Oculocutaneous albinism type 4 is one of the most common types of albinism in Japan

Oculocutaneous albinism (OCA) is a complex genetic disease with great clinical heterogeneity. Four different types of OCA have been reported to date (OCA1, OCA2, OCA3, and OCA4). MATP was recently reported in a single Turkish OCA patient as the fourth pathological gene, but no other patients with OCA4 have been reported. Here, we report the mutational profile of OCA4, determined by genetic analysis of the MATP gene in a large Japanese population with OCA. Of 75 unrelated patients that were screened, 18 individuals (24%) were identified as having OCA4; they harbored seven novel mutations, including four missense mutations (P58S, D157N, G188V, and V507L) and three frameshift mutations (S90CGGCCA-->GC, V144insAAGT, and V469delG), showing that MATP is the most frequent locus for tyrosinase-positive OCA in Japanese patients. We discuss the functional melanogenic activity of each mutant allele, judging from the relationship between the phenotypes and genotypes of the patients. This is the first report on a large group of patients with OCA4.     

Oculocutaneous albinism type 4: six novel mutations in the membrane-associated transporter protein gene and their phenotypes

Oculocutaneous albinism type 4 (OCA4) is an autosomal recessive hypopigmentary disorder caused by mutations in the Membrane-Associated Transporter Protein gene (SLC45A2). The SLC45A2 protein is a 530-amino-acid polypeptide that contains 12 putative transmembrane domains, and appears to be a transporter that mediates melanin synthesis. Eighteen pathological mutations have been reported so far. In this study, six novel mutations, p.Y49C (c.146A > G), p.G89R (c.265G > A), p.C229Y (c.686G > A), p.T437A (c.1309A > G), p.T440A (c.1318A > G) and p.G473D (c.1418G > A) were found in eight Japanese patients with various clinical phenotypes. The phenotypes of OCA4 were as various as the other types of OCA and probably depended on the mutation sites in the SLC45A2 gene.     

一种新型眼皮肤白化病——OCA4

眼皮肤白化病(OCA)在遗传学上是一组由不同基因的突变导致的具有相同或相似临床症状的遗传病。根据涉及基因的不同, OCA进一步分为4型, 即眼皮肤白化病Ⅰ~Ⅳ型(OCA1~OCA4)。OCA4为近年新发现的一种眼皮肤白化病类型, 首报病例是一名土尔其后裔。与小鼠uw基因同源的MATP基因突变导致OCA4表型的发生。MATP 基因定位于5p13.3, 由7个外显子和6个内含子构成, MATP基因在转录水平上受黑素细胞特异性转录因子调控, 编码由530个氨基酸残基构成的膜相关转运蛋白。迄今, 至少已报道了18种MATP基因病理性突变和8种DNA多态性变异。     

Oculocutaneous albinism type 4: six novel mutations in the membrane‐associated transporter protein gene and their phenotypes

Oculocutaneous albinism type 4 (OCA4) is an autosomal recessive hypopigmentary disorder caused by mutations in the Membrane‐Associated Transporter Protein gene (SLC45A2). The SLC45A2 protein is a 530‐amino‐acid polypeptide that contains 12 putative transmembrane domains, and appears to be a transporter that mediates melanin synthesis. Eighteen pathological mutations have been reported so far. In this study, six novel mutations, p.Y49C (c.146A > G), p.G89R (c.265G > A), p.C229Y (c.686G > A), p.T437A (c.1309A > G), p.T440A (c.1318A > G) and p.G473D (c.1418G > A) were found in eight Japanese patients with various clinical phenotypes. The phenotypes of OCA4 were as various as the other types of OCA and probably depended on the mutation sites in the SLC45A2 gene.     

Oculocutaneous albinism with TYRP1 gene mutations in a Caucasian patient

Non-syndromic oculocutaneous albinism (OCA) is a clinically and genetically heterogeneous autosomal recessive disorder with mutations identified in several genes: OCA1 (tyrosinase, TYR), OCA2 (OCA2), OCA3 (tyrosinase-related protein 1, TYRP1), and OCA4 (membrane-associated transporter protein, MATP). OCA3 was thought to be restricted to black populations, where it was clinically described as rufous or brown albinism, until the recent report of a homozygous TYRP1 mutation in Caucasian patients from a consanguineous Pakistani family. Here, we describe a German patient of Caucasian origin, with a light-yellow skin, yellow-gold hair with orange highlights, fair eyelashes, several pigmented naevi, and no tendency to tan, only to burn. Eye-colour is blue-green with substance defects of the iris. Molecular analysis did not reveal any mutation in the TYR and OCA2 genes. Two mutations were found in the TYRP1 gene: a missense mutation (c.1066G>A/p.Arg356Glu) that was inherited from the mother, and a de novo single-base deletion (c.106delT/p.Leu36X). This finding suggests that mutation screening should be extended to the TYRP1 gene in patients from all ethnic origins, at least in cases where no mutations have been identified in the other OCA genes.     

SLC45A2 mutation frequency in Oculocutaneous Albinism Italian patients doesn't differ from other European studies

Background

Oculocutaneous Albinism (OCA) is a heterogeneous group of inherited diseases involving hair, skin and eyes. To date, six forms are recognized on the effects of different melanogenesis genes.OCA4 is caused by mutations in SLC45A2 showing a heterogeneous phenotype ranging from white hair, blue irides and nystagmus to brown/black hair, brown irides and no nystagmus. The high clinic variety often leads to misdiagnosis.Our aim is to contribute to OCA4 diagnosis defining SLC45A2 genetic variants in Italian patients with OCA without any TYR, OCA2 and TYRP1 gene defects.

Materials and methods

After the clinical diagnosis of OCA, all patients received genetic counseling and genetic test. Automatic sequencing of TYR, OCA2, and TYRP1 genes was performed on DNA of 117 albino patients. Multiplex Ligation-dependent Probe Amplification (MLPA) was carried out on TYR and OCA2 genes to increase the mutation rate. SLC45A2 gene sequencing was then executed in the patients with a single mutation in one of the TYR, OCA2, TYRP1 genes and in the patients, which resulted negative at the screening of these genes.

Results

SLC45A2 gene analysis was performed in 41 patients and gene alterations were found in 5 patients. Four previously reported SLC45A2 mutations were found: p.G100S, p.W202C, p.A511E and c.986delC, and three novel variants were identified: p.M265L, p.H94D, and c.1156+1G>A. All the alterations have been detected in the group of patients without mutations in the other OCA genes.

Conclusions

Three new variants were identified in OCA4 gene; the analysis allowed the classification of a patient previously misdiagnosed as OA1 because of skin and hair pigmentation presence. The molecular defects in SLC45A2 gene represent the 3.4% in this cohort of Italian patients, similar to other Caucasian populations; our data differ from those previously published by an Italian researcher group, obtained on a smaller cohort of patients.     

Oculocutaneous Albinism Type 3 (OCA3): Analysis of Two Novel Mutations in <Emphasis Type="Italic">TYRP1</Emphasis> Gene in Two Chinese Patients

Oculocutaneous albinism (OCA) is a genetic disease characterized by the reduction or deficiency of melanin in eyes, skin, and hair. OCA exhibits genetic heterogeneity. Presently, there are four types of OCA named as OCA1, OCA2, OCA3, and OCA4. OCA3 is more common in African born blacks but rarely found in other ethnic populations. Our recent genotyping of patients with OCA of Chinese descent has identified two patients who were not OCA1, OCA2, or OCA4. Examination and analysis of the TYRP1 gene identified them to be having OCA3. PCR and DNA sequencing analysis found that the mutant TYPR1 alleles were present in each of the two patients, c.780-791del/c.1067G>A (p.R356Q) and c.625G>TT (p.G209LfsX1)/c.643C>T (p.H215Y). The c.780-791del and c.1067G>A mutations have been already reported. However, the c.625G>TT and c.643C>T mutations have not been previously reported and were found to be maternal and paternal mutations, respectively. Moreover, population screening and bioinformatic analysis were carried out to determine the effects of these two mutations which revealed that both the mutation were pathogenic. Based on the similar mild phenotype of these two patients, we suggest that OCA3 might be prevalent within the Chinese population.     

Mutation analysis of Korean patients with citrullinemia

Citrullinemia is an autosomal recessive disease due to the mutations in the argininosuccinate synthetase (ASS) gene. Mutation analysis was performed on three Korean patients with citrullinemia. All of the three patients had the splicing mutation previously reported as IVS6-2A>G mutation. Two had Gly324Ser mutation and the other patient had a 67-bp insertion mutation in exon 15. The IVS6-2A>G mutation was reported to be found frequently in Japanese patients with citrullinemia, but Caucasian patients showed the extreme mutational heterogeneity. Although a limited number of Korean patients were studied, the IVS6-2A>G mutation appears to be one of the most frequent mutant alleles in Korean patients with citrullinemia. The Gly324Ser mutation identified in two patients also suggests the possible high frequency of this mutation in Korean patients as well.     

A 4‐bp deletion promoter variant (rs984225803) is associated with mild OCA4 among Japanese patients

Oculocutaneous albinism (OCA) type 4 is one of the most common types of albinism among Japanese population. In some patients who were clinically diagnosed with OCA, we have found a heterozygous pathological mutation in the coding region of SLC45A2, the gene responsible for OCA4, not leading to a DNA‐based diagnosis. In this study, we evaluated pathological variants in the promoter region of SLC45A2 in these patients. The results indicated that the majority of the patients had a 4‐bp deletion in the said region (c.‐492_489delAATG; GenBank accession number: NM_016180 ; rs984225803) in the contralateral allele. These patients displayed a mild phenotype, especially regarding eye manifestations. The results of the luciferase reporter assay and electrophoretic mobility shift assay supported the pathological role of the variant. In addition, four of 220 alleles in Japanese normal control subjects also showed the deletion variant, indicating that this variant could possibly be a skin color‐associated variant.     

The tyrosinase-positive oculocutaneous albinism gene shows locus homogeneity on chromosome 15q11-q13 and evidence of multiple mutations in southern African negroids.

Tyrosinase-positive oculocutaneous albinism (ty-pos OCA) is an autosomal recessive disorder of the melanin pigmentary system. South African ty-pos OCA individuals occur with two distinct phenotypes, with or without darkly pigmented patches (ephelides, or dendritic freckles) on exposed areas of the skin. These phenotypes are concordant within families, suggesting that there may be more than one mutation at the ty-pos OCA locus. Linkage studies carried out in 41 families have shown linkage between markers in the Prader-Willi/Angelman syndrome (PWS/AS) region on chromosome 15q11-q13 and ty-pos OCA. Analysis showed no obligatory crossovers between the alleles at the D15S12 locus and ty-pos OCA, suggesting that the D15S12 locus is very close to or part of the disease locus, which is postulated to be the human homologue, P, of the mouse pink-eyed dilution gene, p. Unlike caucasoid "ty-pos OCA" individuals, negroid ty-pos OCA individuals do not show any evidence of locus heterogeneity. Studies of allelic association between the polymorphic alleles detected at the D15S12 locus and ephelus status suggest that there was a single major mutation giving rise to ty-pos OCA without ephelides. There may, however, be two major mutations causing ty-pos OCA with ephelides, one associated with D15S12 allele 1 and the other associated with D15S12 allele 2. The two loci, GABRA5 and D15S24, flanking D15S12, are both hypervariable, and many different haplotypes were observed with the alleles at the three loci on both ty-pos OCA-associated chromosomes and "normal" chromosomes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mutation analysis of mitogen activated protein kinase 1 gene in Indian cases of 46,XY disorder of sex development

BACKGROUND:

Determination of sex is the result of cascade of molecular events that cause undifferentiated bipotential gonad to develop as a testis or an ovary. A series of genes such as SRY, steroidogenic factor-1 (SF1), AR, SRD5 α, Desert hedgehog (DHH) etc., have been reported to have a significant role in development of sex in the fetus and secondary sexual characteristics at the time of puberty. Recently, mitogen activated protein kinase kinase kinase 1 (MAP3K1) gene was found to be associated with 46, XY disorders of sex development (DSD).

AIM:

The present study is focused to identify mutations in MAP3K1 gene in the cohort of 10 Indian patients with 46,XY DSD including one family with two affected sisters. These patients were already screened for SRY, SF1 and DHH gene, but no mutation was observed in any of these genes.

MATERIALS AND METHODS:

The entire coding regions of MAP3K1 were amplified and sequenced using the gene specific primers.

RESULTS AND DISCUSSIONS:

Sequence analysis of MAP3K1 gene has revealed four variants including one missense, two silent and one deletion mutation. The missense mutation p.D806N was observed in four patients with hypospadias. Two patients showed the presence of silent mutation p.Q1028Q present in exon 14. Another silent mutation p.T428T was observed in a patient with gonadal dysgenesis. We have also observed one deletion mutation p. 942insT present in two patients. The pathogenicity of the missense mutation p.D806N was carried out using in-silico approach. Sequence homology analysis has revealed that the aspartate at 806 was found to be well-conserved across species, indicated the importance of this residue. The score for polyphen analysis of this mutation was found to be 0.999 indicating to be pathogenic mutation. Since, p.D806N mutation was found to be important residue; it might contribute to sexual development. We have reported the presence of mutations/polymorphism in MAP3K1 gene. All the mutations were found to be polymorphism upon comparing to single nucleotide polymorphism database. However, in-silico analysis of the missense mutation revealed to be a pathogenic mutation.     

A frequent tyrosinase gene mutation associated with type I-A (tyrosinase-negative) oculocutaneous albinism in Puerto Rico.

We have determined the mutations in the tyrosinase gene from 12 unrelated Puerto Rican individuals who have type I-A (tyrosinase-negative) oculocutaneous albinism (OCA). All but one individual are of Hispanic descent. Nine individuals were homozygous for a missense mutation (G47D) in exon I at codon 47. Two individuals were heterozygous for the G47D mutation, with one having a missense mutation at codon 373 (T373K) in the homologous allele and the other having an undetermined mutation in the homologous allele. One individual with negroid features was homozygous for a nonsense mutation (W236X). The population migration between Puerto Rico and the Canary Islands is well recognized. Analysis of three individuals with OCA from the Canary Islands showed that one was a compound heterozygote for the G47D mutation and for a novel missense mutation (L216M), one was homozygous for a missense mutation (P81L), and one was heterozygous for the missense mutation P81L. The G47D and P81L missense mutations have been previously described in extended families in the United States. Haplotypes were determined using four polymorphisms linked to the tyrosinase locus. Haplotype analysis showed that the G47D mutation occurred on a single haplotype, consistent with a common founder for all individuals having this mutation. Two different haplotypes were found associated with the P81L mutation, suggesting that this may be either a recurring mutation for the tyrosinase gene or a recombination between haplotypes.     

Prenatal Genotyping of Four Common Oculocutaneous Albinism Genes in 51 Chinese Families

Oculocutaneous albinism(OCA)is an autosomal recessive disorder characterized by hypopigmentation in eyes,hair and skin,accompanied with vision loss.Currently,six genes have been identified as causative genes for non-syndromic OCA(OCA-1w4,6,7),and ten genes for syndromic OCA(HPS-1e9,CHS-1).Genetic counseling of 51 Chinese OCA families(39 OCA-1 with mutations in the TYR gene,6 OCA-2 with mutations in the OCA2 gene,4 OCA-4 with mutations in the SLC45A2 gene,1 HPS-1(Hermanskye Pudlak syndrome-1)with mutation in the HPS1 gene,and 1 mixed OCA-1 and OCA-4)led us to perform the prenatal genetic testing of OCA using amniotic fluid cells through the implementation of our optimized strategy.In our cohort,eleven previously unidentified alleles(PUAs)(5 in TYR,2 in OCA2,and 4 in SLC45A2)were found.Three missense PUAs(p.C112R,p.H363R and p.G379V of TYR)and one in-frame deletional PUA(p.S222del of SLC24A5)led to fetuses with OCA when co-inherited with other disease causative alleles.Three PUAs(p.P152H and p.W272X of TYR,p.A486T of SLC24A5)identified in the OCA probands did not co-transmit with known pathological alleles and thus gave rise to unaffected fetuses.Four PUAs(p.Q83X and p.A658T of TYR,p.G161R and p.G366R of SLC24A5)did not transmit to the unaffected fetuses.In addition,the in vitro transfection assays showed that the p.S192Y variant of TYR produced less pigment compared to the wild-type allele.A fetus with a digenic carrier of OCA-1 and OCA-4 was unaffected.In combination with functional assays,the family inheritance pattern is useful for the evaluation of pathogenicity of PUAs and genetic counseling of OCA.     

A 122.5-kilobase deletion of the P gene underlies the high prevalence of oculocutaneous albinism type 2 in the Navajo population

Oculocutaneous albinism (OCA) is a genetically heterogeneous disorder. There are four known types of OCA: OCA1-OCA4. The clinical manifestations of all types of OCA include skin and hair hypopigmentation and visual impairment. Although there are a few documented observations of high frequency of albinism among Native Americans, including the Hopi, Zuni, Kuna, Jemez, Laguna, San Juan, and Navajo, no causative molecular defect has been previously reported. In the present study, we show that albinism in one Native American population, the Navajo, is caused by a LINE-mediated 122.5-kilobase deletion of the P gene, thus demonstrating that albinism in this population is OCA2. This deletion appears to be Navajo specific, because this allele was not detected in 34 other individuals with albinism who listed other Native American origins, nor has it been reported in any other ethnic group. The molecular characterization of this deletion allele allowed us to design a three-primer polymerase chain reaction system to estimate the carrier frequency in the Navajo population by screening 134 unrelated normally pigmented Navajos. The carrier frequency was found to be approximately 4.5%. The estimated prevalence of OCA2 in Navajos is between approximately 1 per 1,500 and 1 per 2,000. We further estimate that this mutation originated 400-1,000 years ago from a single founder.     

Three single nucleotide polymorphisms leading to non-synonymous amino acid substitution in the human ribonuclease 2 and angiogenin genes exhibit markedly less genetic heterogeneity in six populations

Angiogenin and ribonuclease 2 (RNase 2) are members of the human RNase superfamily. Although three potential single nucleotide polymorphisms (SNPs) in these genes, which could give rise to an amino acid substitution in the protein, have been identified, relevant population data are not available, and accordingly they have not been applied to clinical-genetic analysis. For this purpose, a novel genotyping method for each SNP using the mismatched PCR-restriction fragment length polymorphism technique has been developed. Using this method, the genotype distribution of each SNP was investigated in six populations: Japanese (n = 167), Korean (n = 90), Mongolian (n = 92), Ovambos (n = 86), Turkish (n = 87), and German (n = 70). In all the populations, only one genotype was found in each SNP. Irrespective of differences in ethnic groups, the angiogenin and RNase 2 genes appear to exhibit markedly less genetic heterogeneity with regard to these SNPs.     

Molecular genetic studies and delineation of the oculocutaneous albinism phenotype in the Pakistani population

ABSTRACT: BACKGROUND: Oculocutaneous albinism (OCA) is caused by a group of genetically heterogeneous inherited defects that result in the loss of pigmentation in the eyes, skin and hair. Mutations in the TYR, OCA2, TYRP1 and SLC45A2 genes have been shown to cause isolated OCA. No comprehensive analysis has been conducted to study the spectrum of OCA alleles prevailing in Pakistani albino populations. METHODS: We enrolled 40 large Pakistani families and screened them for OCA genes and a candidate gene, SLC24A5. Protein function effects were evaluated using in silico prediction algorithms and ex vivo studies in human melanocytes. The effects of splice-site mutations were determined using an exon-trapping assay. RESULTS: Screening of the TYR gene revealed four known (p.Arg299His, p.Pro406Leu, p.Gly419Arg, p.Arg278*) and three novel mutations (p.Pro21Leu, p.Cys35Arg, p.Tyr411His) in ten families. Ex vivo studies revealed the retention of an EGFP-tagged mutant (p.Pro21Leu, p.Cys35Arg or p.Tyr411His) tyrosinase in the endoplasmic reticulum (ER) at 37degreesC, but a significant fraction of p.Cys35Arg and p.Tyr411His left the ER in cells grown at a permissive temperature (31degreesC). Three novel (p.Asp486Tyr, p.Leu527Arg, c.1045-15T>G) and two known mutations (p.Pro743Leu, p.Ala787Thr) of OCA2 were found in fourteen families. Exon-trapping assays with a construct containing a novel c.1045-15T>G mutation revealed an error in splicing. No mutation in TYRP1, SLC45A2, and SLC24A5 was found in the remaining 16 families. Clinical evaluation of the families segregating either TYR or OCA2 mutations showed nystagmus, photophobia, and loss of pigmentation in the skin or hair follicles. Most of the affected individuals had grayish-blue colored eyes. CONCLUSIONS: Our results show that ten and fourteen families harbored mutations in the TYR and OCA2 genes, respectively. Our findings, along with the results of previous studies, indicate that the p.Cys35Arg, p.Arg278* and p.Gly419Arg alleles of TYR and the p.Asp486Tyr and c.1045-15T>G alleles of OCA2 are the most common causes of OCA in Pakistani families. To the best of our knowledge, this study represents the first documentation of OCA2 alleles in the Pakistani population. A significant proportion of our cohort did not have mutations in known OCA genes. Overall, our study contributes to the development of genetic testing protocols and genetic counseling for OCA in Pakistani families.     

CFTR mutations in Turkish and North African cystic fibrosis patients in Europe: implications for screening

AIMS: To obtain more insight into the variability of the CFTR mutations found in immigrant cystic fibrosis (CF) patients who are living in Europe now, and to estimate the test sensitivity of different frequently used methods of DNA analysis to detect CF carriers or patients among these Turkish or North African immigrants. METHODS: A survey among 373 European CF centers asking which CFTR mutations had been found in Turkish and North African CF patients. RESULTS: 31 and 26 different mutations were reported in Turkish and North African patients, identifying 64.2% (113/176) and 87.4% (118/135) alleles, respectively (p < 0.001). The mean sensitivity (detection rate) of three most common CFTR mutation panels to detect these mutations differed between Turkish and North African people, 44.9% (79/176) versus 69.6% (94/135) (p < 0.001), and can be increased to 57.4% (101/176) and 79.3% (107/135) (p < 0.001), respectively, by expanding these panels with 13 mutations which have been found on two or more alleles. CONCLUSION: 35.8% and 12.6%, respectively, of CF alleles in Turkish and North African patients living in Europe now had not been identified. Among these populations, the test sensitivity of common CFTR mutation panels is insufficient for use in screening programs in Europe, even after expansion with frequent Turkish and North African mutations. This raises questions about whether and how to implement CF carrier and neonatal screening in a multiethnic society.     

Mutations of the tyrosinase gene in patients with oculocutaneous albinism from various ethnic groups in Israel.

We have analyzed the tyrosinase (TYR) gene in 38 unrelated patients with oculocutaneous albinism (OCA), derived from several different ethnic groups of the diverse population of Israel. We detected TYR gene mutations in 23 of the 34 patients with apparent type I (i.e., tyrosinase-deficient) OCA and in none of the patients with other clinical forms of albinism. Among Moroccan Jews with type IA (i.e., tyrosinase-negative) OCA, we detected a highly predominant mutant allele containing a missense substitution, Gly47Asp (G47D). This mutation occurs on the same haplotype as in patients from the Canary Islands and Puerto Rico, suggesting that the G47D mutation in these ethnically distinct populations may stem from a common origin.     

Polymorphism analysis of the CYP1A1 locus in Koreans: presence of the solitary m2 allele

This study determined the complete genotype and the frequencies of all four mutations [T6235C (m1), A4889G (m2), T5639C (m3) and C4887A (m4)] of the CYP1A1 from 48 healthy Koreans and 17 Korean lung cancer patients. The mutations were analyzed by polymerase chain reaction (PCR)/restriction fragment length polymorphism (RFLP) and single stand conformation polymorphism (SSCP) simultaneously in order to improve accuracy as well as to screen for possible new alleles. Previously, the m2 mutation has always been linked to the m1 mutation. Also, the m1m2 double mutant allele (*2B) was thought to have a positive correlation with lung cancer susceptibility. Here we report the presence of the solitary m2 mutant allele without the m1 mutation (m1+m2) for the first time. This would be an evidence to support the theory of intragenic recombination in the CYP1A1 locus. The m1 mutation frequencies of healthy Koreans and lung cancer patients were 38.5% and 29.4%, respectively. The m2 mutation frequencies of healthy Koreans and lung cancer patients were 25.0% and 14.7%, respectively. Unlike the case for both Japanese and Caucasian lung cancer patients, neither m1 nor m2 mutations were overrepresented in Korean lung cancer patients. The m2 mutation frequency in Korean patients was significantly higher than those for Caucasians (2.7%) and the Japanese (19.8%). The African-American specific m3 mutation and m4 mutation found in Caucasians were not discovered in this study. The CYP1A1 allele with novel mutation was also not present.