Article

Genetic and metabolic bases of two “albino” phenotypes in the leopard frog, Rana pipiens

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Abstract

Preliminary characterizations of albino Rana pipiens from two widely separated geographic origins, Mexico and Michigan, indicated that different metabolic basés underlie the albino phenotype. Albinism in the Mexican frogs was shown to result from a single Mendelian recessive gene, am (amelanotic), and appeared to involve a biochemical failure of the pigment synthesizing system. Melanophores were present in am/am integument which exhibited tyrosinase activity when provided with exogenous tyrosine or L-DOPA. The tyrosinase activity of am/am melanophores showed greater thermolability than did that of wild type malanophores. The “albinism” of tadpoles collected in Michigan was only partial, and was associated with a highly pleiotropic syndrome, abnormal patterning of chromatophore distributions, and metamorphic failure. Poor pigmentation of integumental melanophores appeared associated in part with inhibitors of melanogenesis. Genetic data on the possible mode of inheritance are not yet available.

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... Specifically, aberrant phenotypes may also be associated with underlying pathologies that contribute to reduced fitness (Eagleson et al. 2010, Henle et al. 2017, Smith-Gill et al. 1972. Amphibians in particular are strongly influenced by their environment. ...
... Variable or extreme environmental conditions, especially in the natal environment, can adversely affect physiology and morphology (Hillman et al. 2008). In anurans specifically, it has been suggested that hypomelanism is associated with developmental retardation (Childs 1953, Krings and Reich 2016, Mitchell 2005 and early mortality (Smith 2014, Smith-Gill et al. 1972). Here we report multiple, recent cases of hypomelanism in Rana sylvatica (LeConte) (Wood Frog) larvae from multiple populations in Connecticut, as well as evidence of an association between this phenotype and developmental delay and early mortality. ...
Article
Hypomelanism in natural populations is rare and has been anecdotally associated with developmental retardation and mortality when present in anuran larvae. We report multiple, recent cases of hypomelanism across 5 populations in 2 counties in Connecticut. We also experimentally confirm that this phenotype is associated with extremely delayed metamorphosis and increased mortality.
... The a gene which produces a true albino phenotype in the axolotl is associated with reduced tyrosinase activity (Benjamin, 1970), but it is not known whether this gene is involved with tyrosinase production or inhibition. Similar questions remain concerning the two "albino" phenotypes of leopard frogs described by Smith-Gill, et at, (1972); the "speckle mutation" of Rana pipiens (Browder, 1972), and the cases of intermittent albinism, in Xenopus (Tompkins, 1977). As more "albino" phenotypes of amphibians are studied, it seems likely that discoveries will be made which involve gene action at the levels of tyrosine production, activation, or transport, while others will relate to the formation and structure of the melanosome. ...
Article
SYNOPSIS. Pigmentary mutants in amphibians provide important vehicles for studying basic problems in development. Some of these mutants exert influences on the tissue environment in which the chromatophores differentiate and others involve the expression of pigment in specific types of pigment cells. Melanophores are the best known of all chromatophores, and albinism has been much studied. Genes controlling its expression may operate at different levels. Some are involved in the production of tyrosinase, whileothers affect the melanosomal matrix. In contrast, melanoid mutants are characterized by an overproduction of eumelanin, usually through the differentiation of an excessive number of melanophores. Melanoid mutants of the axolotl also exhibit a great diminution in xanthophore and iridophore number, and the same seems to be true of some melanoid-like mutants of leopard frogs. The pteridine pigments of xanthophores and purines of iridophores are often products of xanthine dehydrogenase (XDH) activity, and it is suspected that the expression of the melanoid phenotype may result from a genetic defect involving this enzyme. This is supported by experiments involving the administration of an XDH inhibitor, allopurinol, to normal larvae. This inhibitor results in the production of partial phenocopies of the melanoid condition. Blue mutants involving either partial or complete diminution of xanthophore and iridophore pigments may also be based upon deficient XDH activity.
... It is known that this mutation eliminates the ability to produce melanocytes, but in all the albino cases reported so far, the keratinized jaw sheaths and labial teeths were still visible (e.g. Smith-Gill, Richards & Nace, 1972;Altig, 2007;Eagleson et al., 2010). Accordingly, we conclude that the coloration of the jaw sheaths and claws of amphibians is not attributable to melanin. ...
Article
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... It is known that this mutation eliminates the ability to produce melanocytes, but in all the albino cases reported so far, the keratinized jaw sheaths and labial teeths were still visible (e.g. Smith-Gill, Richards & Nace, 1972;Altig, 2007;Eagleson et al., 2010). Accordingly, we conclude that the coloration of the jaw sheaths and claws of amphibians is not attributable to melanin. ...
Article
The nuptial pad is a secondary sexual character found in anuran amphibians. It includes modified epidermal and dermal tissues and is usually located on the first digit of the hand of males. In this study, we review the structure and diversity of nuptial pads based on a large-scale sample of morphological and phylogenetic diversity. Our findings show that all nuptial pads are characterized by the presence of specialized mucous glands in the dermal component. We also report the co-occurrence of other types of glands in some species and characterize their histochemistry. We describe three primary nuptial pad morphologies: (1) nuptial pads with papillary epidermal projections (or simply, papillae), in which the epidermal projections are formed by an epidermal and dermal evagination; (2) nuptial pads with non-papillary epidermal projections, in which the epidermal projections lack a dermal core forming a papilla; and (3) smooth nuptial pads, which lack projections but have a slight thickening of the dermal area with respect to the adjacent skin. We compare nuptial pads with other secondary sexual traits and discuss several related topics, including morphological diversity, coloration, hormonal control, taxonomic usefulness, and hypotheses regarding their role in reproduction.
... Secondly there is evidence that some cells contain tyrosinase in inactive form, either as a larger molecule requiring activation by a protease (Barisas & McGuire, 1974; Benson & Triplett, 1974), or because of association with a specific inhibitor (Seiji et al. 1973). This type of mechanism has been invoked to explain a tyrosinase-containing albino mutant of Rana pipiens (Smith-Gill, Richards & Nace, 1972). Whilst the present experiments do not exclude any of these possibilities it is unlikely that the relatively mild homogenization procedures used would have allowed significant activation of proenzyme or removed protein inhibitors of the type described by Seiji et al. (1973) . ...
Article
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Article
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... 1, therefore being a case of full albinism. Albinism or partial albinism is a recessive genetic trait in amphibians (Smith-Gill, Richards and Nace, 1972; Frost-Mason and Mason, 1996), although in some cases it could be favored by environmental distress (Vershinin, 2004), as for example, by parasite infections, and might be associated with other morphological malformations (Johnson et al., 2002). Albinism or partial albinism may affect adversely individual survival (Møller and Mousseau, 2001; Krécsak, 2008), although in laboratory conditions albinism has not been linked to alterations in the development or growth of tadpoles (Corn, 1986). ...
... In amphibian oocytes, the melanogenic pathway is activated independently from other pigmented tissues through mechanisms that are yet to be discovered (Kidson and Fabian, 1989). Accordingly, mutations in genes of the melanogenic pathway that cause organismal albinism also cause unpigmented oocytes, as shown in Rana pipiens, and Ambystoma mexicanum (Bluemink and Hoperskaya, 1975;Browder, 1972;Eppig and Dumont, 1974;Smith-Gill et al., 1972). However, amphibian whitish eggs might not only be the result of a deleterious effect over the melanogenic pathway, but also due to a failure in the stability or transport of melanosomes. ...
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The adaptive role of amphibian oocyte melanic pigmentation and its molecular control are still elusive. Here we present evidence of a polymorphism in egg pigmentation in the emerald glass frog Espadarana prosoblepon. In Ecuadorian natural populations of this species, females can lay dark brown or pale eggs that develop into normal pigmented tadpoles and adults. This trait is a sex-limited phenotype that is inherited like a recessive allele that we called pale eggs like (pel). The pel phenotype is exclusive of oocyte cortical melanic pigmentation, which is reduced in comparison to wild type (wt) dark pigmented oocytes. Consequently, pel early embryos are paler in appearance, with reduced melanic pigmentation distributed to early blastomeres and embryonic ectoderm. However, these embryos form normal melanocyte derived pigmentation. Finally, we discuss the origin of this polymorphism and propose the use of E. prosoblepon as a model to study the adaptive role of egg pigmentation.
... I conclude that labial teeth and jaw sheaths are dark because they are the keratinized (i.e., condensed, pycnotic cells filled with fibrous protein) product of one cell (e.g., labial teeth) or the keratinization of many cells (e.g., jaw sheaths). If mouthparts were pigmented, one would expect the keratinized mouthparts of albino and leucistic tadpoles to be white, but they are dark even with the lack of melanic pigments (Corn 1986; Gradwell 1976; Smith-Gill et al. 1972; pers. obs.). ...
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Some terms used in published accounts of the interactions of tadpole mouthparts and the chytrid fungus Batrachochytrium dendrobatidis are incorrect, inaccurate, or controversial. I suggest means to correct these problems. A first estimate of terms that describe oral anomalies (e.g., malformities versus deformities) in larval amphibians is presented.
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The relationship between gene dosage, enzyme activity, and level of immunologically cross-reacting material (CRM) was examined in mammalian tyrosinase (EC 1.14.18.1) by rocket immunoelectrophoresis. Skin extracts from mice heterozygous (C/c) and homozygous (c/c) for the albino locus contain 46% and 0% of CRM, respectively, as compared with wild-type (C/C) animals. Enzyme activity and CRM level were directly proportional in these genotypes, suggesting that the albino locus controls the quantity of tyrosinase produced in melanocytes.
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Article
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Article
The fine structural differentiation of the retinal pigment epithelium of the albino goldfish (Carassius auratus) in several developmental stages and in the adult was studied. In the 5-mm larva, the retinal pigment cells contained granules whose cores are filled with conglomerates of electron-dense pigments, but they were never pigmented fully as in the control black moor goldfish. Most of the granules have a round or ovoid shape, but granules with an elongate, cigar-like form are occasionally observed. The internal membranous frame-work, which has been reported in unpigmented and lightly pigmented granules in melanocytes of other vertebrates, was rarely observed in the present study. The number of pigment granules increased during the early developmental stages, whereas they decreased conspicuously in the later stages. From these results, the function of one of the albino genes p, is discussed and the following three phenomena are attributed to it: the decrease in formation of cigar-shaped granules, the partial inhibition of pigmentation, and the disintegration of pigment granules during the larval and post-larval stages. In addition to the pigment granules, the differentiation and disappearance of other characteristic cytoplasmic organelles are described. The biological significance of the changes in many of these organelles remains in question.
Article
Statistical analyses of chromatophore densities and morphological states in wild type, burnsi, and kandiyohi: adult Rana pipiens integument yielded the conclusion that disruptive pigmentary pattern is permanently defined by regional chromatophore densities. Spatial chromatophore patterning is enhanced and rendered more visible by the morphological and physiological differences among chromatophores within the various pattern regions. Specifically, (1) chromatophores were differentialy distributed among pattern regions, (2) greater complexity of gross disruptive patterning had greater underlying melanophores densities, (3) there were significant density differences among non-sib individual animals, among fertilization, and among shipment batches, but not among full-sibs, and (4)kandiyohi individuals had more while burnsi individuals had fewer total melanophores than wild type. A stellate morphology was significantly correlated with high melanophore density, although the relationship of melanophore density to melanophore morphology differed among pattern regions and among genotypes. The functional interrelationships of density and morphology, and their role in disruptive patterning and coloration, are discussed.
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1.1. A tyrosinase-positive form of oculocutaneous albinism in the goldfish is described.2.2. Both tyrosinase and peroxidase activity are present in the integuments of xanthic and albino goldfish.3.3. The lack of integumental melanin pigmentation in both xanthic and albino goldfish is due, in part, to the presence of tyrosinase inhibitors.4.4. The tyrosinase inhibitors present in the integument of xanthic and albino goldfish have different properties.5.5. Triton X-100 treatment solubilizes xanthic and albino goldfish integumental tyrosinase.
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We report the first observation of albinism in a natural population of tadpoles of the Brazilian bufonid Rhinella amata and discuss observation in relation to the species conservation status in the area documented.
Chapter
Ranid genetics had its origin with the studies of Moore (1942) on the Burnsi variant of the leopard frog, Rana pipiens. Although three decades have passed since Moore’s classical study, ranid genetics is still in its infancy [for a review of the early literature, see Rostand (1951)]. However, recent establishment of ranid genetics research centers has brightened prospects for more rapid future development in this field.
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In an orange-colored variant of the medaka fish, Oryzias latipes, which is homozygous for b allele, the melanophores represent a tissue-specific differentiation, manifesting an amelanotic appearance in the skin, an incomplete melanogenesis in the choroid and the peritoneum, and mosaic phenotype-like melano-iridophores in the peritoneum. In a wild-type strain of this species carrying the B gene, all melanophores are terminally differentiated irrespective of the tissues in which they are located. This indicates that the deficiency of B gene impairs the differentiation of melanophores in the medaka. Electron microscopy disclosed that the deficiency of B gene causes deterioration of melanogenesis to occur inside the melanosomes and that the manner of deterioration in the melanophores in the skin, the choroid and the peritoneum is different. The ubiquitous occurrence of reflecting platelet-laden melanophores in the peritoneum of this variant and the total absence of a mosaicism in pigment cells of the wild-type strain indicate that the deficiency of B gene predestines melanoblasts distributed in this tissue to an ambiguous state with regard to their differentiation. Little difference is observed between melanosomes maturation in pigment epithelial cells of the orange-colored variant and the wild-type strain, indicating an innocent role of the B gene in their differentiation.
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The need for laboratory strains of amphibians has become critical but their development has been neglected. This article describes the current development of husbandry techniques suitable for adoption by small or large laboratories. The existence of defined amphibians as a scientific resource and their availability on a limited basis is announced.
Article
This study dealt with the effects of mutation at thep (pink-eyed dilution) andc (albinism) loci separately, and at thep andd (Maltese dilution) loci together, on the fine structure of brown and black melanin granules in hair bulb melanocytes of the house mouse. Mutation at thep locus affects size, degree of melanization, and, inbb cells, shape of the granules.pp granules are lightly melanized and are smaller thanPP granules, apparently because they fail to enlarge after the beginning of melanization. Thec allele does not prevent the formation of granule framework, but does prevent melanization. Occasionalcc granules are as large as heavily melanized granules of the correspondingCC genotype. Thec andp alleles have two effects in common. Both produce inbb granules a shift toward the pattern of longitudinal strands and membranes characteristic ofBB granules. Both also cause the occurrence in the melanocyte of round membrane-enclosed bodies of variable internal structure which may be granules in the process of disintegration. Incc melanocytes these effects are so marked thatBBcc cells cannot be reliably distinguished frombbcc. The addition of Maltese dilution to pink-eyed dilution counteracts, though incompletely, the decrease of granule melanization, but intensifies the shift toward the “black” pattern.
Article
White frog spawn gave rise to black-eyed white tadpoles, which later darkened, and developed into normal frogs. The latter produced normal tadpoles, some of which developed into albino adults. The facts can be explained if albinism is recessive, but the dominant allelomorphic gene found in normal frogs produces enough pigment in the eggs of heterozygous females to give black tadpoles, and only comes into action some time after the hatching of the eggs of albino females.
Article
A new genetic trait, axanthic, is described in the Mexican axolotl with a phenotype completely lacking visible xanthophores and iridophores. Animals received from the colony of Dr. L. E. DeLanney at Ithaca, New York, have been mated among themselves for a total of seven spawnings, in which the axanthic trait was inherited as a simple Mendelian recessive. The symbol for this newly found gene isax. Homozygous recessive animals appear normal except for their lack of visible xanthophores and iridophores. The results of the spawnings also indicate that the axanthic gene is not linked to the melanoid gene (m). Its linkage with other known mutants in the axolotl is being tested.
Article
Integument from blue and green areas of the variant blue frog were analyzed biochemically for pteridines and carotenoids. Solvent extraction and absorption spectrophotometry indicated that β carotene was greatly reduced in the blue skin, and present in high quantities in the green skin of the blue frog. Thin layer and paper chromatography indicated that the pteridines were almost totally lacking in the blue skin, and present in normal quantities in the green skin of the blue frog. Light and electron microscopy indicated that the xanthophore pigment cells were either greatly altered or absent from the blue integument and present in the green integument. The fine structure of the xanthphores of the green integument contained the normal ultrastructural components of xanthopores found in regular green integument. The blue integument contained an abnormal cell type that occupied the position in the dermal chromatophore unit normally held by the xanthophores. The possibility of these cells being abnormal xanthophores or some other cell type is discussed.
Article
Albinism in the leopard frog is due to a recessive gene (alb) in the homozygous condition. Heterozygous females produce normal, pigmented eggs. After fertilization of these eggs by sperm from another heterozygote, all progeny remain normally pigmented until after hatching when the albino progeny can be detected. Since melanin deposition in oocytes occurs prior to segregation of the alb and + alleles, the wild-type gene may be transcribed and translated in the oocytes. Alternatively, the product of the + allele may be synthesized exogenously and incorporated into the oocytes during oogenesis. The results of embryonic transplant experiments suggest that the albino gene is expressed within the neural crest derivatives. Albino hosts support differentiation of wild-type melanophores. Albino dorsal mesoderm induces melanophore differentiation in wild-type neural crest derivatives. Albinos were less viable than their wild-type siblings in the laboratory environment. Albino larvae developed scoliosis with high frequency, and albino frogs had a higher mortality rate after metamorphosis than their wild-type siblings.
Article
Three mutations alter the basic pigmentation of the wild-type axolotl. In this study an attempt has been made to describe the biochemical alterations associated with these mutations and to correlate them with the cellular changes observed by other investigators and verified by this author. The a gene has no effect on either pteridine or purine synthesis or on xanthophore or iridiophore differentiation. Rather, it inactivates tyrosinase completely, resulting in the absence of melanin in albino axolotls. The effects of the m gene are primarily on the production of propigment cells by the neural crest. Transplants indicate that more melanophores and fewer xanthophores (than in the wild-type), and no iridiophores are produced in axolotls homozygous for m. Correlated with these observations are a 35% increase in tyrosinase activity and a 40% decrease in pteridine synthesis in melanoid animals. The former may, in part, be due to an increased amount of tyrosinase in each melanophore. Moreover, an accumulation of IDP + ITP, AMP, and an unidentified purine derivative suggest that a somewhat “leaky” enzymatic block in the conversion of IMP into XMP (or of XMP into GMP) may contribute to the reduction and absence, respectively, of fully differentiated xanthophores and iridiophores in melanoid skin. The extent of these contributions remains to be determined. Transplantation experiments indicate that the d gene does not alter the production of propigment cells by the neural crest. The 70% decrease in melanin synthesis (and melanophores) in white axolotls appears to be the result of decreased tyrosinase activity rather than of inhibited melanoblast migration. Likewise, the 50% decrease in pteridine synthesis (and xanthophores) appears to be the result of both decreased (40%) glucose-6-phosphate dehydrogenase activity during embryonic stages and of a “leaky” enzymatic block in the conversion of GMP into biopterin, rather than a result of inhibited xanthoblast migration. Since the former block is operative only during embryonic stages, and since the latter block results in a shunting of GMP into guanine synthesis, normal iridiophore differentiation occurs in axolotls homozygous for d.
Article
A soluble fraction obtained from the epidermis of Rana pipiens contains tyrosinase which either is competitively inhibited or is present as protyrosinase. Exposure of the epidermal preparation to trypsin or chymotrypsin activates the tyrosinase. There is no demonstrable activity before exposure to trypsin; after activation, dorsal (pigmented) epidermis contains roughly as much tyrosinase as ventral (white) epidermis. The activation of protyrosinase by protease offers a new site for the control of pigmentation.
Article
This chapter discusses the aspects of mammalian pigment genetics such as various associated biochemical, physiological, or even behavioral features that represent pleiotropic manifestations of color genes. Genetic studies of mammalian melanin pigmentation are an area of general interest because of the many different color phenotypes at various levels of organization that are amenable to analysis. Melanin pigmentation in mammals depends upon the synthesis of dark or yellow granules by specialized cells. The chapter discusses the experimental and biochemical aspects of gene action at the agouti locus. Studies of the pleiotropic effects of spotting factors, as well as of the interactions between spotting and other color genes, lead to the general conclusion that white spotting is often symptomatic of a more deep-seated genetic disturbance of development or function. The mouse hair-bulb melanocyte resembles the human hair-bulb melanocyte rather than the mouse retinal pigment cell. The pathway from the colorless precursor, tyrosine, to the dark, insoluble melanin polymer is well reviewed on numerous occasions. The copper-containing oxidase with dual specificity, tyrosinase, catalyzes the oxidation of tyrosine to 3, 4-dihydroxyphenylalanine(dopa) and of dopa to dopa quinone. In attempts to clarify the physiological genetics of mammalian melanin pigmentation, a number of techniques for assaying melanogenic activity are employed in the comparison of various color genotypes within different species of laboratory mammals.
Article
This study dealt with the effects of mutation at thep (pink-eyed dilution) andc (albinism) loci separately, and at thep andd (Maltese dilution) loci together, on the fine structure of brown and black melanin granules in hair bulb melanocytes of the house mouse. Mutation at thep locus affects size, degree of melanization, and, inbb cells, shape of the granules.pp granules are lightly melanized and are smaller thanPP granules, apparently because they fail to enlarge after the beginning of melanization. Thec allele does not prevent the formation of granule framework, but does prevent melanization. Occasionalcc granules are as large as heavily melanized granules of the correspondingCC genotype. Thec andp alleles have two effects in common. Both produce inbb granules a shift toward the pattern of longitudinal strands and membranes characteristic ofBB granules. Both also cause the occurrence in the melanocyte of round membrane-enclosed bodies of variable internal structure which may be granules in the process of disintegration. Incc melanocytes these effects are so marked thatBBcc cells cannot be reliably distinguished frombbcc. The addition of Maltese dilution to pink-eyed dilution counteracts, though incompletely, the decrease of granule melanization, but intensifies the shift toward the "black" pattern.
Article
This study dealt with the effect of mutation at theb andd loci on the fine structure of melanin granules in the hair bulb melanocytes of the house mouse. Mutation at theb locus affects both shape and structure of the granules.BB granules are oval, and the structure of the unmelanized granules consists of one or more rolled membranes.bb granules are round, and their internal framework resembles a tangled ball of strands. The principal effect of thed allele on the melanocyte is an increase in the number of granules present, apparently resulting from prolonged retention of granules by the melanocyte. This accumulation is not attributable to any visible property of granule structure or formation. The distribution of unmelanized granules within the melanocyte suggests that both Golgi vesicles and free ribosomes are involved in granule formation. The largest melanized granules in all four genotypes are larger than the largest unmelanized granules, but it is not clear whether growth occurs only by increase in thickness of the melanin deposit or whether there is an addition of new framework.
Article
The Journal of Investigative Dermatology publishes basic and clinical research in cutaneous biology and skin disease.
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