The Norrie disease gene maps to a 150 kb region on chromosome Xp11.3

Association between genetic polymorphisms of synaptophysin (SYP) gene and attention deficit hyperactivity disorder in Korean subjects

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is a common childhood neurodevelopmental disorder, and the prevalence of ADHD among Korean children has attained about 8.5%. Various genetic factors can contribute to the etiology of the disease. Synaptophysin (SYP) regulates neurotransmitter release and synaptic plasticity. According to previous studies, several genetic polymorphisms on SYP were risk factors for ADHD.

OBJECTIVE

We investigated the effect of the SYP gene polymorphisms (rs2293945 and rs3817678) on ADHD in Korean children.

METHODS

In this study, we examined the case-control study in 150 ADHD cases and 322 controls. The genotyping of SYP gene polymorphisms was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Significant associations in the genotype and genetic models of SYP rs2293945 polymorphism between girls with ADHD and control girls were found. The girls with ADHD having the C/T genotype were significantly associated with ADHD. In the dominant model of rs3817678, C/T + T/T genotypes were significantly associated with ADHD. The haplotype analyses showed significant associations from haplotypes of rs2293945 T-rs3817678 G and rs2293945 C-rs3817678 A.

CONCLUSION

Our results imply that the SYP rs2293945 C/T polymorphism in female participants may provide a possible effect on the genetic etiology of ADHD.

Endolymphatic Hydrop Phenotype in Familial Norrie Disease Caused by Large Fragment Deletion of NDP

Norrie disease (ND; OMIM 310600), a rare X-linked recessive genetic disorder, is characterized by congenital blindness and occasionally, sensorineural hearing loss, and developmental delay. The congenital blindness of ND patients is almost untreatable; thus, hearing is particularly important for them. However, the mechanism of hearing loss of ND patients is unclear, and no good treatment is available except wearing hearing-aid. Therefore, revealing the mechanism of hearing loss in ND patients and exploring effective treatment methods are greatly important. In addition, as a serious monogenic genetic disease, convenient gene identification method is important for ND patients and their family members, as well as prenatal diagnosis and preimplantation genetic diagnosis to block intergenerational transmission of pathogenic genes. In this study, a Norrie family with two male patients was reported. This pedigree was ND caused by large fragment deletion of NDP (norrin cystine knot growth factor NDP) gene. In addition to typical severe ophthalmologic and audiologic defects, the patients showed new pathological features of endolymphatic hydrops (EH), and they also showed acoustic nerves abnormal as described in a very recent report. PCR methods were developed to analyze and diagnose the variation of the family members. This study expands the understanding of the clinical manifestation and pathogenesis of ND and provides a new idea for the treatment of patients in this family and a convenient method for the genetic screen for this ND family.

Case report: A case of Norrie disease due to deletion of the entire coding region of NDP gene

Purpose

Norrie disease is a rare X-linked recessive vitreoretinopathy. Variants of the NDP gene are associated with this condition. This case reports aims to demonstrate the variations of clinical presentations and exam findings of this disease.

Observations

A retrospective chart review of the patient's ocular and systemic findings and imaging results was performed. The patient had received genetic testing, including mutational analysis of targeted genes associated with retrolental masses. The patient had a comprehensive eye exam for bilateral leukocoria, demonstrating large retrolental masses, anterior polar cataracts, stretched ciliary processes, and roving eye movements. B-scan ultrasonography and magnetic resonance imaging indicated total, funnel-shaped retinal detachments, which is a unique retinal configuration in Norrie disease. Genetic testing confirmed deletion of the coding region of all three exons in the NDP gene, which confirmed Norrie disease. He has not shown any extraocular involvement to date.

Conclusions and Importance

This is a case demonstrating the association between deletion of the coding region NDP gene and Norrie disease. The phenotypical variation of this disease warrants further studies of genotype-phenotype correlations and mutations of the NDP gene.

The neurobiology of human aggressive behavior: Neuroimaging, genetic, and neurochemical aspects

In modern societies, there is a strive to improve the quality of life related to risk of crimes which inevitably requires a better understanding of brain determinants and mediators of aggression. Neurobiology provides powerful tools to achieve this end. Pre-clinical and clinical studies show that changes in regional volumes, metabolism-function and connectivity within specific neural networks are related to aggression. Subregions of prefrontal cortex, insula, amygdala, basal ganglia and hippocampus play a major role within these circuits and have been consistently implicated in biology of aggression. Genetic variations in proteins regulating the synthesis, degradation, and transport of serotonin and dopamine as well as their signal transduction have been found to mediate behavioral variability observed in aggression. Gene-gene and gene-environment interactions represent additional important risk factors for aggressiveness. Considering the social burden of pathological forms of aggression, more basic and translational studies should be conducted to accelerate applications to clinical practice, justice courts, and policy making.

Monoamino oxidase alleles correlate with the presence of essential hypertension among hypogonadic patients

Background

Monoamine oxidase (MAO) activity has been traditionally implicated in blood pressure through its effects on biogenic amine levels such as catecholamines, serotonin, and dopamine. Nowadays, this role is considered relegated to side‐effects such as orthostatic hypotension and/or hypertensive crisis derived from MAO‐inhibitory treatments in patients with psychiatric disease.

Methods

In the present work we have found an association between a polymorphic variant of MAOB gene and arterial hypertension in obese hypogonadic patients. The study cases comprised a series of 219 nondiabetic males with a body mass index ≥30 kg/m² and aged <45 years. Hypogonadism was defined as subnormal testosterone concentrations, when free testosterone values ranged <65 pg/ml.

Results

MAOB rs3027452‐A allele carriers were significantly over‐represented among hypertensive (HT) patients (25.49%) in comparison to either the non‐HT patients (10%, OR = 3.079 CI₉₅ [1.364–6.952], p = .005, Chi‐square test) and the control population series of nonobese nor hypogonadic males (also 10%, p = .003 Chi‐square test). Upon adjusted, an independent association was shown with the hypogonadic group with hypertension when compared with nonhypertensive hypogonadics (Beta = 3.653, p = .005). When quantitative analysis was performed, hypertensive patients harboring rs3027452‐A allele showed higher systolic blood pressure values (p = .038, Mann–Whitney U‐test) as well as an increased Systolic‐Diastolic range despite following HT treatment (∆mmHg 54 vs. 48 for rs3027452‐A and rs3027452‐G respectively, p‐value .019, Mann–Whitney U‐test). Previous studies on MAOB revealed that rs3027452‐A allele has been correlated to a lower activity of the enzyme, what gives a functional evidence over our observation.

Conclusion

If this result could be extrapolated to other hypertensive patient groups, it would implicate a review of the markers and therapeutic targets on human hypertension.

Introgression of regulatory alleles and a missense coding mutation drive plumage pattern diversity in the rock pigeon

Birds and other vertebrates display stunning variation in pigmentation patterning, yet the genes controlling this diversity remain largely unknown. Rock pigeons (Columba livia) are fundamentally one of four color pattern phenotypes, in decreasing order of melanism: T-check, checker, bar (ancestral), or barless. Using whole-genome scans, we identified NDP as a candidate gene for this variation. Allele-specific expression differences in NDP indicate cis-regulatory divergence between ancestral and melanistic alleles. Sequence comparisons suggest that derived alleles originated in the speckled pigeon (Columba guinea), providing a striking example of introgression. In contrast, barless rock pigeons have an increased incidence of vision defects and, like human families with hereditary blindness, carry start-codon mutations in NDP. In summary, we find that both coding and regulatory variation in the same gene drives wing pattern diversity, and post-domestication introgression supplied potentially advantageous melanistic alleles to feral populations of this ubiquitous urban bird.

Wnt/β-catenin signaling plays an ever-expanding role in stem cell self-renewal, tumorigenesis and cancer chemoresistance

Wnt signaling transduces evolutionarily conserved pathways which play important roles in initiating and regulating a diverse range of cellular activities, including cell proliferation, calcium homeostasis, and cell polarity. The role of Wnt signaling in controlling cell proliferation and stem cell self-renewal is primarily carried out through the canonical pathway, which is the best-characterized the multiple Wnt signaling branches. The past 10 years has seen a rapid expansion in our understanding of the complexity of this pathway, as many new components of Wnt signaling have been identified and linked to signaling regulation, stem cell functions, and adult tissue homeostasis. Additionally, a substantial body of evidence links Wnt signaling to tumorigenesis of cancer types and implicates it in the development of cancer drug resistance. Thus, a better understanding of the mechanisms by which dysregulation of Wnt signaling precedes the development and progression of human cancer may hasten the development of pathway inhibitors to augment current therapy. This review summarizes and synthesizes our current knowledge of the canonical Wnt pathway in development and disease. We begin with an overview of the components of the canonical Wnt signaling pathway and delve into the role this pathway has been shown to play in stemness, tumorigenesis, and cancer drug resistance. Ultimately, we hope to present an organized collection of evidence implicating Wnt signaling in tumorigenesis and chemoresistance to facilitate the pursuit of Wnt pathway modulators that may improve outcomes of cancers in which Wnt signaling contributes to aggressive disease and/or treatment resistance.

Interactions between MAOA and SYP polymorphisms were associated with symptoms of attention-deficit/hyperactivity disorder in Chinese Han subjects

As candidate genes of attention--deficit/hyperactivity disorder (ADHD), monoamine oxidase A (MAOA), and synaptophysin (SYP) are both on the X chromosome, and have been suggested to be associated with the predominantly inattentive subtype (ADHD-I). The present study is to investigate the potential gene-gene interaction (G × G) between rs5905859 of MAOA and rs5906754 of SYP for ADHD in Chinese Han subjects. For family-based association study, 177 female trios were included. For case-control study, 1,462 probands and 807 normal controls were recruited. The ADHD Rating Scale-IV (ADHD-RS-IV) was used to evaluate ADHD symptoms. Pedigree-based generalized multifactor dimensionality reduction (PGMDR) for female ADHD trios indicated significant gene interaction effect of rs5905859 and rs5906754. Generalized multifactor dimensionality reduction (GMDR) indicated potential gene-gene interplay on ADHD RS-IV scores in female ADHD-I. No associations were observed in male subjects in case-control analysis. In conclusion, our findings suggested that the interaction of MAOA and SYP may be involved in the genetic mechanism of ADHD-I subtype and predict ADHD symptoms.

Association between SYP with attention-deficit/hyperactivity disorder in Chinese Han subjects: differences among subtypes and genders

Dysfunction of neurotransmitters has been suggested to be involved in the etiology of attention-deficit/hyperactivity disorder (ADHD). Hence, genes encoding proteins involved in the vesicular release process of those neurotransmitters are attractive candidates in ADHD genetics. One of these genes is SYP, which encodes synaptophysin, a protein known to participate in regulating neurotransmitter release and synaptic plasticity. Several studies have reported an association between SYP and ADHD, but more work is needed to refine the association. In the present study, we attempt to investigate their association in Chinese Han subjects by family-based and case-control studies. Transmission disequilibrium tests (TDTs) in 1112 trios found significant association between SYP and the predominantly inattentive subtype (ADHD-I), especially for males with ADHD-I, both from single nucleotide polymorphism (SNP) and haplotypic analyses. Chi-square tests in 1682 ADHD probands and 957 comparison subjects indicated possible association of SYP with female ADHD and female ADHD-I. However, the associated alleles and haplotypes between males and females were reversed. In conclusion, our results suggested that SYP may be primarily associated with ADHD-I and its genetic mechanism may be gender-specific. Thus, it is necessary to take subtype and gender into account in ADHD genetic studies.

Unilateral sporadic retinal dysplasia: results of histopathologic, immunohistochemical, chromosomal, genetic, and VEGF-A analyses

PURPOSE

To describe new findings in a case of unilateral retinal dysplasia.

METHODS

Histopathologic evaluation of an enucleated globe and analysis with immunohistochemical probes, karyotyping, and genetic analysis for the Norrie gene, and aqueous assay for vascular endothelial growth factor A (VEGF-A).

RESULTS

Histopathological examination of the globe revealed retinal dysplasia with pseudorosette formation, abnormal or absent retinal nuclear lamination, a paucity of disorganized retinal microvasculature, retinal infoldings, advanced gliosis, persistent hyperplastic vitreous, exuberant neovascularization of the vitreous, and iris neovascularization (identical to the findings observed in bilateral Norrie disease). Immunohistochemistry disclosed GFAP-positive and GLUT-1-positive gliosis and retinal and persistent hyperplastic vitreous microvessels that were CD34-positive and GLUT-1-negative. Ki-67-positive retinal cells were polarized toward the subretinal space and absent in the retinal invaginations and pseudorosettes. A normal karyotype was found, and DNA sequencing revealed no known mutation in the region of the Norrie gene (NDP) in sputum or retinal DNA. Aqueous obtained immediately after enucleation contained an exceptionally high concentration of VEGF-A (4.5 ng/mL).

CONCLUSIONS

Despite the failure to find an abnormal NDP allele, other unexplored NDP regions, an undetected defect restricted to retinal tissues, or an autosomal mutation coupled with disrupted signaling pathways may be responsible for the condition. High aqueous VEGF-A suggests that this cytokine may play a role in pathogenesis in conjunction with other pathways.

Contiguous deletion of theNDP,MAOA,MAOB, andEFHC2 genes in a patient with Norrie disease, severe psychomotor retardation and myoclonic epilepsy

Norrie disease (ND) is an X-linked disorder, inherited as a recessive trait that, therefore, mostly affects males. The gene responsible for ND, called NDP, maps to the short arm of chromosome X (Xp11.4-p11.3). We report here an atypical case of ND, consisting of a patient harboring a large submicroscopic deletion affecting not only the NDP gene but also the MAOA, MAOB, and EFHC2 genes. Microarray comparative genomic hybridization (CGH) analysis showed that 11 consecutive bacterial artificial chromosome (BAC) clones, mapping around the NDP gene, were deleted. These clones span a region of about 1 Mb on Xp11.3. The deletion was ascertained by fluorescent in situ hybridization (FISH) analysis with different BAC clones located within the region. Clinical features of the proband include bilateral retinal detachment, microcephaly, severe psychomotor retardation without verbal language skills acquired, and epilepsy. The identification and molecular characterization of this case reinforces the idea of a new contiguous gene syndrome that would explain the complex phenotype shared by atypical ND patients.

Norrie disease gene mutation in a large Costa Rican kindred with a novel phenotype including venous insufficiency

A large Costa Rican kindred has been identified with 15 males affected with congenital blindness, progressive bearing loss, and venous insufficiency. Due to ophthalmological and audio-otological findings, including bilateral retinal dysplasia and detachment, progressive bilateral sensorineural hearing loss, and an X-linked pattern of inheritance, a tentative diagnosis of Norrie disease was considered. However, venous insufficiency is a clinical finding not reportedly associated with Norrie disease. Genetic linkage analysis using microsatellite repeat markers demonstrated linkage to Xp11.23-11.4 (z = 2.723 at theta = 0.0). A candidate gene approach using the Norrie disease gene (NDP), which maps to Xp11.3, revealed a point mutation in the third exon resulting in substitution of phenylalanine for leucine at position 61. The precise function of the gene product, norrin, has yet to be elucidated; however, it has been postulated to be involved in the regulation of neural cell differentiation and proliferation, although hypotheses have been considered for its role in vascular development in the eye. The finding of a mutation in NDP in association with peripheral vascular disease may provide valuable insight into the potential role of this gene in cellular processes.

Isolated Norrie disease in a female caused by a balanced translocation t(X,6)

This is the second report of Norrie disease in a female patient with a de-novo balanced translocation t(X,6) with breakpoint at the location of the Norrie gene. At the age of 3 months, a girl was referred for suspected congenital glaucoma. The right eye was microphthalmic and ultrasonography was compatible with persistent hyperplasia of the primary vitreous. The left eye was also microphthalmic. The left cornea was larger than the right. The anterior chamber was virtual and leukocoria was evident. The eye felt hard digitally. Ultrasonography indicated an organized retinal detachment. The pathologic findings are reported and are compatible with Norrie disease.

Peripheral retinopathy in offspring of carriers of Norrie disease gene mutations. Possible transplacental effect of abnormal Norrin

BACKGROUND

The Norrie disease (ND) gene (Xp11.3) (McKusick 310600) consists of one untranslated exon and two exons partially translated as the Norrie disease protein (Norrin). Norrin has sequence homology and computer-predicted tertiary structure of a growth factor containing a cystine knot motif, which affects endothelial cell migration and proliferation. Norrie disease (congenital retinal detachment), X-linked primary retinal dysplasia (congenital retinal fold), and X-linked exudative vitreoretinopathy (congenital macular ectopia) are allelic disorders.

METHODS

Blood was drawn for genetic studies from members of two families to test for ND gene mutations. Sixteen unaffected family members were examined ophthalmologically. If any retinal abnormality were identified, fundus photography and fluorescein angiography was performed.

RESULTS

Family A had ND (R109stp), and family B had X-linked exudative vitreoretinopathy (R121L). The retinas of 11 offspring of carrier females were examined: three of seven carrier females, three of three otherwise healthy females, and one of one otherwise healthy male had peripheral inner retinal vascular abnormalities. The retinas of five offspring of affected males were examined: none of three carrier females and none of two otherwise healthy males had this peripheral retinal finding.

CONCLUSIONS

Peripheral inner retinal vascular abnormalities similar to regressed retinopathy of prematurity were identified in seven offspring of carriers of ND gene mutations in two families. These ophthalmologic findings, especially in four genetically healthy offspring, strongly support the hypothesis that abnormal Norrin may have an adverse transplacental (environmental) effect on normal inner retinal vasculogenesis.

Mutational analysis of the human MAOA gene

The monoamine oxidases (MAO-A and MAO-B) are the enzymes primarily responsible for the degradation of amine neurotransmitters, such as dopamine, norepinephrine, and serotonin. Wide variations in activity of these isozymes have been reported in control humans. The MAOA and MAOB genes are located next to each other in the p11.3-11.4 region of the human X chromosome. Our recent documentation of an MAO-A-deficiency state, apparently associated with impulsive aggressive behavior in males, has focused attention of genetic variations in the MAOA gene. In the present study variations in the coding sequence of the MAOA gene were evaluated by RT-PCR, SSCP, and sequencing a mRNA or genomic DNA in 40 control males with > 100-fold variations of MAO-A activity, as measured in cultured skin fibroblasts. Remarkable conservation of the coding sequence was found with only 5 polymorphisms observed. All but one of these were in the third codon position and thus did not alter the deduced amino acid sequence. The one amino acid alteration observed, lys --> arg, was neutral and should not affect the structure of the protein. This study demonstrates high conservation of coding sequence in the human MAOA gene in control males, and provides primer sets which can be used to search genomic DNA for mutations in this gene in males with neuropsychiatric conditions.

Specific genetic deficiencies of the A and B isoenzymes of monoamine oxidase are characterized by distinct neurochemical and clinical phenotypes

Monoamine oxidase (MAO) exists as two isoenzymes and plays a central role in the metabolism of monoamine neurotransmitters. In this study we compared the neurochemical phenotypes of previously described subjects with genetically determined selective lack of MAO-A or a lack of both MAO-A and MAO-B with those of two subjects with a previously described X chromosome microdeletion in whom we now demonstrate selective MAO-B deficiency. Mapping of the distal deletion breakpoint demonstrates its location in intron 5 of the MAO-B gene, with the deletion extending proximally into the Norrie disease gene. In contrast to the borderline mental retardation and abnormal behavioral phenotype in subjects with selective MAO-A deficiency and the severe mental retardation in patients with combined MAO-A/MAO-B deficiency and Norrie disease, the MAO-B-deficient subjects exhibit neither abnormal behavior nor mental retardation. Distinct neurochemical profiles characterize the three groups of MAO-deficient patients. In MAO-A-deficient subjects, there is a marked decrease in deaminated catecholamine metabolites and a concomitant marked elevation of O-methylated amine metabolites. These neurochemical changes are only slightly exaggerated in patients with combined lack of MAO-A and MAO-B. In contrast, the only biochemical abnormalities detected in subjects with the MAO-B gene deletion are a complete absence of platelet MAO-B activity and an increased urinary excretion of phenylethylamine. The differences in neurochemical profiles indicate that, under normal conditions, MAO-A is considerably more important than MAO-B in the metabolism of biogenic amines, a factor likely to contribute to the different clinical phenotypes.

An animal model for Norrie disease (ND): gene targeting of the mouse ND gene

In order to elucidate the cellular and molecular processes which are involved in Norrie disease (ND), we have used gene targeting technology to generate ND mutant mice. The murine homologue of the ND gene was cloned and shown to encode a polypeptide that shares 94% of the amino acid sequence with its human counterpart. RNA in situ hybridization revealed expression in retina, brain and the olfactory bulb and epithelium of 2 week old mice. Hemizygous mice carrying a replacement mutation in exon 2 of the ND gene developed retrolental structures in the vitreous body and showed an overall disorganization of the retinal ganglion cell layer. The outer plexiform layer disappears occasionally, resulting in a juxtaposed inner and outer nuclear layer. At the same regions, the outer segments of the photoreceptor cell layer are no longer present. These ocular findings are consistent with observations in ND patients and the generated mouse line provides a faithful model for study of early pathogenic events in this severe X-linked recessive neurological disorder.

A fetus with an X;1 balanced reciprocal translocation and eye disease

A 19 week female fetus is described with a de novo X;1 reciprocal balanced translocation, with the breakpoint on the X chromosome at Xp11.4, and eye pathology consistent with the early stages of Norrie disease. The fetus seems to be an example of a female manifesting an X linked recessive disease, and it was shown that the normal X chromosome was completely inactivated in all cells examined. Norrie disease has been mapped to Xp11.3, and fluorescence in situ hybridisation studies showed that the Norrie disease gene had not obviously been disrupted. Mutation screening by SSCP analysis showed no aberrant fragments of the coding region of the gene. Several eye disease genes map to the same region of the X chromosome, but are excluded on grounds of pathology. One possibility is that this fetus has a Norrie-like eye disease caused by the mutation of another gene located at Xp11.4. If this is so, there are implications for prenatal diagnosis.

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)

Applications of heteroduplex analysis for mutation detection in disease genes

Double-stranded heteroduplex molecules that form between a mutant and wild-type DNA strand are often distinguished from homoduplex molecules upon gel electrophoresis. This method, heteroduplex analysis (HA), can be performed rapidly without radioisotopes or specialized equipment. Modifications and enhancements of the HA method have been developed that increase the sensitivity of detection of single-base pair alterations.

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.

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.

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.