Isolation and characterization of a candidate gene for Norrie disease

Mutations in the Norrie disease gene: a new mutation in a Japanese family

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A bidirectional YAC walk from the Norrie disease (NDP) locus

The region of Xp between DXS7 and the centromere contains the gene for Norrie disease in addition to the genes for several other ophthalmic disorders. A 650-kb YAC containing the loci MAOA, MAOB, and NDP has been used as the starting point for a bidirectional chromosomal walk. A contig of 16 YACs covering between 2 and 3 Mb has been developed in which the following markers/genes are located (in physical order): Xpter--DXS1201 (256ze5)--DXS6668--DXS228--DXS77--MAOA--++ +MAOB--FR12 (pseudogene)--NDP--DXS6670--RRM2P3--DXS6671--DXS742 --Xcen. Seven new STSs are described both for end clones and for internal Alu PCR products from the contig. The contig contains the breakpoint of the t75-2ma-1b (t75) translocation, close to the 5' end of the MAOB gene.

The promoter of the human monoamine oxidase A gene

Monoamine oxidase (MAO) A (EC 1.4.3.4) oxidizes norepinephrine and serotonin and is expressed in a cell type-specific manner. Evidence that MAO A deficient males in a large Dutch kindred suffer from mild mental retardation and occasional episodes of impulsive-aggressive behavior makes it important to understand how the human MAO A promoter is regulated. Workers in multiple laboratories have isolated and characterized protein-coding sequences of the human MAO A gene and the DNA region where mRNA synthesis is initiated. After summarizing our published findings concerning where transcription of the human MAO A gene is initiated, I summarize representative results of transient expression assays aimed at assessing whether some potential gene regulatory agents affect the expression of luciferase from MAO A promoter reporter constructs when transfected into a mouse L cell line which expresses MAO A. These studies revealed no specific regulatory effects of serum, dexamethasone or a stable cyclic-AMP analogue on the human MAO A promoter introduced.

Mutations in the Norrie disease gene

We report our experience to date in mutation identification in the Norrie disease (ND) gene. We carried out mutational analysis in 26 kindreds in an attempt to identify regions presumed critical to protein function and potentially correlated with generation of the disease phenotype. All coding exons, as well as noncoding regions of exons 1 and 2, 636 nucleotides in the noncoding region of exon 3, and 197 nucleotides of 5' flanking sequence, were analyzed for single-strand conformation polymorphisms (SSCP) by polymerase chain reaction (PCR) amplification of genomic DNA. DNA fragments that showed altered SSCP band mobilities were sequenced to locate the specific mutations. In addition to three previously described submicroscopic deletions encompassing the entire ND gene, we have now identified 6 intragenic deletions, 8 missense (seven point mutations, one 9-bp deletion), 6 nonsense (three point mutations, three single bp deletions/frameshift) and one 10-bp insertion, creating an expanded repeat in the 5' noncoding region of exon 1. Thus, mutations have been identified in a total of 24 of 26 (92%) of the kindreds we have studied to date. With the exception of two different mutations, each found in two apparently unrelated kindreds, these mutations are unique and expand the genotype database. Localization of the majority of point mutations at or near cysteine residues, potentially critical in protein tertiary structure, supports a previous protein model for norrin as member of a cystine knot growth factor family (Meitinger et al., 1993). Genotype-phenotype correlations were not evident with the limited clinical data available, except in the cases of larger submicroscopic deletions associated with a more severe neurologic syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel mutation at the initiation codon in the Norrie disease gene in two Japanese families

We have identified a new mutation of Norrie disease (ND) gene in two Japanese males from unrelated families; they showed typical ocular features of ND but no mental retardation or hearing impairment. A mutation was found in both patients at the initiation codon of exon 2 of the ND gene (ATG to GTG), with otherwise normal nucleotide sequences. Their mothers had the normal and mutant types of the gene, which was expected for heterozygotes of the disease. The mutation of the initiation codon would cause the failure of ND gene expression or a defect in translation thereby truncating the amino terminus of ND protein. In view of the rarity and marked heterogeneity of mutations in the ND gene, the present apparently unrelated Japanese families who have lived in the same area for over two centuries presumably share the origin of the mutation.

Molecular genetic approaches to the study of human craniofacial dysmorphologies

Craniofacial dysmorphologies are common, ranging from simple facial disfigurement to complex malformations involving the whole head. With the advent of gene mapping and cloning techniques, the genetic element of both simple and complex human craniofacial dysmorphologies can be investigated. For many of the dysmorphic syndromes, it is possible to find families that display a particular phenotype in either an autosomal dominant, recessive, or X-linked manner. This article focuses on a subgroup of craniofacial dysmorphologies, covering these three main inheritance patterns, that are being studied using molecular biology techniques: DiGeorge syndrome, Treacher Collins syndrome, Greig cephalopolysyndactyly syndrome, acrocallosal syndrome, amelogenesis imperfecta, and X-linked cleft palate with ankyloglossia. Once the mutated or deleted gene or genes for each syndrome have been cloned, patterns of normal and abnormal craniofacial development should be elucidated. This should enhance both diagnosis and treatment of these common and disfiguring disorders.

The molecular biology of Norrie's disease

The Norrie's disease gene has been accurately located on the short arm of the X chromosome. The methodology underlying this achievement and the structure of the three-exon gene is described in this review article. The clinical implications of these recent advances are discussed. Allelic variants of Norrie's disease and the phenomenon of females affected by X-linked disease are also discussed.

Psychiatric genetics. Misbehaving monoamine oxidase gene

A nonsense mutation in the X-linked monoamine oxidase A gene has been associated with sex-linked aggressive behaviour.

Molecular modelling of the Norrie disease protein predicts a cystine knot growth factor tertiary structure

The X-lined gene for Norrie disease, which is characterized by blindness, deafness and mental retardation has been cloned recently. This gene has been thought to code for a putative extracellular factor; its predicted amino acid sequence is homologous to the C-terminal domain of diverse extracellular proteins. Sequence pattern searches and three-dimensional modelling now suggest that the Norrie disease protein (NDP) has a tertiary structure similar to that of transforming growth factor beta (TGF beta). Our model identifies NDP as a member of an emerging family of growth factors containing a cystine knot motif, with direct implications for the physiological role of NDP. The model also sheds light on sequence related domains such as the C-terminal domain of mucins and of von Willebrand factor.

X-arrestin: a new retinal arrestin mapping to the X chromosome

We have been using a differential cDNA cloning approach to isolate human retina-specific and retina-enriched genes [1]. A 1,314 bp cDNA was isolated by this approach, representing a highly retina-specific message encoding a 388 amino acid protein showing 58%, 50%, and 49% homology to bovine beta-arrestin, and bovine and human retinal arrestin (S-antigen), respectively. Chromosomal mapping localized this new arrestin gene to the proximal long arm of the X chromosome, hence it was named X-arrestin. In situ hybridization demonstrated its expression in the inner and outer segments and the inner plexiform regions of the retina.

A mutation in the Norrie disease gene (NDP) associated with X-linked familial exudative vitreoretinopathy

Familial exudative vitreoretinopathy (FEVR) is a hereditary disorder characterized by an abnormality of the peripheral retina. Both autosomal dominant (adFEVR) and X-linked (XLFEVR) forms have been described, but the biochemical defect(s) underlying the symptoms are unknown. Molecular analysis of the Norrie gene locus (NDP) in a four generation FEVR family (shown previously to exhibit linkage to the X-chromosome markers DXS228 and MAOA (Xp11.4-p11.3)) reveals a missense mutation in the highly conserved region of the NDP gene, which caused a neutral amino acid substitution (Leu124Phe), was detected in all of the affected males, but not in the unaffected family members, nor in normal controls. The observations suggest that phenotypes of both XLFEVR and Norrie disease can result from mutations in the same gene.

Recent developments in certain X-linked genetic eye disorders

Over the past few years, genetic diseases of the ocular system have become very active and fast-growing research areas in the vision field. The rapid development of the recombinant DNA techniques together with somatic cell genetics, during the last two decades has fueled this progress. As a result, many genetic disease genes have been localized in the human chromosome and several of them have been isolated and characterized. These and other studies have profoundly enriched our basic understanding of genetic eye disorders. Although gene replacement therapy, prenatal diagnosis and carrier detection have not been extensively tried for genetic eye diseases, such attempts will now be feasible. Molecular analyses made it clear that there are many challenging problems that need attention. This report highlights some of these initial developments, particularly on the X-linked major genetic eye diseases. In order to help the beginners and general audience, a brief description of the clinical pathology and the molecular probes used to locate the genetic defects of certain disorders are presented. Disorders are arranged according to their linkage from telomere to telomere on the chromosome to give a coherent structure. It is hoped that this information is useful and of general interest for the beginners, established investigators and ophthalmologists.

The modular architecture of a new family of growth regulators related to connective tissue growth factor

Recently, several groups have characterized and sequenced members of a new family of growth regulators (originally called cef10, connective tissue growth factor, fisp-12, cyr61, or, alternatively, beta IG-M1 and beta IG-M2), all of which belong to immediate-early genes expressed after induction by growth factors or certain oncogenes. Sequence analysis of this family revealed the presence of four distinct modules. Each module has homologues in other extracellular mosaic proteins such as Von Willebrand factor, slit, thrombospondins, fibrillar collagens, IGF-binding proteins and mucins. Classification and analysis of these modules suggests the location of binding regions and, by analogy to better characterized modules in other proteins, sheds some light onto the structure of this new family.

Methods for finding genes. A major rate-limiting step in positional cloning

Identification of transcribed sequences from within genomic regions has been a major rate-limiting step in the pursuit of genes involved in many human genetic diseases. Early efforts focused primarily on screening of cDNA libraries, identification of evolutionarily conserved sequences, and northern blot hybridization. In recent years, several innovative techniques for gene identification have been devised. These techniques expand the size of the genomic region capable of being scanned for genes, while also allowing detection of genes regardless of their expression patterns. This article reviews several new and older techniques and discusses the advantages and limitations of each.

Inversion (X)(p11.4q22) associated with Norrie disease in a four generation family

We report on a 4-generation family in which Norrie disease occurs together with a pericentric inversion of the X chromosome in all affected males and carrier females. The breakpoint in the short arm of the X chromosome appears to be at the purported location of the Norrie disease gene. This is the second report of an association between Norrie disease and a chromosome aberration involving Xp11, and the first report of a specific gene disruption, thus physical gene location, due to a pericentric chromosome inversion.

In-utero diagnosis of Norrie disease by ultrasonography

Obstetric ultrasonography of an obligate Norrie disease carrier revealed bilateral retinal detachments in a third trimester male fetus. Postnatal examination confirmed the diagnosis of Norrie disease. DNA linkage analysis with the markers L1.28 and MAO had been uninformative for this family. This report suggests that retinal detachment occurs late in the gestation of the affected fetus.

Genome analysis and the human X chromosome

A unified genetic, physical, and functional map of the human X chromosome is being built through a concerted, international effort. About 40 percent of the 160 million base pairs of the X chromosome DNA have been cloned in overlapping, ordered contigs derived from yeast artificial chromosomes. This rapid progress toward a physical map is accelerating the identification of inherited disease genes, 26 of which are already cloned and more than 50 others regionally localized by linkage analysis. This article summarizes the mapping strategies now used and the impact of genome research on the understanding of X chromosome inactivation and X-linked diseases.

The autosomal dominant dystonias

Dystonia is a term used to describe a specific set of abnormal movements that can occur as a symptom of a variety of neurologic disorders, but also as a disease entity in its own right. This review focuses on the primary dystonias and delineates the genetic contribution to these disorders. Included is a description of the well recognized forms of primary dystonias which manifest autosomal dominant inheritance, especially the "classic" type of early onset, generalized torsion dystonia, but also other clinically distinct forms such as myoclonic dystonia, paroxysmal dystonia, and DOPA-responsive dystonia. Also, a summary of the molecular genetic studies pertinent to these disorders and a discussion of the implications of recent genetic research for delineating the wide spectrum of this phenotypically and genetically heterogeneous group of diseases are forthcoming.

Norrie disease is caused by mutations in an extracellular protein resembling C-terminal globular domain of mucins

A candidate gene for Norrie disease, an X-linked disorder characterized by blindness, deafness and mental disturbances, was recently isolated and found to contain microdeletions in numerous patients. No strong homologies were identified. By studying the number and spacing of cysteine residues, we now detect homologies between the Norrie gene product and a C-terminal domain which is common to a group of proteins including mucins. Three newly-characterized missense mutations, replacing evolutionarily conserved cysteines or creating new cysteine codons, emphasize the functional importance of these sites. These findings and the clinical features of this disorder suggest a possible role for the Norrie gene in neuroectodermal cell-cell interaction.

Organization of the human monoamine oxidase genes and long-range physical mapping around them

A 265-kb yeast artificial chromosome containing sequences for human monoamine oxidase A and B (MAO-A and MAO-B) genes has been characterized. These two genes are localized within a region of about 240 kb and are arranged in a tail-to-tail configuration, with the 3' coding sequences separated by about 50 kb. A region about 2.5 Mb around the MAO loci was mapped by pulsed-field gel electrophoresis (PFGE). Comparisons between the restriction maps derived from the YAC and the long-range map derived from genomic digestions were in general agreement. The important features identified include a CpG island at the 5' end of the MAO-A and MAO-B genes, respectively. The combined information supports the order of markers within this region to be DXS77-DXS7-MAOA-MAOB.