Satoshi Ishikiriyama

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.

Partial deletion of the long arm of chromosome 11: ten Japanese children

The clinical features of partial deletion 11q were correlated with the size of the deleted region. Ten Japanese children with partial deletion of 11q were investigated. They were divided into three groups. Three patients in the first group had interstitial deletions and preserved subband q24.1. Six patients in the second group demonstrated terminal deletion of 11q including subband q24.1, with typical features of 11q‐syndrome (Jacobsen syndrome). The third group included only one patient, who had terminal deletion of 11q without characteristics of typical 11q—syndrome. Prominent features of patients in the first group included severe mental and motor developmental delay, seizures, cleft lip and palate, and ophthal‐mological findings. Patients in the second group showed mild to moderate developmental delays without deterioration. Abnormalities in neuroimages, high intensity in the cerebral white matter in T2‐weighted magnetic resonance (MR) images, and recurrent infections were not observed after the age of 7 years. The subject in the third group, with the smallest amount of deleted chromosome, did not show developmental delays, suggesting that some unknown genes related to developmental delays may be located adjacent to subband q24.1. Variation in the deleted parts of 11q resulted in different clinical features in each group.

FBN2, FBN1, TGFBR1, and TGFBR2 analyses in congenital contractural arachnodactyly

FBN2, FBN1, TGFBR1, and TGFBR2 were analyzed by direct sequencing in 15 probands with suspected congenital contractural arachnodactyly (CCA). A total of four novel FBN2 mutations were found in four probands (27%, 4/15), but remaining the 11 did not show any abnormality in either of the genes. This study indicated that FBN2 mutations were major abnormality in CCA, and TGFBR and FBN1 defects may not be responsible for the disorder. FBN2 mutations were only found at introns 30, 31, and 35 in this study. Thus analysis of a mutational hotspot from exons 22 to 36 (a middle part) of FBN2 should be prioritized in CCA as previously suggested.

Birth defects caused by mutations in human GLI3 and mouse Gli3 genes

GLI3 is the gene responsible for Greig cephalopolysyndactyly syndrome (GCPS), Pallister–Hall syndrome (PHS) and Postaxial polydactyly type‐A (PAP‐A). Genetic polydactyly mice such as Pdn/Pdn (Polydactyly Nagoya), XtH/XtH (Extra toes) and XtJ/XtJ (Extra toes Jackson) are the mouse homolog of GCPS, and Gli3tmlUrtt/Gli3tmlUrt is produced as the mouse homolog of PHS. In the present review, relationships between mutation points of GLI3 and Gli3, and resulting phenotypes in humans and mice are described. It has been confirmed that mutation in the upstream or within the zinc finger domain of the GLI3 gene induces GCPS; that in the post‐zinc finger region including the protease cleavage site induces PHS; and that in the downstream of the GLI3 gene induces PAP‐A. A mimicking phenomenon was observed in the mouse homolog. Therefore, human GLI3 and mouse Gli3 genes have a common structure, and it is suggested here that mutations in the same functional regions produce similar phenotypes in human and mice. The most important issue might be that GCPS and PHS exhibit an autosomal dominant trait, but mouse homologs, such as Pdn/Pdn, XtH/XtH, XtJ/XtJ and Gli3tmlUrt/Gli3tmlUrt, are autosomal recessive traits in the manifestation of similar phenotypes to human diseases. It is discussed here how the reduced amounts of the GLI3 protein, or truncated mutant GLI3 protein, disrupt development of the limbs, head and face.

Interstitial duplication 8q22-q24: Report of a case proven by FISH with mapped cosmid probes

We report on a 6-month-old malformed female infant with a de novo interstitial duplication of an 8q22-q24 segment. She had an excess dark-band on the 8q distal region by GTG-banded chromosome analysis, which was likely to be 8q23. We performed FISH analysis using cosmid probes mapped to 8q23 and proved that the patient had an 8q duplication including the 8q23 region.

A NOVEL MUTATION IN L1CAM GENE IN A JAPANESE PATIENT WITH X-LINKED HYDROCEPHALUS

SummaryL1CAM is a member of the immunoglobulin gene superfamily of neural adhesion molecule. Abnormality of the L1CAM gene is associated with X-linked recessive form of congenital hydrocephalus (HSAS; hydrocephalus due to congenital stenosis of aqueduct of Sylvius) and some allelic disorders. Four new patients with congenital hydrocephalus consistent with the X-linked type were described. One of them had a novel mutation in the L1CAM gene.

Novel and recurrent exon 13 mutations of COMP in pseudoachondroplasia.

Pseudoachondroplasia (PSACH; MIM 177170) is an autosomal dominant disorder characterized by short-limbed dwarfism without disorder of face and intelligence, early onset osteoarthritis (OA), and ligamentous laxity. PSACH is caused by mutations in the gene encoding cartilage oligomeric matrix protein (COMP). COMP belongs to the thrombospondin (TSP) family of protein. COMP protein consists of an N-terminal domain, four epidermal growth factor-like repeats, eight calmodulin-like repeats (CLRs), and a C-terminal globular domain [Oldberg et al., 1992]. Most COMPmutations in PSACH patients have been identified within CLRs. The seventh CLR (CLR7) that resides in the exon 13 is the mutation hotspot [Ikegawa et al., 1998]. Genotype–phenotype correlation has been reported between the COMP mutation and PSACH phenotype [Ikegawa et al., 1998; Mabuchi et al., 2003; Song et al., 2003]. Mutations in CLR7 produce more severe short stature than those in elsewhere inCLRs. In ourprevious study, all patients with severe (< 6 SD) short stature hadmutations in CLR7 [Mabuchi et al., 2003]. Here, we report four patients with PSACH who have three types of mutations in exon 13 of theCOMP gene: two are novel and one is recurrent. Short stature of the two patients with novel mutations is mild contrary to the previous observations. Four Japanese patients were identified and followed up for skeletal dysplasias at specialized clinics (Table I). All cases are sporadic. Blood samples were obtained from patients and family members under informed consent. Genomic DNA was extracted from blood samples using the QIAamp DNA Blood mini kit (QIAGEN, Tokyo, Japan). Detection of COMP mutations was performed as described previously [Ikegawa et al., 1998; Mabuchi et al., 2003]. All 19 exons of COMP were screened. All four patients with PSACHwere identified to haveCOMP mutations (Table I). Three types of mutations were identified in exon13, inCLR7ofCOMP. Two of themwerenovelmissense mutations (Fig. 1a,b), and the other (D473del) was recurrent [Briggs et al., 1995; Hecht et al., 1995]. This recurrent mutation is the most common COMP mutation [Deere et al., 1998; Ikegawa et al., 1998]. The missense mutations were not found in 48 normal controls nor in 20 patients with PSACH and 34