Primary cutaneous phalangeal neuroendocrine/squamous cell carcinoma with mixed axillary metastasis

Cutaneous neuroendocrine tumours are rare and aggressive tumours associated with advanced age and immunosuppression. They are typically characterised by a high rate of local recurrence and nodal disease. The presence of a mixed squamous cell component is rare. These tumours are uncommonly found on the hand. We present a case and histological images of a 78-year-old woman with a primary CK20 negative TTF-1 positive cutaneous neuroendocrine tumour with squamous dedifferentiation arising from the fifth digit with axillary metastasis showing a mixed phenotype. Initial biopsy of the lesion was positive for chromogranin, synaptophysin and TTF-1, but negative for CK20, Melan-A and S100. After CT of the thorax abdomen and pelvis and octreotide single positron emission CT demonstrated a 15 mm axillary metastasis and no evidence of distal disease, our patient underwent an amputation of the affected digit and an axillary lymph node dissection. She is currently awaiting adjuvant chemoradiotherapy. Only two cases are reported in the literature to have mixed squamous/neuroendocrine features. We present the first case which is CK20 negative and TTF-1 positive.

Reclassification as NIFTP: a Retrospective Review in a Single Institution with an Emphasis on Workload

The aim of this study was to determine the number of cases of papillary thyroid carcinoma (PTC) which could be reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in our institute over a 10-year period, document their clinical status and assess the number of slides that had to be reviewed per case to exclude NIFTP. The histopathology reports for thyroid resections for all papillary carcinoma over a 10-year period (2007-2016) were reviewed. Five hundred forty-five histopathology reports were reviewed, and 71 cases were identified as potential cases of NIFTP. Forty-nine (69%) cases had been referred from external departments and the slides were not available for review. Of the remaining 22 (31% of 71) cases, 5 were reclassified as NIFTP. The 17 cases that were not reclassified as NIFTP required review of 114 of 356 slides (median 5.5 slides per case) was required to exclude NIFTP. For the 5 NIFTP cases, 58 slides were reviewed (median 12 slides per case). We found that review of the histology reports alone was adequate for exclusion in most cases, e.g. classic PTC or EVPTC cases with documented lymphovascular invasion or capsular invasion. As a single exclusion criterion is required for exclusion from reclassification as NIFTP, this can be achieved efficiently. Two of the five patients received radioactive iodine [RAI] as per standard treatment at time of diagnosis, on the basis of tumour size. None have recurrent or metastatic disease with mean follow-up of 5.8 years.

Paratesticular myositis ossificans of the spermatic cord

A 56-year-old man presented with a painless scrotal lump, enlarging over the preceding 1 month. The lump was roughly 1 cm in size, and located in his left hemiscrotum and separate from the testis. An ultrasound revealed an echogenic focus with dystrophic tissue calcification. Subsequent surgical excision and histopathological analysis revealed it to be late-stage myositis ossificans, a benign, extraosseous formation of the bone or cartilage. We report of only the second described case of myositis ossificans of the spermatic cord in the literature to date.

Oxygen challenge magnetic resonance imaging in healthy human volunteers

Oxygen challenge imaging involves transient hyperoxia applied during deoxyhaemoglobin sensitive (T2*-weighted) magnetic resonance imaging and has the potential to detect changes in brain oxygen extraction. In order to develop optimal practical protocols for oxygen challenge imaging, we investigated the influence of oxygen concentration, cerebral blood flow change, pattern of oxygen administration and field strength on T2*-weighted signal. Eight healthy volunteers underwent multi-parametric magnetic resonance imaging including oxygen challenge imaging and arterial spin labelling using two oxygen concentrations (target FiO₂ of 100 and 60%) administered consecutively (two-stage challenge) at both 1.5T and 3T. There was a greater signal increase in grey matter compared to white matter during oxygen challenge (p < 0.002 at 3T, P < 0.0001 at 1.5T) and at FiO₂ = 100% compared to FiO₂ = 60% in grey matter at both field strengths (p < 0.02) and in white matter at 3T only (p = 0.0314). Differences in the magnitude of signal change between 1.5T and 3T did not reach statistical significance. Reduction of T2*-weighted signal to below baseline, after hyperoxia withdrawal, confounded interpretation of two-stage oxygen challenge imaging. Reductions in cerebral blood flow did not obscure the T2*-weighted signal increases. In conclusion, the optimal protocol for further study should utilise target FiO₂ = 100% during a single oxygen challenge. Imaging at both 1.5T and 3T is clinically feasible.

Cardiac transplant in a family pedigree of hypertrophic cardiomyopathy secondary to a mutation in the AMP gene

The phenotype of this unique condition comprises left ventricular hypertrophy (LVH), accessory pathways, atrial arrhythmia and premature failure of the atrioventricular node. At age 11, his ECG showed marked voltage criteria for LVH but his echocardiography was negative. He declined further screening but was reassessed at 21 years of age. By this time he had developed significant LVH. He had an implantable cardioventer defibrillator (ICD) in 2001. He developed atrial flutter and fibrillation which was initially treated with medical therapy and then radiofrequency ablation.Unfortunately, his condition deteriorated. He was New York Heart Association (NYHA) class 3-4 for most of 2011 and spent the latter part of the year and most of 2012 as an in-patient. An attempt to upgrade his ICD to a cardiac resynchronisation therapy-defibrillator was unsuccessful.In March 2012 he was placed on the transplant waiting list. He received an organ in June. He is now NHYA class 1 and has returned to work part-time.

Transcription of the singed-weak mutation of Drosophila melanogaster: elimination of P-element sequences by RNA splicing and repression of singed transcription in a P genetic background

The dysgenesis-induced, hypermutable singed-weak allele has two incomplete P-elements inserted in a head-to-head configuration in the 5' non-coding exon of the singed bristle locus of Drosophila melanogaster. In the presence of P transposase, each element excises to produce single element derivatives, singed-extreme and singed-(+), that have either an extreme bristle or wild-type phenotype, respectively. In an M background, pseudo-wild-type transcripts are made that initiate at the singed promoter, read through the insertions, and are spliced to remove the P-element sequences and part of the 5' exon. The abundance of the pseudo-wild-type RNAs in pupae correlates with the bristle phenotype, being highest in singed-(+) and lowest in singed-extreme. Other RNAs are made that retain the insertions, or are truncated with respect to the downstream coding singed exons and have their 3' ends within the insertions. The mutants are female-fertile in an M background but sterile in a P background where little singed RNA can be detected. Transgenes containing either a complete P-element or an incomplete P-element known as KP impair the fertility of females carrying the singed-weak mutation, suggesting that the proteins encoded by these two widely distributed P-elements may be responsible for inhibiting transcription of singed-weak in a P background.

A critical review of foot orthoses in the rheumatoid arthritic foot

Foot orthoses are commonly prescribed by health professionals as a form of intervention for the symptomatic foot in rheumatoid arthritis. However, there is a limited evidence base to support the use of foot orthoses in this patient group. This article provides a critical review of the use of foot orthoses in the management of rheumatoid arthritic foot pathologies. A search was conducted in the Cochrane Controlled Trials Register (current issue of the Cochrane Library), Physiotherapy evidence database (PEDro), Medline, The Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Allied and Complementary Medicine (AMED) and from reference lists in journal articles. The language was restricted to English. Searching of the databases was undertaken between December 2004 and March 2005. The results indicated there is no consensus of opinion on the choice of foot orthoses used for the management of pathology in the rheumatoid foot, although there is strong evidence that foot orthoses do reduce pain and improve functional ability. The type of foot orthoses used ranged from simple cushioned insoles to custom-made rigid cast devices. Methodological issues raised included small sample size and poor use of valid and reliable outcome measures. There is limited evidence pertaining to cost-effectiveness. The results indicated a need for further investigation into the most clinically and cost-effective foot orthoses to prescribe in the management of the rheumatoid arthritic foot. This review highlights the need to identify the various types of foot orthoses that are most effective in the management of the established rheumatoid arthritic foot.

A 5.9-kb tandem repeat at the euchromatin-heterochromatin boundary of the X chromosome of Drosophila melanogaster

We present an analysis of a chromosomal walk in the region of the euchromatin-heterochromatin transition at the base of the X chromosome of Drosophila melanogaster. This region is difficult to analyse because of the presence of repeated sequences, and we have used cosmids to walk from the last euchromatic gene, suppressor of forked, towards the pericentric heterochromatin. The proximal 30-kb sequence we have isolated consists of repetitive DNA, including four tandem copies of a 5.9-kb sequence. This tandem repeat is itself a mosaic of other, mostly repeated, sequences, including part of a retrotransposon without long terminal repeats, a simple-sequence region of TAA repeats and part of a retrotransposon with long terminal repeats that has not been previously described. Although sequences homologous to these components are found elsewhere in the genome, this arrangement of repeated sequences is only found at the base of the X chromosome. It is conserved in D. melanogaster strains of different geographic origin, but is not conserved in even closely related species.

The effect of the Lockit epidural catheter clamp on epidural migration: a controlled trial

We investigated the efficacy of using the Lockit epidural catheter clamp in preventing epidural catheter migration in patients receiving postoperative analgesia via an epidural infusion after major surgery. Patients were randomly allocated to receive either a standard epidural dressing, a coiled catheter with transparent adhesive dressing and tape (n = 54), or the Lockit epidural catheter clamp (n = 48). There was no movement from the insertion position in 88% of the Lockit group compared with only 28% in the standard group (p < 0.001). Outward migration of > 2 cm occurred in 26% of the standard group compared with just 6% of the Lockit group (p < 0.01). Inward migration of > 1 cm occurred in 17% of the standard group but in none of the Lockit group (p < 0.01). Catheter migration was assessed as being the cause of analgesic failure in 15% of the standard group but in only 4% of the Lockit group (p < 0.05). We conclude that the Lockit epidural catheter clamp significantly reduces catheter migration in a safe and non-invasive fashion.

The X element, a novel LINE transposable element from Drosophila melanogaster

Whilst analysing the nature of repeated DNA sequences in the transition zone between euchromatin and heterochromatin at the base of the X chromosome of Drosophila melanogaster, we discovered a novel transposable element of the LINE class that we have named the X element. Several apparently complete elements have been cloned and analysed, and one has been sequenced. It is 4740 bp long, with a polyadenylation sequence and a run of A residues at one end. It contains two ORFs: the 5' ORF is related to the retroviral gag gene and encodes a protein with cysteine-rich motifs that are thought to form a "zinc-knuckle" in a nucleic-acid binding protein; the 3' ORF encodes a putative reverse transcriptase that includes the conserved domains found in reverse transcriptases from other LINEs and retroviruses. The DNA sequence and the sequences of the predicted gene products are most similar to other LINEs from D. melanogaster, such as the F, jockey, Doc and BS elements. Southern analysis suggests that there are at least 30 copies in the genome and that some elements are polymorphic between different strains. Analysis of the DNA sequence of the euchromatic arms of the Drosophila genome identified five full-length elements and a similar number of elements that were intact at the 3' end but had variable 5' truncations. Sequences flanking two different insertion sites were used to design PCR primers to assess the occupancy of sites in wild-type flies of different geographical origins. Flies that lacked each of the insertions were found, suggesting that the element is an active transposon.

The Drosophila homologue of the 64 kDa subunit of cleavage stimulation factor interacts with the 77 kDa subunit encoded by the suppressor of forked gene

During mRNA 3' end formation, cleavage stimulation factor (CstF) binds to a GU-rich sequence downstream from the polyadenylation site and helps to stabilise the binding of cleavage-polyadenylation specificity factor (CPSF) to the upstream poly-adenylation sequence (AAUAAA). The 64 kDa subunit of CstF (CstF-64) contains an RNA binding domain and is responsible for the RNA binding activity of CstF. It interacts with CstF-77, which in turn interacts with CPSF. The Drosophila suppressor of forked gene encodes a homologue of CstF-77, and mutations in it affect mRNA 3' end formation in vivo. A Drosophila homologue for CstF-64 has now been isolated, both through homology with the human protein and through protein-protein interaction in yeast with the suppressor of forked gene product. Alignment of CstF-64 homologues shows that the proteins have a conserved N-terminal 200 amino acids, the first half of which is the RNA binding domain with the second half likely to contain the CstF-77 interaction domain; a central region variable in length and rich in glycine, proline and glutamine residues and containing an unusual degenerate repeat motif; and then a conserved C-terminal 50 amino acids. In Drosophila, the CstF-64 gene has a single 63 bp intron, is transcribed throughout development and probably corresponds to l(3)91Cd.

Characterization of a Drosophila homologue of the 160-kDa subunit of the cleavage and polyadenylation specificity factor CPSF

Processing of the 3' end of mRNA precursors depends on several proteins. The multisubunit cleavage and polyadenylation specificity factor (CPSF) is required for cleavage of the mRNA precursor as well as polyadenylation. CPSF interacts with the cleavage stimulatory factor complex (CstF), and this interaction increases the specificity of binding. Following cleavage downstream of the AAUAAA site, CPSF and poly(A) polymerase (PAP) are required for efficient polyadenylation. Recently, it has been shown that 160-kDa subunit of CPSF interacts directly with the 77-kDa subunit of CstF, which is homologous to the product encoded by the Drosophila gene su(f), and with PAP. Here we report the cloning and characterization of a Drosophila homologue of CPSF-160. The 1329-amino acid dCPSF protein exhibits about 45% and 20% sequence identity, respectively, to its mammalian and yeast counterparts over its entire length. We show that the CPSF homologue is expressed throughout development and that CPSF is essential for viability. Mutations in the cpsf gene did not alter the phenotype of homozygous su(f) mutations, suggesting that, for most genes, processing of 3' termini is not sensitive to small changes in cpsf and su(f) dosage.

Rearrangements at a hobo element inserted into the first intron of the singed gene in the unstable sn49 system of Drosophila melanogaster

The cytological structure of the X chromosome and the DNA organisation of the singed locus were examined in five singed bristle mutants of Drosophila melanogaster. These mutants are all derived from the unstable mutant singed-49, isolated from a wild population in the Russian Far East in 1975. Rearrangements were found at a site within the first intron of the singed gene, where a hobo element is inserted in these mutants. One rearrangement, which is associated with a strong bristle phenotype, has an inversion between 2D and the location of singed at 7D, which separates the singed promoter from the singed coding region. Two phenotypically wild-type derivatives have smaller rearrangements within the first intron which do not appear to interfere with singed expression. Two derivatives with bristle phenotypes have more complex rearrangements, and one of them shows a dominant or antimorphic phenotype. DNA blotting and in situ hybridisation experiments show that, in addition to these rearrangements at a hobo element inserted at singed, other hobo elements in these strains have been mobilised. This system is therefore similar to others in which functional hobo elements continue to transpose, resulting in elevated rates of mutation and chromosome rearrangement.

The laryngeal mask as an antipollution device

Anaesthetic pollution is still a problem and recent UK Control of Substances Hazardous to Health (COSHH) recommendations require employers to attempt to control the risk. Fifteen day-case urology operating lists were studied to compare the level of nitrous oxide exposure using face mask or laryngeal mask anaesthesia. Nitrous oxide was avoided in one group until the laryngeal mask was inserted. The use of the laryngeal mask airway showed a significant reduction in the level of pollution, such that recent COSHH recommendations were attained. However, (US) NIOSH levels were only reliably attained by avoiding nitrous oxide until the laryngeal mask was inserted. The laryngeal mask was therefore shown to be a reliable antipollution device.

Neural toxicity of retroviruses

Recombinant retroviruses containing the cDNA for human tyrosine hydroxylase-1 and Escherichia coli lacZ gene were used to infect primary foetal ventral mesencephalon and cortical cultures from rat brain. Severe neuronal toxicity resulted 3-4 days after infection, glial cells seemed to be much more resistant. The toxicity was likely to have resulted from an agent present within the virus-containing medium itself, rather than from the retrovirus itself. The results of this study indicate that retroviruses are not suitable vectors for the introduction of tyrosine hydroxylase into primary neuronal cultures.

A 1.5 kb repeat sequence flanks the suppressor of forked gene at the euchromatin-heterochromatin boundary of the Drosophila melanogaster X chromosome

A 1.5 kilobasepair repeated DNA sequence is duplicated in direct orientation so as to flank the suppressor of forked gene in the euchromatin-heterochromatin transition region on the X chromosome of Drosophila melanogaster. These two copies are almost identical, but DNA blotting, analysis of cloned sequences and database searches show that elsewhere in the genome, homologous sequences are poorly conserved. They are often associated with other repeats, suggesting that they may belong to a scrambled and clustered middle repetitive DNA family. The sequences do not appear to be related to transposable elements and their location in different strains is conserved. In situ hybridization to metaphase chromosomes shows that homologous sequences are concentrated in the pericentric regions of the autosomes and the X chromosome. The sequences are not significantly under-represented in DNA from polytene tissue and must lie in the replicated regions of polytene chromosomes. The almost perfect conservation of the two repeats around suppressor of forked in D. melanogaster suggests they arose by duplication or gene conversion. Suppression of recombination in this chromosomal region presumably allows this unusual organization to be stably maintained. In the X-ray induced allele, suppressor of forked-L26, the sequence between the repeats, including the gene, and one copy of the repeat have been deleted.

Elimination of introns at the Drosophila suppressor-of-forked locus by P-element-mediated gene conversion shows that an RNA lacking a stop codon is dispensable

The suppressor of forked [su(f)] locus affects the phenotype of mutations caused by transposable element insertions at unlinked loci. It encodes a putative 84-kD protein with homology to two proteins involved in mRNA 3' end processing; the product of the yeast RNA14 gene and the 77-kD subunit of human cleavage stimulation factor. Three su(f) mRNAs are produced by alternative polyadenylation. The 2.6- and 2.9-kb mRNAs encode the same 84-kD protein while a 1.3-kb RNA, which terminates within the fourth intron, is unusual in having no stop codon. Using P-element-mediated gene replacement we have copied sequences from a transformation construct into the su(f) gene creating a su(f) allele at the normal genomic location that lacks the first five introns. This allele is viable and appears wild type for su(f) function, demonstrating that the 1.3-kb RNA and the sequences contained within the deleted introns are dispensable for su(f) function. Compared with studies on gene replacement at the white locus, chromosomal breaks at su(f) appear to be less efficiently repaired from ectopic sites, perhaps because of the location of su(f) at the euchromatin/heterochromatin boundary on the X chromosome.

[The unstable system sn(49) in Drosophila melanogaster: results of blot-hybridization and polymerase chain reaction]

A set of 40 strains of alleles of different phenotype and mutation frequency, derived from unstable system sn49 of Drosophila melanogaster, was obtained. A mutation in the singed gene or the formation of a visible de novo mutation in the studied X chromosome served as the criterion for strain isolation. Total DNA was isolated from the obtained strains and used for blot-hybridization and polymerase chain reaction (PCR). Rearrangements were found within the first intron of the singed gene. In the first intron of an allelic derivative of this unstable system, an inserted sequence of at least 4 kb in length was found. Using PCR primers from this intron, fragment length polymorphism in different derivatives was revealed.

Interallelic complementation at the suppressor of forked locus of Drosophila reveals complementation between suppressor of forked proteins mutated in different regions

The Su(f) protein of Drosophila melanogaster shares extensive homologies with proteins from yeast (RNA14) and man (77 kD subunit of cleavage stimulation factor) that are required for 3' end processing of mRNA. These homologies suggest that su(f) is involved in mRNA 3' end formation and that some aspects of this process are conserved throughout eukaryotes. We have investigated the genetic and molecular complexity of the su(f) locus. The su(f) gene is transcribed to produce three RNAs and could encode two proteins. Using constructs that contain different parts of the locus, we show that only the larger predicted gene product of 84 kD is required for the wild-type function of su(f). Some lethal alleles of su(f) complement to produce viable combinations. The structures of complementing and noncomplementing su(f) alleles indicate that 84-kD Su(f) proteins mutated in different domains can act in combination for partial su(f) function. Our results suggest protein-protein interaction between or within wild-type Su(f) molecules.

Distribution of plasminogen activator in different fractions of bovine milk

The type and relative amounts of plasminogen activator (PA) in different fractions of bovine milk obtained from 15 Holstein cows were examined. Raw milk was centrifuged to separate skim milk and a somatic cell pellet. PA was mainly localized within the casein fraction, being 42 times that in the serum, and in association with somatic cells. The predominant form of PA in milk casein was isolated from SDS-PAGE gel extracts and had a molecular mass of approximately 75 kDa. Its activity was increased 4.1-fold (P < 0.01) in the presence of fibrin but was unaffected by the presence of amiloride, indicating that it was due to tissue-PA. The predominant forms of PA associated with milk somatic cells were isolated from SDS-PAGE gel extracts and had molecular masses of approximately 30 and approximately 50 kDa. The activity of both proteins was unaffected by the presence of fibrin but was dramatically reduced by the presence of amiloride, indicating that they represented urokinase-PA.

Distribution of plasminogen activator forms in fractions of goat milk

Distribution of plasminogen activator forms in fractions of goat milk was examined. Raw milk was centrifuged to separate skim milk, cream, and a somatic cell pellet. Somatic cell extracts were obtained by sonication. Skim milk was centrifuged to separate milk serum and casein micelles. Activity of plasminogen activator was detected in casein, serum fractions, and in association with somatic cells. Plasminogen activator forms in milk casein had approximate molecular weights of 75,000, 50,000, and 30,000. The predominant forms of plasminogen activator in milk serum and in association with milk somatic cells had molecular weights of 30,000 and 50,000. Based on fibrin dependency and inhibition of activity in the presence of amiloride, the forms at 30,000 and 50,000 represent urokinase-plasminogen activator, and the form at 75,000 represents tissue-plasminogen activator.

Homology with Saccharomyces cerevisiae RNA14 suggests that phenotypic suppression in Drosophila melanogaster by suppressor of forked occurs at the level of RNA stability

The suppressor of forked [su(f)] locus of Drosophila melanogaster encodes at least one cell-autonomous vital function. Mutations at su(f) can affect the expression of unlinked genes where retroviral-like transposable elements are inserted. Changes in phenotype are correlated with changes in mRNA profiles, indicating that su(f) affects the production and/or stability of mRNAs. We have cloned the su(f) gene by P-element transposon tagging. Alterations in the DNA map of eight lethal alleles were detected in a 4.3-kb region. P-element-mediated transformation using a fragment including this interval rescued all aspects of the su(f) mutant phenotype. The gene is transcribed to produce a major 2.6-kb RNA and minor RNAs of 1.3 and 2.9 kb, which are present throughout development, being most abundant in embryos, pupae, and adult females. The major predicted gene product is an 84- kD protein that is homologous to RNA14 of Saccharomyces cerevisiae, a vital gene where mutation affects mRNA stability. This suggests that phenotypic modification by su(f) occurs at the level of RNA stability.

Distribution and structure of cloned P elements from the Drosophila melanogaster P strain pi 2

P transposable elements of Drosophila melanogaster cloned from the strong P strain pi 2 have been analysed. The structures and chromosomal locations of 26 of the 30-50 elements estimated to be present in pi 2 have been determined. At one location two elements are inserted 100 base pairs (bp) apart, and in a second location two elements are only separated by the 8 bp duplicated upon P-element insertion. In addition to 2.9 kilobase-pair (kbp) elements, elements with 14 different internal deletions from 1.3 to 2.3 kbp in size have been isolated. There are 7 copies of the 2.9 kbp element, 2 copies each of 5 internally deleted elements and a single copy of 9 internally deleted elements. One of the elements found twice is the KP element, which may play a role in the regulation of hybrid dysgenesis in strains which contain many copies of this element. Apart from internal deletions the elements are extremely homogeneous in DNA sequence, with only 2 single base polymorphisms detected twice each in over 16 kbp of P-element sequence. Although transpositions are infrequent in an inbred P cytotype strain such as pi 2, the distribution of these cloned elements indicates that when the genomic library was made, the strain was polymorphic with respect to element location. The distribution and structures of the element are discussed with respect to models for regulation of P-element transposition.

The pogo transposable element family of Drosophila melanogaster

A 190 bp insertion is associated with the white-eosin mutation in Drosophila melanogaster. This insertion is a member of a family of transposable elements, pogo elements, which is of the same class as the P and hobo elements of D. melanogaster. Strains typically have many copies of a 190 bp element, 10-15 elements 1.1-1.5 kb in size and several copies of a 2.1 kb element. The smaller elements all appear to be derived from the largest by single internal deletions so that all elements share terminal sequences. They either always insert at the dinucleotide TA and have perfect 21 bp terminal inverse repeats, or have 22 bp inverse repeats and produce no duplication upon insertion. Analysis by DNA blotting of their distribution and occupancy of insertion sites in different strains suggests that they may be less mobile than P or hobo. The DNA sequence of the largest element has two long open reading frames on one strand which are joined by splicing as indicated by cDNA analysis. RNAs of this strand are made, whose sizes are similar to the major size classes of elements. A protein predicted by the DNA sequence has significant homology with a human centrosomal-associated protein, CENP-B. Homologous sequences were not detected in other Drosophila species, suggesting that this transposable element family may be restricted to D. melanogaster.

Structure and transcription of the singed locus of Drosophila melanogaster

Developmental and genetic studies of the singed gene of Drosophila melanogaster indicate that the gene has a role in somatic cells during the formation of adult bristles and hairs, and in the female germline during oogenesis. During metamorphosis a single 3.6-kilobase (kb) RNA is made, and this RNA is also present in adults and early embryos. Early embryos and adult females have additional 3.3- and 3.0-kb RNAs. The RNAs differ only in the length of the 3' untranslated region and a single gene product of 57 kilodaltons is predicted. Analysis of RNA from females lacking ovaries suggests that the 3.3- and 3.0-kb RNAs are made only in ovaries. The absence of the 3.3- and 3.0-kb RNAs in pupae and the time course of their appearance in adult females after eclosion suggests that transcription of singed in the ovary is from middle to late stages of oogenesis. Analysis of RNA in embryos from the reciprocal crosses between wild type and singed-3 showed that all three RNAs are maternally inherited with very little zygotic transcription in embryos. The mutation singed-3 appears to separate the two requirements for singed function as it has an extreme effect upon bristle development, but does not obviously affect oogenesis. In singed-3, there is a deletion at the 5' end of the gene, but the coding region is intact. Transcription in singed-3 is from a cryptic promoter in the upstream flanking sequences which is sufficiently active during oogenesis for fertility, but less active than the wild-type promoter during metamorphosis. The role of the single singed gene product may be in the asymmetric organization and/or movement of cytoplasmic components.

DNA sequence of the Doc retroposon in the white-one mutant of Drosophila melanogaster and of secondary insertions in the phenotypically altered derivatives white-honey and white-eosin

We analysed the structure of the white locus of Drosophila melanogaster in a family of related white mutants. The white-one mutant has bleach white eyes, and a Doc transposable element is inserted into the promotor region of the white locus. The DNA sequence of this Doc insertion was determined, and showed it to be closely related to other Drosophila melanogaster retroposons such as the I factor and the F, G and jockey elements. There are two long open reading frames, which encode a putative nucleic acid binding protein and a putative reverse transcriptase, respectively. Two independent, partially pigmented derivatives were analysed by cloning sequences from this region. In white-honey a transposable element of the retroviral class, B104, is inserted within the Doc element. In white-eosin there is an insertion within the Doc element of a 190 bp sequence that appears to be a member of a novel family of transposable elements. This pogo element is of the same structural class as the Drosophila melanogaster P and hobo elements. These data are consistent with the hypothesis that the Doc retroposon cannot excise, and that, for the white-one mutation, flies with altered phenotypes are most often generated by the insertion of additional transposable elements.

Molecular and cytogenetic analysis of the heterochromatin-euchromatin junction region of the Drosophila melanogaster X chromosome using cloned DNA sequences

We have used three cloned DNA sequences consisting of (1) part of the suppressor of forked transcription unit, (2) a cloned 359-bp satellite, and (3), a type I ribosomal insertion, to examine the structure of the base of the X chromosome of Drosophila melanogaster where different chromatin types are found in juxtaposition. A DNA probe from the suppressor of forked locus hybridizes exclusively to the very proximal polytenized part of division 20, which forms part of the beta-heterochromatin of the chromocenter. The cloned 359-bp satellite sequence, which derives from the proximal mitotic heterochromatin between the centromere and the ribosomal genes, hybridizes to the under replicated alpha-heterochromatin of the chromocenter. The type I insertion sequence, which has major locations in the ribosomal genes and in the distal mitotic heterochromatin of the X chromosome, hybridizes as expected to the nucleolus but does not hybridize to the beta-heterochromatic division 20 of the polytene X chromosome. Our molecular data reveal that the suppressor of forked locus, which on cytogenetic grounds is the most proximal ordinary gene on the X chromosome, is very close to the junction of the polytenized and non-polytenized region of the X chromosome. The data have implications for the structure of beta-heterochromatin-alpha-heterochromatin junction zones in both mitotic and polytene chromosomes, and are discussed with reference to models of chromosome structure.

Structural analysis of Doc transposable elements associated with mutations at the white and suppressor of forked loci of Drosophila melanogaster

DNA sequences from two spontaneous mutations of Drosophila melanogaster associated with insertion of a Doc transposable element have been cloned. In white-one, the element is inserted in the white locus close to where transcription initiates. In a lethal allele of suppressor of forked, su(f)S2, the element is inserted within the transcription unit in the protein coding region. Four other Doc elements have been cloned from a wild-type strain. Doc is a member of the class of transposable elements known as retroposons, which includes the D. melanogaster F, G, Jockey, and I elements. There is no sequence homology between the ends of the Doc element. The 3' or right end terminates with a polyadenylation signal sequence followed by a stretch of oligo-A. The length of the oligo-A varies between elements, and a duplication of variable size is found as a direct repeat flanking inserted Doc elements. Members of the family are conserved at the 3' end, but may be truncated at the 5' or left end. These structural features suggest a mechanism of transposition via an RNA intermediate.

P element insertions and rearrangements at the singed locus of Drosophila melanogaster

DNA from the singed gene of Drosophila melanogaster was isolated using an inversion between a previously cloned P element at cytological location 17C and the hypermutable allele singed-weak. Five out of nine singed mutants examined have alterations in their DNA maps in this region. The singed locus is a hotspot for mutation during P-M hybrid dysgenesis, and we have analyzed 22 mutations induced by P-M hybrid dysgenesis. All 22 have a P element inserted within a 700-bp region. The precise positions of 10 P element insertions were determined and they define 4 sites within a 100-bp interval. During P-M hybrid dysgenesis, the singed-weak allele is destabilized, producing two classes of phenotypically altered derivatives at high frequency. In singed-weak, two defective P elements are present in a "head-to-head" or inverse tandem arrangement. Excision of one element results in a more extreme singed bristle phenotype while excision of the other leads to a wild-type bristle phenotype.

DNA sequence of the white locus of Drosophila melanogaster

The DNA sequence of the white locus of Drosophila melanogaster is presented. This 14,100 base-pair sequence includes the region of the locus required for wild-type levels of expression and control of expression. We also report the sequence of a complementary DNA clone which established the position of the 3' end of the white RNA on this genomic sequence. The probable exon-intron structure of the gene has been predicted from the DNA sequence of the regions known to be represented in the RNA. The amino acid sequence of the protein which would be produced by translation of this RNA suggests that the white locus gene product may be a membrane protein. The DNA sequence rearrangements associated with seven insertion mutants (white-dominant-zeste-like (wDZL), white-spotted (wsp), white-honey (wh), white-zeste-mottled (wzm), white-apricot (wa), white-buff (wbf) and white-hd81b11 (whd81b11)), one deletion mutant (white-spotted 4 (wsp4)) and one internal duplication mutant (white-ivory (wi)) have been determined and positioned on the wild-type sequence. The positions of these insertions and those of previously characterized insertions associated with six other mutations suggest that some insertions within an intron may still allow the production of correctly spliced RNA, but affect the amount, and correspondingly the expression of the w locus.

Effects of transposable element insertions on RNA encoded by the white gene of Drosophila

We have examined the manner in which transposable element insertions affect the expression of the white gene of Drosophila by analyzing polyadenylated RNA of flies with each of nine insertions in or near the gene. In five mutants having insertions in the transcribed sequences of white, transcripts initiating at the white promoter are truncated within the insertions. Two insertions in the 3 kb intron of white alter neither the amount nor the structure of the mature white RNA. An insertion near the 5' end of the gene blocks the accumulation of any white transcripts. Another insertion, located 1.2 kb upstream from the transcribed region of the gene, causes a mutant phenotype yet surprisingly has no obvious effect on the structure or abundance of the major white RNA. We also show that a mutation at each of two other loci that modulate the phenotype of the white-apricot insertion mutant are correlated with small but significant changes in the pattern of white transcripts.

Structures of P transposable elements and their sites of insertion and excision in the Drosophila melanogaster genome

We have isolated and characterized several members of the P transposable element family from a Drosophila melanogaster P strain. Large 2.9 kb elements are present as multiple highly conserved copies together with smaller (0.5-1.6 kb), heterogeneous elements. The complete DNA sequences of the 2.9 kb element and four small elements (previously isolated from hybrid-dysgenesis-induced mutations of the white locus) have been determined. Each small element appears to have arisen from the 2.9 kb element by a different internal deletion. P elements have 31 bp perfect inverse terminal repeats and upon insertion duplicate an 8 bp sequence found only once at the site of insertion. Three of the insertions into the white locus occurred at the same nucleotide, indicating a high degree of local site specificity for insertion. The basis of this specificity has been investigated by DNA sequence analysis of the sites where 18 P elements are found. A revertant of one of the white locus mutants has been found to result from precise excision of the P element, restoring the wild-type DNA sequence.

Transformation of mouse fibroblasts to methotrexate resistance by a recombinant plasmid expressing a prokaryotic dihydrofolate reductase

A recombinant plasmid has been constructed for the expression of inserted DNA sequences coding for polypeptide chains using the simian virus 40 early promoter and splicing and polyadenylylation signals from the rabbit beta-globin gene. The coding regions for two prokaryotic methotrexate-resistant dihydrofolate reductases were introduced into the expression vector. When mouse fibroblasts were exposed to these recombinant plasmids, it was possible to select methotrexate-resistant clones that had integrated the plasmids and produced a chimeric RNA coding for the prokaryotic enzyme.

The ovalbumin gene-sequence of putative control regions

We present the sequence of regions of the chicken ovalbumin gene believed to be important in the control of initiation of transcription, splicing, and transcription termination or polyadenylation. Comparison with corresponding areas of other genes reveals some homologous regions which might play a role in these processes.

No more than seven interruptions in the ovalbumin gene: comparison of genomic and double-stranded cDNA sequences

We have determined the sequence of ovalbumin RNA (ov-mRNA) using a double-stranded cDNA (dscDNA) plasmid. We have also determined the sequence of the previously characterized exonic regions of the chicken ovalbumin gene. The comparison of these various sequences has shown that there are no additional interruptions in the mRNA-coding sequences above those 7 already characterized. There is only one single base discrepancy between the two mRNA sequences determined using the dscDNA or the genomic clones. This demonstrates the accuracy and reproducibility of the cloning and sequencing techniques. The ovalbumin mRNA sequence was found to be 1872 nucleotides in length, 13 nucleotides larger than the previous value reported by McReynolds et al. [Nature 273, 723-728 (1978)].

Organisation and sequences at the 5' end of a cloned complete ovalbumin gene

A clone which contains the complete chicken ovalbumin gene, including its leader coding sequences, has been isolated. From electron microscopic analysis of this DNA we conclude that the minimal size of the transcriptional unit for ovalbumin is 7.7 kilobases. The DNA sequence of the region surrounding the 5' end of the ovalbumin gene is presented. Comparison of this sequence with those of other eukaryotic genes reveals striking similarities, possibly related to a promoter region, approximately 30 base pairs upstream from the site coding for the 5' end of the mRNA.

Ovalbumin gene: evidence for a leader sequence in mRNA and DNA sequences at the exon-intron boundaries

Selected regions of cloned EcoRI fragments of the chicken ovalbumin gene have been sequenced. The positions where the sequences coding for ovalbumin mRNA (ov-mRNA) are interrupted in the genome have been determined, and a previously unreported interruption in the DNA sequences coding for the 5' nontranslated region of the messenger has been discovered. Because directly repeated sequences are found at exon-intron boundaries, the nucleotide sequence alone cannot define unique excision-ligation points for the processing of a possible ov-mRNA precursor. However, the sequences in these boundary regions share common features; this leads to the proposal that there are, in fact, unique excision-ligation points common to all boundaries.