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.     

A novel P gene missense mutation in a Japanese patient with oculocutaneous albinism type II (OCA2)

BACKGROUND: Oculocutaneous albinism type II (OCA2) is an autosomal recessively inherited disorder, characterized by white hair and skin, and loss of pigment in the eyes. Mutations in P gene have been shown to result in OCA2. So far, two cases have been reported from Japan. OBJECTIVE: We had an opportunity to examine a case of albinism, and screened the mutations of tyrosinase and P gene. METHODS: Genomic DNA was prepared from peripheral leukocytes. All of the exons and flanking introns of tyrosinase and P gene were PCR-direct-sequenced. RESULTS: Although no mutations were found in tyrosinase, we found two missense substitutions, A481T and Q799H in P gene. The A481T has previously been shown to result in partial function of the P protein. CONCLUSION: The Q799H mutation is not a common polymorphism among normal Japanese, seems most likely to be a pathological OCA2 mutation among Japanese with this form of albinism.     

眼皮肤白化病1家系致病基因鉴定

【摘要】 目的 利用全外显子测序及Sanger测序技术对两兄弟眼皮肤白化病患者的（OCA）家系进行致病基因筛选和鉴定。方法 收集1个OCA家系的临床资料,提取家系成员的外周血DNA,通过全外显子组测序技术对先证者的全外显子编码区进行直接测序以寻找可能存在的基因突变,并利用Sanger测序进行一代验证。结果 先证者及其弟弟均表现为全身皮肤、毛发变白,双眼球震颤,畏光,虹膜半透明,结膜充血,双眼屈光不正。先证者父母、祖父母、外祖父母及子女表型均正常,父母非近亲结婚。两兄弟OCA2基因中均出现3个杂合变异,即c.1290T>A无义突变、c.1363A>G错义突变和c.1204T>C错义突变。其中,OCA2 c.1204T>C尚未有报道,为OCA2基因的新突变位点。此外,先证者父亲OCA2基因存在杂合变异c.1204T>C;先证者母亲OCA2基因存在杂合变异c.1290T>A及c.1363A>G;先证者儿子OCA2基因存在杂合变异c.1290T>A;先证者女儿OCA2基因存在杂合变异c.1204T>C,先证者弟弟的女儿OCA2基因存在杂合变异c.1290T>A。结论 本研究中2例OCA2患者均出现3处OCA2基因突变,其中c.1290T>A无义突变可能是导致该家系临床表型的突变位点,这些发现丰富了OCA2的致病基因突变谱。     

Genetic testing for oculocutaneous albinism type 1 and 2 and Hermansky-Pudlak syndrome type 1 and 3 mutations in Puerto Rico

Hermansky-Pudlak syndrome (HPS) (MIM #203300) is a heterogeneous group of autosomal recessive disorders characterized by oculocutaneous albinism (OCA), bleeding tendency, and lysosomal dysfunction. HPS is very common in Puerto Rico (PR), particularly in the northwest part of the island, with a frequency of approximately 1:1,800. Two HPS genes and mutations have been identified in PR, a 16-base pair (bp) duplication in HPS1 and a 3,904-bp deletion in HPS3. In Puerto Ricans with more typical OCA, the most common mutation of the tyrosinase (TYR) (human tyrosinase (OCA1) gene) gene was G47D. We describe screening 229 Puerto Rican OCA patients for these mutations, and for mutations in the OCA2 gene. We found the HPS1 mutation in 42.8% of cases, the HPS3 deletion in 17%, the TYR G47D mutation in 3.0%, and a 2.4-kb deletion of the OCA2 gene in 1.3%. Among Puerto Rican newborns, the frequency of the HPS1 mutation is highest in northwest PR (1:21; 4.8%) and lower in central PR (1:64; 1.6%). The HPS3 gene deletion is most frequent in central PR (1:32; 3.1%). Our findings provide insights into the genetics of albinism and HPS in PR, and provide the basis for genetic screening for these disorders in this minority population.     

Ten novel mutations of the ADAR1 gene in Japanese patients with dyschromatosis symmetrica hereditaria

Dyschromatosis symmetrica hereditaria (DSH) is a pigmentary genodermatosis of autosomal-dominant inheritance. We have reported 20 different mutations of the adenosine deaminase acting on RNA 1 gene (ADAR1) in patients with DSH since we had clarified that the disease is caused by a mutation of the ADAR1 gene in 2003. In this study, we report 10 novel mutations responsible for DSH: p.Q102fsX123, p.T369fsX374, p.S664fsX677, p.R892L, p.I913R, p.R916Q, p.P990fsX1016, p.C1081S, p.C1169F, and p.K1187X.     

Trichothiodystrophy group A: A first Japanese patient with a novel homozygous nonsense mutation in the GTF2H5 gene

Trichothiodystrophy group A (TTD‐A) is one of the three types of photosensitive TTD and is a very rare genodermatosis with deficient post‐ultraviolet (UV) DNA repair. We herein describe the first Japanese case with a novel mutation in the GTF2H5 gene responsible for TTD‐A. A 5‐year‐old male, born as a collodion baby from healthy non‐consanguineous parents, exhibited sun sensitivity, brittle hair, ichthyosis, cataracts and mental/physical retardation. He demonstrated neither neurological abnormalities nor pigmentary changes following sun exposure. The patient's primary fibroblasts were hypersensitive to killing by UV (D₀ = 1.5 J/m²), and the post‐UV unscheduled DNA synthesis was 13% of normal. A host cell reactivation complementation analysis showed a decreased DNA capacity without recovery after transfecting any xeroderma pigmentosum genes. We identified a novel homozygous mutation (c.166G>T) in the coding region of the GTF2H5 gene that resulted in a predicted amino acid change: p.E55X. Thus far, only one Japanese case of TTD with a mutation of the XPD gene had been reported. The present case is the first of TTD‐A and the second case of TTD in Japan, suggesting that it is necessary to differentiate TTD from other photosensitive disorders, although the incidence of TTD is very low in Japan compared to that observed in Western countries.     

A splicing mutation of the tyrosinase gene causes yellow oculocutaneous albinism in a Japanese patient with a pigmented phenotype

BACKGROUND: Yellow oculocutaneous albinism (OCA) that is caused by tyrosinase gene mutations shows two characteristics: extreme hypopigmentation at birth and the eventual development of yellow or blond hair. OBJECTIVE: We studied a Japanese girl who had brown hair, a lighter skin color than her unaffected family and brown eyes at 9 months of age. METHODS: We performed direct sequencing analyses of the tyrosinase gene in her genomic DNA. RESULTS: The patient was a compound heterozygote for the +DeltaC310 mutation (known to result in absent melanogenic activity) and a second t-->a transition at the 3' end of intron 2. CONCLUSION: The t-->a transition has previously been reported as a splicing mutation in other Caucasian patients with a typical yellow OCA phenotype. However, this patient showed much more pigmentation than that reported in Caucasians. Therefore, we estimate that the mild phenotype results from her genetic pigment background.     

Perforating necrobiosis lipoidica in a girl with type 1 diabetes mellitus: a new case reported

Necrobiosis lipoidica is an idiopathic dermatological condition that is strongly associated with diabetes mellitus. It is more commonly seen in women than men. The average age of onset is 30-40 years. Necrobiosis Lipoidica diabeticorum is an extremely rare finding in childhood diabetes. We describe the case of a 13-year-old girl who has had type 1 diabetes mellitus since she was 8 years old. The patient presented with 2 well-defined, persistent plaques with a depressed central area and elevated purple peripheral ring, one on the right thigh and the other over the lateral left leg. Histopathologic evaluation of the patient's biopsy confirmed the diagnosis of necrobiosis lipoidica with transfollicular elimination. Our patient is the second pediatric case described with perforating necrobiosis lipoidica. We review the literature and discuss clinical features, several complications, and the most recent treatment options for necrobiosis lipoidica in diabetic children.