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R H Scheller

Publications and source records attributed to R H Scheller.

227 records · Page 13Linked to original sources
PubMed1982

A family of genes that codes for ELH, a neuropeptide eliciting a stereotyped pattern of behavior in Aplysia.

We describe a particularly advantageous experimental system for studying gene structure, expression and modulation in the nervous system. In the marine mollusc Aplysia, the bag cells, two discrete clusters of neurons, secrete a peptide of known behavioral function. This neuroactive peptide, egg-laying hormone (ELH), produces a characteristic and stereotypic behavioral repertoire, consisting first of a cessation of walking and inhibition of feeding, followed by head waving and egg laying. We have cloned the genes encoding ELH and characterized their organization and expression. At least five distinct genes for ELH exist within the chromosome. Sequence analysis of one recombinant clone unambiguously identifies a contiguous stretch of nucleotides that encodes the 36 amino acids of ELH. Transcription of this small multigene family results in the expression of at least five distinct RNA transcripts encoding ELH. The pattern of transcripts differs strikingly in different tissues: bag cells express three distinct mRNA species, whereas the atrial gland, a secretory reproductive gland, expresses two distinct mRNAs. Several other neuronal and nonneuronal tissues do not express ELH RNA. In vitro these mRNAs produce a series of long polypeptide precursors that must be processed to generate the active ELH peptide. This processing event is likely to generate several additional neuroactive peptides. Thus the same peptide, ELH, may be released in association with different combinations of other neuroactive peptides. The concept of combinatorial sets of neuropeptides, each bearing one overlapping peptide ELH, and each directing a differing pattern of behavior, greatly expands the information potential of a small set of genes.

Animals↗
PubMed1981

Organization and expression of multiple actin genes in the sea urchin.

A set of at least 11 actin genes has been isolated from genomic recombinant deoxyribonucleic acid libraries of the sea urchin Strongylocentrotus purpuratus. Most of the isolates derive from a library which represents the genome of a single animal. There are at least five distinct types of sea urchin actin gene, some of which are represented by multiple copies in the genome. The actin gene types are distinguished by nonhomologous flanking sequences and intervening sequences, though the protein coding sequences appear in most cases to be quite similar. Eight of the 11 genes isolated have been recovered in lambda recombinants that contain two actin genes, linked at 5- to 9-kilobase distances. Restriction map overlaps suggest that the genome contains an array of at least three of these genes spaced over about 30 kilobases of deoxyribonucleic acid. In the linkage patterns observed, actin genes of diverse types were linked to each other. In early embryos, actin messenger ribonucleic acid (RNA) transcripts of 1.8 and 2.2 kilobases were found, and the longer of these transcripts was more prevalent in the maternal RNA of the egg. From RNA gel blot experiments, we conclude that the two transcripts derive from different actin gene types. Different repetitive sequences were located to either side of most of the actin genes, and in most observed cases the repeat sequences which were adjacent to actin genes of a given type were similar. The repeat sequences flanking the actin genes belonged to families which were transcribed, but those repeats in the neighborhood of the actin genes which have been investigated were not themselves represented in the stable RNAs of eggs or early embryos.

Actins↗
PubMed1978

Evolutionary change in the repetition frequency of sea urchin DNA sequences.

The frequency of occurrence of particular repetitive sequence families has been estimated in the DNA of the three sea urchin species Strongylocentrotus purpuratus. Strongylocentrotus franciscanus and Lytechinus pictus using individual cloned S. purpuratus repetitive sequence elements. Cloned repetitive sequence elements as described by Scheller et al. (1977a) were prepared by reassociation of S. purpuratus DNA fragments to repetitive Cot, digestion with single-strand-specific nuclease S1 and ligation of synthetic restriction sites to their ends. The sequences were cloned by insertion at the Eco RI site of plasmid RSF2124, labeled, strand-separated and reassociated with 800--900 nucleotide long unlabeled DNA. Both kinetic (genomic DNA excess) and saturation (cloned DNA excess) estimates of frequencies were made. For nine cloned fragments, the ratio of the repetition frequency in S. purpuratus DNA to that in S. franciscanus DNA ranges from about 20 to about 1. In the four cases examined, only a few copies were detected in the DNA of L. pictus. Estimates have also been made of frequency changes in many repetitive families by measuring the reassociation of labeled repetitive DNA fractions of each species with total DNA from other species. In each reciprocal comparison, the labeled repetitive sequences reassociate more slowly with DNA of other species than with DNA of the species from which they were prepared. Thus it appears that the dominant repetitive sequence families in the DNA of each species are present at lower frequencies in the DNA of closely related species. Measurements of thermal stability have been made of S. purpuratus cloned repetitive sequences reassociated with S. franciscanus DNA or S. purpuratus DNA. Most families have changed both in frequency and sequence, although some have changed little in sequence but show great changes in frequency.

Animals↗
PubMed1978

Repetitive sequence transcripts in the mature sea urchin oocyte.

The expression of interspersed repetitive sequences in the RNA of mature sea urchin oocytes was investigated. 3H-DNA tracers representing short interspersed repetitive sequences a few hundred nucleotides long, and long repetitive sequences approximately 2000 nucleotides long, were prepared from genomic DNA of the sea urchin, Strongylocentrotus purpuratus. These tracers were reacted with excess RNA from the mature oocyte. About 80% of the reactable short repeat tracer and 35% of the long repeat tracer hybridized. Thus most of the repetitive sequence families in the short repeat tracer are represented in oocyte RNA, and transcripts complementary to both strands of many repeat sequences are present. The kinetics of the reaction show that some transcripts are highly prevalent (greater than 10(5) copies per oocyte), while others are rare (approximately 10(3) copies per oocyte). Nine cloned repetitive sequences were labeled, strand-separated and reacted with the oocyte RNA. Transcripts of both strands of all nine repeats were found in the RNA. The prevalence of transcripts of the cloned repeat families varied from approximately 3000 to 100,000 copies per oocyte. Studies with both cloned and genomic tracers show that transcript prevalence is independent of the genomic reiteration frequency of the transcribed repetitive sequences. Most of the families represented by prevalent transcripts have fewer than 200 copies per haploid genome. The RNA molecules with which the cloned repeats react are at least 1000-2000 nucleotides in length. Other experiments show that a majority of the members of repeat families represented by prevalent transcripts in the oocyte RNA are interspersed among single-copy sequence elements in the genome.

Animals↗
PubMed1978

Specific representation of cloned repetitive DNA sequences in sea urchin RNAs.

Nine cloned repetitive sequences were labeled, strands-separated and individually hybridized with RNA extracted from the nuclei of gastrula stage sea urchin embryos and of adult sea urchin intestine cells. The concentration of transcripts complementary to each cloned sequence was measured by RNA excess hybridization kinetics and by a DNA excess titration method. Transcripts of certain of the repeat families are present at over 100 times the concentration of transcripts of other families in each RNA. The set of repetitive sequence families highly represented in intestine nuclear RNA is different from that highly represented in gastrula nuclear RNA. Together with the results obtained with mature oocyte RNA and presented in the accompanying paper by Costantini et al. (1978), these findings show that quantitative patterns of repetitive sequence representation in RNA are specific to each cell type. Both strands of all of the nine cloned repeats are represented at some level in all the RNAs studied. Usually, though not always, the concentration of transcripts complementary to the two strands of each repeat do not differ by more than a factor of two. The cloned tracers do not react with polysomal messenger RNA, and the nuclear RNA molecules with which they hybridize are many times larger than the repetitive sequences themselves.

Animals↗
PubMed1978

Characteristics of individual repetitive sequence families in the sea urchin genome studied with cloned repeats.

Cloned repetitive sequences from the S. purpuratus genome a few hundred to approximately 1000 nucleotides long were used to investigate the characteristics of individual repetitive sequence families. They wer terminally labeled by the kinase procedure and reacted with sheared S. purpuratus DNA. Repetition frequencies were measured for 26 individual families and were found to vary from a few to several thousand copies per genome. Estimates of sequence divergence were made for 18 cloned repeat families by measuring thermal stability of the heteroduplexes formed between the genomic DNA and the cloned fragments, compared with that of the renatured cloned fragments. The difference was less than 4 degrees C for three of the 18 families, and less than 10 degress C for 13 of the 18 families. These 13 repetitive sequence families lack any detectable highly divergent sequence relatives, and the results reported are shown not to change when the renaturation criterion is lowered below 55 degrees C in 0.18 M Na+. Five of the 18 cloned families displayed greater sequence divergence. The average sequence divergence of the total short repetitive sequence fraction of S. purpuratus DNA was found to match closely the average of the divergences of the cloned repeat sequences.

Base Sequence↗
PubMed1977

Chemical synthesis of restriction enzyme recognition sites useful for cloning.

By a triester chemical synthesis method, three decameric DNA's have been made; these act as substrates for several restriction endonucleases, including Eco RI, Bam I, and Hind III. These homogenous decamers form duplexes that can be efficiently blunt-end ligated to themselves or to other DNA molecules by the action of T4 DNA ligase and thus are useful tools for molecular cloning experiments.

Base Sequence↗