Tatsuro Kondoh

Spontaneous In Vivo Reversion of an Inherited Mutation in the Wiskott-Aldrich Syndrome

The Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency disease, arising from mutations of the WAS-protein (WASP) gene. Previously, we have reported that mononuclear cells from WAS patients showed lack/reduced of the intracellular WASP (WASPdim) by flow cytometric analysis, and analysis of WASP by flow cytometry (FCM-WASP) was useful for WAS diagnosis. In this study, we report a WAS patient who showed the unique pattern of FCM-WASP. The patient had the small population of normal expression of WASP (WASPbright) mononuclear cells together with the major WASPdim population. The WASPbright cells were detected in T cells, not in B cells or in monocytes. Surprisingly, the molecular studies of the WASPbright cells revealed that the inherited mutation of WASP gene was reversed to normal. His mother was proved as a WAS carrier, and HLA studies and microsatellite polymorphic studies proved that the WASPbright cells were derived from the patient himself. Therefore, we concluded that the WASPbright cells were resulted from spontaneous in vivo reversion of the inherited mutation. Furthermore, the scanning electron microscopic studies indicated that WASP-positive cells from the patient restored the dense microvillus surface projections that were hardly observed in the WASPdim cells. This case might have significant implications regarding the prospects of the future gene therapy for WAS patients.

Functional analysis of PTPN11/SHP-2 mutants identified in Noonan syndrome and childhood leukemia

AbstractNoonan syndrome (NS) is characterized by short stature, characteristic facial features, and heart defects. Recently, missense mutations of PTPN11, the gene encoding protein tyrosine phosphatase (PTP) SHP-2, were identified in patients with NS. Further, somatic mutations in PTPN11 were detected in childhood leukemia. Recent studies showed that the phosphatase activities of five mutations identified in NS and juvenile myelomonocytic leukemia (JMML) were increased. However, the functional properties of the other mutations remain unidentified. In this study, in order to clarify the differences between the mutations identified in NS and leukemia, we examined the phosphatase activity of 14 mutants of SHP-2. We identified nine mutations, including a novel F71I mutation, in 16 of 41 NS patients and two mutations, including a novel G503V mutation, in three of 29 patients with leukemia. Immune complex phosphatase assays of individual mutants transfected in COS7 cells showed that ten mutants identified in NS and four mutants in leukemia showed 1.4-fold to 12.7-fold increased activation compared with wild-type SHP-2. These results suggest that the pathogenesis of NS and leukemia is associated with enhanced phosphatase activity of mutant SHP-2. A comparison of the phosphatase activity in each mutant and a review of previously reported cases showed that high phosphatase activity observed in mutations at codons 61, 71, 72, and 76 was significantly associated with leukemogenesis.

Sotos syndrome and haploinsufficiency of NSD1: clinical features of intragenic mutations and submicroscopic deletions

Sotos syndrome (MIM 117550) is a congenital developmental disorder characterised by overgrowth and advanced bone age in infancy to early childhood, mental retardation, and various minor anomalies such as macrocephaly, prominent forehead, hypertelorism, downward slanting palpebral fissures, large ears, high and narrow palate, and large hands and feet.1,2 It is also frequently associated with brain, cardiovascular, and urinary anomalies3–6 and is occasionally accompanied by malignant lesions such as Wilms tumour and hepatocarcinoma.7,8 This condition has been classified as an autosomal dominant disorder, because several familial cases consistent with dominant inheritance have been described previously.9 Thus, sporadic cases accounting for most of the Sotos syndrome patients are assumed to be the result of de novo dominant mutations. We have recently shown that Sotos syndrome is caused by haploinsufficiency of the gene for NSD1 (nuclear receptor binding Su-var, enhancer of zeste, and trithorax domain protein 1).10 NSD1 consists of 23 exons and encodes at least six functional domains possibly related to chromatin regulations (SET, PWWP-I, PWWP-II, PHD-I, PHD-II, and PHD-III), in addition to 10 putative nuclear localisation signals.11 It is expressed in several tissues including fetal/adult brain, kidney, skeletal muscle, spleen, and thymus11 and is likely to interact with nuclear receptors as a bifunctional transcriptional cofactor.12 In this paper, we report on clinical findings in Japanese patients with proven point mutations in NSD1 and those with submicroscopic deletions involving the entire NSD1 gene and discuss genotype-phenotype correlation. This study consisted of five patients with heterozygous NSD1 point mutations and 21 patients with heterozygous submicroscopic deletions involving the entire NSD1 gene. The mutations were identified by direct sequencing of exons 2–23 and their flanking introns covering the whole coding region of NSD1 ,11 using genomic DNA extracted from peripheral leucocytes or …

Subtelomere specific microarray based comparative genomic hybridisation: a rapid detection system for cryptic rearrangements in idiopathic mental retardation

Mental retardation (MR) occurs in 2–3% of the general population, and more than half of MR patients are categorised as idiopathic—that is, the cause is unknown.1,2 Patients with idiopathic MR are presumed to be affected with certain genetic disorders or undetectable chromosomal abnormalities. MR may also be caused by environmental factors independently or by their interaction with genetic factors. Subtelomeric rearrangements comprise about half of segmental aneusomies,3 and are one of the major causes of MR.4,5 A recent review showed that subtelomeric rearrangements were detected in 131 (5.1%) of 2585 children with MR.1,4–6 Conventional cytogenetic analysis can detect many, but not all, rearrangements, depending on its powers of resolution.4 Other methods, such as fluorescent in situ hybridisation (FISH) using a complete set of subtelomeric probes, multicolour FISH (M-FISH), comparative genomic hybridisation (CGH), spectrum karyotyping, multiple amplifiable probe hybridisation, primed in situ labelling, and genotyping have been designed to detect subtelomeric rearrangements, but none of them is ideal in terms of sensitivity and/or efficiency.4,6 Microarray based CGH is a promising, high throughput method of detecting subtelomeric rearrangements.4 Veltman et al recently reported a microarray CGH system using crude bacterial/plasmid derived artificial chromosome (BAC/PAC) DNA for the analysis of subtelomeric aberrations, and suggested that degenerate oligonucleotide primed (DOP)-PCR products could also be used instead of crude clone DNA, although the performance of DOP-PCR products might be less sensitive.7 We have developed a microarray CGH system to identify rearrangements involving a subtelomeric region, using DOP-PCR that amplifies subtelomeric BAC/PAC DNA. Here we describe details of the method and the results of microarray CGH analyses of five cases of Wolf-Hirschhorn syndrome (WHS) associated with terminal 4p deletions as positive controls, and of 69 patients with idiopathic MR with or without multiple …

Molecular characterization of inv dup del(8p): Analysis of five cases

We analyzed five patients with inverted duplication deletion of 8p [inv dup del(8p)] using fluorescence in situ hybridization (FISH) and short tandem repeat polymorphism (STRP) analysis. In all patients, inv dup del(8p) consisted of a deleted distal segment, an intact in‐between segment, and a duplicated proximal segment. In all of them, the proximal breakpoint of the deletion and one of the breakpoints of the duplication were identical, each located at one of the two olfactory receptor gene clusters at 8p23. FISH analysis showed all their mothers to be heterozygous carriers of an 8p23 inversion [inv(8)(p23)]. STRP analysis indicated that the deletions occurred in maternally derived chromosomes. The duplicated segments had two copies of maternal, either heterozygous or homozygous alleles. These findings support and reinforce those in 16 patients with inv dup del(8p) and their parents by Floridia et al. [1996: Am J Hum Genet 58:785–796] and subsequent additional studies of 10 of them by Giglio et al. [2001: Am J Hum Genet 68:874–883]. Based on these findings, we propose a model for the inv dup del(8p) formation. The inverted segment and its normal counterpart in inv(8)(p23) heterozygous carrier mothers form a loop at the pachytene period of meiosis I. Inv dup del(8p) with heterozygous duplication is formed through at least one meiotic recombination within the loop. Inv dup del(8p) with the homozygous duplication arises through two meiotic recombinations on the inv(8)(p23) chromosome (one within the loop and the other between the loop and centromere). Subsequent rescue by eliminating a part of the duplicated segment and a centromere enables formation of viable inv dup del(8p). The frequency of the inv(8)(p23) allele is 39% in a normal Japanese population, comparable to 26% in Europeans Giglio et al. [2001: Am J Hum Genet 68:874–883]. The proposed mechanism of formation of inv dup del(8p) requires two independent events (a recombination within the loop and subsequent rescue), which may explain its rarity.

Comprehensive genetic analysis of relevant four genes in 49 patients with Marfan syndrome or Marfan‐related phenotypes

In order to evaluate the contribution of FBN1, FBN2, TGFBR1, and TGFBR2 mutations to the Marfan syndrome (MFS) phenotype, the four genes were analyzed by direct sequencing in 49 patients with MFS or suspected MFS as a cohort study. A total of 27 FBN1 mutations (22 novel) in 27 patients (55%, 27/49), 1 novel TGFBR1 mutation in 1 (2%, 1/49), and 2 recurrent TGFBR2 mutations in 2 (4%, 2/49) were identified. No FBN2 mutation was found. Three patients with either TGFBR1 or TGFBR2 abnormality did not fulfill the Ghent criteria, but expressed some overlapping features of MFS and Loeys–Dietz syndrome (LDS). In the remaining 19 patients, either of the genes did not show any abnormalities. This study indicated that FBN1 mutations were predominant in MFS but TGFBRs defects may account for approximately 5–10% of patients with the syndrome.

47,XX,UPD(7)mat,+r(7)pat/46,XX,UPD(7)mat mosaicism in a girl with Silver-Russell syndrome (SRS): possible exclusion of the putative SRS gene from a 7p13-q11 region.

Maternal uniparental disomy for chromosome 7 (UPD7) may present with a characteristic phenotype reminiscent of Silver-Russell syndrome (SRS). Previous studies have suggested that approximately 10% of SRS patients have maternal UPD7. We describe a girl with a mos47,XX,+mar/46,XX karyotype associated with the features of SRS. Chromosome painting using a chromosome 7 specific probe pool showed that the small marker was a ring chromosome 7 (r(7)). PCR based microsatellite marker analysis of the patient detected only one maternal allele at each of 16 telomeric loci examined on chromosome 7, but showed both paternal and maternal alleles at four centromeric loci. Considering her mosaic karyotype composed of diploid cells and cells with partial trisomy for 7p13-q11, the allele types obtained at the telomeric loci may reflect the transmission of one maternal allele in duplicate, that is, maternal UPD7 (complete isodisomy or homodisomy 7), whereas those at the centromeric loci were consistent with biparental contribution to the trisomic region. It is most likely that the patient originated in a 46,XX,r(7) zygote, followed by duplication of the maternally derived whole chromosome 7 in an early mitosis, and subsequent loss of the paternally derived ring chromosome 7 in a subset of somatic cells. The cell with 46,XX,r(7) did not survive thereafter because of the monosomy for most of chromosome 7. If the putative SRS gene is imprinted, it can be ruled out from the 7p11-q11 region, because biparental alleles contribute to the region in our patient.

Molecular and clinical findings and their correlations in Silver-Russell syndrome: implications for a positive role of IGF2 in growth determination and differential imprinting regulation of the IGF2–H19 domain in bodies and placentas

Silver-Russell syndrome (SRS) is characterized by growth failure and dysmorphic features and is frequently caused by hypomethylation (epimutation) of the H19-DMR. Although molecular and clinical studies have extensively been performed for SRS patients themselves, such studies have not been carried out for placentas. We identified 20 epimutation-positive and 40 epimutation-negative Japanese SRS patients and obtained placental weight data from 12 epimutation-positive and ten epimutation-negative patients and paraffin-embedded placental tissues for molecular and histological examinations from three epimutation-positive and two epimutation-negative patients. Methylation patterns were comparable between leukocytes and placentas in both epimutation-positive and epimutation-negative patients. Epimutations resulted in virtually no IGF2 expression and biallelic slight H19 expression in the leukocytes and obviously reduced IGF2 expression of paternal origin and nearly normal H19 expression of maternal origin in the placentas. Epimutation-positive patients had characteristic body phenotype and small placentas with hypoplastic chorionic villi, and epimutation-negative patients had somewhat small placentas with hypoplastic chorionic villi or massive infarction. Furthermore, significant correlations were identified between the H19-DMR methylation index and the body and placental sizes and between the placental weight and the body size in the epimutation-positive patients, whereas such correlations were not detected for the head circumference. These results suggest (1) characteristic phenotype and reduced IGF2 expression in the epimutation-positive placentas; (2) similarities and differences in the epigenetic control of the IGF2–H19 domain between leukocytes and placentas; (3) a positive role of the IGF2 expression level, as reflected by the methylation index, in the determination of body and placental growth in epimutation-positive patients, except for the brain where IGF2 is expressed biallelically; (4) involvement of placental dysfunction in prenatal growth failure; and (5) relevance of both (epi)genetic factor(s) and environmental factor(s) to SRS in epimutation-negative patients.

Preferential Paternal Origin of Microdeletions Caused by Prezygotic Chromosome or Chromatid Rearrangements in Sotos Syndrome

Sotos syndrome (SoS) is characterized by pre- and postnatal overgrowth with advanced bone age; a dysmorphic face with macrocephaly and pointed chin; large hands and feet; mental retardation; and possible susceptibility to tumors. It has been shown that the major cause of SoS is haploinsufficiency of the NSD1 gene at 5q35, because the majority of patients had either a common microdeletion including NSD1 or a truncated type of point mutation in NSD1. In the present study, we traced the parental origin of the microdeletions in 26 patients with SoS by the use of 16 microsatellite markers at or flanking the commonly deleted region. Deletions in 18 of the 20 informative cases occurred in the paternally derived chromosome 5, whereas those in the maternally derived chromosome were found in only two cases. Haplotyping analysis of the marker loci revealed that the paternal deletion in five of seven informative cases and the maternal deletion in one case arose through an intrachromosomal rearrangement, and two other cases of the paternal deletion involved an interchromosomal event, suggesting that the common microdeletion observed in SoS did not occur through a uniform mechanism but preferentially arose prezygotically.

Phenotypic consequences of genetic variation at hemizygous alleles: Sotos syndrome is a contiguous gene syndrome incorporating coagulation factor twelve (FXII) deficiency.

Purpose: We tested the hypothesis that Sotos syndrome (SoS) due to the common deletion is a contiguous gene syndrome incorporating plasma coagulation factor twelve (FXII) deficiency. The relationship between FXII activity and the genotype at a functional polymorphism of the FXII gene was investigated.Methods: A total of 21 patients including those with the common deletion, smaller deletions, and point mutations, and four control individuals were analyzed. We examined FXII activity in patients and controls, and analyzed their FXII 46C/T genotype using direct DNA sequencing.Results: Among 10 common deletion patients, seven patients had lower FXII activity with the 46T allele of the FXII gene, whereas three patients had normal FXII activity with the 46C allele. Two patients with smaller deletions, whose FXII gene is not deleted had low FXII activity, but one patient with a smaller deletion had normal FXII. Four point mutation patients and controls all had FXII activities within the normal range.Conclusion: FXII activity in SoS patients with the common deletion is predominantly determined by the functional polymorphism of the remaining hemizygous FXII allele. Thus, Sotos syndrome is a contiguous gene syndrome incorporating coagulation factor twelve (FXII) deficiency.