Maria Leine Guion-Almeida

Haploinsufficiency of a Spliceosomal GTPase Encoded by EFTUD2 Causes Mandibulofacial Dysostosis with Microcephaly

Mandibulofacial dysostosis with microcephaly (MFDM) is a rare sporadic syndrome comprising craniofacial malformations, microcephaly, developmental delay, and a recognizable dysmorphic appearance. Major sequelae, including choanal atresia, sensorineural hearing loss, and cleft palate, each occur in a significant proportion of affected individuals. We present detailed clinical findings in 12 unrelated individuals with MFDM; these 12 individuals compose the largest reported cohort to date. To define the etiology of MFDM, we employed whole-exome sequencing of four unrelated affected individuals and identified heterozygous mutations or deletions of EFTUD2 in all four. Validation studies of eight additional individuals with MFDM demonstrated causative EFTUD2 mutations in all affected individuals tested. A range of EFTUD2-mutation types, including null alleles and frameshifts, is seen in MFDM, consistent with haploinsufficiency; segregation is de novo in all cases assessed to date. U5-116kD, the protein encoded by EFTUD2, is a highly conserved spliceosomal GTPase with a central regulatory role in catalytic splicing and post-splicing-complex disassembly. MFDM is the first multiple-malformation syndrome attributed to a defect of the major spliceosome. Our findings significantly extend the range of reported spliceosomal phenotypes in humans and pave the way for further investigation in related conditions such as Treacher Collins syndrome.

Frontonasal dysplasia: analysis of 21 cases and literature review

Twenty-one patients with frontonasal dysplasia were studied. A 2:1 male-to-female sex ratio and increased paternal and maternal ages at the time of conception were found. The significance is uncertain because of small sample size and lack of normal mean values for parental age in Brazil. Apparently, our series is the first to report macrocephaly (six cases). Our series also had a high frequency of patients with agenesis of the corpus callosum (12 cases), basal encephalocele (10 cases), lipoma of the corpus callosum (four cases), and mental deficiency (11 cases). Three patients had the combination of agenesis of the corpus callosum, mental deficiency, and micropenis. It is concluded that frontonasal dysplasia is pathogenetically heterogeneous, representing a regional defect which may not be a single developmental field or sequence. Causal genesis includes a dominantly inherited form, dup(2q), and autosomal recessive Shanske syndrome. Of unknown genesis are two subsets of frontonasal dysplasia patients: 1) the combination of agenesis of the corpus callosum, tibial hypoplasia, and hallucal duplication and 2) ophthalmofrontonasal dysplasia or oculoauriculofrontonasal dysplasia with associated ear tags and epibulbar dermoids.

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.

Craniofrontonasal syndrome: Study of 41 patients

Of 41 patients with craniofrontonasal syndrome, 35 were female and 6 were male. Although most cases were sporadic, 7 familial instances were found. Craniofrontonasal syndrome represents a unique, incompletely understood X-linked disorder. Unusual manifestations in females included thick, wiry, and curly hair (49%), anterior cranium bifidum (6%), axillary pterygia (9%), unilateral breast hypoplasia (postpubertal; 11%), and asymmetric lower limb shortness (14%).

Lower lip pits and anorectal anomalies in Kabuki syndrome

We report on a Brazilian girl with Kabuki syndrome (KS) and lower lip pits and anorectal anomalies. To our knowledge, four patients with KS were described as having anorectal anomalies [Matsumura et al., 1992: J Ped Surg 27:1600-1602]. Lower lip pits were observed only in a KS patient described by Franceschini et al. [1993: Am J Med Genet 47:423-425].

Mutations in Endothelin 1 Cause Recessive Auriculocondylar Syndrome and Dominant Isolated Question-Mark Ears

Auriculocondylar syndrome (ACS) is a rare craniofacial disorder with mandibular hypoplasia and question-mark ears (QMEs) as major features. QMEs, consisting of a specific defect at the lobe-helix junction, can also occur as an isolated anomaly. Studies in animal models have indicated the essential role of endothelin 1 (EDN1) signaling through the endothelin receptor type A (EDNRA) in patterning the mandibular portion of the first pharyngeal arch. Mutations in the genes coding for phospholipase C, beta 4 (PLCB4) and guanine nucleotide binding protein (G protein), alpha inhibiting activity polypeptide 3 (GNAI3), predicted to function as signal transducers downstream of EDNRA, have recently been reported in ACS. By whole-exome sequencing (WES), we identified a homozygous substitution in a furin cleavage site of the EDN1 proprotein in ACS-affected siblings born to consanguineous parents. WES of two cases with vertical transmission of isolated QMEs revealed a stop mutation in EDN1 in one family and a missense substitution of a highly conserved residue in the mature EDN1 peptide in the other. Targeted sequencing of EDN1 in an ACS individual with related parents identified a fourth, homozygous mutation falling close to the site of cleavage by endothelin-converting enzyme. The different modes of inheritance suggest that the degree of residual EDN1 activity differs depending on the mutation. These findings provide further support for the hypothesis that ACS and QMEs are uniquely caused by disruption of the EDN1-EDNRA signaling pathway.

Frontonasal dysplasia, macroblepharon, eyelid colobomas, ear anomalies, macrostomia, mental retardation and CNS structural anomalies: defining the phenotype.

We report a Brazilian boy, born to normal and nonconsanguineous parents showing, among other signs, brachycephaly, a wide forehead, a widows peak, hypertelorism, wide palpebral fissures with multiple eyelid colobomas, a broad nasal root, a long philtrum, macrostomia, prominent lips, a high arched palate, a midline alveolar cleft, a small and grooved chin, ear anomalies, structural anomaly of the corpus callosum, and mental retardation. To our knowledge this additional patient defines a particular clinical condition previously reported [Guion-Almeida M.L. Richieri-Costa A. (1999) Clinical Dysmorphol 8;1-4; Masuno M. et al. (2000) Clin Dysmorphol 9:59-60].

Oculoauriculovertebral spectrum with radial defects: a new syndrome or an extension of the oculoauriculovertebral spectrum? Report of fourteen Brazilian cases and review of the literature

The first and second branchial arches are embryonic primordium that contributes to craniofacial development. Interferences in normal development of these structures result in variable maxillary, mandibular, and ear abnormalities. These anomalies can be isolated or part of some known and unknown conditions, among them, the oculoauriculovertebral spectrum (OAVS). Malformations of the external ear or microtia are mandatory features of the OAVS and occur as an isolated malformation (population frequency of 0.03%), or in association with other anomalies such as mandible hypoplasia, epibulbar dermoids, and spinal vertebral defects. Extreme variability of phenotypic manifestations is the main feature of the OAVS and, developmental anomalies are not restricted to facial structures. Cardiac, pulmonary, renal, skeletal, and central nervous system involvements have been observed in patients presented with this condition. Radial defects, although rare, have been reported. In this study, we report on the clinical aspects of 14 Brazilian patients with first and second branchial arches abnormalities associated with radial defects and we compared these data with those of 26 cases in the literature. We postulate that radial defects associated with OAVS might represent a subset within this spectrum.

Recurrent 22q11.2 deletion in a sibship suggestive of parental germline mosaicism in velocardiofacial syndrome.

Deletions of chromosome 22q11.2 are recognized as the main cause of a number of clinical phenotypes, including velocardiofacial syndrome (VCFS) and DiGeorge syndrome (DGS). Velocardiofacial syndrome is a relatively common developmental disorder that is characterized by craniofacial anomalies and conotruncal heart defects. Most 22q11.2 deletions occur sporadically, although the deletion may be transmitted in some cases. The present performed a molecular analysis in one family including a patient with clinical diagnosis of VCFS and his sister with a suggestive phenotype. Six polymorphic 22q11.2 markers (i.e. D22S420, D22S264, D22S941, D22S306, D22S425 and D22S257) were used for genotype analysis of the DNA from the patients and unaffected relatives. The results revealed a 22q11.2 deletion in the patient and his sister from one of six markers (i.e. D22S941). Genotype analysis demonstrated that the deletion in this sib was of maternal origin. The results suggest that the mother probably has gonadal mosaicism. The other relatives present normal DNA profiles for all markers. These results have implications for genetic counseling because of a risk of transmission by germ cells carrying the deletion, even when parents present with a normal DNA profile in their blood cells.

Auriculo-condylar syndrome: mapping of a first locus and evidence for genetic heterogeneity

Auriculo-condylar syndrome (ACS), an autosomal dominant disorder of first and second pharyngeal arches, is characterized by malformed ears (‘question mark ears’), prominent cheeks, microstomia, abnormal temporomandibular joint, and mandibular condyle hypoplasia. Penetrance seems to be complete, but there is high inter- and intra-familial phenotypic variation, with no evidence of genetic heterogeneity. We herein describe a new multigeneration family with 11 affected individuals (F1), in whom we confirm intra-familial clinical variability. Facial asymmetry, a clinical feature not highlighted in other ACS reports, was highly prevalent among the patients reported here. The gene responsible for ACS is still unknown and its identification will certainly contribute to the understanding of human craniofacial development. No chromosomal rearrangements have been associated with ACS, thus mapping and positional cloning is the best approach to identify this disease gene. To map the ACS gene, we conducted linkage analysis in two large ACS families, F1 and F2 (F2; reported elsewhere). Through segregation analysis, we first excluded three known loci associated with disorders of first and second pharyngeal arches (Treacher Collins syndrome, oculo-auriculo-vertebral spectrum, and Townes–Brocks syndrome). Next, we performed a wide genome search and we observed evidence of linkage to 1p21.1–q23.3 in F2 (LOD max 3.01 at θ=0). Interestingly, this locus was not linked to the phenotype segregating in F1. Therefore, our results led to the mapping of a first locus of ACS (ACS1) and also showed evidence for genetic heterogeneity, suggesting that there are at least two loci responsible for this phenotype.