, indicating co-ordinate temporal and spatial regul...

The major sperm proteins (MSPs) are a family of closely related, small, basic proteins comprising 15% of the protein in Caenorhabditis elegans sperm. They are encoded by a multigene family of more than 50 genes, including many pseudogenes. MSP gene transcription occurs only in late primary spermatocytes. In order to study the genomic organization o...

Ascaris lumbricoides var. suum is a parasitic nematode of pigs. Its embryos undergo chromatin diminution between the third and fifth cleavages, resulting in the loss of about 30% of the DNA from all somatic precursor cells while the germ line DNA stays intact. Most of the eliminated DNA has been shown to be satellite sequences. Theodor Boveri [(191...

During the development of pseudopodial spermatozoa of the nematode, Caenorhabditis elegans, protein synthesis stops before differentiation is completed. Colloidal gold conjugates of monoclonal antibody SP56, which binds to the surface of spermatozoa, and TR20, which recognizes the major sperm cytoplasmic protein (MSP), were used to label thin secti...

Four monoclonal antibodies that are directed against antigens present in sperm and absent from other worm tissues were characterized. Antibody TR20 is directed against the major sperm proteins, a family of small, abundant, cytoplasmic proteins that have been previously described (Klass, M. R., and D. Hirsh, 1981, Dev. Biol., 84:299-312; Burke, D. J...

DNA fragments corresponding to genes encoding the MSP of Caenorhabditis elegans sperm have been isolated by recombinant DNA techniques. Analyses of individual genomic clones suggest that there are multiple MSP genes that are dispersed in the genome. From restriction enzyme digests of genomic DNA fractionated and hybridized with an MSP complementary...

Spermiogenesis in nematodes involves the activation of sessile spherical spermatids to motile bipolar amoeboid spermatozoa. In Caenorhabditis elegans males spermiogenesis is normally induced by copulation. Spermatids transferred to hermaphrodites as well as some of those left behind in the male become spermatozoa a few minutes after mating. Spermio...

Using an affinity-purified antibody to the major sperm protein (MSP) in Caenorhabditis elegans sperm we have shown by immunofluorescence that the MSP is localized in the fibrous bodies of spermatocytes and early spermatids, in the cytoplasm of late spermatids, and in the pseudopods of spermatozoa. The MSP can also form crystalline inclusions in mut...

The pseudopods of Caenorhabditis elegans spermatozoa move actively causing some cells to translocate when the sperm are dissected into a low osmotic strength buffered salts solution. On time-lapse video tapes, pseudopodial projections can be seen moving at 20-45 micrometers/min from the tip to the base of the pseudopod. This movement occurs whether...

Two distinct types of surface membrane rearrangement occur during the differentiation of Caenorhabditis elegans spermatids into amoeboid spermatozoa. The first, detected by the behavior of latex beads attached to the surface, is a nondirected, intermittent movement of discrete portions of the membrane. This movement starts when spermatids are stimu...

Latex beads and wheat germ agglutinin (WGA) were used to examine the movement of membrane components on amoeboid spermatozoa of Caenorhabditis elegans. The behavior of beads attached to the cell revealed continuous, directed movement from the tip of the pseudopod to its base, but no movement on the cell body. Lectin receptors are also cleared from...

Excerpt The capping of cross-linked surface receptors on lymphocytes and other cells and the centripetal movement of surface-attached particles on crawling cells are examples of directed surface membrane movement (Bray 1978). One possible mechanism for moving membrane components is that cytoskeletal proteins recognize cross-linked surface receptors...

Taking advantage of conditions that allow spermatogenesis in vitro, the timing and sequence of morphological changes leading from the primary spermatocyte to the spermatozoon is described by light and electron microscopy. Together with previous studies, this allows a detailed description of the nuclear, cytoplasmic, and membrane changes occurring d...

The amoeboid motility of spermatozoa from the nematode Ascaris lumbricoides observed in vitro is described. Pseudopodial movements and filopodial extensions occur rhythmically with a period of about 18 sec. A small fraction of spermatozoa translocate in the direction of the extending pseudopod at velocities up to 11 μm/min. Immunofluorescence demon...

Seven new fertilization-defective mutants of C. elegans have been isolated and characterized; six are temperature sensitive, one is absolute and all are autosomal recessive. One mutation is in a previously described gene, while the other six define six new fer genes that appear to code for sperm-specific functions necessary for normal fertilization...

The sodium- and potassium-transporting ionophore monensin induces the maturation of Caenorhabditis elegans spermatids to spermatozoa in vitro. Rearrangement of cytoplasm, fusion of membranous organelles with the plasma membrane and growth of pseudopodia, all characteristic of in vivo spermiogenesis, occur within five minutes after exposure to monen...

The process of fertilization by hermaphrodite and male sperm is described. In the hermaphrodite fertilization occurs in the spermatheca by the first sperm to contact the oocyte. Other sperm that contact the oocyte are swept into the uterus but they crawl back into the spermatheca to fertilize subsequent oocytes so that every sperm fertilizes an ooc...

Movement patterns of Schistosoma mansoni miracidia were examined in several concentrations and gradients of snail-conditioned water (SCW). Miracidia surrounded by uniform concentrations of SCW swam at the same speed and exhibited the same rate of turning (angular velocity) as did control miracidia swimming in spring water. However, miracidia in gra...

A temperature-sensitive mutation, isx-1(hc17), is reported in the nematode Caenorhabditis elegans which alters the sexual phenotypes of both genotypic sexes. At the restrictive temperature, XX animals are functionally female rather than hermaphroditic due to the absence of spermatogenesis, and XO animals develop as intersexes. These intersexes have...

We describe a new technique for testing responses of Schistosoma mansoni miracidia to chemicals. Miracidia in spring water were placed in a chamber shaped like the Greek letter phi. Small volumes of test chemicals were inoculated into one side of the chamber. After 30 sec a dam was inserted to bisect the chamber and the percentage of miracidia on t...

The isolation and characterization of three Caenorhabditis elegans temperature-sensitive mutants that are defective at fertilization are described. All three are alleles of the gene fer-1. At the restrictive temperature of 25 degrees, mutant hermaphrodites make sperm and oocytes in normal numbers. No oocytes are fertilized, although they pass throu...

Schistosoma mansoni is a parasitic flatworm transmitted by snails which infects millions of people in tropical countries with poor sanitation, where new irrigation schemes, population growth and continued poverty have increased the prevalence of infection. Larval worms, emerging from freshwater snails, penetrate human skin and mature in intestinal...

The complete structure of the anterior sensory nervous system of the small nematode C. elegans has been determined by reconstruction from serial section electronmicrographs. There are 58 neurons in the tip of the head. Fifty-two of these are arranged in sensilla. These include six inner labial sensilla, six outer labial sensilla, four cephalic sens...

This paper describes two polyacrylamide gel fractionators. One can be easily constructed from disposable syringes and used for fractionating standard-size analytical gels. The second is more complex but can be used for fractionating miniature gels. A rapid method of preparing gel fractions for liquid-scintillation counting is also presented. The me...

Complete T4 tail fibers and four precursor structures (half fibers) were purified from lysates of mutant-infected Escherichia coli cells, using serum blocking assays for tail fiber antigens to monitor the isolation procedures. Each of the final preparations showed a single major electrophoretic component on polyacrylamide gels. The purified structu...

This paper describes an apparatus for rapid destaining of acrylamide gels by transverse electrophoresis. A removable gel supporting rack allows staining, rapid destaining, and photography of gels without handling the individual gels.