Nance-Horan syndrome protein, NHS, associates with epithelial cell junctions

Genetic Variants in Protein Tyrosine Phosphatase Non-Receptor Type 23 Are Responsible for Mesiodens Formation

A mesiodens is a supernumerary tooth located in the midline of the premaxilla. To investigate the genetic cause of mesiodens, clinical and radiographic examination were performed on 23 family members of a two-generation Hmong family. Whole exome sequencing (WES) or Sanger sequencing were performed in 22 family members and two unrelated Thai patients with mesiodens. WES in the Hmong family revealed a missense mutation (c.1807G>A;p.Glu603Lys) in PTPN23 in seven affected members and six unaffected members. The mode of inheritance was autosomal dominance with incomplete penetrance (53.84%). Two additional mutations in PTPN23, c.2248C>G;p.Pro750Ala and c.3298C>T;p.Arg1100Cys were identified in two unrelated patients with mesiodens. PTPN23 is a regulator of endosomal trafficking functioning to move activated membrane receptors, such as EGFR, from the endosomal sorting complex towards the ESCRT-III complex for multivesicular body biogenesis, lysosomal degradation, and subsequent downregulation of receptor signaling. Immunohistochemical study and RNAscope on developing mouse embryos showed broad expression of PTPN23 in oral tissues, while immunofluorescence showed that EGFR was specifically concentrated in the midline epithelium. Importantly, PTPN23 mutant protein was shown to have reduced phosphatase activity. In conclusion, mesiodens were associated with genetic variants in PTPN23, suggesting that mesiodens may form due to defects in endosomal trafficking, leading to disrupted midline signaling.

Short Stature Syndromes: Case Series from India

Syndromes causing short stature include Noonan syndrome (NS), Williams syndrome, and Silver-Russell syndrome (SRS). SRS is a primordial dwarfism with genetic heterogeneity. The SRS children present with prenatal growth retardation, neonatal hypoglycemia, feeding difficulties, physical asymmetry, with scoliosis and cardiac defect in some cases. The incidence is up to 1 in 100,000. Uniparental disomy, methylation abnormalities, and variants in some genes have been found underlying such phenotype. Growth hormone therapy has been used to improve the height gain in these patients. NS has genetic heterogeneity and most patients present with short stature with or without cardiac defect. Multiple genetic variants, mostly autosomal dominant, contribute to the phenotype. With the availability of next-generation sequencing, more and more genetic disorders causing short stature are being identified in different ethnic populations like Kabuki syndrome and Nance-Horan syndrome. Here, we present some cases of SRS and other additional syndromes with dysmorphism seen in past 5 years.

Genetic Associations with Immune-mediated Outcomes after Allogeneic Hematopoietic Cell Transplantation

A recipient variant correlated with DPB1 expression is associated with the risks of GVHD and relapse after unrelated HCT.

Larger cohorts would be needed to detect other genotypic associations with aGVHD, cGVHD, and relapse after allogeneic HCT.

Previous studies have identified more than 200 genetic variants associated with acute or chronic graft-versus-host disease (aGVHD; cGVHD) or recurrent malignancy after allogeneic hematopoietic cell transplantation (HCT). We tested these candidate donor and recipient variants in a cohort of 4270 HCT recipients of European ancestry and in subcohorts of 1827 sibling and 1447 unrelated recipients who had 10/10 HLA-A, B, C, DRB1, and DQB1-matched donors. We also carried out a genome-wide association study (GWAS) for these same outcomes. The discovery and replication analysis of candidate variants identified a group of closely linked recipient HLA-DPB1 single-nucleotide polymorphisms (SNPs) associated with an increased risk of aGVHD and a corresponding decreased risk of recurrent malignancy after unrelated HCT. These results reflect a correlation with the level of HLA-DPB1 expression previously shown to affect the risks of aGVHD and relapse in unrelated recipients. Our GWAS identified an association of cGVHD with a locus of X-linked recipient intron variants in NHS, a gene that regulates actin remodeling and cell morphology. Evaluation of this association in a second replication cohort did not confirm the original replication results, and we did not reach any definitive conclusion regarding the validity of this discovery. The cohort used for our study is larger than those used in most previous HCT studies but is smaller than those typically used for other genotype-phenotype association studies. Genomic and disease data from our study are available for further analysis in combination with data from other cohorts.

Genome sequencing in congenital cataracts improves diagnostic yield

Congenital cataracts are one of the major causes of childhood-onset blindness around the world. Genetic diagnosis provides benefits through avoidance of unnecessary tests, surveillance of extraocular features, and genetic family information. In this study, we demonstrate the value of genome sequencing in improving diagnostic yield in congenital cataract patients and families. We applied genome sequencing to investigate 20 probands with congenital cataracts. We examined the added value of genome sequencing across a total cohort of 52 probands, including 14 unable to be diagnosed using previous microarray and exome or panel-based approaches. Although exome or genome sequencing would have detected the variants in 35/52 (67%) of the cases, specific advantages of genome sequencing led to additional diagnoses in 10% (5/52) of the overall cohort, and we achieved an overall diagnostic rate of 77% (40/52). Specific benefits of genome sequencing were due to detection of small copy number variants (2), indels in repetitive regions (2) or single-nucleotide variants (SNVs) in GC-rich regions (1), not detectable on the previous microarray, exome sequencing, or panel-based approaches. In other cases, SNVs were identified in cataract disease genes, including those newly identified since our previous study. This study highlights the additional yield of genome sequencing in congenital cataracts.

EPHA2 Segregates with Microphthalmia and Congenital Cataracts in Two Unrelated Families

EPHA2 is a transmembrane tyrosine kinase receptor that, when disrupted, causes congenital and age-related cataracts. Cat-Map reports 22 pathogenic EPHA2 variants associated with congenital cataracts, variable microcornea, and lenticonus, but no previous association with microphthalmia (small, underdeveloped eye, ≥2 standard deviations below normal axial length). Microphthalmia arises from ocular maldevelopment with >90 monogenic causes, and can include a complex ocular phenotype. In this paper, we report two pathogenic EPHA2 variants in unrelated families presenting with bilateral microphthalmia and congenital cataracts. Whole genome sequencing through the 100,000 Genomes Project and cataract-related targeted gene panel testing identified autosomal dominant heterozygous mutations segregating with the disease: (i) missense c.1751C>T, p.(Pro584Leu) and (ii) splice site c.2826-9G>A. To functionally validate pathogenicity, morpholino knockdown of epha2a/epha2b in zebrafish resulted in significantly reduced eye size ± cataract formation. Misexpression of N-cadherin and retained fibre cell nuclei were observed in the developing lens of the epha2b knockdown morphant fish by 3 days post-fertilisation, which indicated a putative mechanism for microphthalmia pathogenesis through disruption of cadherin-mediated adherens junctions, preventing lens maturation and the critical signals stimulating eye growth. This study demonstrates a novel association of EPHA2 with microphthalmia, suggesting further analysis of pathogenic variants in unsolved microphthalmia cohorts may increase molecular diagnostic rates.

Genome-wide DNA methylation profiles may reveal new possible epigenetic pathogenesis of sporadic congenital cataract

Aim: To investigate the possible epigenetic pathogenesis of sporadic congenital cataract. Materials & methods: We conducted whole genome bisulfite sequencing on peripheral blood from sporadic binocular or monocular congenital cataract patients and cataract-free participants. Results: We found massive differentially methylated regions within the whole genomes between any two groups. Meanwhile, we identified five genes (ACTN4, ACTG1, TUBA1A, TUBA1C, TUBB4B) for the binocular and control groups and TUBA1A for the monocular and control groups as the core differentially methylated region-related genes. The proteins encoded by these core genes are involved in building cytoskeleton and intercellular junctions. Conclusion: Changes in the methylation levels of core genes may disturb the function of cytoskeleton and intercellular junctions, eventually leading to sporadic congenital cataract.

Great clinical variability of Nance Horan syndrome due to deleterious NHS mutations in two unrelated Spanish families

Background: Nance-Horan syndrome (NHS) is an X-linked rare congenital disorder caused by mutations in the NHS gene. Clinical manifestations include congenital cataracts, facial and dental dysmorphism and, in some cases, intellectual disability. The aim of the present work was to identify the genetic cause of this disease in two unrelated Spanish NHS families and to determine the relative involvement of this gene in the pathogenesis.Materials and methods: Four members of a two-generation family, three males and one female (Family 1), and seven members of a three-generation family, two males and five females (Family 2) were recruited and their index cases were screened for mutations in the NHS gene and 26 genes related with ocular congenital anomalies by NGS (Next Generation Sequencing).Results: Two pathogenic variants were found in the NHS gene: a nonsense mutation (p.Arg373X) and a frameshift mutation (p.His669ProfsX5). These mutations were found in the two unrelated NHS families with different clinical manifestations.Conclusions: In the present study, we identified two truncation mutations (one of them novel) in the NHS gene, associated with NHS. Given the wide clinical variability of this syndrome, NHS may be difficult to detect in individuals with subtle clinical manifestations or when congenital cataracts are the primary clinical manifestation which makes us suspect that it can be underdiagnosed. Combination of genetic studies and clinical examinations are essential for the clinical diagnosis optimization.

SGEF forms a complex with Scribble and Dlg1 and regulates epithelial junctions and contractility

The canonical Scribble polarity complex is implicated in regulation of epithelial junctions and apical polarity. Here, we show that SGEF, a RhoG-specific GEF, forms a ternary complex with Scribble and Dlg1, two members of the Scribble complex. SGEF targets to apical junctions in a Scribble-dependent fashion and functions in the regulation of actomyosin-based contractility and barrier function at tight junctions as well as E-cadherin-mediated formation of adherens junctions. Surprisingly, SGEF does not control the establishment of polarity. However, in 3D cysts, SGEF regulates the formation of a single open lumen. Interestingly, SGEF's nucleotide exchange activity regulates the formation and maintenance of adherens junctions, and in cysts the number of lumens formed, whereas SGEF's scaffolding activity is critical for regulation of actomyosin contractility and lumen opening. We propose that SGEF plays a key role in coordinating junctional assembly and actomyosin contractility by bringing together Scribble and Dlg1 and targeting RhoG activation to cell-cell junctions.

A novel NHS mutation in a Chinese family with Nance‑Horan Syndrome

Nance‑Horan syndrome (NHS) is a rare X‑linked disorder with various clinical manifestations. The present study aimed to identify the pathogenic mutation causing NHS in a three‑generation Chinese family with 4 individuals presenting primarily with congenital cataracts. The genomic DNA of 5 individuals was collected, and family history and clinical information were recorded. Whole exome sequencing was performed on the proband, and candidate mutations were filtered by a series of screening processes and validated by Sanger sequencing. The identified pathogenic mutation was confirmed by co‑segregation analysis. Finally, a novel frameshift mutation (NM_001291867.1: c.302dupA; p.Ala102fs) was identified in the NHS actin remodeling regulator (NHS) gene, which co‑segregated with congenital cataracts in this family. Carrier females exhibited similar but milder clinical symptoms compared with the affected male. These clinical symptoms were consistent with the phenotypic features of the NHS‑associated disease, NHS. In summary, the present study identified a novel NHS mutation in a Chinese family with atypical NHS; the results broaden the known pathogenic mutation spectrum of NHS and will aid in the genetic counseling of patients with NHS. The data from the present study also suggest that genetic analysis may be required for the diagnosis of this disease.

Whole exome sequencing identified a novel truncation mutation in the NHS gene associated with Nance-Horan syndrome

Background

Nance-Horan syndrome (NHS) is an X-linked inheritance disorder characterized by bilateral congenital cataracts, and facial and dental dysmorphism. This disorder is caused by mutations in the NHS gene. However, NHS may be difficult to detect in individuals with subtle facial dysmorphism and dental abnormalities in whom congenital cataracts are the primary clinical manifestations.

Methods

In this study, we present a three-generation family with NHS. Whole exome sequencing was performed to determine the potential pathogenic variant in the proband. Further validation was explored with Sanger sequencing in 9 of the available individuals of the family and additional 200 controls.

Results

A novel truncation mutation in gene NHS (c.C4449G, p.Tyr1483Ter) was found in the proband, who presented with a long-narrow face, prominent nose and large anteverted pinnae ear, screw-driver like incisors, mild mulberry like molars, one missing maxillary second molar and malocclusion. We found this mutation was detected in 2 male patients and 4 female carriers in the family. However, the mutation was never detected in the control subjects.

Conclusions

In conclusion, we identified a novel truncation mutation in the NHS gene, which might associate with NHS. Our review on the NHS studies illustrated that NHS has significantly clinical heterogeneity. And NHS mutations in the NHS-affected individuals typically result in premature truncation of the protein. And the new mutation revealed in this study would highlight the understanding of the causative mutations of NHS.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0725-3) contains supplementary material, which is available to authorized users.

A novel small deletion in the NHS gene associated with Nance-Horan syndrome

Nance-Horan syndrome is a rare X-linked recessive inherited disease with clinical features including severe bilateral congenital cataracts, characteristic facial and dental abnormalities. Data from Chinese Nance-Horan syndrome patients are limited. We assessed the clinical manifestations of a Chinese Nance-Horan syndrome pedigree and identified the genetic defect. Genetic analysis showed that 3 affected males carried a novel small deletion in NHS gene, c.263_266delCGTC (p.Ala89TrpfsTer106), and 2 female carriers were heterozygous for the same variant. All 3 affected males presented with typical Nance-Horan syndrome features. One female carrier displayed lens opacities centered on the posterior Y-suture in both eyes, as well as mild dental abnormalities. We recorded the clinical features of a Chinese Nance-Horan syndrome family and broadened the spectrum of mutations in the NHS gene.

Drosophila melanogaster Guk-holder interacts with the Scribbled PDZ1 domain and regulates epithelial development with Scribbled and Discs Large

Epithelial cell polarity is controlled by components of the Scribble polarity module, and its regulation is critical for tissue architecture and cell proliferation and migration. In Drosophila melanogaster, the adaptor protein Guk-holder (Gukh) binds to the Scribbled (Scrib) and Discs Large (Dlg) components of the Scribble polarity module and plays an important role in the formation of neuromuscular junctions. However, Gukh's role in epithelial tissue formation and the molecular basis for the Scrib-Gukh interaction remain to be defined. We now show using isothermal titration calorimetry that the Scrib PDZ1 domain is the major site for an interaction with Gukh. Furthermore, we defined the structural basis of this interaction by determining the crystal structure of the Scrib PDZ1-Gukh complex. The C-terminal PDZ-binding motif of Gukh is located in the canonical ligand-binding groove of Scrib PDZ1 and utilizes an unusually extensive network of hydrogen bonds and ionic interactions to enable binding to PDZ1 with high affinity. We next examined the role of Gukh along with those of Scrib and Dlg in Drosophila epithelial tissues and found that Gukh is expressed in larval-wing and eye-epithelial tissues and co-localizes with Scrib and Dlg at the apical cell cortex. Importantly, we show that Gukh functions with Scrib and Dlg in the development of Drosophila epithelial tissues, with depletion of Gukh enhancing the eye- and wing-tissue defects caused by Scrib or Dlg depletion. Overall, our findings reveal that Scrib's PDZ1 domain functions in the interaction with Gukh and that the Scrib-Gukh interaction has a key role in epithelial tissue development in Drosophila.

Congenital diaphragmatic hernia as a part of Nance-Horan syndrome?

Nance-Horan syndrome is a rare X-linked developmental disorder characterized by bilateral congenital cataract, dental anomalies, facial dysmorphism, and intellectual disability. Here, we identify a patient with Nance-Horan syndrome caused by a new nonsense NHS variant. In addition, the patient presented congenital diaphragmatic hernia. NHS gene expression in murine fetal diaphragm was demonstrated, suggesting a possible involvement of NHS in diaphragm development. Congenital diaphragmatic hernia could result from NHS loss of function in pleuroperitoneal fold or in somites-derived muscle progenitor cells leading to an impairment of their cells migration.

Nance-Horan syndrome in females due to a balanced X;1 translocation that disrupts the NHS gene: Familial case report and review of the literature

The Nance-Horan syndrome is an X-linked disorder characterized by congenital cataract, facial features, microcornea, microphthalmia, and dental anomalies; most of the cases are due to NHS gene mutations on Xp22.13. Heterozygous carrier females generally present less severe features, and up to 30% of the affected males have intellectual disability. We describe two patients, mother and daughter, manifesting Nance-Horan syndrome. The cytogenetic and molecular analyses demonstrated a 46,X,t(X;1)(p22.13;q22) karyotype in each of them. No copy-number genomic imbalances were detected by high-density microarray analysis. The mother had a preferential inactivation of the normal X chromosome; expression analysis did not detect any mRNA isoform of NHS. This is the first report of Nance-Horan syndrome due to a skewed X chromosome inactivation resulting from a balanced translocation t(X;1) that disrupts the NHS gene expression, with important implications for clinical presentation and genetic counseling.

NHS Gene Mutations in Ashkenazi Jewish Families with Nance-Horan Syndrome

PURPOSE

To describe ocular and extraocular abnormalities in two Ashkenazi Jewish families with infantile cataract and X-linked inheritance, and to identify their underlying mutations.

METHODS

Seven affected members were recruited. Medical history, clinical findings, and biometric measurements were recorded. Mutation analysis of the Nance-Horan syndrome (NHS) gene was performed by direct sequencing of polymerase chain reaction-amplified exons.

RESULTS

An unusual anterior Y-sutural cataract was documented in the affected male proband. Other clinical features among examined patients included microcorneas, long and narrow faces, and current or previous dental anomalies. A nonsense mutation was identified in each family, including a previously described 742 C>T, p.(Arg248*) mutation in Family A, and a novel mutation 2915 C>A, p.(Ser972*) in Family B.

CONCLUSIONS

Our study expands the repertoire of NHS mutations and the related phenotype, including newly described anterior Y-sutural cataract and dental findings.

A novel NHS mutation causes Nance-Horan Syndrome in a Chinese family

Background

Nance-Horan Syndrome (NHS) (OMIM: 302350) is a rare X-linked developmental disorder characterized by bilateral congenital cataracts, with occasional dental anomalies, characteristic dysmorphic features, brachymetacarpia and mental retardation. Carrier females exhibit similar manifestations that are less severe than in affected males.

Methods

Here, we report a four-generation Chinese family with multiple affected individuals presenting Nance-Horan Syndrome. Whole-exome sequencing combined with RT-PCR and Sanger sequencing was used to search for a genetic cause underlying the disease phenotype.

Results

Whole-exome sequencing identified in all affected individuals of the family a novel donor splicing site mutation (NM_198270: c.1045 + 2T > A) in intron 4 of the gene NHS, which maps to chromosome Xp22.13. The identified mutation results in an RNA processing defect causing a 416-nucleotide addition to exon 4 of the mRNA transcript, likely producing a truncated NHS protein.

Conclusions

The donor splicing site mutation NM_198270: c.1045 + 2T > A of the NHS gene is the causative mutation in this Nance-Horan Syndrome family. This research broadens the spectrum of NHS gene mutations, contributing to our understanding of the molecular genetics of NHS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-016-0360-9) contains supplementary material, which is available to authorized users.

Autozygosity in a Turkish family with scoliosis, blindness, and arachnodactyly syndrome

BACKGROUND AND OBJECTIVES

Blindness-scoliosis-arachnodactyly syndrome has been described in a family with parental consanguinity. We present the strategy employed to determine the gene locus responsible for the syndrome.

DESIGN AND SETTING

A retrospective study of blindness-scoliosis-arachnodactyly syndrome patients at the Department of Medical Genetics, Erciyes University, between 2009-2010.

PATIENTS AND METHODS

Whole genome single nucleotide polymorphisms (SNPs) were scanned using a 250K Affymetrix array. We visually evaluated runs of homozygosity shared by two affected brothers that segregated in the entire pedigree with different combinations due to the unclear affected status of some siblings. Two and multiple-point LOD (logarithm [base 10] of odds) score analyses were performed by easyLINKAGEplus v5.08.

RESULTS

Five homozygous blocks over 2 Mb shared by two affected brothers segregated with phenotype in two affected and three unaffected siblings and in the mother whose phenotypes were unequivocal. The longest homozygous block in this analysis was on chromosome 14 between 67817621bp (rs7148416) and 82508151bp (rs17117757). When another sister with positive eye findings was added to the analysis, this region was narrowed to between 67817621bp (rs7148416) and 75657598bp (rs11626830), with a maximum LOD score of 2.3956 by two-point analysis. Three candidate genes were detected in this region.

CONCLUSION

This study contributes to the existing literature on the region 67817621 bp 82508151 bp (rs17117757) on chromosome 14 and the three candidate genes, which could be responsible for the syndrome.

Identification of a novel NHS mutation in a Chinese family with Nance-Horan syndrome

PURPOSE

To identiy the disease causing mutation in a Chinese family presenting with early-onset cataract and dental anomalies.

MATERIALS AND METHODS

A specific Hereditary Eye Disease Enrichment Panel (HEDEP) (personalized customization by MyGenostics, Baltimore, MD) based on targeted exome capture technology was used to collect the protein coding regions of 30 early-onset cataract associated genes, and high throughput sequencing was done with Illumina HiSeq 2000 platform. The identified variant was confirmed with Sanger sequencing.

RESULTS

A novel deletion in exon 4 (c.852delG) of NHS gene was identified; the identified 1 bp deletion altered the reading frame and was predicted to result in a premature stop codon after the addition of twelve novel amino acid (p.S285PfsX13). This mutation co-segregated in affected males and obligate female carriers, but was absent in 100 matched controls.

CONCLUSIONS

Our findings broaden the spectrum of NHS mutations causing Nance-Horan syndrome and phenotypic spectrum of the disease in Chinese patients.

Identification of a novel mutation in a Chinese family with Nance-Horan syndrome by whole exome sequencing

OBJECTIVE

Nance-Horan syndrome (NHS) is a rare X-linked disorder characterized by congenital nuclear cataracts, dental anomalies, and craniofacial dysmorphisms. Mental retardation was present in about 30% of the reported cases. The purpose of this study was to investigate the genetic and clinical features of NHS in a Chinese family.

METHODS

Whole exome sequencing analysis was performed on DNA from an affected male to scan for candidate mutations on the X-chromosome. Sanger sequencing was used to verify these candidate mutations in the whole family. Clinical and ophthalmological examinations were performed on all members of the family.

RESULTS

A combination of exome sequencing and Sanger sequencing revealed a nonsense mutation c.322G>T (E108X) in exon 1 of NHS gene, co-segregating with the disease in the family. The nonsense mutation led to the conversion of glutamic acid to a stop codon (E108X), resulting in truncation of the NHS protein. Multiple sequence alignments showed that codon 108, where the mutation (c.322G>T) occurred, was located within a phylogenetically conserved region. The clinical features in all affected males and female carriers are described in detail.

CONCLUSIONS

We report a nonsense mutation c.322G>T (E108X) in a Chinese family with NHS. Our findings broaden the spectrum of NHS mutations and provide molecular insight into future NHS clinical genetic diagnosis.

A Turkish family with Nance-Horan Syndrome due to a novel mutation

Nance-Horan Syndrome (NHS) is a rare X-linked syndrome characterized by congenital cataract which leads to profound vision loss, characteristic dysmorphic features and specific dental anomalies. Microcornea, microphthalmia and mild or moderate mental retardation may accompany these features. Heterozygous females often manifest similarly but with less severe features than affected males. We describe two brothers who have the NHS phenotype and their carrier mother who had microcornea but not cataract. We identified a previously unreported frameshift mutation (c.558insA) in exon 1 of the NHS gene in these patients and their mother which is predicted to result in the incorporation of 11 aberrant amino acids prior to a stop codon (p.E186Efs11X). We also discussed genotype-phenotype correlation according to relevant literature.

The N and C termini of ZO-1 are surrounded by distinct proteins and functional protein networks

BACKGROUND

Biotin ligase tagging with ZO-1 was applied to identify a more complete tight junction proteome.

RESULTS

Identical but also different proteins and functional networks were identified near the N and C ends of ZO-1.

CONCLUSION

The ends of ZO-1 are embedded in different functional subcompartments of the tight junction.

SIGNIFICANCE

Biotin tagging with ZO-1 expands the tight junction proteome and defines subcompartments of the junction. The proteins and functional protein networks of the tight junction remain incompletely defined. Among the currently known proteins are barrier-forming proteins like occludin and the claudin family; scaffolding proteins like ZO-1; and some cytoskeletal, signaling, and cell polarity proteins. To define a more complete list of proteins and infer their functional implications, we identified the proteins that are within molecular dimensions of ZO-1 by fusing biotin ligase to either its N or C terminus, expressing these fusion proteins in Madin-Darby canine kidney epithelial cells, and purifying and identifying the resulting biotinylated proteins by mass spectrometry. Of a predicted proteome of ∼9000, we identified more than 400 proteins tagged by biotin ligase fused to ZO-1, with both identical and distinct proteins near the N- and C-terminal ends. Those proximal to the N terminus were enriched in transmembrane tight junction proteins, and those proximal to the C terminus were enriched in cytoskeletal proteins. We also identified many unexpected but easily rationalized proteins and verified partial colocalization of three of these proteins with ZO-1 as examples. In addition, functional networks of interacting proteins were tagged, such as the basolateral but not apical polarity network. These results provide a rich inventory of proteins and potential novel insights into functions and protein networks that should catalyze further understanding of tight junction biology. Unexpectedly, the technique demonstrates high spatial resolution, which could be generally applied to defining other subcellular protein compartmentalization.

A homozygous mutation in the tight-junction protein JAM3 causes hemorrhagic destruction of the brain, subependymal calcification, and congenital cataracts

The tight junction, or zonula occludens, is a specialized cell-cell junction that regulates epithelial and endothelial permeability, and it is an essential component of the blood-brain barrier in the cerebrovascular endothelium. In addition to functioning as a diffusion barrier, tight junctions are also involved in signal transduction. In this study, we identified a homozygous mutation in the tight-junction protein gene JAM3 in a large consanguineous family from the United Arab Emirates. Some members of this family had a rare autosomal-recessive syndrome characterized by severe hemorrhagic destruction of the brain, subependymal calcification, and congenital cataracts. Their clinical presentation overlaps with some reported cases of pseudo-TORCH syndrome as well as with cases involving mutations in occludin, another component of the tight-junction complex. However, massive intracranial hemorrhage distinguishes these patients from others. Homozygosity mapping identified the disease locus in this family on chromosome 11q25 with a maximum multipoint LOD score of 6.15. Sequence analysis of genes in the candidate interval uncovered a mutation in the canonical splice-donor site of intron 5 of JAM3. RT-PCR analysis of a patient lymphoblast cell line confirmed abnormal splicing, leading to a frameshift mutation with early termination. JAM3 is known to be present in vascular endothelium, although its roles in cerebral vasculature have not been implicated. Our results suggest that JAM3 is essential for maintaining the integrity of the cerebrovascular endothelium as well as for normal lens development in humans.

A novel syndrome of paediatric cataract, dysmorphism, ectodermal features, and developmental delay in Australian Aboriginal family maps to 1p35.3-p36.32

BACKGROUND

A novel phenotype consisting of cataract, mental retardation, erythematous skin rash and facial dysmorphism was recently described in an extended pedigree of Australian Aboriginal descent. Large scale chromosomal re-arrangements had previously been ruled out. We have conducted a genome-wide scan to map the linkage region in this family.

METHODS

Genome-wide linkage analysis using Single Nucleotide Polymorphism (SNP) markers on the Affymetrix 10K SNP array was conducted and analysed using MERLIN. Three positional candidate genes (ZBTB17, EPHA2 and EPHB2) were sequenced to screen for segregating mutations.

RESULTS

Under a fully penetrant, dominant model, the locus for this unique phenotype was mapped to chromosome 1p35.3-p36.32 with a maximum LOD score of 2.41. The critical region spans 48.7 cM between markers rs966321 and rs1441834 and encompasses 527 transcripts from 364 annotated genes. No coding mutations were identified in three positional candidate genes EPHA2, EPHB2 or ZBTB17. The region overlaps with a previously reported region for Volkmann cataract and the phenotype has similarity to that reported for 1p36 monosomy.

CONCLUSIONS

The gene for this syndrome is located in a 25.6 Mb region on 1p35.3-p36.32. The known cataract gene in this region (EPHA2) does not harbour mutations in this family, suggesting that at least one additional gene for cataract is present in this region.

Identification of a microdeletion at Xp22.13 in a Taiwanese family presenting with Nance-Horan syndrome

Nance-Horan syndrome (NHS) is a rare X-linked disorder characterized by congenital cataracts, dental anomalies and mental retardation. The disease has been linked to a novel gene termed NHS located at Xp22.13. The majority of pathogenic mutations of the disease include nonsense mutations and small deletions and insertions that lead to truncation of the NHS protein. In this study, we identified a microdeletion of ∼ 0.92 Mb at Xp22.13 detected by array-based comparative genomic hybridization in two brothers presenting congenital cataract, dental anomalies, facial dysmorphisms and mental retardation. The deleted region encompasses the REPS2, NHS, SCML1 and RAI2 genes, and was transmitted from their carrier mother who presented only mild cataract. Our findings are in line with several recent case reports to indicate that genomic rearrangement involving the NHS gene is an important genetic etiology underlying NHS.

The Nance-Horan syndrome protein encodes a functional WAVE homology domain (WHD) and is important for co-ordinating actin remodelling and maintaining cell morphology

Nance–Horan syndrome (NHS) is an X-linked developmental disorder, characterized by bilateral congenital cataracts, dental anomalies, facial dysmorphism and mental retardation. Null mutations in a novel gene, NHS, cause the syndrome. The NHS gene appears to have multiple isoforms as a result of alternative transcription, but a cellular function for the NHS protein has yet to be defined. We describe NHS as a founder member of a new protein family (NHS, NHSL1 and NHSL2). Here, we demonstrate that NHS is a novel regulator of actin remodelling and cell morphology. NHS localizes to sites of cell–cell contact, the leading edge of lamellipodia and focal adhesions. The N-terminus of isoforms NHS-A and NHS-1A, implicated in the pathogenesis of NHS, have a functional WAVE homology domain that interacts with the Abi protein family, haematopoietic stem/progenitor cell protein 300 (HSPC300), Nap1 and Sra1. NHS knockdown resulted in the disruption of the actin cytoskeleton. We show that NHS controls cell morphology by maintaining the integrity of the circumferential actin ring and controlling lamellipod formation. NHS knockdown led to a striking increase in cell spreading. Conversely, ectopic overexpression of NHS inhibited lamellipod formation. Remodelling of the actin cytoskeleton and localized actin polymerization into branched actin filaments at the plasma membrane are essential for mediating changes in cell shape, migration and cell contact. Our data identify NHS as a new regulator of actin remodelling. We suggest that NHS orchestrates actin regulatory protein function in response to signalling events during development.

Ophthalmic pathology of Nance-Horan syndrome: case report and review of the literature

BACKGROUND

Nance-Horan syndrome (NHS) is a rare X-linked disorder typified by dense congenital central cataracts, microcornea, anteverted and simplex pinnae, brachymetacarpalia, and numerous dental anomalies due in most cases to a mutation in the NHS gene.

MATERIAL AND METHODS

We present a case of clinical manifestation and ocular pathology in a patient with NHS. This article also reviews and discusses the relevant literature.

RESULTS

Classic and novel ocular pathological findings of a young male with NHS are described, including congenital cataracts, infantile glaucoma, scleral staphyloma, and severe retinal cystoid degeneration.

CONCLUSIONS

We report a new pathological finding of severe retinal cystoid degeneration in this NHS patient and confirm abnormal development of the anterior chamber angle structure. These findings, coupled with our analysis of the available NHS literature, provide new understanding of the histopathological basis of ocular abnormalities and vision loss in NHS.

X-linked cataract and Nance-Horan syndrome are allelic disorders

Nance-Horan syndrome (NHS) is an X-linked developmental disorder characterized by congenital cataract, dental anomalies, facial dysmorphism and, in some cases, mental retardation. Protein truncation mutations in a novel gene (NHS) have been identified in patients with this syndrome. We previously mapped X-linked congenital cataract (CXN) in one family to an interval on chromosome Xp22.13 which encompasses the NHS locus; however, no mutations were identified in the NHS gene. In this study, we show that NHS and X-linked cataract are allelic diseases. Two CXN families, which were negative for mutations in the NHS gene, were further analysed using array comparative genomic hybridization. CXN was found to be caused by novel copy number variations: a complex duplication-triplication re-arrangement and an intragenic deletion, predicted to result in altered transcriptional regulation of the NHS gene. Furthermore, we also describe the clinical and molecular analysis of seven families diagnosed with NHS, identifying four novel protein truncation mutations and a novel large deletion encompassing the majority of the NHS gene, all leading to no functional protein. We therefore show that different mechanisms, aberrant transcription of the NHS gene or no functional NHS protein, lead to different diseases. Our data highlight the importance of copy number variation and non-recurrent re-arrangements leading to different severity of disease and describe the potential mechanisms involved.

Congenital cataracts and their molecular genetics

Cataract can be defined as any opacity of the crystalline lens. Congenital cataract is particularly serious because it has the potential for inhibiting visual development, resulting in permanent blindness. Inherited cataracts represent a major contribution to congenital cataracts, especially in developed countries. While cataract represents a common end stage of mutations in a potentially large number of genes acting through varied mechanisms in practice most inherited cataracts have been associated with a subgroup of genes encoding proteins of particular importance for the maintenance of lens transparency and homeostasis. The increasing availability of more detailed information about these proteins and their functions and is making it possible to understand the pathophysiology of cataracts and the biology of the lens in general.

Genetic diseases of junctions

Tight junctions, gap junctions, adherens junctions, and desmosomes represent intricate structural intercellular channels and bridges that are present in several tissues, including epidermis. Clues to the important function of these units in epithelial cell biology have been gleaned from a variety of studies including naturally occurring and engineered mutations, animal models and other in vitro experiments. In this review, we focus on mutations that have been detected in human diseases. These observations provide intriguing insight into the biological complexities of cell-cell contact and intercellular communication as well as demonstrating the spectrum of inherited human diseases that are associated with mutations in genes encoding the component proteins. Over the last decade or so, human gene mutations have been reported in four tight junction proteins (claudin 1, 14, 16, and zona occludens 2), nine gap junction proteins (connexin 26, 30, 30.3, 31, 32, 40, 43, 46, and 50), one adherens junction protein (P-cadherin) and eight components of desmosomes (plakophilin (PKP) 1 and 2, desmoplakin, plakoglobin--which is also present in adherens junctions, desmoglein (DSG) 1, 2, 4, and corneodesmosin). These discoveries have often highlighted novel or unusual phenotypes, including abnormal skin barrier function, alterations in epidermal differentiation, and developmental anomalies of various ectodermal appendages, especially hair, as well as a range of extracutaneous pathologies. However, this review focuses mainly on inherited disorders of junctions that have an abnormal skin phenotype.

Interdomain interactions in the tumor suppressor discs large regulate binding to the synaptic protein GukHolder

Multidomain scaffolding proteins are central components of many signaling pathways and are commonly found at membrane specializations. Here we have shown that multiple interdomain interactions in the scaffold Discs Large (Dlg) regulate binding to the synaptic protein GukHolder (GukH). GukH binds the Src homology 3 (SH3) and guanylate kinase-like (GK) protein interaction domains of Dlg, whereas an intramolecular interaction between the two domains inhibits association with GukH. Regulation occurs through a PDZ domain adjacent to the SH3 that allows GukH to interact with the composite SH3-GK binding site, but PDZ ligands inhibit GukH binding such that Dlg forms mutually exclusive PDZ ligand and GukH cellular complexes. The PDZ-SH3-GK module is a common feature of membrane associate guanylate kinase scaffolds such as Dlg, and these results indicate that its supramodular architecture leads to regulation of Dlg complexes.