Rika Kosaki

Characterization and Mutation Analysis of Human LEFTY A and LEFTY B, Homologues of Murine Genes Implicated in Left-Right Axis Development

Members of the transforming growth factor (TGF)-beta family of cell-signaling molecules have been implicated recently in mammalian left-right (LR) axis development, the process by which vertebrates lateralize unpaired organs (e.g., heart, stomach, and spleen). Two family members, Lefty1 and Lefty2, are expressed exclusively on the left side of the mouse embryo by 8.0 days post coitum. This asymmetry is lost or reversed in two murine models of abnormal LR-axis specification, inversus viscerum (iv) and inversion of embryonic turning (inv). Furthermore, mice homozygous for a Lefty1 null allele manifest LR malformations and misexpress Lefty2. We hypothesized that Lefty mutations may be associated with human LR-axis malformations. We now report characterization of two Lefty homologues, LEFTY A and LEFTY B, separated by approximately 50 kb on chromosome 1q42. Each comprises four exons spliced at identical positions. LEFTY A is identical to ebaf, a cDNA previously identified in a search for genes expressed in human endometrium. The deduced amino acid sequences of LEFTY A and LEFTY B are more similar to each other than to Lefty1 or Lefty2. Analysis of 126 human cases of LR-axis malformations showed one nonsense and one missense mutation in LEFTY A. Both mutations lie in the cysteine-knot region of the protein LEFTY A, and the phenotype of affected individuals is very similar to that typically seen in Lefty1-/- mice with LR-axis malformations.

Imprinting of human GRB10 and its mutations in two patients with Russell-Silver syndrome.

Documentation of maternal uniparental disomy of chromosome 7 in 10% of patients with Russell-Silver syndrome (RSS), characterized by prenatal and postnatal growth retardation and dysmorphic features, has suggested the presence of an imprinted gene on chromosome 7 whose mutation is responsible for the RSS phenotype. Human GRB10 on chromosome 7, a homologue of the mouse imprinted gene Grb10, is a candidate, because GRB10 has a suppressive effect on growth, through its interaction with either the IGF-I receptor or the GH receptor, and two patients with RSS were shown to have a maternally derived duplication of 7p11-p13, encompassing GRB10. In the present study, we first demonstrated that the GRB10 gene is also monoallelically expressed in human fetal brain tissues and is transcribed from the maternally derived allele in somatic-cell hybrids. Hence, human GRB10 is imprinted. A mutation analysis of GRB10 in 58 unrelated patients with RSS identified, within the N-terminal domain of the protein, a P95S substitution in two patients with RSS. In these two cases, the mutant allele was inherited from the mother. The fact that monoallelic GRB10 expression was observed from the maternal allele in this study suggests but does not prove that these maternally transmitted mutant alleles contribute to the RSS phenotype.

Isoform-Specific Imprinting of the Human PEG1/MEST Gene

We thank Mr. Taichi Suzuki, from Tokyo Technical College, for excellent laboratory assistance. This work was supported, in part, by a grant from the Pharmacia-Upjohn Fund for Growth & Development Research.

Molecular pathology of Shprintzen–Goldberg syndrome

Kenjiro Kosaki,* Daisuke Takahashi, Toru Udaka, Rika Kosaki, Morio Matsumoto, Shigeharu Ibe, Takeshi Isobe, Yoko Tanaka, and Takao Takahashi Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan Department of Orthopedic Surgery, Keio University School of Medicine, Tokyo, Japan Department of Clinical Genetics and Molecular Medicine, National Children’s Medical Center, Tokyo, Japan Department of Orthopedic Surgery, Ibaraki Prefectural Rehabilitation Center, Ibaraki, Japan Department of Pediatrics, Ibaraki Children’s Hospital, Ibaraki, Japan Department of Pediatrics, Tokyo Dental College Ichikawa General Hospital, Chiba, Japan

Mutations in B3GALT6, which Encodes a Glycosaminoglycan Linker Region Enzyme, Cause a Spectrum of Skeletal and Connective Tissue Disorders

Proteoglycans (PGs) are a major component of the extracellular matrix in many tissues and function as structural and regulatory molecules. PGs are composed of core proteins and glycosaminoglycan (GAG) side chains. The biosynthesis of GAGs starts with the linker region that consists of four sugar residues and is followed by repeating disaccharide units. By exome sequencing, we found that B3GALT6 encoding an enzyme involved in the biosynthesis of the GAG linker region is responsible for a severe skeletal dysplasia, spondyloepimetaphyseal dysplasia with joint laxity type 1 (SEMD-JL1). B3GALT6 loss-of-function mutations were found in individuals with SEMD-JL1 from seven families. In a subsequent candidate gene study based on the phenotypic similarity, we found that B3GALT6 is also responsible for a connective tissue disease, Ehlers-Danlos syndrome (progeroid form). Recessive loss-of-function mutations in B3GALT6 result in a spectrum of disorders affecting a broad range of skeletal and connective tissues characterized by lax skin, muscle hypotonia, joint dislocation, and spinal deformity. The pleiotropic phenotypes of the disorders indicate that B3GALT6 plays a critical role in a wide range of biological processes in various tissues, including skin, bone, cartilage, tendon, and ligament.

OEIS complex with del(3)(q12.2q13.2)

Most cases of omphalocele-exstrophy-imperforate anusspinal defects (OEIS) complex (cloacal exstrophy) occur sporadically, but there have been several reports of recurrence in siblings [Smith et al., 1992], including monozygotic twins [Koffler et al., 1978; Redman et al., 1981; McLaughlin et al., 1984], suggesting a genetic contribution to the pathogenesis of this condition. In your journal, Thauvin-Robinet et al. [2004] recently reported a case of cloacal exstrophy with a de novo unbalanced translocationbetween the longarmof chromosome 9 and the long arm of chromosomeY, resulting in a 9q34.1-qter deletion [Thauvin-Robinet et al., 2004]. They argued that their case represented the first report of cloacal exstrophy accompanied by an unbalanced chromosomal defect and that their observation supported the notion that genetic defect(s) may be responsible for the pathogenesis of cloacal exstrophy. Here, we report a patientwith cloacal exstrophywho exhibited a de novo deletion at another chromosomal location, 3q12.2-3q13.2.

Identification of COL2A1 mutations in platyspondylic skeletal dysplasia, Torrance type

Platyspondylic lethal skeletal dysplasias (PLSDs) are a heterogeneous group of chondrodysplasias characterised by severe platyspondyly and limb shortening. The most common form of PLSD is thanatophoric dysplasia (TD), which has been divided into two types, TD1 (MIM 187600) and TD2 (MIM 187610). Three other types of PLSD, or TD variants have been distinguished from TD, the San Diego (PLSD-SD; MIM 270230), Torrance (PLSD-T; MIM 151210), and Luton (PLSD-L; MIM 151210) types.1,2 PLSD-L is now considered to be a mild phenotypic variant of PLSD-T. Mutations in the fibroblast growth factor receptor 3 ( FGFR3 ) gene were identified in TD and PLSD-SD,3 but not in PLSD-T and PLSD-L.3,4 PLSD-T is a common subtype of PLSD.2 The radiological characteristics include wafer-like vertebral bodies, severe hypoplasia of the lower ilia, extremely short long bones with ragged metaphyses, and bowing of the radius. Its chondro-osseous histology is characterised by hypercellularity with slightly large chondrocytes in the resting cartilage and normal columnisation with incorporation of cartilage into bone at the chondro-osseous junction.1,2 These radiological and histological findings of the disorder can be used to discriminate it from other lethal or semilethal skeletal dysplasias including TD. Perinatal death is generally considered to be inevitable in PLSD-T. Recently, however, non-lethal phenotypes of the disorder with better ossified vertebral bodies have been proposed, based on the observations of two affected families. One family included an affected mother who survived to adulthood and her affected daughter who died soon after birth,5,6 and the other family included an affected mother and her son, both of whom are living.4 These observations raise the question of whether PLSD-T represents a single entity with a wide clinical spectrum or a heterogeneous group of disorders with superficial radiological similarities. Here we describe two examples of …

Absent inner dynein arms in a fetus with familial hydrocephalus-situs abnormality

We report a family in which a healthy, unrelated couple had a male fetus with bilateral ventriculomegaly, a normal liveborn girl, a hydatidiform molar pregnancy, a female fetus with ventriculomegaly and situs abnormalities, and a male fetus with hydrocephalus, a three‐lobed left lung, and defective tracheal cilia with absent inner dynein arms and a single centriole. A mutation analysis of FOXJ1 and POLL in the last fetus with ciliary defect revealed no mutation within their coding regions. The presence of three affected fetuses of both sexes in a family with phenotypically normal parents suggests that the condition was inherited as an autosomal recessive trait. A thorough evaluation of the thoracic and abdominal situs is recommended before counseling a family of a child with hydrocephalus, because the recognition of situs defects may point to the diagnosis of primary ciliary defect and recurrence risk of 25% for siblings. This figure is much higher than the general risk of 1–2% for siblings of a patient with isolated hydrocephalus.

Donepezil significantly improves abilities in daily lives of female Down syndrome patients with severe cognitive impairment: a 24-week randomized, double-blind, placebo-controlled trial.

Objective: Down syndrome (DS) patients share certain neuropathological features with Alzheimer disease patients. A randomized, double-blind, placebo-controlled study was performed to investigate the efficacy and safety of donepezil, an Alzheimer disease drug, for DS patients. Method: Twenty-one DS patients with severe cognitive impairment were assigned to take donepezil (3 mg daily) or a placebo for 24 weeks, and evaluated for activities in daily lives by concisely modified International Classification of Functioning, Disability and Health (ICF) scaling system. Results: ICF scores significantly increased without any adverse effects in the donepezil group in comparison to those in the placebo control. Among the individual functions tested, there was a dramatic improvement in the global mental functions and in specific mental functions. Conclusions: Donepezil may effectively and safely improve overall functioning of DS patients with severe cognitive impairment.

Position-specific expression of Hox genes along the gastrointestinal tract

ABSTRACT  Hox genes play a critical role in morphogenesis of the early embryo along the anteroposterior axis. In mammals, 39 Hox genes with extensive homology are organized into 13 paralogous groups, forming four clusters on four separate chromosomes. The genes within each cluster are arranged in a 3′ to 5′ direction and expressed in a temporally and spatially coordinated manner along the anteroposterior axis in the vertebrae, limbs and viscera, including the gastrointestinal tract, but little is known about their spatial expression in the adult gastrointestinal tract. We used the quantitative polymerase chain reaction (PCR) intercalater method with SYBR GreenTM to quantify human Hox gene expression in the adult gastrointestinal tract tissue: esophagus, stomach, duodenum, jejunum, ileum, ileocecum, cecum, ascending colon, transverse colon, descending colon and rectum. Hox gene expression was normalized to glyceraldehyde‐3‐phosphate‐dehydrogenase (GAPDH) gene expression. The spatial expression pattern was analyzed by the multivariate method. The expression level of all 39 Hox genes could be measured in a reproducible manner. Genes with higher expression in the foregut‐derived segments tended to have lower expression in hindgut‐derived segments, whereas those with low expression in the former tended to have higher in the latter. Principal components analysis and permax analysis revealed a position‐specific expression pattern of Hox genes along the anteroposterior axis of the adult gastrointestinal tract. The pattern recapitulates the expression pattern in the embryonic gastrointestinal tract. We suggest that Hox genes may play a pivotal role in the position‐specific regenerative process of intestinal epithelial cells.