Maternal effects determine effective lethal phase of carnation-light synthetic lethal in Drosophila melanogaster.
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Animals↗
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Results for “Eye Color”
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Structure of chromosomal rearrangements induced by the FB transposable element in Drosophila.
Examination of 10 chromosomal rearrangements induced by foldback transposable elements in Drosophila demonstrates that sequences located between two closely linked elements are frequently deleted. Rearrangement and recombination events occurring within or adjacent to a foldback element are also observed. The type and frequency of rearrangement generated depend on element structure and the organization of flanking DNA.
Alleles↗
Malaria. A mosquito transformed.
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Animals↗
A product of the prune locus of Drosophila is similar to mammalian GTPase-activating protein.
The X-linked prune (pn) eye-colour mutation of Drosophila melanogaster has a highly specific, complementary lethal interaction with the conditional dominant Killer of prune (awdK-pn) mutation. Although awdK-pn flies have no apparent phenotype on their own, pn awdK-pn double mutants die as second or third larval instars. The awd locus encodes a nucleoside diphosphate kinase, an enzyme that catalyses the transfer of high-energy phosphate bonds between nucleoside diphosphates and nucleoside triphosphates, which is essential for the normal development of Drosophila. Analysis of the pn locus has suggested that the complementary DNA, TcD37, encodes a putative pn+ product. Here we report the nucleotide sequence of TcD37 and the similarity of its deduced protein product to the catalytic domain of mammalian GTPase-activating proteins (GAPs); GAPs stimulate the GTPase activity of Ras (ref. 6), which are plasma membrane-bound proteins involved in the regulation of cell proliferation and differentiation. These results suggest that the Drosophila TcD37 protein participates in a biochemical pathway similar to that of Ras and GAPs in mammals and yeast. We propose that the interaction between pn and awd is due to a neomorphic mutation that enhances the ability of AwdK-pn nucleoside diphosphate kinase to induce a regulatory GTPase into a GTP-bound 'on' state, whereas Pn modulates the activity of this GTPase either by switching it to a GDP-bound 'off' state or by interfering with its effector function.
Amino Acid Sequence↗
Genetic modification of heterochromatic association and nuclear organization in Drosophila.
Heterochromatin is the highly compact, usually pericentromeric, region of eukaryotic chromosomes. Unlike the more gene-rich euchromatin, heterochromatin remains condensed during interphase, when it is sequestered to the periphery of the nucleus. Here we show, by using fluorescent in situ hybridization to interphase diploid nuclei of Drosophila, that the insertion of heterochromatin into a euchromatic gene, which results in position-effect variegation (PEV), also causes the aberrant association of the gene and its homologous copy with heterochromatin. In correlation with the gene's mutant variegating phenotype, the cytological association of the heterochromatic region is affected by chromosomal distance from heterochromatin and by genic modifiers of PEV. Proteins that are thought to be involved in the formation of heterochromatin can therefore influence the interphase nuclear position of a chromosomal region. This suggests that heterochromatin and proteins involved in its formation provide a structural framework for the interphase nucleus.
Animals↗
The multicentre south European study 'Helios'. I: Skin characteristics and sunburns in basal cell and squamous cell carcinomas of the skin.
The aim of this study was to investigate constitutional and environmental determinants of non-melanocytic skin cancer among different populations from south Europe. Between 1989 and 1993 we interviewed incident cases and a random population sample of controls from five centres where a cancer registry was operating, whereas we selected a sample of hospital-based cases and controls from three other centres. Controls were stratified according to the age and sex distribution of cases. In all, 1549 cases of basal cell carcinoma (BCC), 228 of squamous cell carcinoma (SCC) and 1795 controls were interviewed. Both cancers affected primarily sun-exposed sites such as face, head and neck, but the prevalence of BCC on the trunk was higher than for SCC. Pigmentary traits such as hair and eye colour as well as tendency to sunburn were strong and independent indicators of risk for both BCC and SCC. In SCC, adjusted odds ratios (ORs) ranged from 1.6 for fair hair colour to 12.5 for red hair. Light-blonde hair entailed a risk of about 2 for BCC. Pale eye colour was associated with a risk of 1.8 for SCC and 1.4 for BCC. Subjects who always burn and never tan showed an adjusted OR of 2.7 for BCC and 2.0 for SCC. A history of sunburns and a young age at first sunburn were associated with an increased risk for BCC only (OR 1.7). Pigmentary traits and sun sensitivity of the skin confirmed their role as risk indicators. The effect of sunburns, as an indicator of both exposure and sun sensitivity of the skin, is less clear. Nevertheless, its association with BCC suggests, by analogy with melanoma, a relationship with intense sun exposure. Conversely, SCC would require prolonged exposure to sunlight.
Adolescent↗
Risk of cutaneous melanoma in relation to the numbers, types and sites of naevi: a case-control study.
The atypical mole syndrome (AMS) phenotype, characterised by a large number of common naevi as well as atypical naevi, has been described in families with a genetic susceptibility to melanoma. However, the importance of this phenotype for melanoma in the general population has not been conclusively determined. This study was designed to examine the types and distribution of naevi as well as the prevalence of the AMS phenotype in melanoma patients in England compared with controls. A total of 426 cutaneous melanoma cases (61% of all incident cases) aged 16-75 years were recruited between 1989 and 1993 from the north-east Thames region of the UK and 416 controls from the same age group were recruited over the same period and from the same region. Each subject answered a questionnaire covering demographic details, sun exposure history and other risk factors and underwent a skin examination with total body naevus count performed by a dermatologist. The AMS phenotype was defined using a scoring system. Atypical naevi gave the highest relative risk for cutaneous melanoma, with an odds ratio (OR) of 28.7 (P < 0.0001) for four or more atypical naevi compared with none. Many common naevi were also an important risk factor: the OR for 100 or more naevi 2 mm or above in diameter compared with 0-4 naevi was 7.7 (P < 0.0001). Melanoma was also associated with naevi on sun-exposed sites but also with naevi on non-sun-exposed sites such as the dorsum of the feet, buttocks and anterior scalp. Sixteen per cent of the cases had the AMS phenotype compared with 2% of the controls (OR 10.4, P < 0.0001). The AMS phenotype was more common in males than females (P = 0.008). The odds ratio for the presence of the AMS phenotype was dependent on age, with an odds ratio of 16.1 (95% CI 4.6-57.5) for the presence of the AMS phenotype if aged less than 40 compared with an odds ratio of 6.9 (95% CI 2.9-16.6) if aged 40 or more. The AMS phenotype was strongly predictive of an increased risk of melanoma outside the familial context.
Adolescent↗
The Hudson-Stahli line. I: An epidemiological study.
The overall prevalence of Hudson-Stahli line in a group of 550 subjects was 65 per cent with bilateral involvement and a further 4 per cent with unilateral involvement; analysis of two subgroups, with either blue/grey iris colour or with brown/green colour, suggested that the incidence is slightly higher in the latter group, particularly in the third to fifth decades. Irrespective of iris colour, the incidence rises with age. Both the length and the density of the line increase with age. For a given age, brown/green eyes have longer lines than blue/green eyes, but similar densities. Concordance of length and density between the right and left eyes of a pair is seen in about 80 per cent of subjects.
Adolescent↗
Orbital colour Doppler imaging.
Colour Doppler imaging (CDI) is an ultrasonic method for qualitatively and quantitatively assessing blood flow. Recently this technique has been adapted for investigation of the orbital, optic nerve and ocular vasculature. We discuss the history, principles and methodology of this examination technique for ophthalmology. Also described are normal haemodynamic characteristics as well as the findings in common pathological states involving derangements of orbital blood flow. Although CDI is relatively new to ophthalmology it has already proved to be of benefit in conditions with altered orbital, ocular and optic nerve blood flow. In the future it is expected that the indications for the applications of CDI will become more clearly defined and that orbital CDI will be more widely available and utilised, especially in the investigation of vascular diseases of the orbit, optic nerve and retina.
Arterial Occlusive Diseases↗
Images of Lisch nodules across the spectrum.
The presence of melanocytic hamartomas on the iris, known eponymously as Lisch nodules, is highly characteristic of neurofibromatosis type 1 (NF1). Early recognition of NF1 is vital for optimal detection of associated tumours and for genetic counselling of family members. Although the iris nodules are probably not visible at birth, their prevalence in patients with NF1 gradually increases from birth to about 50% of 5-year-olds, 75% of 15-year-olds and 95-100% of adults over the age of 30. Iris hamartomas in NF1 are elevated, pale brown lesions that vary in appearance depending on the underlying colour of the iris. Colour illustrations are shown in this article, enabling the clinician readily to differentiate hamartomas from other iris lesions.
Adolescent↗
Clinical and morphological features of Waardenburg syndrome type II.
Evaluation of 4-month-old girl who presented with congenital cataracts revealed heterochromia iridis, fundus hypopigmentation, residual white forelock and sensory neural hearing loss--findings consistent with Waardenburg syndrome type II. Bilateral peripheral iridectomies performed at lensectomy provided tissue for evaluation. Light microscopy revealed fewer melanocytes in the blue iris than in the brown. Electron microscopic examination showed a significant (p = 0.0001) reduction in melanosome size in the blue iris, and the nerve endings contained fewer vesicles. A defect in neural crest cell migration and melanin synthesis may be responsible for the heterochromia iridis seen in Waardenburg syndrome type II.
Cataract↗
An allele-specific suppressor of white-coral in Drosophila melanogaster.
A new allele of white-coral (wco2) was isolated from Canton S after mutagenesis. Many common laboratory stocks were found to carry a suppressor gene (Su(wco2)) which alters the phenotype of wco2 flies toward wild-type. The Su(wco2) is allele-specific (it does not suppress wco), dominant, homozygous viable, located near Su(bwV1) on the right arm of chromosome 2, and shows a simple gene-dosage effect. The degree of suppression is sensitive to the genetic background. There appears to be selection for Su(wco2) in a genotype where it does not affect eye pigmentation.
Alleles↗
Lack of recombination between the X chromosomes of different members of the Anopheles gambiae complex.
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Animals↗
Effect of larval crowding on adult mating behaviour in Drosophila melanogaster.
The effect of larval density on male mating success has been investigated with two strains of Drosophila melanogaster, a wild strain and a mutant strain, under low and high larval competition, and four different genotypic frequencies. The results show a strong sexual selection against mutant males when flies have been raised under low larval competition. Under high larval competition, there is a reduction in mating disadvantage of mutant males. In both instances, a frequency-dependent sexual selection exists. These results explain adequately the evolution of experimental populations where egg to adult viability and male mating success are the most important components of fitness.
Alleles↗
Manifestations of microphthalmia.
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Animals↗
Waardenburg syndrome type 2 caused by mutations in the human microphthalmia (MITF) gene.
Waardenburg syndrome type 2 (WS2) is a dominantly inherited syndrome of hearing loss and pigmentary disturbances. We recently mapped a WS2 gene to chromosome 3p12.3-p14.1 and proposed as a candidate gene MITF, the human homologue of the mouse microphthalmia (mi) gene. This encodes a putative basic-helix-loop-helix-leucine zipper transcription factor expressed in adult skin and in embryonic retina, otic vesicle and hair follicles. Mice carrying mi mutations show reduced pigmentation of the eyes and coat, and with some alleles, microphthalmia, hearing loss, osteopetrosis and mast cell defects. Here we show that affected individuals in two WS2 families have mutations affecting splice sites in the MITF gene.
Amino Acid Sequence↗
Molecular basis of mouse microphthalmia (mi) mutations helps explain their developmental and phenotypic consequences.
Mutations in the mouse microphthalmia (mi) gene affect the development of a number of cell types including melanocytes, osteoclasts and mast cells. Recently, mutations in the human mi gene (MITF) were found in patients with Waardenburg Syndrome type 2 (WS2), a dominantly inherited syndrome associated with hearing loss and pigmentary disturbances. We have characterized the molecular defects associated with eight murine mi mutations, which vary in both their mode of inheritance and in the cell types they affect. These molecular data, combined with the extensive body of genetic data accumulated for murine mi, shed light on the phenotypic and developmental consequences of mi mutations and offer a mouse model for WS2.
Alleles↗