Mutation analysis of theFRAS1 gene demonstrates new mutations in a propositus with Fraser syndrome

Disease mechanisms of monogenic congenital anomalies of the kidney and urinary tract American Journal of Medical Genetics Part C

Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) is a developmental disorder of the kidney and/or genito-urinary tract that results in end stage kidney disease (ESKD) in up to 50% of children. Despite the congenital nature of the disease, CAKUT accounts for almost 10% of adult onset ESKD. Multiple lines of evidence suggest that CAKUT is a Mendelian disorder, including the observation of familial clustering of CAKUT. Pathogenesis in CAKUT is embryonic in origin, with disturbances of kidney and urinary tract development resulting in a heterogeneous range of disease phenotypes. Despite polygenic and environmental factors being implicated, a significant proportion of CAKUT is monogenic in origin, with studies demonstrating single gene defects in 10%-20% of patients with CAKUT. Here, we review monogenic disease causation with emphasis on the etiological role of gene developmental pathways in CAKUT.

Transgene-mediated skeletal phenotypic variation in zebrafish

When considering relationships between genotype and phenotype we frequently ignore the fact that the genome of a typical animal, notably including that of a fish and a human, harbours a huge amount of foreign DNA. Such DNA, in the form of transposable elements, can affect genome function in a major way, and transgene biology needs to be included in our understanding of the genome. Here we examine an unexpected phenotypic effect of the chromosomally integrated transgene fli1a-F-hsp70l:Gal4VP16 that serves as a model for transgene function generally. We examine larval fras1 mutant zebrafish (Danio rerio). Gal4VP16 is a potent transcriptional activator that is already well known for toxicity and mediating unusual transcriptional effects. In the presence of the transgene, phenotypes in the neural crest-derived craniofacial skeleton, notably fusions and shape changes associated with loss of function fras1 mutations, are made more severe, as we quantify by scoring phenotypic penetrance, the fraction of mutants expressing the trait. A very interesting feature is that the enhancements are highly specific for fras1 mutant phenotypes, occurring in the apparent absence of more widespread changes. Except for the features due to the fras1 mutation, the transgene-bearing larvae appear generally healthy and to be developing normally. The transgene behaves as a genetic partial dominant: a single copy is sufficient for the enhancements, yet, for some traits, two copies may exert a stronger effect. We made new strains bearing independent insertions of the fli1a-F-hsp70l:Gal4VP16 transgene in new locations in the genome, and observed increased severities of the same phenotypes as observed for the original insertion. This finding suggests that sequences within the transgene, for example Gal4VP16, are responsible for the enhancements, rather than the effect on neighbouring host sequences (such as an insertional mutation). The specificity and biological action underlying the traits are subjects of considerable interest for further investigation, as we discuss. Our findings show that work with transgenes needs to be undertaken with caution and attention to detail.

Novel loss of function variants in FRAS1 AND FREM2 underlie renal agenesis in consanguineous families

INTRODUCTION

Congenital anomalies of the kidney and urinary tract (CAKUT) are a group of abnormalities that affect structure of the kidneys or other structures of the urinary tract. The majority of CAKUT are asymptomatic and are diagnosed prenatally by ultrasound scanning or found incidentally in postnatal life. CAKUT varies in severity and may lead to life-threatening kidney failure and end-stage kidney disease. Renal agenesis, a severe form of CAKUT, is a congenital absence of one or both kidneys. Bilateral renal agenesis belongs to a group of prenatally lethal renal diseases and is often detected on fetal ultrasound scanning during the investigation of oligohydramnios. Approximately 40% of fetuses with bilateral renal agenesis are stillborn or die a few hours postnatally. Mutations in many renal development genes have been shown to be associated with renal agenesis.

METHODS

Six consanguineous Saudi Arabian families were recruited to study the molecular genetic causes of recurrent miscarriages and lost fetuses due to oligohydramnios, renal agenesis and other congenital anomalies. Whole exome sequencing was employed to underlying detect genetic defects.

RESULTS

Novel loss of function variants were detected in FRAS1 and FREM2. In FRAS1, a homozygous splice site variant c.9780+2T>C was found in an affected fetus, segregating form each parent. In addition, in three other families both parents were heterozygous for a frameshift variant (c.8981dupT; p.His2995Profs*3) and splice site variants (c.5217+1G>C and c.8098+2T>A), respectively. In FREM2, a homozygous nonsense variant (c.2303C>G; p.Ser768*) was found in an affected fetus, segregating from both parents. In another family, both parents carried a FREM2 heterozygous frameshift variant (c.3969delC; p.Asn1323Lysfs*5).

CONCLUSION

We describe consanguineous families with clinical features of antenatal oligohydramnios and bilateral renal agenesis, in whom we have identified novel pathogenic variants in FRAS1 and FREM2. These finding highlights the association between mutations in FRAS1 and FREM2 and antenatal/perinatal death.

Two unrelated families with variable expression of Fraser syndrome due to the same pathogenic variant in the FRAS1 gene

We report on two unrelated families of Polish origin with variable expression of Fraser syndrome (FS; MIM#219000) due to homozygosity for the same pathogenic variant, c.6963_6964dup, of FRAS1. In one family, the disorder presented with perinatal and prenatal lethality. One affected female from family 2 who was followed-up for 32 years, represented a relatively favorable long-term outcome. She displayed the typical craniofacial dysmorphism, including right cryptophthalmos, cutaneous syndactyly, abnormalities of the stomathognatic system, bilateral atresia of the external ear canals resulting in conductive hearing loss, and malformations of the larynx, spleen, kidney, and genitourinary tract. Her intellectual capacities were normal. Our observations illustrate that expression and severity of FS, even when caused by the same pathogenic variant, may be quite different ranging from a lethal disorder to a condition with multiple physical malformations but normal psychomotor development. In addition, we propose that the FRAS1 c.6963_6964dup variant may be a founder mutation in the Polish population. Therefore, it would be reasonable to test specifically for this variant first in any FS1 patient of Polish ancestry.

Fraser syndrome without cryptophthalmos: Two cases

Fraser syndrome (MIM#219000) is an autosomal recessive disorder, characterized by the association of cryptophthtalmos, syndactyly of the four extremities, urinary tract abnormalities and laryngo-tracheal anomalies. This condition is due to homozygous or compound heterozygous mutations in the FRAS/FREM complex genes: FRAS1, FREM2 and GRIP1. Here we report two atypical cases of Fraser syndrome due to mutations in the FRAS1 gene without cryptophthalmos. The first proband had syndactyly of three extremities, bilateral nostril coloboma, dysplastic ears with bilateral conductive hearing loss, blepharophimosis and lacrimal duct abnormalities. FRAS1 sequencing identified two pathogenic compound heterozygous variants: a nonsense variant in exon 70 and a missense variant in exon 24. The second proband had membranous syndactyly of the four extremities, left renal agenesis, laryngeal and ano-rectal malformations, dysplastic ears and bilateral conductive hearing loss. FRAS1 sequencing identified a pathogenic homozygous variant in the last exon of the gene. This first description of molecularly confirmed cases with Fraser syndrome without cryptophthalmos could contribute to further delineation of the clinical spectrum of Fraser syndrome, especially for possible phenotypically milder cases. Larger cohorts are required to try to refer the hypothesis of genotype-phenotype correlation.

The Molecular Basis of Human Anophthalmia and Microphthalmia

Human eye development is coordinated through an extensive network of genetic signalling pathways. Disruption of key regulatory genes in the early stages of eye development can result in aborted eye formation, resulting in an absent eye (anophthalmia) or a small underdeveloped eye (microphthalmia) phenotype. Anophthalmia and microphthalmia (AM) are part of the same clinical spectrum and have high genetic heterogeneity, with >90 identified associated genes. By understanding the roles of these genes in development, including their temporal expression, the phenotypic variation associated with AM can be better understood, improving diagnosis and management. This review describes the genetic and structural basis of eye development, focusing on the function of key genes known to be associated with AM. In addition, we highlight some promising avenues of research involving multiomic approaches and disease modelling with induced pluripotent stem cell (iPSC) technology, which will aid in developing novel therapies.

Translating genomics to the clinical diagnosis of disorders/differences of sex development

The medical and psychosocial challenges faced by patients living with Disorders/Differences of Sex Development (DSD) and their families can be alleviated by a rapid and accurate diagnostic process. Clinical diagnosis of DSD is limited by a lack of standardization of anatomical and endocrine phenotyping and genetic testing, as well as poor genotype/phenotype correlation. Historically, DSD genes have been identified through positional cloning of disease-associated variants segregating in families and validation of candidates in animal and in vitro modeling of variant pathogenicity. Owing to the complexity of conditions grouped under DSD, genome-wide scanning methods are better suited for identifying disease causing gene variant(s) and providing a clinical diagnosis. Here, we review a number of established genomic tools (karyotyping, chromosomal microarrays and exome sequencing) used in clinic for DSD diagnosis, as well as emerging genomic technologies such as whole-genome (short-read) sequencing, long-read sequencing, and optical mapping used for novel DSD gene discovery. These, together with gene expression and epigenetic studies can potentiate the clinical diagnosis of DSD diagnostic rates and enhance the outcomes for patients and families.

A homozygous mutation p.Arg2167Trp in FREM2 causes isolated cryptophthalmos

Cryptophthalmos (CO, MIM: 123570) is rare congenital anomalies of eyelid formation, which can occur alone or in combination with multiple congenital anomalies as part of Fraser syndrome (FS) or Manitoba Oculotrichoanal syndrome. Causal mutations have been identified for these syndromes but not in the isolated cases. Here, we described two patients from two unrelated Chinese families: one with unilateral isolated CO, while the other with unilateral CO and renal agenesis. A novel homozygous mutation (c.6499C>T: p.Arg2167Trp) and compound heterozygote mutations (c.15delG; c.6499C>T: p.Arg2167Trp) in FREM2 (NM_172862) were identified for the two patients, respectively. The deletion mutation c.15delG resulted in a frameshift and triggered the nonsense-mediated mRNA decay. For the shared missense mutation, p.Arg2167Trp altered a conserved residue and was predicted to affect protein structure by in silico analysis. Functional analysis revealed that Arg2167Trp mutant decreased its interaction with FRAS1 related extracellular matrix 1 (FREM1) and impaired the function of the FRAS1-FRAS1 related extracellular matrix 1 (FREM2)-FREM1 ternary complex required for normal embryogenesis. Furthermore, considering that mutation (c.5914C>T: p.Glu1972Lys) in FREM2 causes FS, a severe systemic disorder, we also compared these two different missense mutations. Our results showed that p.Arg2167Trp had a weaker effect in interrupting interactions between FREM2 and FREM1 than FS-associated missense mutation p.Glu1972Lys. Overall, our data demonstrate that the homozygous mutation p.Arg2167Trp in FREM2 causes isolated CO, which will facilitate our better understanding of the molecular mechanisms underlying the disease.

Choanal atresia and stenosis: Development and diseases of the nasal cavity

Proper craniofacial development in vertebrates depends on growth and fusion of the facial processes during embryogenesis. Failure of any step in this process could lead to craniofacial anomalies such as facial clefting, which has been well studied with regard to its molecular etiology and cellular pathogenesis. Nasal cavity invagination is also a critical event in proper craniofacial development, and is required for the formation of a functional nasal cavity and airway. The nasal cavity must connect the nasopharynx with the primitive choanae to complete an airway from the nostril to the nasopharynx. In contrast to orofacial clefts, defects in nasal cavity and airway formation, such as choanal atresia (CA), in which the connection between the nasal airway and nasopharynx is physically blocked, have largely been understudied. This is also true for a narrowed connection between the nasal cavity and the nasopharynx, which is known as choanal stenosis (CS). CA occurs in approximately 1 in 5,000 live births, and can present in isolation but typically arises as part of a syndrome. Despite the fact that CA and CS usually require immediate intervention, and substantially affect the quality of life of affected individuals, the etiology and pathogenesis of CA and CS have remained elusive. In this review I focus on the process of nasal cavity development with respect to forming a functional airway and discuss the cellular behavior and molecular networks governing this process. Additionally, the etiology of human CA is discussed using examples of disorders which involve CA or CS. This article is categorized under: Signaling Pathways > Cell Fate Signaling Comparative Development and Evolution > Model Systems Birth Defects > Craniofacial and Nervous System Anomalies.

Involvement of the bone morphogenic protein/SMAD signaling pathway in the etiology of congenital anomalies of the kidney and urinary tract accompanied by cryptorchidism

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT), such as renal dysplasia, hydronephrosis, or vesicoureteral reflux, are the most common causes of end-stage renal disease. However, the genetic etiology of CAKUT remains unclear. In this study, we performed whole exome sequencing (WES) to elucidate the genetic etiology of symptomatic CAKUT and CAKUT accompanied by cryptorchidism.

METHODS

Three patients with unilateral renal dysplasia accompanied by ipsilateral cryptorchidism were included in this analysis. Genomic DNA was extracted from peripheral blood, and WES was performed. Disease-specific single nucleotide polymorphisms (SNPs) were determined by comparison with the human genome reference sequence (hg19). Additionally, we searched for SNPs that were common to all three patients, with a particular focus on the coding regions of the target genes.

RESULTS

In total, 8710 SNPs were detected. Of the genes harboring these SNPs, 32 associated with renal or testicular development were selected for further analyses. Of these, eight genes (i.e., SMAD4, ITGA8, GRIP1, FREM1, FREM2, TNXB, BMP8B, and SALL1) carried a single amino acid substitution that was common to all three patients. In particular, SNPs in SMAD4 (His290Pro and His291Pro) have not been reported previously in patients with symptomatic CAKUT. Of the candidate genes, four genes (i.e., ITGA8, GRIP1, FREM1, and FREM2) were Fraser syndrome-related genes, encoding proteins that functionally converged on the glial cell-derived neurotrophic factor/RET/bone morphogenic protein (BMP) signaling pathways. As another candidate gene, the protein encoded by BMP8B activates the nuclear translocation of SMAD4, which regulates the expression of genes associated with the differentiation of primordial germ cells or testicular development. Additionally, BMP4, a member of the BMP family, regulates the interaction between metanephric mesenchyme and ureteric buds by suppressing GDNF.

CONCLUSIONS

Taken together, our findings suggested that the development of the kidney and urinary tract is intimately linked with that of male reproductive organs via BMP/SMAD signaling pathways.

Novel Insights into the Pathogenesis of Monogenic Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidneys and urinary tract (CAKUT) comprise a large spectrum of congenital malformations ranging from severe manifestations, such as renal agenesis, to potentially milder conditions, such as vesicoureteral reflux. CAKUT causes approximately 40% of ESRD that manifests within the first three decades of life. Several lines of evidence indicate that CAKUT is often caused by recessive or dominant mutations in single (monogenic) genes. To date, approximately 40 monogenic genes are known to cause CAKUT if mutated, explaining 5%-20% of patients. However, hundreds of different monogenic CAKUT genes probably exist. The discovery of novel CAKUT-causing genes remains challenging because of this pronounced heterogeneity, variable expressivity, and incomplete penetrance. We here give an overview of known genetic causes for human CAKUT and shed light on distinct renal morphogenetic pathways that were identified as relevant for CAKUT in mice and humans.

Cell therapy for basement membrane-linked diseases

For most disorders caused by mutations in genes encoding basement membrane (BM) proteins, there are at present only limited treatment options available. Genetic BM-linked disorders can be viewed as especially suited for treatment with cell-based therapy approaches because the proteins that need to be restored are located in the extracellular space. In consequence, complete and permanent engraftment of cells does not necessarily have to occur to achieve substantial causal therapeutic effects. For these disorders cells can be used as transient vehicles for protein replacement. In addition, it is becoming evident that BM-linked genetic disorders are modified by secondary diseases mechanisms. Cell-based therapies have also the ability to target such disease modifying mechanisms. Thus, cell therapies can simultaneously provide causal treatment and symptomatic relief, and accordingly hold great potential for treatment of BM-linked disorders. However, this potential has for most applications and diseases so far not been realized. Here, we will present the state of cell therapies for BM-linked diseases. We will discuss use of both pluripotent and differentiated cells, the limitation of the approaches, their challenges, and the way forward to potential wider implementation of cell therapies in the clinics.

Pharyngeal morphogenesis requires fras1-itga8-dependent epithelial-mesenchymal interaction

Both Fras1 and Itga8 connect mesenchymal cells to epithelia by way of an extracellular 'Fraser protein complex' that functions in signaling and adhesion; these proteins are vital to the development of several vertebrate organs. We previously found that zebrafish fras1 mutants have craniofacial defects, specifically, shortened symplectic cartilages and cartilage fusions that spare joint elements. During a forward mutagenesis screen, we identified a new zebrafish mutation, b1161, that we show here disrupts itga8, as confirmed using CRISPR-generated itga8 alleles. fras1 and itga8 single mutants and double mutants have similar craniofacial phenotypes, a result expected if loss of either gene disrupts function of the Fraser protein complex. Unlike fras1 mutants or other Fraser-related mutants, itga8 mutants do not show blistered tail fins. Thus, the function of the Fraser complex differs in the craniofacial skeleton and the tail fin. Focusing on the face, we find that itga8 mutants consistently show defective outpocketing of a late-forming portion of the first pharyngeal pouch, and variably express skeletal defects, matching previously characterized fras1 mutant phenotypes. In itga8 and fras1 mutants, skeletal severity varies markedly between sides, indicating that both mutants have increased developmental instability. Whereas fras1 is expressed in epithelia, we show that itga8 is expressed complementarily in facial mesenchyme. Paired with the observed phenotypic similarity, this expression indicates that the genes function in epithelial-mesenchymal interactions. Similar interactions between Fras1 and Itga8 have previously been found in mouse kidney, where these genes both regulate Nephronectin (Npnt) protein abundance. We find that zebrafish facial tissues express both npnt and the Fraser gene fibrillin2b (fbn2b), but their transcript levels do not depend on fras1 or itga8 function. Using a revertible fras1 allele, we find that the critical window for fras1 function in the craniofacial skeleton is between 1.5 and 3 days post fertilization, which coincides with the onset of fras1-dependent and itga8-dependent morphogenesis. We propose a model wherein Fras1 and Itga8 interact during late pharyngeal pouch morphogenesis to sculpt pharyngeal arches through epithelial-mesenchymal interactions, thereby stabilizing the developing craniofacial skeleton.

Etiologies of uterine malformations

Ranging from aplastic uterus (including Mayer-Rokitansky-Kuster-Hauser syndrome) to incomplete septate uterus, uterine malformations as a group are relatively frequent in the general population. Specific causes remain largely unknown. Although most occurrences ostensibly seem sporadic, familial recurrences have been observed, which strongly implicate genetic factors. Through the study of animal models, human syndromes, and structural chromosomal variation, several candidate genes have been proposed and subsequently tested with targeted methods in series of individuals with isolated, non-isolated, or syndromic uterine malformations. To date, a few genes have garnered strong evidence of causality, mainly in syndromic presentations (HNF1B, WNT4, WNT7A, HOXA13). Sequencing of candidate genes in series of individuals with isolated uterine abnormalities has been able to suggest an association for several genes, but confirmation of a strong causative effect is still lacking for the majority of them. We review the current state of knowledge about the developmental origins of uterine malformations, with a focus on the genetic variants that have been implicated or associated with these conditions in humans, and we discuss potential reasons for the high rate of negative results. The evidence for various environmental and epigenetic factors is also reviewed. © 2016 Wiley Periodicals, Inc.

fras1 shapes endodermal pouch 1 and stabilizes zebrafish pharyngeal skeletal development

Lesions in the epithelially expressed human gene FRAS1 cause Fraser syndrome, a complex disease with variable symptoms, including facial deformities and conductive hearing loss. The developmental basis of facial defects in Fraser syndrome has not been elucidated. Here we show that zebrafish fras1 mutants exhibit defects in facial epithelia and facial skeleton. Specifically, fras1 mutants fail to generate a late-forming portion of pharyngeal pouch 1 (termed late-p1) and skeletal elements adjacent to late-p1 are disrupted. Transplantation studies indicate that fras1 acts in endoderm to ensure normal morphology of both skeleton and endoderm, consistent with well-established epithelial expression of fras1. Late-p1 formation is concurrent with facial skeletal morphogenesis, and some skeletal defects in fras1 mutants arise during late-p1 morphogenesis, indicating a temporal connection between late-p1 and skeletal morphogenesis. Furthermore, fras1 mutants often show prominent second arch skeletal fusions through space occupied by late-p1 in wild type. Whereas every fras1 mutant shows defects in late-p1 formation, skeletal defects are less penetrant and often vary in severity, even between the left and right sides of the same individual. We interpret the fluctuating asymmetry in fras1 mutant skeleton and the changes in fras1 mutant skeletal defects through time as indicators that skeletal formation is destabilized. We propose a model wherein fras1 prompts late-p1 formation and thereby stabilizes skeletal formation during zebrafish facial development. Similar mechanisms of stochastic developmental instability might also account for the high phenotypic variation observed in human FRAS1 patients.

A puzzle over several decades: eye anomalies with FRAS1 and STRA6 mutations in the same family

Fraser syndrome (FS) and microphthalmia syndromic 9 (MCOPS9) are autosomal recessive conditions with distinct, and some overlapping features affecting the ocular, respiratory and cardiac systems. Mutations in FRAS1 and FREM2 occur in FS, and mutations in STRA6 occur in MCOPS9. We report two sibships, in the same family, where four deceased offspring had ocular, respiratory and cardiac abnormalities. Two sibs with microphthalmia had syndactyly and laryngeal stenosis, suggesting a clinical diagnosis of FS. Our results indicate that they were compound heterozygotes for novel FRAS1 mutations, p.Cys729Phe and p.Leu3813Pro. The other two sibs, first cousins to the first sib pair, had anophthalmia, lung hypoplasia and cardiac anomalies, suggesting a retrospective diagnosis of MCOPS9. Our results indicate compound heterozygous STRA6 mutations, a novel frameshift leading to p.Tyr18* and a p.Thr644Met mutation. The one surviving individual from these sibships is heterozygous for the p.Tyr18*STRA6 mutation and has bilateral ocular colobomata and microphthalmia. This work emphasises the need for careful phenotypic characterisation to determine genes for assessment in ocular syndromic conditions. It also indicates that heterozygous STRA6 mutations may rarely contribute to microphthalmia and coloboma.

Expression of the fras1/frem gene family during zebrafish development and fin morphogenesis

Mouse studies have highlighted the requirement of the extracellular matrix Fras and Frem proteins for embryonic epidermal adhesion. Mutations of the genes encoding some of these proteins underlie the blebs mouse mutants, whereas mutations in human FRAS1 and FREM2 cause Fraser syndrome, a congenital disorder characterized by embryonic blistering and renal defects. We have cloned the zebrafish homologues of these genes and characterized their evolutionary diversification and expression during development. The fish gene complement includes fras1, frem1a, frem1b, frem2a, frem2b, and frem3, which display complex overlapping and complementary expression patterns in developing tissues including the pharyngeal arches, hypochord, musculature, and otic vesicle. Expression during fin development delineates distinct populations of epidermal cells which have previously only been described at a morphological level. We detect relatively little gene expression in epidermis or pronephros, suggesting that the essential role of these proteins in mediating their development in humans and mice is recently evolved.

Fraser syndrome: affected siblings born to nonconsanguineous parents and diagnosed at autopsy

Fraser syndrome (MIM 219000) is a rare genetic disorder with major features including cryptophthalmos, syndactyly, and genital anomalies. We report 2 independently autopsied children of the same nonconsanguineous parents. The siblings exhibit similar clinical features, all of which are consistent with a diagnosis of Fraser syndrome. The gross and microscopic findings provide insight into the highly variable clinical presentation of Fraser syndrome. Molecular diagnostic studies of the index case failed to identify one of the known gene mutations in the FRAS1 and FREM2 genes associated with Fraser syndrome. This raises the possibility that other genes or undetected mutations in the FRAS1/FREM2 genes may cause Fraser syndrome.

Supramodular nature of GRIP1 revealed by the structure of its PDZ12 tandem in complex with the carboxyl tail of Fras1

The scaffold protein GRIP1 (glutamate receptor interacting protein 1) binds to and regulates both the trafficking and membrane organization of a large number of transmembrane proteins. Mutation of GRIP1 in mice displays essentially the same phenotype of the mutations of Fras1 or Frem2, which are the animal models of the human genetic disorder Fraser syndrome. However, the molecular basis governing the interaction between GRIP1 and Fras1/Frem2 is unknown. Here, we show that interaction between Fras1 and GRIP1 requires the first two PDZ domains (PDZ1 and PDZ2) to be connected in tandem, as the folding of PDZ1 strictly depends on the covalent attachment of PDZ2. The crystal structure of GRIP1 PDZ12 in complex with the Fras1 C-terminal peptide reveals that the PDZ12 tandem forms a supramodule in which only the peptide-binding groove of PDZ1 is bound with the Fras1 peptide. The GRIP1 PDZ12/Fras1 peptide complex not only provides a mechanistic explanation of the link between GRIP1 and the Fraser syndrome but may also serve as a foundation for searching for potential mutations in GRIP1 that could lead to the Fraser syndrome.

Manitoba Oculotrichoanal (MOTA) syndrome: report of eight new cases

The Manitoba Oculotrichoanal (MOTA) syndrome was initially described by Marles et al. [1992; Am J Med Genet 42: 793-799] in Aboriginal patients of the Island Lake region of Northern Manitoba. Characteristic findings in affected patients included unilateral upper eyelid coloboma or cryptophthalmus with ipsilateral aberrant anterior hairline pattern and anal anomalies. We describe here seven new patients of the same extended kindred of Cree/Ojibway ethnicity of the Island Lake region and an eighth patient of Caucasian Dutch parents with clinical findings consistent with the diagnosis of MOTA syndrome. Two of the patients have bilateral, instead of unilateral, abnormal anterior hairline patterns. Omphalocele, a feature previously not identified, is present in three of them. The most consistent features appear to be hypertelorism and a broad or notched tip of the nose. Due to the obvious clinical overlap with Fraser syndrome, FRAS1 gene was screened in two of the affected and no mutation was found [Slavotinek et al., submitted].