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At least 217 records · Page 12Linked to original sources
PubMed1993

Genetic mapping of the Kallmann syndrome and X linked ocular albinism gene loci.

The X linked form of Kallmann syndrome (KAL) and X linked ocular albinism (OA1) have both been mapped to Xp22.3. We have used a dinucleotide repeat polymorphism at the Kallmann locus to type 17 X linked ocular albinism families which had previously been typed for the Xg blood group (XG) and the DNA markers DXS237 (GMGX9), DXS143 (dic56), and DXS85 (782). Close linkage was found between KAL and OA1 with a maximum lod score (Zmax) of 30.14 at a recombination fraction (theta max) of 0.06 (confidence interval for theta: 0.03-0.10). KAL was also closely linked to DXS237 (Zmax = 15.32; theta max = 0.05; CI 0.02-0.12) and DXS143 (Zmax = 14.57; theta max = 0.05; CI 0.02-0.13). There was looser linkage to the Xg blood group (XG) and to DXS85 (782). Multipoint linkage analysis gave the map: Xpter-XG-0.13-DXS237-0.025-KAL-0.025-DXS143-0.01 5-OA1-0.09-DXS85-Xcen. Placement of OA1 proximal to DXS143 was supported by odds of 2300:1 compared to other orders. This confirms our previous localisation of OA1 and improves the genetic mapping of both disease loci.

Albinism↗
PubMed2005

A patient with subclinical oculocutaneous albinism type 2 diagnosed on getting severely sunburned.

P-gene-related oculocutaneous albinism (OCA2) is an autosomal recessive disorder. The phenotype is typically somewhat less severe than that of the tyrosinase-negative type (OCA1A). One of the mutations in the P gene, A481T, is associated with a mild phenotype, occasionally with no distinctive skin manifestations, which is called subclinical OCA. We present a Japanese patient having the A481T mutant allele in the P gene with subclinical oculocutaneous albinism diagnosed on getting severely sunburned. The A481T mutant allele is relatively common in the Caucasian population as well as in Japan, indicating that a number of subclinical patients of OCA2 might exist not only in Japan, but also all over the world.

Adult↗
PubMed2003

Configuration of the optic chiasm in humans with albinism as revealed by magnetic resonance imaging.

PURPOSE: To determine whether the size and configuration of the optic chiasm in humans with albinism is different from that in normal control subjects. METHODS: Seventeen patients and 15 control subjects underwent magnetic resonance imaging of the entire head. Images were reformatted to the chiasm region and analyzed with observer-independent morphometry and measurements by a blinded observer. RESULTS: The albino group showed significantly smaller chiasmatic widths, smaller optic nerves and tracts, and wider angles between nerves and tracts. Statistical morphometry showed a different configuration of the optic chiasm. CONCLUSIONS: Size and configuration of the optic chiasm in humans with albinism are distinctly different from those in normal control subjects and reflect the atypical crossing of optic fibers.

Adult↗
PubMed1991

A tyrosinase gene missense mutation in temperature-sensitive type I oculocutaneous albinism. A human homologue to the Siamese cat and the Himalayan mouse.

Type I oculocutaneous albinism (OCA) is an autosomal recessive disorder in which deficient synthesis of melanin pigment results from abnormal activity of melanocyte tyrosinase. A novel type I OCA phenotype in which hypopigmentation is related to local body temperature is associated with a missense substitution in tyrosinase, codon 422 CGG (Arg)----CAG (Gln). This substitution results in a tyrosinase polypeptide that is temperature-sensitive. This form of type I OCA thus is homologous to the temperature-related forms of albinism seen in the Siamese cat and the Himalayan mouse.

Adult↗
PubMed1976

Albinism and schizophreniform psychosis: a pedigree study.

The author presents a pedigree study of albinism associated with schizophreniform psychosis and concludes that the evidence of an association between the two traits is strong; the evidence for genetic linkage is suggestive. The pineal hormone melatonin and the melanocyte-stimulating hormone inhibitory factor may be etiologic determinants of psychosis associated with albinism.

Adult↗
PubMed2000

Malignant melanoma in a patient with oculocutaneous albinism.

BACKGROUND: Sun-induced malignancies (basal cell and squamous cell carcinomas) are common in oculocutaneous albinism, however, the incidence of malignant melanoma is a topic of controversy. OBJECTIVE: We have reviewed the literature and report a case of a woman with oculocutaneous albinism with an amelanotic melanoma of the anterior chest wall. RESULTS: There are only 26 previously reported cases (both case reports and African albino population studies) in 25 patients in the literature. A 27th case with immunohistochemical and ultrastructural evaluation is presented. CONCLUSIONS: It appears that melanoma, a malignancy for which sun exposure and light colouration are felt to be major risk factors, has a low incidence among a population that is both hypopigmented and often exposed to high levels of ultraviolet light. This low incidence is poorly understood and frequently disputed.

Albinism, Oculocutaneous↗
PubMed2017

OCA2 splice site variant in German Spitz dogs with oculocutaneous albinism.

We investigated a German Spitz family where the mating of a black male to a white female had yielded three puppies with an unexpected light brown coat color, lightly pigmented lips and noses, and blue eyes. Combined linkage and homozygosity analysis based on a fully penetrant monogenic autosomal recessive mode of inheritance identified a critical interval of 15 Mb on chromosome 3. We obtained whole genome sequence data from one affected dog, three wolves, and 188 control dogs. Filtering for private variants revealed a single variant with predicted high impact in the critical interval in LOC100855460 (XM_005618224.1:c.377+2T>G LT844587.1:c.-45+2T>G). The variant perfectly co-segregated with the phenotype in the family. We genotyped 181 control dogs with normal pigmentation from diverse breeds including 22 unrelated German Spitz dogs, which were all homozygous wildtype. Comparative sequence analyses revealed that LOC100855460 actually represents the 5'-end of the canine OCA2 gene. The CanFam 3.1 reference genome assembly is incorrect and separates the first two exons from the remaining exons of the OCA2 gene. We amplified a canine OCA2 cDNA fragment by RT-PCR and determined the correct full-length mRNA sequence (LT844587.1). Variants in the OCA2 gene cause oculocutaneous albinism type 2 (OCA2) in humans, pink-eyed dilution in mice, and similar phenotypes in corn snakes, medaka and Mexican cave tetra fish. We therefore conclude that the observed oculocutaneous albinism in German Spitz is most likely caused by the identified variant in the 5'-splice site of the first intron of the canine OCA2 gene.

Albinism, Oculocutaneous↗
PubMed1988

Oculocutaneous albinism associated with congenital glaucoma.

An infant with oculocutaneous albinism and congenital glaucoma is described. The association of these two uncommon congenital disorders might suggest a common defective factor. Theoretically this patient broadens the spectrum of disorders of neural crest cell migration associated with albinism.

Albinism↗
PubMed1990

Localization of the X-linked ocular albinism gene (OA1) between DXS278/DXS237 and DXS143/DXS16 by linkage analysis.

Linkage analysis was performed in six families segregating for X-linked ocular albinism of the Nettleship-Falls type using four polymorphic DNA markers from the distal Xp. Linkage was found between the disease locus (OA1) and the loci DXS237 (theta max = 0.06, Zmax = 2.82), DXS278 (theta max = 0.03, Zmax = 5.27) and DXS16 (theta max = 0.10, Zmax = 2.33). The analysis of multiple informative meioses suggests that OA1 maps between DXS278/DXS237 and DXS143/DXS16. Multipoint linkage analysis slightly favours the order DXS278/DXS237-OA1-DXS16. These data refine the genetic localization of OA1 and may be useful for carrier detection in X-linked ocular albinism by DNA analysis.

Albinism, Ocular↗
PubMed1992

Aspects of albinism.

Genetic, clinical and electrophysiological aspects of albinism are described. Emphasis is placed on electrophysiological features which help to distinguish albinism from other clinical conditions, and on stimulating and recording factors which can affect the clarity of VEP results.

Albinism, Ocular↗
PubMed1997

Clinical and molecular characterization of a family affected with X-linked ocular albinism (OA1)

Thirty-one members of a family affected with X-linked ocular albinism (OA1) were studied to characterize the clinical phenotype and identify the disease-causing mutation. The family members were examined with ophthalmoscopy, electroretinography, and Goldmann perimetry. Linkage analysis was performed with markers from the OA1 locus. Exons 2 and 8 of the OA1 gene were assayed with the polymerase chain reaction (PCR). The six affected males had visual acuities ranging from 20/40 to 20/200. All had nystagmus, iris transillumination, and foveal hypoplasia. The eldest affected male had 20/40 vision and was asymptomatic. The level of the visual acuity of the affected males was not related to the degree of retinal pigmentation. All seven female carriers had normal visual function but were found to have iris transillumination defects and variable retinal pigmentary appearance ranging from minimal pigmentary disturbance, patchy and diffuse hypopigmentation, to classic 'mud-splattered' appearance. Linkage analysis was consistent with a disease-causing mutation at the OA1 locus. PCR analysis revealed a deletion which includes at least the portion of the OA1 gene between exons 2 and 8. Affected males with X-linked ocular albinism can have a visual disability that ranges from almost none to legal blindness, and the female carriers can have variable retinal pigmentary appearance. Mutation screening of the OA1 gene can be used to confirm the diagnosis in isolated males of some families, and genetic linkage analysis can be used to accurately identify carriers even when the specific mutation cannot be identified.

Adult↗
PubMed1997

Electronystagmographic investigation in X-linked ocular albinism.

Albinism represents the most frequent cause of nystagmus induced by visual sensory disorders. We studied five patients aged between three and five years with ocular albinism with the aim of identifying the characteristics of nystagmic oscillations. The patients underwent complete ophthalmological examination and electronystagmography (ENG). ENG revealed either pendular or jerk waveforms (or both) with the same complex effects of fixation seen in those with idiopathic congenital nystagmus. Three children presented face turn due to reduced severity of nystagmus in lateroversion. Latent nystagmus was not observed.

Albinism, Ocular↗
PubMed2000

Expression pattern of the ocular albinism type 1 (Oa1) gene in the murine retinal pigment epithelium.

PURPOSE: Mutations in the OA1 gene cause ocular albinism type 1 (OA1), an X-linked form of albinism affecting only the eye, with skin pigmentation appearing normal. To better understand the pathogenesis of this disease the time of onset and the pattern of expression of the mouse homolog of the OA1 gene were monitored during eye development. The localization of Oa1 mRNA was studied and compared with the expression of other genes involved in melanosomal biogenesis. METHODS: The Oa1 expression pattern during eye development and after birth was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. Localization of Oa1 mRNA was compared with TYROSINASE: (TYR:), pink-eyed dilution (p), and Pax2 expression patterns. RESULTS: RT-PCR revealed that Oa1 expression began at embryonic day (E)10.5 and was maintained until adulthood. By in situ hybridization analysis Oa1 transcripts were detected in the retinal pigment epithelium (RPE) beginning at E10.5 in the dorsal part of the eyecup and in the same area where transcripts of other genes involved in pigmentation are found. Of note, the expression pattern of these genes was complementary to Pax2 expression, which was restricted to the ventral side of the optic cup. At later stages, expression of Oa1, TYR:, and p expanded to the entire RPE and ciliary body. CONCLUSIONS: Oa1 expression can be detected at early stages of RPE development, together with other genes involved in pigmentation defects. Oa1 is likely to play an important function in melanosomal biogenesis in the RPE beginning during the earliest steps of melanosome formation.

Albinism, Ocular↗
PubMed1975

[Pigment dispersion in a family with albinism (author's transl)].

A report is given on a family wherein two males showed albinism; of the female members, who all had been light blonde in childhood, two were carriers (one of them with pigment changes in the iris and the fundus), a third had no ocular changes, while the fourth showed the typical phenomenon of bilateral idiopathic pigment dispersion without glaucoma. The occurrence of pigment dispersion in a family with albinism has not yet been described. It is regarded as accidental combination.

Adult↗
PubMed1992

The tyrosinase-positive oculocutaneous albinism locus maps to chromosome 15q11.2-q12.

Tyrosinase-positive oculocutaneous albinism (ty-pos OCA), an autosomal recessive disorder of the melanin biosynthetic pathway, is the most common type of albinism occurring worldwide. In southern African Bantu-speaking negroids it has an overall prevalence of about 1/3,900. Since the basic biochemical defect is unknown, a linkage study with candidate loci, candidate chromosomal regions, and random loci was undertaken. The ty-pos OCA locus was found to be linked to two arbitrary loci, D15S10 and D15S13, in the Prader-Willi/Angelman chromosomal region on chromosome 15q11.2-q12. The pink-eyed dilute locus, p, on mouse chromosome 7, maps close to a region of homology on human chromosome 15q, and we postulate that the ty-pos OCA and p loci are homologous.

Albinism, Oculocutaneous↗
PubMed2004

Genetic analysis of oculocutaneous albinism type 1 (OCA1) in Indian families: two novel frameshift mutations in the TYR Gene.

PURPOSE: Oculocutaneous albinism type 1 (OCA1) patients demonstrate a partial or total lack of melanin in the skin, hair and eye. OCA1 is an autosomal recessive genetic disorder caused by mutations in the TYR gene located at chromosome band 11q14-q25. The purpose of this study was to carry out genetic analysis of OCA1 in Indian families. METHODS: Genomic DNA was isolated from blood leukocytes of all the individuals in this study. Haplotype analysis was performed at the TYR locus using informative microsatellite markers. Eight sets of primers were used to amplify the entire coding region of the TYR gene for bidirectional direct sequencing mutation analysis. RESULTS: Two novel deletions (c.937del8, c.1379del2) and a previously known nonsense mutation (R278X) in the TYR gene were identified from a total of 8 oculocutaneous albinism patients in India. CONCLUSIONS: Our study reports the distribution of two novel frameshift and a previously reported nonsense mutations in four OCA1 families from the Indian population. These findings will contribute to the development of a diagnostic method for OCA1 carrier status and genetic counseling for OCA1 affected families.

Albinism, Oculocutaneous↗
PubMed2005

[Mutations and polymorphisms of the P gene associated with oculocutaneous albinism type II].

Oculocutaneous albinism typeII(OCA2), the most common type of albinism, is an autosomal recessive disorder. It is caused by mutations in the P gene, which is located on chromosome 15q11.1-q12 and divided into 24 exons and 23 introns. P gene codes for 838-amino-acid integral membrane protein with 12 putative transmembrane domains, but the exact function is not clear yet. There are at least 60 pathologic mutations and 43 non-pathologic polymorphisms have been found. Pathologic mutations include missense mutations, nonsense mutations, frameshift mutations and splice-sit mutations. But unlike TYR gene, most of P gene mutations are located on the C-terminal and don' t cluster in defined regions. It is difficult to define the pathologic mutations since many non-pathologic polymorphisms also lie in exons. Some non-pathologic missense mutations may be associated with phenotypic variation in normally pigmented individuals and need to further study.

Albinism, Oculocutaneous↗
PubMed2005

[Oculocutaneous albinism in French overseas territories (Reunion, French Guyana, Martinique) and Mayotte. Study of 21 cases in 16 families].

The dual purpose of this study was to determine the genotype of patients with oculocutaneous albinism type 1 and 2 based on analysis of tyrosinase and P gene mutations and to attempt to establish a correlation between phenotype and genotype. This study included a total of 21 Caucasian, Indian and Black African patients from La Reunion, la Martinique, French Guyana and Mayotte. PCR-sequencing of genomic DNA was performed to detect tyrosinase gene mutations and PCR-separation of PCR products by agarose gel electrophoresis was performed to detect 2.7kb deletion allele of the P gene. Tyrosinase gene mutations were identified in two cases, i.e., on eheterozygous guanine "g" deletion (c.572 delG) with a frameshift (Gly191fs) resulting in apremature termination signal at codon 225 in a Caucasian patient from La Reunion and one homozygous missense mutation, Glycine419Arginine, in an Indian patient from La Reunion. The 2.7-kb deletion allele of the P gene was detected in three Black African patients, i.e. two in the homozygous state in siblings from Mayotte and one in the heterozygous state in a girl from la Martinique. The latter patient whose mother was from la Martinique inherited the mutation from her father who was from Cameroon. This study shows that characterization of tyrosinase and P gene mutations in albinos patients is crucial to (a) differentiate subjects with oculocutaneous albinism types 1 and 2 and establish a correlation between phenotype and genotype, (b) identify healthy heterozygous carriers among the patient's immediate family (parents and siblings) and (c) allow prenatal diagnosis during subsequent pregnancies in couples who have already engendered albino children with severe visual phenotype and documented mutation(s).

Adolescent↗