Shin-ichi Sonta

Mutations in SIP1 , encoding Smad interacting protein-1, cause a form of Hirschsprung disease

Hirschsprung disease (HSCR) is sometimes associated with a set of characteristics including mental retardation, microcephaly, and distinct facial features, but the gene mutated in this condition has not yet been identified. Here we report that mutations in SIP1, encoding Smad interacting protein-1, cause disease in a series of cases. SIP1 is located in the deleted segment at 2q22 from a patient with a de novo t(2;13)(q22;q22) translocation. SIP1 seems to have crucial roles in normal embryonic neural and neural crest development.

Inhibition of nuclear factor-κB-mediated transcription by association with the amino-terminal enhancer of split, a groucho-related protein lacking WD40 repeats.

The amino-terminal enhancer of split (AES) encodes a 197-amino acid protein that is homologous to the NH2-terminal domain of the DrosophilaGroucho protein but lacks COOH-terminal WD40 repeats. Although theDrosophila Groucho protein and its mammalian homologs, transducin-like enhancer of split proteins, are known to act as non-DNA binding corepressors, the role of the AES protein remains unclarified. Using the yeast two-hybrid system, we have identified the protein-protein interaction between AES and the p65 (RelA) subunit of the transcription factor nuclear factor κB (NF-κB), which activates various target genes involved in inflammation, apoptosis, and embryonic development. The interaction between AES and p65 was confirmed byin vitro glutathione S-transferase pull down assay and by in vivo co-immunoprecipitation study. In transient transfection assays, AES repressed p65-driven gene expression. AES also inhibited NF-κB-dependent gene expression induced by tumor necrosis factor α, interleukin-1β, and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1, which is an upstream kinase for NF-κB activation. These data indicate that AES acts as a corepressor for NF-κB and suggest that AES may play a pivotal role in the regulation of NF-κB target genes.

Genomic Organization and Expression Pattern of Mouse Neuroglycan C in the Cerebellar Development

Neuroglycan C (NGC) is a membrane-spanning chondroitin sulfate proteoglycan with an epidermal growth factor module that is expressed predominantly in the brain. Cloning studies with mouse NGC cDNA revealed the expression of three distinct isoforms (NGC-I, -II, and -III) in the brain and revealed that the major isoform showed 94.3% homology with the rat counterpart. The NGC gene comprised six exons, was approximately 17 kilobases in size, and was assigned to mouse chromosome band 9F1 by fluorescence in situhybridization. Western blot analysis demonstrated that, although NGC in the immature cerebellum existed in a proteoglycan form, most NGC in the mature cerebellum did not bear chondroitin sulfate chain(s), indicating that NGC is a typical part-time proteoglycan. Immunohistochemical studies showed that only the Purkinje cells were immunopositive in the cerebellum. In the immature Purkinje cells, NGC, probably the proteoglycan form, was immunolocalized to the soma and thick dendrites on which the climbing fibers formed synapses, not to the thin branches on which the parallel fibers formed synapses. This finding suggests the involvement of NGC in the differential adhesion and synaptogenesis of the climbing and parallel fibers with the Purkinje cell dendrites.

PCBs, Hexachlorobenzene and DDE are not Associated with Recurrent Miscarriage

Problem:  A case‐control study was designed to evaluate any associations between high exposure to polychlorinated biphenyls (PCB), hexachlorobenzene (HCB) and the 1,1,1,‐trichloro‐2,2‐bis (p‐chlorophenyl) ethane (DDT) metabolite 1,1‐dichloro‐2,2‐bis (p‐chlorophenyl) ethylene (DDE) and recurrent miscarriage and immunoendocrine abnormalities.

Cloning and chromosomal mapping of the human gene of neuroglycan C (NGC), a neural transmembrane chondroitin sulfate proteoglycan with an EGF module

Neuroglycan C (NGC) is a 150 kDa transmembrane chondroitin sulfate proteoglycan with a 120 kDa core glycoprotein that was originally isolated from the developing rat brain. A rabbit antiserum, raised against a recombinant polypeptide representing a protein of the rat NGC core protein, recognized an NGC homolog in homogenates of brains of various vertebrates including humans. Because of the possible involvement of this proteoglycan in the etiology of a human neuronal disease, we cloned a complete coding sequence from a human brain cDNA library using a rat NGC cDNA as a probe. The predicted protein contains 539 amino acids and shows 86% homology with the rat counterpart. The domain structure characteristic of rat NGC was completely conserved in human NGC, which consisted of an N-terminal signal sequence, a chondroitin sulfate-attachment domain, an acidic amino acid cluster, an EGF-like domain, a transmembrane domain and a cytoplasmic tail. Northern blot analysis revealed that a single transcript of 2.4 kb was detectable in the brain, but not in other human tissues. By fluorescence in situ hybridization (FISH) analysis, the human NGC gene was assigned to the chromosomal 3p21.3 band, where the Sotos syndrome has been mapped. Involvement of the NGC gene in the etiology of the Sotos syndrome remains to be examined.

Parental origin and cell stage of non‐disjunction of double trisomy in spontaneous abortion

ABSTRACT  Using polymorphic analysis of microsatellites, we investigated the parental origin and mechanism of double trisomies seen in cases of spontaneous abortion. We obtained chorionic villi from spontaneous abortions, and peripheral blood from females who experienced abortion and their spouses. Chromosomal analysis of 170 cases revealed four cases with double  trisomy.  The  karyotypes  of  these cases are 48,XX,+16,+22, 48,XXY,+18, 48,XX,+15,+21 and 48,XX,+2,+5. In the present study, the incidence of double trisomy was 2.4% of spontaneous abortions. Polymorphic analysis of microsatellites indicated that extra chromosomes were all of maternal origin in the four cases of double trisomy. The predominance of maternal origin in cases of double trisomy is similar to cases of single trisomy. The result also indicated that both extra chromosomes in two cases occurred by non‐disjunction at the first meiotic division, and extra chromosomes in the other two cases occurred by non‐disjunction at the first mitotic division. The mean maternal age in cases of double trisomy was significantly higher than that in cases of single trisomy. These findings suggest the possibility that abnormal separation of two or more chromosomes may occur simultaneously in oogonia, and that this phenomenon may increase in relation to the increase in age of women.

Paternal uniparental disomy of chromosome 14 and unique exchange of chromosome 7 in cases of spontaneous abortion

AbstractTo investigate the involvement of uniparental disomies (UPDs) in spontaneous abortion, the polymorphic patterns of microsatellites on each chromosome were analyzed in 164 cases of abortion. Eighty-three of the 164 cases had chromosomal abnormalities. In 79 of the remaining 81 cases with normal karyotypes, the microsatellite analysis revealed that biparental patterns were present in the informative microsatellites in all chromosomes. In one of the remaining two cases, however, the polymorphic patterns of chromosome 14 appeared to be both of paternal origin. The patterns of the distal of the long arm were homozygous, and those of the remaining region were heterozygous. That is, this fetus had paternal UPD 14, originating from meiosis I nondisjunction. In the other case, the polymorphic patterns of the distal one third of the long arm of chromosome 7 were uniparental (maternal) in origin whereas those of the remaining region of this chromosome were biparental. These findings thus suggested that this chromosome might have originated from chromatid exchange between the long arms of paternal and maternal chromosome 7 at the first mitotic division. Microsatellite analysis, however, produced no evidence of duplication or deletion of any segments. The findings also suggest the possibility that some UPDs may cause spontaneous abortion.

Maternal uniparental disomy of chromosome 16 in a case of spontaneous abortion

AbstractTo investigate the involvement of uniparental disomies (UPDs) in spontaneous abortions, we analyzed in detail the polymorphism of microsatellites on each chromosome in cases of abortion. Of the 52 spontaneous abortions investigated, 25 had a normal karyotype. The polymorphic analysis of these cases revealed that, in the villi from 24 of the 25 cases, biparental patterns were present in informative microsatellites in all autosomes. In the remaining case with a 46,XX karyotype (case 18), however, the informative patterns of the microsatellites of chromosome 16 appeared to be both of maternal origin. The results also showed that the region from the distal end of the short arm to near the middle point of the long arm of chromosome 16 (pter to D16S3107) were heterozygous, and those of the remaining region of the long arm (D16S3018 to qter) were homozygous. That is, this fetus had maternal isodisomy and heterodisomy of chromosome 16, originating from a maternal, meiosis I non-disjunction of dyad 16 that accompanied a crossover at near the middle point of the long arm. The present finding suggests that some UPDs may become a cause for spontaneous abortions.

Molecular analysis of Japanese patients with Rett syndrome: Identification of five novel mutations and genotype-phenotype correlation Communicated by Mark H. Paalman Online Citation: Human Mutation, Mutation in Brief #443 (2001) Online http://journals.wiley.com/1059-7794/pdf/mutation/443.pdf

Rett syndrome is an X-linked dominant neurodevelopmental disorder that affects females almost exclusively. The recent identification of mutations of the methyl-CpG-binding protein 2 gene (MECP2) in patients with RTT, encouraged us to analyze the gene in 37 Japanese patients divided into classical RTT (14 cases), variant RTT (13 cases), and mentally retarded patients with Rett-like features (10 cases). Mutations in MECP2 were identified from most of the patients with classical and variant RTT (25 of 27 cases). Six reported common mutations were detected in 17 cases, and rare single nucleotide substitutions were found in 3 patients. In addition, one insertion mutation (1189insA) and four deletion mutations including one double deletion mutant (451delG, 100del4, 1124del53 and 881del289 plus 1187del8) were newly identified. In the 10 mentally retarded patients with Rett-like features, however, no mutation was detected in the coding region of MECP2. The finding of MECP2 mutations in 92.5% of patients with RTT indicates that RTT fulfilling the diagnostic criteria are due to genetic alteration.

Assignment of the IκB-β gene NFKBIB to human chromosome band 19q13.1 by in situ hybridization

We have isolated the full-length NFKBIB cDNA clone from a human placenta Matchmaker cDNA library (Clontech, Palo Alto CA) by two-hybrid screening using yeast (Iwabuchi et al., 1994). The NFKBIB gene (alias IKBB, TRIP9) encodes the IÎB-ß protein, an inhibitory molecule of transcription factor NF-ÎB (reviewed by Baeuerle and Baichwal, 1997; Okamoto et al., 1997; Baldwin, 1996; Beg and Baldwin, 1993). The IÎB proteins comprise a distinct family including the following members: IÎB-· and IÎB-ß, which are cytoplasmic in location and inhibit the DNA binding of NF-ÎB (Ghosh and Baltimore, 1990; Link et al., 1992); the product of the bcl-3 proto-oncogene (Nolan et al., 1993), which is nuclear in location and inhibits the DNA-binding of NF-ÎB but, paradoxically, activates transcription when interacting with a homodimer complex of p50, one of the subunits of NF-ÎB (Bours et al., 1993; Fujita et al., 1993); and the proteins corresponding to the C-terminal portions of p105 and p100, which are synthesized by alternative splicing of the respective genes and act as IÎB molecules, thus named IÎB-Á and IÎB-‰, respectively (Inoue et al., 1992; Dobrzanski et al., 1995). It is noted that the human IÎB-ß gene was initially identified as a transcriptional co-activator for thyroid hormone receptor and thus named TRIP9 (Lee et al., 1995). Since NF-ÎB regulates a large number of genes that positively control various aspects of the immune and inflammatory response, IÎB proteins are considered to be crucial regulators of these biological responses. Moreover, recent studies have indicated that NF-ÎB blocks the apoptosis pathway (Beg and Baltimore, 1996; Wu et al., 1996; Wang et al., 1996), thus also highlighting the regulatory role of IÎB proteins. We have localized the NFKBIB gene to chromosome 19 band q13.1. The genetic loci did not reveal any association with a hereditary disease whose causative gene has not been identified. However, we found that NFKBIB mapped in the close vicinity of bcl-3 located at 19q13.2 (McKeithan et al., 1990). It is likely that these two genes share the same ancestral origin and might have been generated by localized gene duplication.