A clinical study of the craniofacial features in Apert syndrome

A clinical study of the craniofacial features in Apert syndrome is based on our experience with 136 cases. Characteristics included hyperacrobrachycephaly, steep wide forehead, flat occiput, common craniofacial asymmetry, ocular hypertelorism and proptosis, downslanting palpebral fissures, divergent upgaze and esotropic downgaze, a tendency towards large ears, and marked depression of the nasal bridge. The nose is short and wide with a bulbous tip, and the anterior facial height is reduced. Common features during infancy included horizontal grooves above the supraorbital ridges that disappear with age, a break in the continuity of the eyebrows, and a trapezoidal-shaped mouth at rest. Radiographic aspects of Apert syndrome were also assessed. Tables are provided which compare the craniofacial features of Apert and Crouzon syndromes.

X-linked Opitz syndrome: novel mutations in the MID1 gene and redefinition of the clinical spectrum

Opitz (or G/BBB) syndrome is a pleiotropic genetic disorder characterized by hypertelorism, hypospadias, and additional midline defects. This syndrome is heterogeneous with an X-linked (XLOS) and an autosomal dominant (ADOS) form. The gene implicated in the XLOS form, MID1, encodes a protein containing a RING-Bbox-Coiled-coil motif belonging to the tripartite motif (TRIM) family. To further clarify the molecular basis of XLOS, we have undertaken mutation analysis of the MID1 gene in patients with Opitz syndrome (OS). We found novel mutations in 11 of 63 male individuals referred to us as sporadic or familial X-linked OS cases. The mutations are scattered throughout the gene, although more are represented in the 3' region. By reviewing all the MID1-mutated OS patients so far described, we confirmed that hypertelorism and hypospadias are the most frequent manifestations, being present in almost every XLOS individual. However, it is clear that laryngo-tracheo-esophageal (LTE) defects are also common anomalies, being manifested by all MID1-mutated male patients. Congenital heart and anal abnormalities are less frequent than reported in literature. In addition, we can include limb defects in the OS clinical synopsis as we found a MID1-mutated patient showing syndactyly. The low frequency of mutations in MID1 and the high variability of the phenotype suggest the involvement of other genes in the OS phenotype.

Control of mTORC1 signaling by the Opitz syndrome protein MID1

Mutations in the MID1 gene are causally linked to X-linked Opitz BBB/G syndrome (OS), a congenital disorder that primarily affects the formation of diverse ventral midline structures. The MID1 protein has been shown to function as an E3 ligase targeting the catalytic subunit of protein phosphatase 2A (PP2A-C) for ubiquitin-mediated degradation. However, the molecular pathways downstream of the MID1/PP2A axis that are dysregulated in OS and that translate dysfunctional MID1 and elevated levels of PP2A-C into the OS phenotype are poorly understood. Here, we show that perturbations in MID1/PP2A affect mTORC1 signaling. Increased PP2A levels, resulting from proteasome inhibition or depletion of MID1, lead to disruption of the mTOR/Raptor complex and down-regulated mTORC1 signaling. Congruously, cells derived from OS patients that carry MID1 mutations exhibit decreased mTORC1 formation, S6K1 phosphorylation, cell size, and cap-dependent translation, all of which is rescued by expression of wild-type MID1 or an activated mTOR allele. Our findings define mTORC1 signaling as a downstream pathway regulated by the MID1/PP2A axis, suggesting that mTORC1 plays a key role in OS pathogenesis.

A zebrafish model of Roberts syndrome reveals that Esco2 depletion interferes with development by disrupting the cell cycle

The human developmental diseases Cornelia de Lange Syndrome (CdLS) and Roberts Syndrome (RBS) are both caused by mutations in proteins responsible for sister chromatid cohesion. Cohesion is mediated by a multi-subunit complex called cohesin, which is loaded onto chromosomes by NIPBL. Once on chromosomes, cohesin binding is stabilized in S phase upon acetylation by ESCO2. CdLS is caused by heterozygous mutations in NIPBL or cohesin subunits SMC1A and SMC3, and RBS is caused by homozygous mutations in ESCO2. The genetic cause of both CdLS and RBS reside within the chromosome cohesion apparatus, and therefore they are collectively known as "cohesinopathies". However, the two syndromes have distinct phenotypes, with differences not explained by their shared ontology. In this study, we have used the zebrafish model to distinguish between developmental pathways downstream of cohesin itself, or its acetylase ESCO2. Esco2 depleted zebrafish embryos exhibit features that resemble RBS, including mitotic defects, craniofacial abnormalities and limb truncations. A microarray analysis of Esco2-depleted embryos revealed that different subsets of genes are regulated downstream of Esco2 when compared with cohesin subunit Rad21. Genes downstream of Rad21 showed significant enrichment for transcriptional regulators, while Esco2-regulated genes were more likely to be involved the cell cycle or apoptosis. RNA in situ hybridization showed that runx1, which is spatiotemporally regulated by cohesin, is expressed normally in Esco2-depleted embryos. Furthermore, myca, which is downregulated in rad21 mutants, is upregulated in Esco2-depleted embryos. High levels of cell death contributed to the morphology of Esco2-depleted embryos without affecting specific developmental pathways. We propose that cell proliferation defects and apoptosis could be the primary cause of the features of RBS. Our results show that mutations in different elements of the cohesion apparatus have distinct developmental outcomes, and provide insight into why CdLS and RBS are distinct diseases.

Recurrent Mutations in the Basic Domain of TWIST2 Cause Ablepharon Macrostomia and Barber-Say Syndromes

Ablepharon macrostomia syndrome (AMS) and Barber-Say syndrome (BSS) are rare congenital ectodermal dysplasias characterized by similar clinical features. To establish the genetic basis of AMS and BSS, we performed extensive clinical phenotyping, whole exome and candidate gene sequencing, and functional validations. We identified a recurrent de novo mutation in TWIST2 in seven independent AMS-affected families, as well as another recurrent de novo mutation affecting the same amino acid in ten independent BSS-affected families. Moreover, a genotype-phenotype correlation was observed, because the two syndromes differed based solely upon the nature of the substituting amino acid: a lysine at TWIST2 residue 75 resulted in AMS, whereas a glutamine or alanine yielded BSS. TWIST2 encodes a basic helix-loop-helix transcription factor that regulates the development of mesenchymal tissues. All identified mutations fell in the basic domain of TWIST2 and altered the DNA-binding pattern of Flag-TWIST2 in HeLa cells. Comparison of wild-type and mutant TWIST2 expressed in zebrafish identified abnormal developmental phenotypes and widespread transcriptome changes. Our results suggest that autosomal-dominant TWIST2 mutations cause AMS or BSS by inducing protean effects on the transcription factor's DNA binding.

Hypertelorism: interorbital growth, measurements, and pathogenetic considerations

Normal pre- and post-natal changes in the interorbital distance are described. Causes of illusory hypertelorism include flat nasal bridge, epicanthic folds, exotropia, widely-spaced eyebrows, narrow palpebral fissures, and dystopia canthorum. Measurements of hypertelorism may involve soft tissues or bone, and a number of indices have also been proposed. Various types of measurements are evaluated and recommendations suggested. Possible pathogenetic mechanisms for hypertelorism include: early ossification of the lesser wings of the sphenoid; failure in nasal capsule development allowing the primitive brain vesicle to protrude into the space normally occupied by the capsule resulting in morphokinetic arrest in the position of the eyes; and disturbances of the cranial base in Apert syndrome. Associations with increased interorbital distance are also discussed: orofacial clefting, nonprotruding lipomas of the corpus callosum, calcification of the falx cerebri, duplication of the crista galli, wrinkling of the nose, and tissue tags of the nose. Finally, experimental models of hypertelorism in animals are discussed.

The roles of cohesins in mitosis, meiosis, and human health and disease

Mitosis and meiosis are essential processes that occur during development. Throughout these processes, cohesion is required to keep the sister chromatids together until their separation at anaphase. Cohesion is created by multiprotein subunit complexes called cohesins. Although the subunits differ slightly in mitosis and meiosis, the canonical cohesin complex is composed of four subunits that are quite diverse. The cohesin complexes are also important for DNA repair, gene expression, development, and genome integrity. Here we provide an overview of the roles of cohesins during these different events as well as their roles in human health and disease, including the cohesinopathies. Although the exact roles and mechanisms of these proteins are still being elucidated, this review serves as a guide for the current knowledge of cohesins.

Fibroblast growth factor receptor 3 mutation in nonsyndromic coronal synostosis: clinical spectrum, prevalence, and surgical outcome

OBJECT

A recurrent point mutation in the fibroblast growth factor receptor 3 gene that converts proline 250 into arginine has been reported recently in cases of apparently nonsyndromic coronal craniosynostosis. The goal of the present study was to examine the phenotype of patients in whom this mutation was present, to determine the prevalence of the condition, and to assess the functional and the morphological outcome of the surgically treated patients.

METHODS

A DNA analysis was performed in 103 children suffering from apparently isolated coronal synostosis, 41 of whom had bilateral and 62 of whom had unilateral disease. There were 31 boys and 72 girls in the study group. Sixty cases were sporadic and 43 were familial; the 43 familial cases arose in 33 unrelated families. The mutation was found in seven (12%) of 60 sporadic cases and in 24 (73%) of the 33 families. The functional and morphological results were assessed in all surgically treated patients who had at least 1 year of follow up and who were at least 3 years of age at the time of assessment. A comparison was made between patients with the mutation and those without.

CONCLUSIONS

The most typical presentation was seen in girls and consisted of a bicoronal synostosis resulting in a severe brachycephaly associated with mild hypertelorism and marked bulging of the temporal fossae, which resulted in a huge enlargement of the upper part of the face. The most frequently associated extracranial anomaly was brachydactyly, identified either clinically or radiologically. Based on the proportion of bilateral and unilateral coronal synostoses, the present data indicate that the mutation is associated with more severe cases and that girls with the mutation are more severely affected than boys. The functional and morphological results were worse in patients in whom the mutation was present as compared with those in whom it was not.

Clinical and molecular delineation of the Greig cephalopolysyndactyly contiguous gene deletion syndrome and its distinction from acrocallosal syndrome

Greig cephalopolysyndactyly syndrome (GCPS) is caused by haploinsufficiency of GLI3 on 7p13. Features of GCPS include polydactyly, macrocephaly, and hypertelorism, and may be associated with cognitive deficits and abnormalities of the corpus callosum. GLI3 mutations in GCPS patients include point, frameshift, translocation, and gross deletion mutations. FISH and STRP analyses were applied to 34 patients with characteristics of GCPS. Deletions were identified in 11 patients and the extent of their deletion was determined. Nine patients with deletions had mental retardation (MR) or developmental delay (DD) and were classified as severe GCPS. These severe GCPS patients have manifestations that overlap with the acrocallosal syndrome (ACLS). The deletion breakpoints were analyzed in six patients whose deletions ranged in size from 151 kb to 10.6 Mb. Junction fragments were found to be distinct with no common sequences flanking the breakpoints. We conclude that patients with GCPS caused by large deletions that include GLI3 are likely to have cognitive deficits, and we hypothesize that this severe GCPS phenotype is caused by deletion of contiguous genes.

Terminal deletion of 6p results in a recognizable phenotype

With improved cytogenetic techniques, small deletions and duplications are being identified with increased frequency. We report four cases with terminal deletions involving the 6p24- and 6p25-pter chromosomal segment who exhibit a distinct, recognizable pattern of malformations including hypertelorism, downslanting palpebral fissures, flat nasal bridge, Dandy-Walker malformation/variant, congenital heart defects, anterior eye-chamber abnormalities, hearing loss, and developmental delay. We also compare the clinical aspects of these patients to those of previously reported cases in the literature with similar terminal deletions of chromosome 6p. Routine chromosome analysis can miss this deletion, therefore, high-resolution chromosome analysis is indicated for individuals who exhibit these distinct features. Furthermore, individuals with this deletion should have an ophthalmologic exam, cardiac evaluation, head imaging, renal ultrasound, and formal hearing evaluation.

Cohesinopathies of a feather flock together

Roberts Syndrome (RBS) and Cornelia de Lange Syndrome (CdLS) are severe developmental maladies that present with nearly an identical suite of multi-spectrum birth defects. Not surprisingly, RBS and CdLS arise from mutations within a single pathway--here involving cohesion. Sister chromatid tethering reactions that comprise cohesion are required for high fidelity chromosome segregation, but cohesin tethers also regulate gene transcription, promote DNA repair, and impact DNA replication. Currently, RBS is thought to arise from elevated levels of apoptosis, mitotic failure, and limited progenitor cell proliferation, while CdLS is thought to arise, instead, from transcription dysregulation. Here, we review new information that implicates RBS gene mutations in altered transcription profiles. We propose that cohesin-dependent transcription dysregulation may extend to other developmental maladies; the diagnoses of which are complicated through multi-functional proteins that manifest a sliding scale of diverse and severe phenotypes. We further review evidence that cohesinopathies are more common than currently posited.

A longitudinal study on influence of primary facial deformities on maxillofacial growth in patients with cleft lip and palate

OBJECTIVE

The goal of this study was to use three-dimensional (3D) analysis to characterize the primary facial deformities in children with unilateral cleft lip and palate (UCLP) and then serially analyze the relationships between facial deformities and maxillofacial growth from infancy to adolescence.

PARTICIPANTS

Twenty-one Japanese subjects with unilateral cleft lip and alveolus (UCLA) and 20 with UCLP who had been operated on and then followed up for more than 15 years were enrolled in this study.

MAIN OUTCOME MEASURES

Facial cast models taken at cheiloplasty were scanned with a 3D laser scanner. Lateral cephalographs taken when subjects were 15 years of age or older were traced, and linear and angular measurements were calculated. The correlation between primary facial forms and maxillofacial morphology in adolescence was analyzed.

RESULTS

Three-dimensional analysis showed larger ocular hypertelorism, wider cleft, greater deviation of the columella base, and more severe retruded position of the affected nasal alar base in subjects with UCLP than those with UCLA. Total surface area of the upper lips in subjects with UCLP was significantly smaller than those with UCLA. Correlation analyses revealed that the width of cleft lip, deviation of the columella base, difference of the nose base width, and surface area of the upper lip were statistically correlated with the maxillary length, the anterior position of the maxillary alveolar base, the posterior facial height, and the high angle of the mandible.

CONCLUSION

The subjects who had less severe facial deformities and more tissue volume of the upper lips at cheiloplasty showed better maxillofacial growth.

Crouzon syndrome: cephalometric analysis and evaluation of pathogenesis

Crouzon syndrome is a craniofaciostenosis characterized by brachycephaly, ocular proptosis, and maxillary retrusion. The hypothesis has been forwarded that an alteration in anterior cranial base synchondrosis activity is responsible for the skeleton abnormalities which are associated with this disorder. The present work was aimed at assessing this pathogenetic hypothesis. Cephalometry was used as the analysis method and care was taken in determining the three-dimensional measurements of some functional spaces (e.g., orbit, rhinopharynx, and nasal cavity). The results indicate that in Crouzon syndrome the craniofacial alterations depend not only on reduced synchondrosis activity of the anterior cranial base, but also of the posterior cranial base.

Michels syndrome, Carnevale syndrome, OSA syndrome, and Malpuech syndrome: Variable expression of a single disorder (3MC syndrome)?

We report on a 3-year-old girl with Michels syndrome, a rare condition characterized by craniosynostosis, blepharophimosis, ptosis, epicanthus inversus, cleft lip/palate, abnormal supra-umbilical abdominal wall, and mental deficiency. The phenotypic findings are compared with the six previously reported Michels cases, and with patients referred to as Carnevale, OSA, and Malpuech syndromes. Michels syndrome is characterized by cleft lip and palate, anterior chamber anomalies, blepharophimosis, epicanthus inversus, and craniosynostosis. Carnevale syndrome shows hypertelorism, downslanting palpebral fissures, ptosis, strabismus synophrys, large and fleshy ears, and lozenge-shaped diastasis around the umbilicus. OSA syndrome resembles Carnevale, with humeroradial synostoses, and spinal anomalies as extra features. Malpuech syndrome shows IUGR, hypertelorism, cleft lip and palate, micropenis, hypospadias, renal anomalies, and caudal appendage. All are autosomal recessive. Despite the presence of apparently distinctive key features, it appears that these four entities share multiple similarities in the facial Gestalt and the pattern of MCA. Those similarities lead us to postulate that they belong to the same spectrum, which could be referred to as "3MC syndrome" (Malpuech-Michels-Mingarelli-Carnevale syndrome).

Familial Del(18p) syndrome

We report on sibs and their mother, all with del(18p). The propositus, an 11-month-old, had developmental delay, round face, hypertelorism, large ears, broad nasal bridge, upturned nostrils, micrognathia, a high palate, redundant skin around the neck, micropenis, and cryptorchidism. The elder sister, a two and 7/12-year-old, had round face, hypertelorism, broad nasal bridge, narrow and high palate, redundant skin around the neck, short fingers, and hypoplastic genitalia. Their mother had microcephaly, hypertelorism, prominent columella, broad nasal bridge, wide mouth, high palate, malaligned teeth, and clinodactyly of the fifth fingers. Serial photographs of the mother showed that the characteristic round face in infancy changed to long face with age. The present report suggests that the mother with del(18p) may be fertile, and proper genetic counseling and long follow-up is necessary for the patient with del(18p) syndrome.

Basilar multiplane cephalometric analysis

This article presents a method of cephalometric tracing and analysis using the basilar view cephalogram and discusses its role in diagnosis and treatment planning. Landmarks and structures found in each of three separate basilar planes are defined and instructions for tracings are presented. The analysis is applied to the study of orbital hypertelorism, craniofacial synostosis, and hemicraniofacial microsomia. The multiplane tracing technique is demonstrated to provide a three-dimensional concept of deformities in the craniofacial skeleton. A method to determine an anteroposterior midline construct from structures in the cranial base is described. As is practiced with the lateral cephalogram, presurgical tracings of the basilar film may be manipulated to simulate the skeletal changes anticipated in surgery.

Pigmentary anomalies in the multiple lentigines syndrome: Is it distinct from LEOPARD syndrome?

We observed 2 families with 26 individuals affected by multiple lentigines syndrome (MLS). All patients had extensive generalized lentigines, including in the axillary and inguinal regions, diffuse hyperpigmentation, hypopigmented patches, and hyperpigmented patches, many of which appeared clinically to be cafe au lait spots. Multiple lentigines syndrome should be considered in the differential diagnosis of multiple cafe au lait spots in children, particularly since the spots are usually present before the lentigines develop and may be clinically indistinguishable from the cafe au lait spots of neurofibromatosis. No significant noncutaneous features occurred in the two families with three generations of affected individuals, suggesting that MLS is a distinct entity. However, patients with the noncutaneous abnormalities of the LEOPARD syndrome have been described in families in which most members had pigmentary lesions only. Therefore, patients with multiple lentigines should be evaluated for noncutaneous abnormalities, particularly hearing loss and cardiac anomalies. Similarly, until investigators demonstrate lack of genetic linkage between MLS and LEOPARD syndrome, genetic counseling of patients affected by the cutaneous features of the former should include the potential for noncutaneous features in offspring.

Greig syndrome in a large kindred due to reciprocal chromosome translocation t(6;7)(q27;p13)

We report on cases of Greig syndrome segregating in a large kindred over four generations due to reciprocal translocation t(6;7)(q27;p13) and on a patient from this pedigree with a severe malformation syndrome due to duplication 7(p13----pter). The clinical findings are discussed as possible consequence of a gene mutation due to the break at 7p13.

New cases of Bohring–Opitz syndrome, update, and critical review of the literature

We report on four additional unrelated cases of Bohring-Opitz syndrome with the highly characteristic phenotype of facial anomalies including bulging forehead over the metopic suture, frontal nevus flammeus, exophthalmos, hypertelorism, upslanting palpebral fissures, and cleft lip and/or palate, as well as flexion deformities of the upper limbs, multiple other anomalies, and severe failure to thrive. We also update the clinical outcome of the patients reported in the original article by Bohring et al. [Am J Med Genet 85:438-446] and critically review the subsequently published cases considered to have Bohring-Opitz syndrome.

Intercanthal and interpupillary distance in the black population

Intercanthal distance is an important measurement in the evaluation of congenital deformities and posttraumatic telecanthus. In this study 100 black patients (71 female and 29 male) were measured for intercanthal and interpupillary distance. For the overall group the mean intercanthal distance was 33.9 +/- 3.0 mm; previous studies of white persons and mixed populations indicate an average of 32 +/- 3 mm. The mean interpupillary distance for this study was 63.7 +/- 3.7 mm; previous studies indicate an average of 63 +/- 3 mm. This study suggests that the intercanthal and interpupillary distances in blacks are similar to findings of previous studies on whites and mixed populations.

Variations in dysfunction of sister chromatid cohesion in esco2 mutant zebrafish reflect the phenotypic diversity of Roberts syndrome

Mutations in ESCO2, one of two establishment of cohesion factors necessary for proper sister chromatid cohesion (SCC), cause a spectrum of developmental defects in the autosomal-recessive disorder Roberts syndrome (RBS), warranting in vivo analysis of the consequence of cohesion dysfunction. Through a genetic screen in zebrafish targeting embryonic-lethal mutants that have increased genomic instability, we have identified an esco2 mutant zebrafish. Utilizing the natural transparency of zebrafish embryos, we have developed a novel technique to observe chromosome dynamics within a single cell during mitosis in a live vertebrate embryo. Within esco2 mutant embryos, we observed premature chromatid separation, a unique chromosome scattering, prolonged mitotic delay, and genomic instability in the form of anaphase bridges and micronuclei formation. Cytogenetic studies indicated complete chromatid separation and high levels of aneuploidy within mutant embryos. Amongst aneuploid spreads, we predominantly observed decreases in chromosome number, suggesting that either cells with micronuclei or micronuclei themselves are eliminated. We also demonstrated that the genomic instability leads to p53-dependent neural tube apoptosis. Surprisingly, although many cells required Esco2 to establish cohesion, 10-20% of cells had only weakened cohesion in the absence of Esco2, suggesting that compensatory cohesion mechanisms exist in these cells that undergo a normal mitotic division. These studies provide a unique in vivo vertebrate view of the mitotic defects and consequences of cohesion establishment loss, and they provide a compensation-based model to explain the RBS phenotypes.

Hirschsprung disease, mental retardation and dysmorphic facial features in five unrelated children

We report five patients with Hirschsprung disease, severe mental retardation and dysmorphic facial features including hypertelorism, prominent forehead and dysmorphic ears. All four boys had hypospadias. All had postnatally retarded growth. One of them had a de novo apparently balanced translocation 46,XY,t(2;11)(q22.2;q21). There are several reports on patients with Hirschsprung disease, mental retardation and various dysmorphic features. Some of them, especially those reported by Tanaka et al. [(1993) Pediatr Neurol 9:479-481], Lurie et al. [(1994) Genet Couns 5:11-14] and Mowat et al. [(1998) J Med Genet 35:617-623] closely resemble our patients suggesting that they have the same malformation syndrome.

Clinical variation of Aarskog syndrome in a large family with 2189delA in the FGD1 gene

The clinical diagnosis of ASS (Aarskog-Scott syndrome or Faciogenital Dysplasia) was made in seven individuals belonging to a large Arabic family, which was supported by molecular studies revealing a 2189delA mutation in exon 15 of the FDG1 gene. The affected individuals in this family demonstrated clinical variability particularly in their cognitive skills, raising the question whether other genetic factors might be involved in the phenotypic evolution of ASS.

The non-redundant function of cohesin acetyltransferase Esco2: some answers and new questions

Cohesin and cohesin regulatory proteins function in an essential pathway enabling proper cohesion and segregation of sister chromatids. Additionally, these proteins are involved in double-strand break (DSB) repair and transcriptional regulation. Mutations in Establishment of cohesion 1 homolog 2 (Esco2), an evolutionary conserved cohesin acetyltransferase, are the cause of Roberts syndrome (RBS), a human congenital disorder. To explore the mechanism by which the deficiency in Esco2 affects cohesin's functions, we generated a mouse harboring a conditional Esco2 allele. To our surprise and in marked contrast to RBS, mouse Esco2 turns out to be a cell viability factor, the absence of which results in severe chromosome segregation defects and apoptosis. We found that the acetylation of the cohesin subunit Smc3 is significantly reduced in Esco2-deficient cells resulting in a marked reduction of Sororin recruitment to several, but not all cohesin bound loci. Here, we provide evidence that Esco2 is also required for DSB repair, which is consistent with previous studies in RBS cells.