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At least 253 records · Page 14Linked to original sources
PubMed2005

Inheritance of a recessive transgene-associated character controlling albinism in transgenic bean (Phaseolus vulgaris L.).

We identified a transgenic line exhibiting albinism during our work to introduce genes through genetic engineering in dry bean (Phaseolus vulgaris). The transgenic mother plant (R0) presented a normal phenotype and generated albino and normal green plants in the first generation (R1). The segregation ratio of the albino character in the R1 and R2 generations fitted the expected ratio for a character controlled by a single recessive gene linked to a foreign gus gene, suggesting that albinism could be a consequence of insertional mutation caused by introduction of the exogenous gene. Analysis by electron microscope revealed that the albino cells possessed no chloroplasts and a greater number of mitochondria when compared to normal green plants. This transgenic bean line may be used in understanding the genetic control of chloroplast genesis, for acquiring additional knowledge of genomic structure or in physiological studies. This is the first described transgene-associated mutant bean plant.

Chloroplasts↗
PubMed2004

Barley anther culture: assessment of carbohydrate effects on embryo yield, green plant production and differential plastid development in relation with albinism.

Sugars and polyols were tested at different steps of anther culture in barley (Hordeum vulgare L.) to elucidate their influence on both the overall yield of androgenesis and the structure of plastids in relation to albinism. During the pretreatment period, the osmotic regulation in the medium was beneficial to microspore embryogenesis regardless of the type and concentration of the tested osmoticum. The use of mannitol (300 mOsm/kg), sorbitol (180 mOsm/kg), PEG (240 mOsm/kg) and sucrose (180 mOsm/kg) gave the best results in terms of green plant production, although the influence of each substance differed according to the studied parameter. Similarly, during anther culture the regulation of the osmotic pressure in the medium had various effects, according to the osmoticum used. The best results were obtained using mannitol (364 mOsm/kg), providing 139.7 green plants per 100 plated anthers. Plastids were examined by electron microscopy following both pretreatment and culture. In the presence of mannitol and PEG, plastids did not accumulate starch at any stage of the protocol but they started to differentiate into chloroplasts in the microspore-derived embryos. Using sorbitol and sucrose, plastids differentiated poorly but accumulated large amounts of starch, suggesting that these sugars are metabolized by micropores and microspore derived structures. However, the accumulation of starch was not correlated with the occurrence of albinism. These results indicated that, in barley, the osmotic regulation was favourable to switch the microspore gametophytic program toward a sporophytic program regardless of the nature of the osmoticum. In addition, during the pretreatment period, mannito was found to be the most suitable osmoticum for subsequent embryo development.

Hordeum↗
PubMed2004

The microphthalmia transcription factor (Mitf) controls expression of the ocular albinism type 1 gene: link between melanin synthesis and melanosome biogenesis.

Melanogenesis is the process that regulates skin and eye pigmentation. Albinism, a genetic disease causing pigmentation defects and visual disorders, is caused by mutations in genes controlling either melanin synthesis or melanosome biogenesis. Here we show that a common transcriptional control regulates both of these processes. We performed an analysis of the regulatory region of Oa1, the murine homolog of the gene that is mutated in the X-linked form of ocular albinism, as Oa1's function affects melanosome biogenesis. We demonstrated that Oa1 is a target of Mitf and that this regulatory mechanism is conserved in the human gene. Tissue-specific control of Oa1 transcription lies within a region of 617 bp that contains the E-box bound by Mitf. Finally, we took advantage of a virus-based system to assess tissue specificity in vivo. To this end, a small fragment of the Oa1 promoter was cloned in front of a reporter gene in an adeno-associated virus. After we injected this virus into the subretinal space, we observed reporter gene expression specifically in the retinal pigment epithelium, confirming the cell-specific expression of the Oa1 promoter in the eye. The results obtained with this viral system are a preamble to the development of new gene delivery approaches for the treatment of retinal pigment epithelium defects.

Animals↗
PubMed2003

Six novel P gene mutations and oculocutaneous albinism type 2 frequency in Japanese albino patients.

Type 2 oculocutaneous albinism (OCA2) is an autosomal recessive disorder that results from mutations in the P gene that codes one of the melanosomal proteins, the function of which remains unknown. In this paper, we report the frequency of OCA2, 8%, among the Japanese albino population, six novel mutations containing four missense substitutions (P198L, P211L, R10W, M398I), and two splice site mutations (IVS15+1 G>A, IVS24-1 G>C). One of them, R10W, was within the putative signal peptide at the N-terminal of the P protein. This is the first report on the frequency of OCA2 in the Japanese albino population.

Adult↗
PubMed1964

ALBINISM AND WATER ESCAPE PERFORMANCE IN THE MOUSE.

Observation of six inbred strains of mice in a water escape test revealed that albino strains perform markedly slower than non-albino strains. Performances of F(1), F(2), and backcross offspring of selected crosses between these strains indicated that there is an association between the homozygous condition for albinism (cc) and slow performance in the water escape test.

Albinism↗
PubMed1964

SEX-LINKED ALBINISM IN THE JAPANESE QUAIL.

From a single white Coturnix chick hatched in August 1963, a white colony has been developed. The results of breeding experiments are consistent with the view that the albinism is sex-linked and recessive. It appears likely that the mutation occurred in the first white female hatched, or her sire.

Albinism↗
PubMed1978

Human albinism. Light and electron microscopy study.

The eyes of a 13-year-old leukemic boy with the attributes of tyrosinase-negative oculocutaneous albinism were obtained for light and electron microscopic study. Repeated examinations had failed to reveal WBCs with giant oxidase-positive granules, and leukemic involvement of the fundus never occurred. Light microscopic examination of horizontal and vertical sections through the retina confirms earlier reports that the fovea is absent in albinos. The synaptic apparatus of the photoreceptor terminals appears abnormal. The rough endoplasmic reticulum of the retinal pigment epithelial cells is sparse though the presence of phagosomes suggests that phagocytic function is intact. Suggestions as to the importance that the morphological findings may have on albino visual function are made.

Acute Disease↗
PubMed1978

Heterogeneity in Waardenburg's syndrome. Report of a family with ocular albinism.

A family had the following manifestations of Waardenburg's syndrome (WS): prominent nasal root, white forelock, premature graying of the hair, freckled pigmentation of pale skin, hypoplastic heterochromia irides, heterochromia of the ocular fundi, congenital sensorineural hearing loss, and autosomal dominant heredity. This family differs from those previously reported in that none of its members showed dystopia of the inner canthi or lower puncta. In addition, four siblings had the combination of hyperopia-estropia-amblyopia, as well as ocular albinism, manifested by foveal hypoplasia and transilluminable irides. Observations on this family support prior suggestions of heterogeneity in WS.

Abnormalities, Multiple↗
PubMed1996

Histology of fetal eyes with oculocutaneous albinism.

The diagnosis of tyrosinase-negative oculocutaneous albinism (OCA) was made in a 19-week-old fetus by skin biopsy. Because the parents had an 11-year-old son with tyrosinase-negative OCA, they requested that the fetus be aborted at the 20th week of gestation. A histological analysis of the eyes was performed. Throughout the retina, the ganglion cell layer was separated from the inner neuroblastic layer by the inner plexiform layer. However, the number of ganglion cells was decreased and the nerve fiber layer was immature. Bipolar and horizontal cells had begun to segregate into the inner nuclear layer. Rods and cones were identifiable in the posterior, but not peripheral, retina. Cones were more numerous in the center of the retina, and no rod-free area was identifiable. In addition, the ciliary body (epithelial folds, blood vessels in the mesodermal connective tissue core, and ciliary muscle) was less developed than in a normal fetus. Melanosomes in the retinal pigment epithelium only contained filaments without melanization and were therefore classified as stage I or II melanosomes. However, the ciliary epithelium also contained some stage III melanosomes with melanin adherent to the filaments.

Abortion, Therapeutic↗
PubMed1997

Utility of linked markers in genetic counseling: estimation of carrier risks in X-linked ocular albinism.

We apply a method proposed by Rogatko et al. [1995: Am J Med Genet 59:24-32] to estimate carrier risks using genetic linkage data. The method is illustrated for X-linked ocular albinism. Linkage data from pedigrees were combined with genome mapping data to compute carrier risks for individuals with unknown carrier status based on pedigree data alone. We considered two situations. First, a linkage map with some ambiguity in the gene order was considered. This analysis allows us to examine the effect of incomplete genetic map information on risk computations. Second, published physical and meiotic mapping information was used to derive a linkage map that could be assumed known without ambiguity. In both situations, the mean and median estimate of carrier risk differed significantly from that obtained using pedigree relationships only, in that the computed risk was significantly different from the a priori value of 0.5. The 95% CI's associated with point estimates of risk made using the known map or an map with ambiguity did not overlap in some cases. These results suggest that the risk estimate and the confidence with which a risk estimate can be imparted may depend on the genetic map and marker data used in the risk estimation procedure. We conclude that the method presented here can be used to estimate genetic risk under a variety of analytical conditions.

Albinism, Ocular↗
PubMed1999

Albinism and agenesis of the corpus callosum with profound developmental delay: Vici syndrome, evidence for autosomal recessive inheritance.

We report on two sibs and two other unrelated patients with agenesis of corpus callosum, oculocutaneous albinism, repeated infections, and cardiomyopathy. All manifested postnatal growth retardation, microcephaly, and profound developmental delay. Additional central nervous system anomalies present in at least one patient included hypoplasia of the cerebellar vermis, white matter neuronal heterotopia, or bilateral schizencephaly. Repeated viral, bacterial, and fungal infections were consistent with a primary immunodeficiency. However, immunological studies showed variable, nonspecific findings. Cardiomyopathy with progressive heart failure or infection led to death before age 2 years in three of the patients. This syndrome was first described by Vici et al. [1988: Am. J. Med. Genet. 29:1-8]. The four patients reported herein confirm this unique disorder. Affected sibs of both sexes born to unaffected parents provide evidence for autosomal recessive inheritance.

Adult↗
PubMed1998

Mutations of the human tyrosinase gene associated with tyrosinase related oculocutaneous albinism (OCA1). Mutations in brief no. 204. Online.

Mutations in the human tyrosinase gene produce tyrosinase-related oculocutaneous albinism (OCA1, MIM #203100). Tyrosinase is a copper containing enzyme and is responsible for catalyzing the rate limiting step in melanin biosynthesis, the hydroxylation of tyrosine to dopaquinone. We report 13 new mutations in the tyrosinase gene associated with OCA1A (without pigment) and OCA1B (with pigment) including 9 missense mutations (H19Q, R521, R77C, G97R, C289R, L312V, P313R, F340L and H404P), two nonsense mutations (W80X and R116X) and two frameshift mutations (53delG and 223 delG). Our previous work has defined clusters of missense mutations that appear to represent functional domains of the enzyme, and three of the missense mutations fall into these clusters including two (F340L and H404P) that flank the copper B bindng site and the missense mutation R52I that is located in the amino terminal end cluster of the protein. The G97R missense mutation is the first identified within the epidermal growth factor (EGF)-like sequence and the H19Q missense mutation alters the cleavage site of the signal peptide sequence. Mutational analysis can provide a definitive diagnosis of the type of OCA as well as help structure/function analysis.

Albinism, Oculocutaneous↗
PubMed1999

Insertion/deletion mutations of type I oculocutaneous albinism in chinese patients from Taiwan.

Type I oculocutaneous albinism (OCA1) is an autosomal recessive disorder, which is caused by the reduction or the absence of tyrosinase activity in melanocytes of the skin, hair and eyes. Although tyrosinase mutations of OCA1 have been extensively analyzed in most populations worldwide, there is no systemic study of OCA1 mutation in Chinese patients. By use of single strand conformation polymorphism and direct sequencing, we had detected 21 mutant alleles out of 24 OCA1 chromosomes screened (87.5%). Detected mutant alleles include one splicing site, three insertion/deletion and five missense mutations, of which the splicing site nucleotide alteration (IVS 1-3C>G) and two each of the insertion/deletion (232-233 ins GGG and 861-862 del TT) and missense mutations (Cys 289 Gly and Trp 400 Leu) are novel. The ins/del mutations accounts for about 37.5% in Chinese OCA1 alleles. The 232-233 ins GGG, one of the novel mutations, was found to be most frequent (25%) among the OCA1 alleles in Chinese. Through this study, we found that while some of the OCA mutant alleles were identified in other populations, ethnic difference still exists. Hum Mutat 14:542, 1999.

Albinism, Oculocutaneous↗
PubMed1983

Unusual combination of genetic defects in a Sicilian boy: G gamma delta beta thalassemia, G gamma A gamma heterocellular HPFH, beta (0) thalassemia, and albinism.

We describe the clinical and hematological findings in a 5-year-old boy with G gamma A gamma delta beta thalassemia, a G gamma A gamma heterocellular form of HPFH, beta(0) thalassemia, and albinism. Clinically he manifested only the characteristics of beta-thalassemia trait and not the typical picture of doubly heterozygous beta thal/delta beta thal. The simultaneous presence of heterocellular HPFH improves gamma chain synthesis, thus reducing the alpha chain excess. It is also possible that gene expression can be modified by the presence of other genetic anomalies.

Albinism↗
PubMed1984

X-linked inheritance of ocular albinism with late-onset sensorineural deafness.

We have investigated a large Afrikaner kindred in which seven males had ocular albinism and late-onset sensorineural deafness (OASD). The pattern of inheritance of OASD is X-linked recessive. To the best of our knowledge, this association has not previously been reported and in order to establish syndromic identity we describe and discuss the condition in this article.

Adult↗
PubMed1985

Hairbulb tyrosinase activity in oculocutaneous albinism: suggestions for pathway control and block location.

Hairbulb tyrosinase activity was determined in 72 individuals with five types of oculocutaneous albinism (OCA) and 64 obligate heterozygotes. Type IA (tyrosinase-negative) and type IB (yellow mutant) individuals had low or no measurable tyrosinase activity, and heterozygotes for these two types could be detected with this assay. Type II (tyrosinase-positive) individuals had moderate to high activity, and the heterozygotes for this type could not be detected. Type III (minimal pigment) individuals had low activity, and heterozygote levels were useful in detecting this type of OCA. Type VI (Hermansky-Pudlak syndrome) individuals had moderate to no measurable activity, and heterozygotes for this type could not be detected. The implication of the tyrosinase assay results in light of the phenotype and the possible location of the pigment block in these forms of OCA are discussed.

Albinism↗
PubMed1992

Tyrosinase gene mutations in type I (tyrosinase-deficient) oculocutaneous albinism define two clusters of missense substitutions.

Type I (tyrosinase-deficient) oculocutaneous albinism (OCA) results from mutations of the gene encoding tyrosinase, the enzyme that catalyzes the first 2 steps of melanin pigment biosynthesis. In type IA (tyrosinase-negative) OCA tyrosinase enzymatic activity is completely absent, and in type IB ("yellow") OCA tyrosinase activity is greatly reduced. Here, we describe 11 novel mutations of the tyrosinase gene in Caucasian patients with these 2 forms of type I OCA. Type I OCA in Caucasians appears to result from a great variety of different uncommon alleles. More than 80% of the known missense substitutions associated with type I OCA cluster within 2 relatively small regions of the tyrosinase polypeptide, suggesting that these may correspond to functionally important sites within the enzyme.

Albinism, Oculocutaneous↗
PubMed1993

Molecular basis of type I (tyrosinase-related) oculocutaneous albinism: mutations and polymorphisms of the human tyrosinase gene.

Type I (tyrosinase related) oculocutaneous albinism (OCA) results from mutations of the tyrosinase gene on chromosome 11q that lead to reduced or absent melanin pigment synthesis. The phenotype of Type I OCA is broad, ranging from a total lack to only a moderate reduction of melanin, and the phenotypic variation is associated with different mutant alleles at the tyrosinase locus. A total of 36 mutations have been identified in Type I OCA including 24 missense, 4 nonsense, and 8 frameshift mutations. The majority of affected individuals have been compound heterozygotes with different maternal and paternal alleles. Six polymorphic sites for haplotype analysis have been identified in the tyrosinase gene including 2 in the promoter region, 2 in the coding region associated with alternative amino acids in the protein, and 2 RFLPs in the first intron.

Albinism, Oculocutaneous↗