Michiyo Okada

National Research Institute for Child Health and Development, Tokyo, Edo, Tōkyō, Japan

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Publications (6)52.49 Total impact

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    ABSTRACT: Human chromosome 14q32.2 carries a cluster of imprinted genes including paternally expressed genes (PEGs) such as DLK1 and RTL1 and maternally expressed genes (MEGs) such as MEG3 (also known as GTL2), RTL1as (RTL1 antisense) and MEG8 (refs. 1,2), together with the intergenic differentially methylated region (IG-DMR) and the MEG3-DMR. Consistent with this, paternal and maternal uniparental disomy for chromosome 14 (upd(14)pat and upd(14)mat) cause distinct phenotypes. We studied eight individuals (cases 1-8) with a upd(14)pat-like phenotype and three individuals (cases 9-11) with a upd(14)mat-like phenotype in the absence of upd(14) and identified various deletions and epimutations affecting the imprinted region. The results, together with recent mouse data, imply that the IG-DMR has an important cis-acting regulatory function on the maternally inherited chromosome and that excessive RTL1 expression and decreased DLK1 and RTL1 expression are relevant to upd(14)pat-like and upd(14)mat-like phenotypes, respectively.
    Nature Genetics 03/2008; 40(2):237-42. · 35.21 Impact Factor
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    ABSTRACT: Although chromosome X open reading frame 6 (CXorf6) has been shown to be a causative gene for hypospadias, its molecular function remains unknown. To clarify this, we first examined CXorf6 protein structure, identifying homology to mastermind-like 2 (MAML2) protein, which functions as a co-activator in canonical Notch signaling. Transactivation analysis for wild-type CXorf6 protein by luciferase assays showed that CXorf6 significantly transactivated the promoter of a noncanonical Notch target gene hairy/enhancer of split 3 (Hes3) without demonstrable DNA-binding capacity. Transactivation analysis was also performed for the previously described three apparently pathologic nonsense mutations, indicating that E124X and Q197X proteins had no transactivation function, whereas R653X protein retained a nearly normal transactivation function. Subcellular localization analysis revealed that wild-type and R653X proteins co-localized with MAML2 protein in nuclear bodies, whereas E124X and Q197X proteins were incapable of localizing to nuclear bodies. Thus, further studies were performed for R653X, revealing the occurrence of nonsense mediated mRNA decay in vivo. Next, transient knockdown of CXorf6 was performed using small interfering RNA, showing reduced testosterone production in mouse Leydig tumor cells. Furthermore, steroidogenic factor 1 (SF1) protein bound to a specific sequence in the upstream of the CXorf6 coding region and exerted a transactivation activity. These results suggest that CXorf6 transactivates the Hes3 promoter, augments testosterone production, and contains the SF1 target sequence, thereby providing the first clue to clarify the biological role of CXorf6. We designate CXorf6 as MAMLD1 (mastermind-like domain-containing 1) based on its characteristic structure.
    Journal of Biological Chemistry 03/2008; 283(9):5525-32. · 4.65 Impact Factor
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    ABSTRACT: Although Kallmann syndrome (KS) caused by heterozygous loss of function mutations of the fibroblast growth factor receptor 1 gene (FGFR1) is occasionally associated with characteristic features, such as dental agenesis and cleft palate, FGFR1 mutations remain unidentified in several KS patients with such characteristic features. We examined a 14-yr-old Japanese boy with hypogonadotropic hypogonadism, olfactory dysfunction, and dental agenesis and his fertile mother with olfactory dysfunction and dental agenesis. Direct sequencing was performed for FGFR1 using leukocyte genomic DNA from the proband and leukocyte and nail genomic DNA from the mother. To examine a possible somatic mutation, a specific forward primer was designed to introduce a BstXI site into the normal allele only, and nested PCR amplification, followed by BstXI digestion, was carried out three times with different reverse primers. After standard PCR amplifications, a heterozygous 2-bp deletion at exon 10 (1317_1318delTG), which is predicted to cause a frameshift at the 439th codon for serine and resultant termination at the 461st codon (S439fsX461), was identified in the proband, but was not found in the mother. After selective amplification of the mutant allele, this deletion was detected in nail DNA, but not in leukocyte DNA, from the mother. The results suggest that the 2-bp deletion took place as a somatic mutation in the mother and was transmitted to the boy because of germline mosaicism. Such a somatic mutation occurs in some apparently FGFR1 mutation-negative KS patients with dental agenesis.
    Journal of Clinical Endocrinology &amp Metabolism 05/2006; 91(4):1415-8. · 6.43 Impact Factor
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    ABSTRACT: Genotyping analysis was performed for Gly146Ala polymorphism in the gene for steroidogenic factor-1 (SF-1), which is known to reduce the transactivation function by approximately 20%, in 72 cryptorchid patients and 136 control males, revealing that the Ala allele, the Ala/Gly genotype, and the Ala/Ala plus Ala/Gly genotype frequencies were significantly higher in the patients than in the control males. The results suggest that the Gly146Ala polymorphism may be a susceptibility factor for the development of cryptorchidism (CO).
    Fertility and sterility 04/2006; 85(3):787-90. · 3.97 Impact Factor
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    ABSTRACT: Steroidogenic factor-1 (SF-1) regulates the transcription of multiple genes involved in the androgen biosynthesis, and SF-1 Gly146Ala polymorphism is known to reduce the transactivation function by approximately 20%. To examine whether the Gly146Ala polymorphism constitutes a susceptibility factor for the development of micropenis (MP), we analyzed this polymorphism in a total of 52 patients with micropenis (T-MP) consisting of 30 patients with severe MP below -2.5 SD (S-MP) and 22 patients with mild MP from -2.1 SD to -2.5 SD (M-MP), together with 115 control males. The Ala allele, the Ala/Gly genotype, and the Ala/Ala plus Ala/Gly genotype frequencies were significantly higher in the S-MP patients than in the control males, whereas the allele and the genotype frequencies were comparable between the M-MP patients and the control males. The results suggest that the SF-1 Gly146Ala polymorphism may constitute a susceptibility factor for the development of S-MP, and that M-MP can be regarded as a normal variation in terms of the polymorphism effect.
    Endocrine Journal 09/2005; 52(4):445-8. · 2.23 Impact Factor
  • Endocrine Journal - ENDOCR J. 01/2005; 52(4):445-448.