Published papers

次世代シーケンス手法の分析的妥当性を、バリアントデータを用いて検証した。常染色体上の指定難病遺伝子における既知疾患原因バリアントの領域のうち99.3%が今回の分析的妥当性の検証用領域に含まれていることが示された。全ゲノムシーケンス(WGS)のシーケンスライブラリ作成ではレプリケートや別キット使用時でもほぼ同値で高い再現性が獲得された。GenQA(Genomics Quality Assessment)による外部精度評価では、原因と考えられるバリアントについてSangerシーケンスによる確認実験を行ってから、最終的な2家系分の報告書を英語で作成し、GenQAへ提出した。数ヵ月後、Genotyping、Interpretation、Clerical Accuracyの各項目2点満点で合計6点満点中6点の最高点の評価書とGenQAによる外部精度評価実施済施設である証明書が送られてきた。

Background: Mutations in the FBXO28 gene, which encodes FBXO28, one of the F-box protein family, may cause developmental and epileptic encephalopathy (DEE). FBXO28-related DEE is radiologically characterized by cerebral atrophy, delayed/abnormal myelination, and brain malformation; however, no neurochemical analyses have been reported. Case report: A female Japanese infant presented with severe psychomotor delay, epileptic spasms, and visual impairment. Whole-exome sequencing revealed a de novo variant of the FBXO28 gene, leading to the diagnosis of FBXO28-related DEE. Magnetic resonance (MR) spectroscopy at 6, 12, and 32 months revealed decreased N-acetylaspartate and choline-containing compounds and increased levels of myoinositol. Conclusion: MR spectroscopy revealed neurochemical derangement in FBXO28-related DEE, that is, disturbed myelination secondary to neuronal damage with astrogliosis.

Background: Pontocerebellar hypoplasia (PCH) is increasingly known as a degenerative disease rather than simple “hypoplasia”. At least 21 disease-causing genes have been identified for PCH so far. Because PCH is very heterogenous, prognostic prediction based solely on clinical or radiologic findings is not feasible. Case presentation: Here, we report two siblings who had a fulminant neonatal course. The documentation of pontocerebellar hypoplasia by postmortem brain CT imaging in one of the siblings and a subsequent complex and comprehensive whole genome analysis established that both siblings had bi-allelic compound heterozygous variants (a splicing variant and a deletion) in the SLC25A46 gene which encodes a solute carrier protein essential for mitochondrial function. Long-read whole genome sequencing was required to confirm the presence of the deletion. The fulminant courses suggest that SLC25A46-related PCH is an acutely progressive degenerative condition starting in utero, rather than a simple static hypoplasia. Conclusion: The genomic analysis was instrumental and essential to solving the enigma of the unexplained neonatal deaths of these two siblings and to provide accurate genetic counseling.

The Xenopus homologue to the ubiquitin-activating enzyme (El) from a Xenopus ovary is described. The deduced amino acid sequence is highly homologous to El from other species. © 2000 OPA (Overseas Publishers Association) N.V.

We report a female patient with late-onset epileptic spasms (ESs) of a rare form, distinct from those seen in typical West syndrome, in association with a heterozygous frameshift CASK mutation (c.1896dupC (p.C633fs*2)). She has a phenotype of microcephaly with pontine and cerebellar hypoplasia (MICPCH), and has had intractable ESs in clusters since 3years 8months of age with multifocal, particularly bifrontal, epileptic discharges in electroencephalogram. The available literature on patients with both ESs and CASK mutations has been reviewed, revealing that four of the five female children, including the present girl, had late-onset ESs, in contrast to the four males, who tended toward early-onset ESs.

We previously produced mice with human hepatocyte (h-hep) chimeric livers by transplanting h-heps into albumin enhancer/promoter-driven urokinase-type plasminogen activator-transgenic severe combined immunodeficient (SCID) mice with liver disease. The chimeric livers were constructed with h-heps, mouse hepatocytes, and mouse hepatic sinusoidal cells (m-HSCs). Here, we investigated the morphological features of the chimeric livers and the h-hep gene expression profiles in the xenogeneic animal body. To do so, we performed immunohistochemistry, morphometric analyses, and electron microscopic observations on chimeric mouse livers, and used microarray analyses to compare gene expression patterns in hepatocytes derived from chimeric mouse hepatocytes (c-heps) and h-heps. Morphometric analysis revealed that the ratio of hepatocytes to m-HSCs in the chimeric mouse livers were twofold higher than those in the SCID mouse livers, corresponding to twin-cell plates in the chimeric mouse liver. The h-heps in the chimeric mouse did not show hypoxia even in the twin-cell plate structure, probably because of low oxygen consumption by the h-heps relative to the mouse hepatocytes (m-heps). Immunohistochemical and electron microscopic examinations revealed that the sinusoids in the chimeric mouse livers were normally constructed with h-heps and m-HSCs. However, a number of microvilli projected into the intercellular clefts on the lateral aspects of the hepatocytes, features typical of a growth phase. Microarray profiles indicated that ∼82% of 16 605 probes were within a twofold range difference between h-heps and c-heps. Cluster and principal component analyses showed that the gene expression patterns of c-heps were extremely similar to those of h-heps. In conclusion, the chimeric mouse livers were normally reconstructed with h-heps and m-HSCs, and expressed most human genes at levels similar to those in human livers, although the chimeric livers showed morphological characteristics typical of growth. © 2013 USCAP, Inc All rights reserved.

It has been well documented that variants in genes encoding centrosomal proteins cause primary autosomal recessive microcephaly, although the association between centrosomal defects and the etiology of microcephaly syndromes is not fully understood. Polo-like kinase 4 (PLK4) is one of the centrosomal proteins required for centriole duplication. We here describe a patient with microcephaly and chorioretinopathy that harbors compound heterozygous missense variants, c.[442A>G]; [2336G>A], in the PLK4 gene. One of these variants, c.442A>G (p.(M148V)), resides in the kinase domain, and the other, c.2336G>A (p.(C779Y)), in the polo-box domain. Aberrant spindle formation was observed in a LCL derived from this patient. Overexpression experiments of the variant PLK4 proteins demonstrated that the p.(C779Y) but not the p.(M148V) had lost centriole overduplication ability. The altered mobility pattern of both variant proteins on a western blot further suggested alterations in post-translation modification. Our data lend support to the hypothesis that impaired centriole duplication caused by PLK4 variants may be involved in the etiology of microcephaly disorder.

We identified a novel mutation in ASH1L in a patient with severe intellectual disability, growth failure, microcephaly, facial dysmorphism, myelination delay, and skeletal abnormalities. ASH1L is a histone methyltransferase that associates with the transcribed region of all active genes examined, including Hox genes. It catalyzes H3K36 methylation and plays important roles in development. There has been increasing evidence that heterozygous mutation of ASH1L is associated with ID and autism spectrum disorders. We suggest that ASH1L abnormalities may cause a novel MCA/ID syndrome.