Congenital Fibrosis Of The Extraocular Muscles Type 1 Research Articles

A loss of function mutation in the filaggrin gene associated with ichthyosis vulgaris and rheumatoid arthritis

IntroductionMutations in the filaggrin ( FLG) gene are known to cause ichthyosis vulgaris.MethodsWe used whole-genome sequencing (WGS) technology to investigate the genetic causes of rare and complex inherited diseases including rheumatoid arthritis, ichthyosis, and congenital fibrosis of the extraocular muscles type 1 (CFEOM1) in a Chinese family. WGS was performed in four topics, and the identified candidate mutations were further verified through Sanger sequencing.ResultsWe identified a mutation in FLG gene (g.152280098 C>A, p.E2422∗) that may be associated with ichthyosis and arthritis. Moreover, a mutation in KIF21A (g.39726207 G>A, p.R954 W) was also determined in affected members as the cause of CFEOM1. The gene interaction network demonstrated an interesting correlation between FLG and genes associated with arthritis and ichthyosis. Functional enrichment analysis of these interacting genes revealed several possible pathways that might be linked to arthritis and ichthyosis.ConclusionIn general, we confirmed a loss of function mutation in the FLG gene associated with ichthyosis vulgaris and rheumatoid arthritis in this family.

The recurrent TUBB3 Gly98Ser substitution is the first described to inconsistently result in CFEOM3

Missense variants in TUBB3 have historically been associated with either congenital fibrosis of the extraocular muscles type 3 (CFEOM3) or malformations of cortical development (MCD). Until a recent report identified two amino acid substitutions in four patients that had clinical features of both disorders, pathogenic variants of TUBB3 were thought distinct to either respective disorder. Three recurrent de novo Gly71Arg TUBB3 substitutions and a single patient with a de novo Gly98Ser substitution blurred the MCD and CFEOM3 phenotypic distinctions. Here we report a second patient with a missense c.292G>A (p.Gly98Ser) substitution, but without CFEOM3, the first reported evidence that even the same TUBB3 substitution can produce a spectrum of TUBB3 syndrome phenotypes. Our patient presented with amblyopia, exotropia, optic disc pallor, and developmental delay. Neuroimaging identified hypoplasia of the corpus callosum, interdigitation of the frontal lobe gyri, and dysplasia or hypoplasia of the optic nerves, basal ganglia, brainstem, and cerebellum. This report identifies the TUBB3 Gly98Ser substitution to be recurrent but inconsistently including CFEOM3, and identifies the absence of joint contractures and the presence of optic disc abnormalities that may be genotype-specific to the TUBB3 Gly98Ser substitution.

Clinical characteristics of a KIF21A mutation in a Chinese family with congenital fibrosis of the extraocular muscles type 1.

The aim of the study is to characterize the clinical ocular phenotype with congenital fibrosis of the extraocular muscles type 1 (CFEOM1) and to confirm whether the kinesin family member 21A (KIF21A) mutation was the pathogenic gene in this Chinese family.Three affected individuals and 2 asymptomatic kinsfolk from a Chinese family underwent comprehensive ophthalmic examinations, orbital computerized tomography (CT), and postoperative histological examinations were performed in the proband. All the recruited members were screened for 3 exons (8, 20, and 21) of KIF21A mutations using the polymerase chain reaction (PCR) amplification and direct sequencing of corresponding PCR products.All patients shared the clinical characteristics including bilateral ophthalmoplegia, blepharoptosis, hypertropic, and exotropic position with inability to raise either eye above the midline and a chin-up head position. Direct DNA sequence analysis from the affected members revealed a missense mutation in KIF21A (c.2860C>T, p.R954W). The unaffected members did not harbor the p.R954W mutation. The candidate mutation was not present in multiple web-accessible and in-house exome databases.The p.Arg954Trp mutation of KIF21A was the causative mutation in this Chinese pedigree with CFEOM1.

Reversal of axonal growth defects in an extraocular fibrosis model by engineering the kinesin-microtubule interface.

Mutations in human β3-tubulin (TUBB3) cause an ocular motility disorder termed congenital fibrosis of the extraocular muscles type 3 (CFEOM3). In CFEOM3, the oculomotor nervous system develops abnormally due to impaired axon guidance and maintenance; however, the underlying mechanism linking TUBB3 mutations to axonal growth defects remains unclear. Here, we investigate microtubule (MT)-based motility in vitro using MTs formed with recombinant TUBB3. We find that the disease-associated TUBB3 mutations R262H and R262A impair the motility and ATPase activity of the kinesin motor. Engineering a mutation in the L12 loop of kinesin surprisingly restores a normal level of motility and ATPase activity on MTs carrying the R262A mutation. Moreover, in a CFEOM3 mouse model expressing the same mutation, overexpressing the suppressor mutant kinesin restores axonal growth in vivo. Collectively, these findings establish the critical role of the TUBB3-R262 residue for mediating kinesin interaction, which in turn is required for normal axonal growth and brain development.

Diagnostic Distinctions and Genetic Analysis of Patients Diagnosed with Moebius Syndrome

To improve diagnostic assessment in Moebius syndrome by (1) creating more selective diagnostic subgroups and (2) conducting genetic evaluation in a large patient cohort. Prospective, observational study. Attendees of 3 consecutive Moebius syndrome conferences held in the United States, with a prior diagnosis of Moebius syndrome, were invited to participate. Participants underwent standardized ophthalmologic examination for Moebius syndrome minimum diagnostic criteria (MDC) (congenital, nonprogressive facial palsy, and abduction deficit) and genetic testing for HOXA1, HOXB1, and TUBB3 mutations. The number of patients meeting MDC and the number of patients with confirmed genetic mutation. A total of 112 participants from 107 families enrolled. Nineteen percent of participants (21/112) did not meet accepted MDC for Moebius syndrome because they had abduction deficits without facial palsy or facial palsy with full ocular motility. All 5 families with 2 affected individuals had at least 1 family member in this category, including 2 siblings with comitant strabismus who harbored a HOXB1 mutation. Four unrelated participants, also not meeting MDC, had large-angle exotropia, vertical gaze deficiency, and ptosis consistent with congenital fibrosis of the extraocular muscles type 3 (CFEOM3); 1 patient harbored a novel TUBB3 mutation, and 3 patients harbored previously reported de novo TUBB3 mutations. Three percent of participants (3/112) met MDC but also had restricted vertical gaze. The remaining 88 participants (79%) met MDC and had full vertical gaze. This group had relatively homogeneous findings, and none had a family history of Moebius syndrome. Two previously undescribed phenomena were observed in this category: (1) volitional Bell's phenomenon and (2) intorsion with fixation. Although the genetic contributors to classic Moebius syndrome remain elusive, accuracy in clinical evaluation will properly subdivide patients to facilitate genetic testing as new candidate genes are identified. Failure to test ocular motility may lead to misdiagnosis of Moebius syndrome, especially in patients who have facial palsy with full ductions. Patients with exotropia, vertical gaze limitation, and ptosis do not have classic Moebius syndrome and may have TUBB3 mutations associated with CFEOM3. To optimize genetic analysis, we propose adding "full vertical motility" to the MDC for Moebius syndrome.

CFEOM1-Associated Kinesin KIF21A Is a Cortical Microtubule Growth Inhibitor

Mechanisms controlling microtubule dynamics at the cell cortex play a crucial role in cell morphogenesis and neuronal development. Here, we identified kinesin-4 KIF21A as an inhibitor of microtubule growth at the cell cortex. In vitro, KIF21A suppresses microtubule growth and inhibits catastrophes. In cells, KIF21A restricts microtubule growth and participates in organizing microtubule arrays at the cell edge. KIF21A is recruited to the cortex by KANK1, which coclusters with liprin-α1/β1 and the components of the LL5β-containing cortical microtubule attachment complexes. Mutations in KIF21A have been linked to congenital fibrosis of the extraocular muscles type 1 (CFEOM1), a dominant disorder associated with neurodevelopmental defects. CFEOM1-associated mutations relieve autoinhibition of the KIF21A motor, and this results in enhanced KIF21A accumulation in axonal growth cones, aberrant axon morphology, and reduced responsiveness to inhibitory cues. Our study provides mechanistic insight into cortical microtubule regulation and suggests that altered microtubule dynamics contribute to CFEOM1 pathogenesis.

Spatiotemporal expression pattern of KIF21A during normal embryonic development and in congenital fibrosis of the extraocular muscles type 1 (CFEOM1)

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is a rare inherited strabismus syndrome characterized by non-progressive ophthalmoplegia. We previously identified that CFEOM1 results from heterozygous missense mutations in KIF21A, which encodes a kinesin motor protein. Here we evaluate the expression pattern of KIF21A in human brain and muscles of control and CFEOM1 patients, and during human and mouse embryonic development. KIF21A is expressed in the cell bodies, axons, and dendrites of many neuronal populations including those in the hippocampus, cerebral cortex, cerebellum, striatum, and motor neurons of the oculomotor, trochlear, and abducens nuclei from early development into maturity, and its spatial distribution is not altered in the CFEOM1 tissues available for study. Multiple splice isoforms of KIF21A are identified in human fetal brain, but none of the reported CFEOM1 mutations are located in or near the alternatively spliced exons. KIF21A immunoreactivity is also observed in extraocular and skeletal muscle biopsies of control and CFEOM1 patients, where it co-localizes with triadin, a marker of the excitation–contractile coupling system. The diffuse and widespread expression of KIF21A in the developing human and mouse central and peripheral nervous system as well as in extraocular muscle does not account for the restricted ocular phenotype observed in CFEOM1, nor does it permit the formal exclusion of a myogenic etiology based on expression patterns alone.

KIF21A novel deletion and recurrent mutation in patients with congenital fibrosis of the extraocular muscles-1

Kinesin family member 21A (KIF21A) mutation is the most common cause for congenital fibrosis of the extraocular muscles type 1 (CFEOM1) in populations worldwide. However, only 12 missense mutations have been reported to date. In this study, KIF21A screening was performed in two Chinese families with CFEOM1. Ophthalmological examinations were performed. The coding exons and adjacent intronic regions of KIF21A were analyzed with cycle sequencing. The novel mutation identified was further evaluated in 150 normal control individuals and available family members. Two heterozygous mutations in KIF21A, c.3000_3002delTGA (p.Asp1001del) and c.2861G>A (p.Arg954Gln), were detected in two families. The novel deletion involves a conserved residue in the coiled-coil domain of KIF21A and is co-segregated with the disease in the examined family, yet was absent in the 300 control chromosomes. In addition, apart from typical phenotypes for CFEOM1, optic disc hypoplasia was also observed in two patients. Deletion mutation in KIF21A has not been previously reported. Our study expands the KIF21 mutation spectrum. This study adds to the current state of knowledge about KIF21A mutations and CFEOM1, which may improve future clinical practice.

Evidence of an Asymmetrical Endophenotype in Congenital Fibrosis of Extraocular Muscles Type 3 Resulting fromTUBB3Mutations

Orbital magnetic resonance imaging (MRI) was used to investigate the structural basis of motility abnormalities in congenital fibrosis of the extraocular muscles type 3 (CFEOM3), a disorder resulting from missense mutations in TUBB3, which encodes neuron-specific beta-tubulin isotype III. Ophthalmic examinations in 13 volunteers from four CFEOM3 pedigrees and normal control subjects, were correlated with TUBB3 mutation and MRI findings that demonstrated extraocular muscle (EOM) size, location, contractility, and innervation. Volunteers included clinically affected and clinically unaffected carriers of R262C and D417N TUBB3 amino acid substitutions and one unaffected, mutation-negative family member. Subjects with CFEOM3 frequently had asymmetrical blepharoptosis, limited vertical duction, variable ophthalmoplegia, exotropia, and paradoxical abduction in infraduction. MRI demonstrated variable, asymmetrical levator palpebrae superioris and superior rectus EOM atrophy that correlated with blepharoptosis, deficient supraduction, and small orbital motor nerves. Additional EOMs exhibited variable hypoplasia that correlated with duction deficit, but the superior oblique muscle was spared. Ophthalmoplegia occurred only when the subarachnoid width of CN3 was <1.9 mm. A-pattern exotropia was frequent, correlating with apparent lateral rectus (LR) muscle misinnervation by CN3. Optic nerve (ON) cross sections were subnormal, but rectus pulley locations were normal. CFEOM3 caused by TUBB3 R262C and D417N amino acid substitutions features abnormalities of EOM innervation and function that correlate with subarachnoid CN3 hypoplasia, occasional abducens nerve hypoplasia, and subclinical ON hypoplasia that can resemble CFEOM1. Clinical and MRI findings in CFEOM3 are more variable than those in CFEOM1 and are often asymmetrical. Apparent LR innervation by the inferior rectus motor nerve is an overlapping feature of Duane retraction syndrome and CFEOM1. These findings suggest that CFEOM3 is an asymmetrical, variably penetrant, congenital cranial dysinnervation disorder leading to secondary EOM atrophy.

A major mutation of KIF21A associated with congenital fibrosis of the extraocular muscles type 1 (CFEOM1) enhances translocation of Kank1 to the membrane

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is associated with heterozygous mutations in the KIF21A gene, including a major (R954W) and a minor (M947T) mutation. Kank1, which regulates actin polymerization, cell migration and neurite outgrowth, interacted with the third and fourth coiled-coil domains of KIF21A protein at its ankyrin-repeat domain. While both KIF21AR954W and KIF21AM947T enhanced the formation of a heterodimer with the wild type, KIF21AWT, these mutants also enhanced the interaction with Kank1. Knockdown of KIF21A resulted in Kank1 predominantly occurring in the cytosolic fraction, while KIF21AWT slightly enhanced the translocation of Kank1 to the membrane fraction. Moreover, KIF21AR954W significantly enhanced the translocation of Kank1 to the membrane fraction. These results suggest that KIF21A regulates the distribution of Kank1 and that KIF21A mutations associated with CFEOM1 enhanced the accumulation of Kank1 in the membrane fraction. This might cause an abrogation of neuronal development in cases of CFEOM1 through over-regulation of actin polymerization by Kank1.

Unexpected clinical involvement of hereditary total leuconychia with congenital fibrosis of the extraocular muscles in three generations

We report familial segregation of hereditary total leuconychia (HTL) with ptosis and restriction of ocular motility due to congenital fibrosis of the extraocular muscles type 1 (CFEOM1) in three generations. In this family, 4 people have HTL and ptosis, and there is restriction of ocular motility due to CFEOM1 in 10 members of the family. To our knowledge, this is the first description of familial segregation of CFEOM1 and HTL, and the second report of unexpected clinical involvement of CFEOM1. We suggest that CFEOM1 is not an isolated phenomenon in these cases. These phenotypes provide valuable insight into the function of the gene(s) localized to 12q13, giving a new perspective on the clinical component of molecular dysmorphology, but this requires further clarification.

049: Magnetic resonance imaging (MRI) of the endophenotype of congenital fibrosis of the extraocular muscles type 3 (CFEOM3)

Introduction: We used MRI to characterize abnormalities in CFEOM3, an autosomal-dominant atypical form of congenital fibrosis featuring asymmetry and variable penetrance.

Congenital Fibrosis of the Extraocular Muscles Type 1, Distinctive Conjunctival Changes and Intrapapillary Disc Colobomata

A 6-month-old boy presented with a congenital eye movement disorder consistent with congenital fibrosis of the extraocular muscles type 1 (CFEOM1). Mutational analysis confirmed the most common mutation in the CFEOM1 gene KIF21A. In addition to the typical findings in CFEOM1, distinctive conjunctival changes and small bilateral optic disc colobomata were also noted. It is suggested that optic disc colobomata represent a new association of CFEOM1.

Novel and Recurrent KIF21A Mutations in Congenital Fibrosis of the Extraocular Muscles Type 1 and 3

To characterize the disease-causing mutations and associated clinical phenotypes in 5 Chinese families with congenital fibrosis of the extraocular muscles (CFEOM). Ophthalmic investigations included visual acuity, levator function, documentation of compensatory head position, ocular motility, and slitlamp and fundus examinations. The kinesin family member 21A gene (KIF21A) was sequenced for mutation detection. Genotyping and linkage analysis were performed for the KIF21A/FEOM1 and FEOM3 loci. Four families were clinically classified as having CFEOM type 1 (CFEOM1) with full expression of severe ptosis and ophthalmoplegia. One family had CFEOM type 3 (CFEOM3) with typically varying expression of phenotypes between individuals. Recurrent heterozygous KIF21A mutations were identified in 2 CFEOM1 families (2860C>T) and the CFEOM3 family (2861G>A). In another CFEOM1 family, a novel missense mutation (84C>G, C28W) was revealed. The novel KIF21A mutation 84C>G demonstrated in a CFEOM1 family affects the kinesin motor domain, supporting that mutations may also occur outside the commonly involved coiled-coil domain. The 2861G>A mutation found in a CFEOM3 family has been previously reported in CFEOM1, further supporting that different phenotypes can arise from identical mutations. Clinical Relevance Clinical and genetic characterization are complementary tools for diagnostic, prognostic, and treatment purposes in CFEOM.

Mutation p.Arg954Trp of KIF21A Causes Congenital Fibrosis of the Extraocular Muscles in a Chinese Family

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is an autosomal dominant strabismus disorder associated with defects of the oculomotor nerve. In this study, we identified a Chinese family with CFEOM1 for four generations. Linkage analysis mapped the causative gene of the family to 12q with a Lod score 2.1 for polymorphic marker D12S85, where KIF21A is located. Direct DNA sequence analysis identified a 2860C→T change in exon 21, resulting in a tryptophan substitution for arginine in codon 954 of KIF21A. SSCP (single-stranded conformational polymorphism) analysis showed that mutation p.Arg954Trp of KIF21A co-segregated with the affected members, but was absent in the unaffected individuals in the family and 150 normal controls. Our results indicate that mutation p.Arg954Trp of the KIF21A is the genetic basis of the Chinese family with CFEOM1.

Recurrent Mutation of the KIF21A Gene in Japanese Patients with Congenital Fibrosis of the Extraocular Muscles

To report recurrent mutation of the KIF21A gene in three Japanese families in which some members have congenital fibrosis of the extraocular muscles type 1 (CFEOM1), and to describe the clinical characteristics of the families. Standard ocular examinations were performed on 18 normal and affected members of three unrelated families. To detect mutations, we determined the DNA sequence of exons 8, 20, and 21 and the splice sites of the KIF21A gene. All affected members had a heterozygous mutation of the KIF21A gene in exon 21 (R954W). Clinically, each patient had congenital bilateral ptosis, an infraducted primary position of each eye, and the inability to raise either eye above midline. The KIF21A gene mutation R954W was detected in the patients with CFEOM1 screened in this study, all of whom were Japanese, reflecting similar reports from Europe, America, the Middle East, and Japan. We suggest that mutations of the KIF21A gene contribute to the development of CFEOM1 regardless of ethnicity. We also found that the delimitation of the KIF21A gene mutation site enabled us to efficiently detect the KIF21A gene mutation despite the large number of KIF21A gene exons.

Magnetic Resonance Imaging Evidence For Widespread Orbital Dysinnervation in Congenital Fibrosis of Extraocular Muscles Due to Mutations inKIF21A

High-resolution orbital magnetic resonance imaging (MRI) was used to investigate the structural basis of ocular motility abnormalities in humans with congenital fibrosis of the extraocular muscles type 1 (CFEOM1) due to missense mutations in the developmental kinesin KIF21A. Clinical ophthalmic and motility findings in 19 volunteers from six unrelated CFEOM1 pedigrees harboring four of the six reported KIF21A mutations and 23 normal control subjects were correlated with MRI studies demonstrating extraocular muscle (EOM) size, location, contractility, and innervation. Subjects with CFEOM1 had severe bilateral blepharoptosis, limited supraduction, and variable ophthalmoplegia. In affected subjects, MRI demonstrated atrophy of the levator palpebrae superioris and superior rectus EOMs and small or absent orbital motor nerves. The oculomotor nerve was most severely hypoplastic, but the abducens was also affected. EOMs exhibited variable atrophy and an abnormally bright T1 signal. Subjects with the R954W and R954Q substitutions frequently exhibited A-pattern strabismus, with misinnervation of the lateral rectus muscle by an oculomotor nerve branch. Rectus pulley locations were generally normal. Subjects with CFEOM1 exhibited subclinical but highly significant reduction from normal in mean optic nerve size (P < 0.001). Comparing clinical and MRI phenotypes did not reveal distinguishing features among KIF21A mutations. Orbital imaging in CFEOM1 due to various amino acid substitutions in the kinesin KIF21A demonstrates consistent abnormalities of motor and sensory innervation in the orbit. These findings suggest that neuronal disease is primary in CFEOM1, with myopathy arising secondary to abnormal innervation and minimal rectus pulley abnormality secondary to reduced EOM forces.

Congenital Fibrosis of Extraocular Muscles Type 1 with Progression of Ophthalmoplegia

Background Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is a congenital, non-progressive autosomal-dominant disorder with bilateral oculomotor nerve palsy due to mutations in the kinesin motor protein gene KIF21A. - Results We present a 60-year old patient with CFEOM1 due to the common C2860T mutation in KIF21A. At the age of 37, he complained about newly occurred diplopia, which implies the capability of binocular vision before. The divergence of both globes progressed and the poor residual movement on attempted adduction and upgaze completely disappeared during the sixths decade. Clinical and electromyographic examination showed isolated involvement of the oculomotor nerve. - Conclusion Apparently, progression of impaired ocular motility is not contradictory to the diagnosis of this congenital developmental disorder. Mechanical, contracture-like mechanisms as known from other types of strabism or persistent overuse of the reduced number of oculomotor a-motoneurons are generally considered as a reason for clinical progression. However, regarding the underlying known molecular basis of CFEOM1, a continuous disease progression due to the kinesin dysfunction cannot be excluded.

Identification of KIF21A mutations as a rare cause of congenital fibrosis of the extraocular muscles type 3 (CFEOM3).

Three congenital fibrosis of the extraocular muscles phenotypes (CFEOM1-3) have been identified. Each represents a specific form of paralytic strabismus characterized by congenital restrictive ophthalmoplegia, often with accompanying ptosis. It has been demonstrated that CFEOM1 results from mutations in KIF21A and CFEOM2 from mutations in PHOX2A. This study was conducted to determine the incidence of KIF21A and PHOX2A mutations among individuals with the third CFEOM phenotype, CFEOM3. All pedigrees and sporadic individuals with CFEOM3 in the authors' database were identified, whether the pedigrees were linked or consistent with linkage to the FEOM1, FEOM2, and/or FEOM3 loci was determined, and the appropriate pedigrees and the sporadic individuals were screened for mutations in KIF21A and PHOX2A. Twelve CFEOM3 pedigrees and 10 CFEOM3 sporadic individuals were identified in the database. The structures of eight of the pedigrees permitted the generation of meaningful linkage data. KIF21A was screened in 17 probands, and mutations were identified in two CFEOM3 pedigrees. One pedigree harbored a novel mutation (2841G-->A, M947I) and one harbored the most common and recurrent of the CFEOM1 mutations identified previously (2860C-->T, R954W). None of CFEOM3 pedigrees or sporadic individuals harbored mutations in PHOX2A. The results demonstrate that KIF21A mutations are a rare cause of CFEOM3 and that KIF21A mutations can be nonpenetrant. Although KIF21A is the first gene to be associated with CFEOM3, the results imply that mutations in the unidentified FEOM3 gene are the more common cause of this phenotype.

Heterozygous mutations of the kinesin KIF21A in congenital fibrosis of the extraocular muscles type 1 (CFEOM1).

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1; OMIM #135700) is an autosomal dominant strabismus disorder associated with defects of the oculomotor nerve. We show that individuals with CFEOM1 harbor heterozygous missense mutations in a kinesin motor protein encoded by KIF21A. We identified six different mutations in 44 of 45 probands. The primary mutational hotspots are in the stalk domain, highlighting an important new role for KIF21A and its stalk in the formation of the oculomotor axis.