A missense mutation in the tyrosinase gene explains acromelanism in domesticated canaries.

Acromelanism is a form of albinism observed in several vertebrate species. In mammals, acromelanism is known to be caused by mutations in the tyrosinase gene (TYR) that induce a temperature-sensitive behavior of melanin synthesis, resulting in a characteristic hair color gradient. In birds, several phenotypes consistent with acromelanism have been reported, but their genetic basis remains unknown. This study aimed to identify the genetic basis of an acromelanistic phenotype in domesticated canaries known as pearl and test whether it is caused by the same molecular mechanism described for mammals. To do this, we compared the genomes of pearl and non-pearl canaries and searched for potentially causative genetic mutations. Our results suggest that the pearl phenotype is caused by a mutation in the TYR gene encoding a TYR-P45H missense substitution. Our findings further suggest that reports of acromelanism in other bird species might be explained by TYR mutations.

First observation of a chimpanzee with albinism in the wild: Social interactions and subsequent infanticide.

Albinism-the congenital absence of pigmentation-is a very rare phenomenon in animals due to the significant costs to fitness of this condition. Both humans and non-human individuals with albinism face a number of challenges, such as reduced vision, increased exposure to ultraviolet radiation, or compromised crypticity resulting in an elevated vulnerability to predation. However, while observations of social interactions involving individuals with albinism have been observed in wild non-primate animals, such interactions have not been described in detail in non-human primates (hereafter, primates). Here, we report, to our knowledge, the first sighting of an infant with albinism in wild chimpanzees (Pan troglodytes schweinfurthii), including social interactions between the infant, its mother, and group members. We also describe the subsequent killing of the infant by conspecifics as well as their behavior towards the corpse following the infanticide. Finally, we discuss our observations in relation to our understanding of chimpanzee behavior or attitudes towards individuals with very conspicuous appearances.

Albinism in Artibeus planirostris (Chiroptera, Phyllostomidae) in the Caatinga biome and updated list of albino bats in Brazil.

Albinism is a genetic disorder that results in a deficiency in melanin production. This type of chromatic alteration may affect several vertebrate species, but is rarely observed in nature. In Brazil, for the bat group, only 15 albino individuals have been registered. Here we present a new case for Artibeus planirostris. A pregnant female of this species with alopecia was captured in the Caatinga biome. A compilation of the distribution of albino bats in Brazil is presented.

First record of albinism in the lanternshark family, Etmopteridae.

A single albino specimen of the lanternshark, Lucifer's dogfish (Etmopterus lucifer), is reported here. The specimen was found among museum collections, having been captured near Cape Palliser, off the North Island of New Zealand in 1984. Morphometrics are reported, and with no retainment of pigmentation, the specimen is considered a complete albino. This is the first record of albinism for the family Etmopteridae and one of a handful of records for any deep-sea chondrichthyans.

A novel nonsense mutation in the tyrosinase gene is related to the albinism in a capuchin monkey (Sapajus apella).

BACKGROUND: Oculocutaneous Albinism (OCA) is an autosomal recessive inherited condition that affects the pigmentation of eyes, hair and skin. The OCA phenotype may be caused by mutations in the tyrosinase gene (TYR), which expresses the tyrosinase enzyme and has an important role in the synthesis of melanin pigment. The aim of this study was to identify the genetic mutation responsible for the albinism in a captive capuchin monkey, and to describe the TYR gene of normal phenotype individuals. In addition, we identified the subject's species. RESULTS: A homozygous nonsense mutation was identified in exon 1 of the TYR gene, with the substitution of a cytosine for a thymine nucleotide (C64T) at codon 22, leading to a premature stop codon (R22X) in the albino robust capuchin monkey. The albino and five non-albino robust capuchin monkeys were identified as Sapajus apella, based on phylogenetic analyses, pelage pattern and geographic provenance. One individual was identified as S. macrocephalus. CONCLUSION: We conclude that the point mutation C64T in the TYR gene is responsible for the OCA1 albino phenotype in the capuchin monkey, classified as Sapajus apella.

Intraocular Ossification in the GSP/pe Chicken With Imperfect Albinism.

The eyes of 2 male and 2 female GSP/pe chickens, the imperfect albino strain, were investigated at 52 weeks of age. Aged chickens of the GSP/pe colony became blind with bilateral ocular enlargement and opaque lenses. Affected eyes (bilateral in 2 males and unilateral in 2 females) were hard and difficult to section; histologic specimens were processed after decalcification. A large portion of the posterior chamber was occupied by cancellous bone containing fibrous and cartilaginous foci. Osseous tissues developed adjacent to the choroid, and no retinal pigment epithelium (RPE) was detected between osseous tissues and the choroid. Small segments of degenerate neuronal retina were scattered in the osseous tissue. The irises and ciliary bodies were deformed by osseous tissue, and the lenses had severe cataracts. These observations suggest that the intraocular osseous tissue may be derived from RPE in the hereditary incomplete-albino strain of chickens.

Activation of the Albino Sterlet Acipenser ruthenus Eggs by UV-Irradiated Bester Hybrid Spermatozoa to Provide Gynogenetic Progeny.

Meiotic gynogenesis was induced in the albino form of sterlet Acipenser ruthenus by activation of eggs with UV-irradiated bester (Huso huso x Acipenser ruthenus) spermatozoa followed by inhibition of the second meiotic division performed by a heat shock. Obtained putative gynogenetic progeny were all albinos. The genetic verification based on three microsatellite DNA markers confirmed the only maternal inheritance of the progeny from the gynogenetic experimental groups. Cytogenetic analysis proved the gynogenetic sterlets were diploids. Application of the albino phenotype together with the molecular and the cytogenetic diagnostic approaches enabled to evaluate the efficiency of the spermatozoa irradiation and application of the heat shock to restore diploid state in the gynogenetic zygotes.

Identification of a transparent mutant tiger barb Puntius tetrazona and its use for in vivo observation of a Pleistophora sp. (Microsporidia) infection.

A transparent mutant tiger barb Puntius tetrazona was identified and characterized by its transparent body, which allows clear visualization of internal organs. Hybridization of this mutant with the albino variant produces a transparent and albinoid double phenotype, and the transparency of this mutant is controlled by a recessive allele. Light microscopic and ultrastructural examinations show that in contrast to normal individuals, transparent mutants lack iridophores, and light penetrates unimpeded through the body. Pleistophora sp. infection was observed in vivo, allowing live observation of parasite dissemination and the consequent pathological alterations in the fish body as well as the simultaneous acquisition of data on the dynamics and spatial pattern of pathogenic invasion. It is superior to common fish models, as dynamic experimental data can be obtained from individual fish.

NONPIGMENTED VERSUS PIGMENTED: HEALTH VARIABLES AND GENETICS OF ALBINO FLORIDA GREEN TURTLE (CHELONIA MYDAS) HATCHLINGS COMPARED WITH NORMALLY PIGMENTED HATCHLINGS FROM THE SAME CLUTCH.

At the time of hatchling emergence from a nest laid on Juno Beach, Florida, US, by a normally pigmented green turtle (Chelonia mydas), 23 albino hatchlings and 75 normally pigmented hatchlings were observed. This condition is rarely seen in sea turtles, and little is known about blood analytes and genetics of albino wildlife to date. Therefore, the objective of our study was to assess and compare morphometric measurements (mass, minimum straight carapace length, body condition index), carapacial scute anomalies, a suite of hematologic and plasma biochemical analytes, and two glucose analysis methodologies (glucometer and dry chemistry analysis) in albino (n=20) versus normally pigmented (n=24) hatchlings from this nest. Genetic analyses were completed to identify paternal contributions of hatchlings and to test Mendelian inheritance assumptions. Although morphometric measurements, scute anomalies, and leukocyte morphology were similar between albino and normally pigmented hatchlings, several differences were observed in blood analyte data: immature erythrocytes, packed cell volume, heterophil:lymphocyte ratio, and glucose concentrations (by both methodologies) were significantly higher, whereas absolute immature heterophils, absolute lymphocytes, number of erythrocyte micronuclei, sodium, and chloride were significantly lower in albino hatchlings compared with normally pigmented hatchlings. Considerations for these differences include a stress response from sampling (e.g., timing of procedures or possibly from photosensitivity or reduced visual acuity in albinos) and different osmoregulation, which may reflect physiologic variations or stress. There was a small positive bias (0.10 mmol/L) with glucose by glucometer, similar to reports in other sea turtle species and confirming its suitability for use in hatchlings. All albino hatchlings analyzed (n=10) were from the same father, but the normally pigmented hatchlings (n=24) were from two other fathers. These findings provide insight into the physiology and genetics of albinism in sea turtles.

A genetic typing method for albino mutation in the Mongolian gerbil by PCR-RFLP analysis.

1. We established a PCR-RFLP analysis targeting R77H mutation in the Tyr gene as a more effective genotyping to identify carrier (C/c) with the albino allele and the agouti phenotypes. 2. Our breeding system, which targets the R77H site, is a useful cue for detecting C/c carriers with the agouti-phenotype and helps us to obtain albinos by mating agouti-phenotype carriers.

Rescue from oculocutaneous albinism type 4 using medaka slc45a2 cDNA driven by its own promoter.

Patients and vertebrate mutants with oculocutaneous albinism type 4 (OCA4) have mutations in the solute carrier family 45 member 2 (slc45a2) gene. However, there is no empirical evidence for this gene-phenotype relationship. There is a unique OCA4 mutant in medaka (b) that exhibits albinism only in the skin, but the mechanism underlying this phenotype is also unknown. In this study, we rescued medaka OCA4 phenotypes, in both the eyes and the skin, by micro-injection of an slc45a2-containing genomic fragment or slc45a2 cDNA driven by its own 0.9-kb promoter. We also identified a spontaneous nucleotide change of 339 bp in the promoter as the b mutation. There are multiple transcription start sites in medaka slc45a2, as in its human ortholog, and only the shortest and eye-specific mRNA is transcribed with the b mutation. Interestingly, we further revealed a conserved pyrimidine (Py)-rich sequence of approximately 10 bp in the promoter by medaka-pufferfish comparative genomics and verified that it plays an indispensable role for expression of slc45a2 in the skin. Further studies of the 0.9-kb promoter identified in this study should provide insights into the cis/trans-regulatory mechanisms underlying the ocular and cutaneous expression of slc45a2.

Genetic abnormality of the visual pathways in a "white" tiger.

"White"tigers show an inherited reduction of pigment, produced by an autosomal recessive gene. The brain of one of these tigers shows an abnormality of the visual pathways similar to abnormalities that are associated with albinism in many other mammals. There is a close relationship between the reduced pigment formation, the pathway abnormality, and strabismus.

Optokinetic eye movements in albino rabbits: inversion in anterior visual field.

When visual contrasts are restricted to the anterior sector (90 degrees to 180 degrees) of the albino rabbit's visual field, eye position is dramatically unstable, and when such contrasts are moved, horizontal optokinetic eye movements are inverted: the direction of pursuit is opposite to that of the stimulus. In the posterior visual field stability and optokinetic reactions are normal, as in all parts of the pigmented rabbit's visual field. This phenomenon may be one more of the complex of visual system defects linked to albinism.

Comparative transcriptome analysis reveals expression signatures of albino Russian sturgeon, Acipenseriformes gueldenstaedtii.

Albinism is a genetically inherited condition that is caused by a series of genetic abnormalities leading to a reduction in melanin production. Russian sturgeon is one of the most valuable freshwater fish species worldwide, and albino individuals have been found in fish farms. Due to its complicated genome and scarce genome-wide genetic resources, the underlying molecular basis of albinism in Russian sturgeon is unknown. In the present study, we first generated transcriptome profile of Acipenser gueldenstaedtii using pooled tissues, which provided reliable reference sequences for future molecular genetic studies. A total of 369,441 contigs were assembled, corresponding to 32,965 unique genes. A comparative analysis of the transcripts from the skin of albino and wildtype individuals was conducted afterwards. A total of 785 unique genes were differentially expressed, including the upregulation of 385 genes and the downregulation of 400 genes in albino individuals. The expression pattern of 16 selected differentially expressed genes was validated using qRT-PCR. Additional annotation, GO enrichment analysis and gene pathway analysis indicated that the melanogenesis pathway may be interrupted in albinism. Eight potential causative genes that were highly likely to be responsible for sturgeon albinism were identified, including Dct, Tyrp1b, Slc45a2, Ctns, Pmela, Pmelb, Cd63, and Bloc1s3, which were found to be significantly down-regulated in albino Russian sturgeon. Moreover, a sliding window analysis of the ratio of nonsynonymous to synonymous nucleotide substitution rates (Ka/Ks) ratios indicated that seven out of the eight genes underwent positive selection during evolution. Our results provide a valuable basis for understanding the molecular mechanism of albinism in fish species and will facilitate future genetic selection and breeding of sturgeon with market-favored traits in aquaculture.

Genetic disorders of vision revealed by a behavioral screen of 400 essential loci in zebrafish.

We examined optokinetic and optomotor responses of 450 zebrafish mutants, which were isolated previously based on defects in organ formation, tissue patterning, pigmentation, axon guidance, or other visible phenotypes. These strains carry single point mutations in >400 essential loci. We asked which fraction of the mutants develop blindness or other types of impairments specific to the visual system. Twelve mutants failed to respond in either one or both of our assays. Subsequent histological and electroretinographic analysis revealed unique deficits at various stages of the visual pathway, including lens degeneration (bumper), melanin deficiency (sandy), lack of ganglion cells (lakritz), ipsilateral misrouting of axons (belladonna), optic-nerve disorganization (grumpy and sleepy), inner nuclear layer or outer plexiform layer malfunction (noir, dropje, and possibly steifftier), and disruption of retinotectal impulse activity (macho and blumenkohl). Surprisingly, mutants with abnormally large or small eyes or severe wiring defects frequently exhibit no discernible behavioral deficits. In addition, we identified 13 blind mutants that display outer-retina dystrophy, making this syndrome the single-most common cause of inherited blindness in zebrafish. Our screen showed that a significant fraction (approximately 5%) of the essential loci also participate in visual functions but did not reveal any systematic genetic linkage to particular morphological traits. The mutations uncovered by our behavioral assays provide distinct entry points for the study of visual pathways and set the stage for a genetic dissection of vertebrate vision.

Genetic and developmental analysis of some new color mutants in the goldfish, Carassius auratus.

The genotypes of three color mutants in goldfish: a depigmentation character of larval melanophores, albinism and a recessive-transparent character, were analyzed by crossing experiments. The depigmentation character in the common goldfish is controlled by two dominant multiple genes, Dp1 and Dp2, and only fish with double recessive alleles dp1dp1 dp2dp2 can retain larval melanophores throughout life. Albinism is also controlled by double autosomal genes, p and c. The genotype of an albino fish is represented by PP CC; the non-albino fish is PP CC. Fish with either a pp CC or pp Cc genotype are albino when scored at the time of melanosome differentiation in the pigment retina, but after the time of skin melanophore diffrentiation, they change to the nonalbino type under the control of the C gene. The recessive-transparent character is controlled by a single autosomal gene, g. The mechanisms of gene expression of these characters were proposed as a result of observation and/or experimental data on the differentiation processes of their phenotypes, and the genotypes of these color mutant goldfish were considered in relation to the "gene duplication hypothesis in the Cyprinidae."

Visual abnormalities in albino wallabies: a brief note.

Abnormally reduced uncrossed retinofugal pathways and abnormally low retinal cell densities have been described in albinos of a number of species of eutherian mammal, but have not been studied in marsupials. The optic chiasm of marsupials differs from that of the eutherian brains that have been studied, with uncrossed fibres segregating from crossed fibres prechiasmatically in the marsupials, but not in the eutherians. We have examined the optic chiasm and the retina in albino and normally pigmented wallabies (Macropus rufogriseus) to determine whether the abnormalities found in eutherian albinos are also present in this marsupial. The uncrossed pathway of the albino wallaby is smaller than that of the pigmented animals and the cell density in the retinal ganglion cell layer is reduced at the area centralis. We conclude that the characteristic albino abnormalities are present in both groups of mammals in spite of the other known differences in the visual pathways. The albino mutation acts at the chiasm in a similar manner in both groups even though the determinants of the chiasmatic pathway differ.

Elevated dark-adapted thresholds in albino rodents.

Albino mice and rats have elevated dark-adapted thresholds compared to normally pigmented animals. The absolute dark-adapted incremental threshold for black mice is about 1.5 log units lower than the threshold for albino mice when measured by single-unit recordings from the superior colliculus. Cell counts from the outer nuclear layer in albino mice are not significantly different from those in black mice, indicating that the elevated dark-adapted thresholds are not due to light damage of photoreceptor cells. No photoreceptor outer segment damage was found in these albino animals at the light or electron microscopic level. These experiments have been repeated in hooded and albino rats. The thresholds from albino rats were about 2 log units higher than the thresholds from pigmented rats in the dark-adapted state. The proximity of the retinal pigment epithelium (RPE) and the pigmented choroid to the photoreceptors in these animals suggests that a reduction in ocular melanin in hypopigmented animals may be causal to their elevated thresholds.