Clinical and Genetic Studies of the First Monozygotic Twins with Pfeiffer Syndrome.

Objective: To report the clinical and radiographic findings and molecular etiology of the first monozygotic twins affected with Pfeiffer syndrome. Methods: Clinical and radiographic examination and whole exome sequencing were performed on two monozygotic twins with Pfeiffer syndrome. Results: An acceptor splice site mutation in FGFR2 (c.940-2A>G) was detected in both twins. The father and both twins shared the same haplotype, indicating that the mutant allele was from their father's chromosome who suffered severe upper airway obstruction and subsequent obstructive sleep apnea. Hypertrophy of nasal turbinates appears to be a newly recognized finding of Pfeiffer syndrome. Increased intracranial pressure in both twins were corrected early by fronto-orbital advancement with skull expansion and open osteotomy, in order to prevent the more severe consequences of increased intracranial pressure, including hydrocephalus, the bulging of the anterior fontanelle, and the diastasis of suture. Conclusions: Both twins carried a FGFR2 mutation and were discordant for lambdoid synostosis. Midface hypoplasia, narrow nasal cavities, and hypertrophic nasal turbinates resulted in severe upper airway obstruction and subsequent obstructive sleep apnea in both twins. Hypertrophy of the nasal turbinates appears to be a newly recognized finding of Pfeiffer syndrome. Fronto-orbital advancement with skull expansion and open osteotomy was performed to treat increased intracranial pressure in both twins. This is the first report of monozygotic twins with Pfeiffer syndrome.

Missense Pathogenic variants in KIF4A Affect Dental Morphogenesis Resulting in X-linked Taurodontism, Microdontia and Dens-Invaginatus.

The etiology of dental anomalies is multifactorial; and genetic and environmental factors that affect the dental lamina have been implicated. We investigated two families of European ancestry in which males were affected by taurodontism, microdontia and dens invaginatus. In both families, males were related to each other via unaffected females. A linkage analysis was conducted in a New Zealand family, followed by exome sequencing and focused analysis of the X-chromosome. In a US family, exome sequencing of the X-chromosome was followed by Sanger sequencing to conduct segregation analyses. We identified two independent missense variants in KIF4A that segregate in affected males and female carriers. The variant in a New Zealand family (p.Asp371His) predicts the substitution of a residue in the motor domain of the protein while the one in a US family (p.Arg771Lys) predicts the substitution of a residue in the domain that interacts with Protein Regulator of Cytokinesis 1 (PRC1). We demonstrated that the gene is expressed in the developing tooth bud during development, and that the p.Arg771Lys variant influences cell migration in an in vitro assay. These data implicate missense variations in KIF4A in a pathogenic mechanism that causes taurodontism, microdontia and dens invaginatus phenotypes.

ADAMTSL1 and mandibular prognathism.

Mandibular prognathism is characterized by a prognathic or prominent mandible. The objective of this study was to find the gene responsible for mandibular prognathism. Whole exome sequencing analysis of a Thai family (family 1) identified the ADAMTSL1 c.176C>A variant as the potential defect. We cross-checked our exome data of 215 people for rare variants in ADAMTSL1 and found that the c.670C>G variant was associated with mandibular prognathism in families 2 and 4. Mutation analysis of ADAMTSL1 in 79 unrelated patients revealed the c.670C>G variant was also found in family 3. We hypothesize that mutations in ADAMTSL1 cause failure to cleave aggrecan in the condylar cartilage, and that leads to overgrowth of the mandible. Adamtsl1 is strongly expressed in the condensed mesenchymal cells of the mouse condyle, but not at the cartilage of the long bones. This explains why the patients with ADAMTSL1 mutations had abnormal mandibles but normal long bones. This is the first report that mutations in ADAMTSL1 are responsible for the pathogenesis of mandibular prognathism.

Oral manifestations in patients and dogs with mucopolysaccharidosis Type VII.

Mucopolysaccharidosis Type VII (MPS7, also called ß-glucuronidase deficiency or Sly syndrome; MIM 253220) is an extremely rare autosomal recessive lysosomal storage disease, caused by mutations in the GUSB gene. ß-glucuronidase (GUSB) is a lysosomal hydrolase involved in the stepwise degradation of glucuronic acid-containing glycosaminoglycans (GAGs). Patients affected with MPS VII are not able to completely degrade glucuronic acid-containing GAGs, including chondroitin 4-sulfate, chondroitin 6-sulfate, dermatan sulfate, and heparan sulfate. The accumulation of these GAGs in lysosomes of various tissues leads to cellular and organ dysfunctions. Characteristic features of MPS VII include short stature, macrocephaly, hirsutism, coarse facies, hearing loss, cloudy cornea, short neck, valvular cardiac defects, hepatosplenomegaly, and dysostosis multiplex. Oral manifestations in patients affected with MPS VII have never been reported. Oral manifestations observed in three patients consist of wide root canal spaces, taurodontism, hyperplastic dental follicles, malposition of unerupted permanent molars, and failure of tooth eruption with malformed roots. The unusual skeletal features of the patients include maxillary hypoplasia, hypoplastic midface, long mandibular length, mandibular prognathism, hypoplastic and aplastic mandibular condyles, absence of the dens of the second cervical vertebra, and erosion of the cortex of the lower border of mandibles. Dogs affected with MPS VII had anterior and posterior open bite, maxillary hypoplasia, premolar crowding, and mandibular prognathism. Unlike patients with MPS VII, the dogs had unremarkable mandibular condyles. This is the first report of oral manifestations in patients affected with MPS VII.

Genetic regulatory pathways of split-hand/foot malformation.

Split-hand/foot malformation (SHFM) is caused by mutations in TP63, DLX5, DLX6, FGF8, FGFR1, WNT10B, and BHLHA9. The clinical features of SHFM caused by mutations of these genes are not distinguishable. This implies that in normal situations these SHFM-associated genes share an underlying regulatory pathway that is involved in the development of the central parts of the hands and feet. The mutations in SHFM-related genes lead to dysregulation of Fgf8 in the central portion of the apical ectodermal ridge (AER) and subsequently lead to misexpression of a number of downstream target genes, failure of stratification of the AER, and thus SHFM. Syndactyly of the remaining digits is most likely the effects of dysregulation of Fgf-Bmp-Msx signaling on apoptotic cell death. Loss of digit identity in SHFM is hypothesized to be the effects of misexpression of HOX genes, abnormal SHH gradient, or the loss of balance between GLI3A and GLI3R. Disruption of canonical and non-canonical Wnt signaling is involved in the pathogenesis of SHFM. Whatever the causative genes of SHFM are, the mutations seem to lead to dysregulation of Fgf8 in AER cells of the central parts of the hands and feet and disruption of Wnt-Bmp-Fgf signaling pathways in AER.

Split hand-split foot-ectodermal dysplasia and amelogenesis imperfecta with a TP63 mutation.

We report on a mother and son who were affected with split hand-split foot (formerly described as ectrodactyly), ectodermal dysplasia, hyperpigmentation of skin, and dystrophic nails. Their hair was wiry, brownish, and slow-growing. Scanning electron micrography of their scalp hair showed hypoplastic hair bulbs, partial loss of hair cuticles, and frayed hair shafts. The son was affected with amelogenesis Imperfecta (hypocalcification, hypoplasia, and hypomaturation types), in the primary and permanent dentition. An unerupted supernumerary maxillary second premolar and fusion of mandibular incisors were observed in the primary dentition and their permanent successors. Mutation analysis showed a c.588-2A > C mutation in TP63 in the mother and her son. It is predicted that an alternative splice site was used, specifically the AG located just three nucleotides upstream. Use of this site is predicted to include three extra nucleotides in the transcript and thus incorporation of a single extra amino acid (p.Thr195_Tyr196insPro). This is the first time that amelogenesis imperfecta, fusion of teeth, and a supernumerary premolar have been shown to be associated with a TP63 mutation.

Mutation in SAM domain of TP63 is associated with nonsyndromic cleft lip and palate and cleft palate.

Mutations in sterile alpha motif (SAM) domain of TP63 have been reported to be associated with ankyloblepharon-ectodermal dysplasia-cleft lip/palate syndrome and Rapp-Hodgkin syndrome. SAM domain, a protein-protein interaction module, is found in cytoplasmic signaling proteins and several transcriptional regulatory proteins which are involved in development and differentiation. Here, we report on a SAM domain mutation (p.Asp564His) in TP63 that predisposed the patients to have nonsyndromic cleft palate and nonsyndromic cleft lip and palate.

A novel homozygous Arg222Trp missense mutation in WNT7A in two sisters with severe Al-Awadi/Raas-Rothschild/Schinzel phocomelia syndrome.

Al-Awadi/Raas-Rothschild/Schinzel phocomelia (AARRS) syndrome, a rare autosomal recessive disorder, comprises malformations of upper and lower limbs with severely hypoplastic pelvis and abnormal genitalia. Mutations in WNT7A have been reported as cause of the syndrome. We report on two sisters in a Thai family with short and malformed long bones, absent fibulae, flexion contracture of digits, and a/hypoplastic nails. Fusion between severely malformed femora and slender tibiae has never been reported in patients with WNT7A mutations. Lower limbs were more severely malformed than the upper ones and the pelvis was also severely affected. Multiple fusions of long bones and of the femoral heads to the acetabula were evident. A novel homozygous missense mutation in coding exon 4 of the WNT7A was detected in both affected daughters (c.664C > T) leading to an amino acid exchange from arginine to tryptophan (p.Arg222Trp; R222W). The phenotype is likely to result from an abnormality of all three signaling centers in the developing limb resulting in ventralization with a loss of dorsal structures (aplasia/hypoplasia of nails) a loss of anterior-posterior identity (single distal bones in lower limb without polarity) and an outgrowth defect resulting in distal truncations.

Mesomelic dysplasia Kantaputra type is associated with duplications of the HOXD locus on chromosome 2q.

Mesomelic dysplasia Kantaputra type (MDK) is characterized by marked mesomelic shortening of the upper and lower limbs originally described in a Thai family. To identify the cause of MDK, we performed array CGH and identified two microduplications on chromosome 2 (2q31.1-q31.2) encompassing ∼481 and 507 kb, separated by a segment of normal copy number. The more centromeric duplication encompasses the entire HOXD cluster, as well as the neighboring genes EVX2 and MTX2. The breakpoints of the duplication localize to the same region as the previously identified inversion of the mouse mutant ulnaless (Ul), which has a similar phenotype as MDK. We propose that MDK is caused by duplications that modify the topography of the locus and as such result in deregulation of HOXD gene expression.

DeltaNp63 knockdown mice: A mouse model for AEC syndrome.

Dominant mutations in TP63 cause ankyloblepharon ectodermal dysplasia and clefting (AEC), an ectodermal dysplasia characterized by skin fragility. Since DeltaNp63alpha is the predominantly expressed TP63 isoform in postnatal skin, we hypothesized that mutant DeltaNp63alpha proteins are primarily responsible for skin fragility in AEC patients. We found that mutant DeltaNp63alpha proteins expressed in AEC patients function as dominant-negative molecules, suggesting that the human AEC skin phenotype could be mimicked in mouse skin by downregulating DeltaNp63alpha. Indeed, downregulating DeltaNp63 expression in mouse epidermis caused severe skin erosions, which resembled lesions that develop in AEC patients. In both cases, lesions were characterized by suprabasal epidermal proliferation, delayed terminal differentiation, and basement membrane abnormalities. By failing to provide structural stability to the epidermis, these defects likely contribute to the observed skin fragility. The development of a mouse model for AEC will allow us to further unravel the genetic pathways that are normally regulated by DeltaNp63 and that may be perturbed in AEC patients. Ultimately, these studies will not only contribute to our understanding of the molecular mechanisms that cause skin fragility in AEC patients, but may also result in the identification of targets for novel therapeutic approaches aimed at treating skin erosions. (c) 2009 Wiley-Liss, Inc.

Contiguous gene syndrome of holoprosencephaly and hypotrichosis simplex: association with an 18p11.3 deletion.

We report a patient with a unique combination of features, including microcephaly; mental retardation; poorly developed frontal lobes; hypoplastic pituitary gland; hypothyroidism; alopecia universalis; single maxillary central incisor; taurodontism; median palatal ridge; longitudinally grooved nails; and scoliosis. His unbalanced karyotype was found to be 45,XY,der(15;18)(q10;q10). The constellation of anomalies appears to represent a contiguous gene syndrome caused, at least in part, by deletion of TGIF and the gene responsible for hereditary hypotrichosis simplex. The phenotype of our patient differs other reported patients with del(18p). Possible explanations include (1) the effects of a different deleted region, (2) a positional effect caused by a gene close by, or (3) by interruption of a different gene resulting from chromosomal translocation.

A newly recognized polyosteolysis/hyperostosis syndrome.

We report a newly recognized bone disorder consisting of polyostotic expansile osteolysis affecting long bones and iliac bones; hyperostosis of the skull, thoracic cage, and medial portion of both clavicles; pectus carinatum; gigantiform synovial masses of the elbows and knees; atrial septal defect; cardiomegaly; unilateral cryptorchidism; and mental deficiency. Affected bones can be grouped into four general types of skeletal pathology: (1) expansile osteolysis, (2) osteolysis without expansion, (3) expansion without osteolysis, and (4) hyperostosis. Some bones remained unaffected. We have named the condition "polyosteolysis/hyperostosis syndrome." It is clearly at variance with any previously reported bone disorder, including familial expansile osteolysis, juvenile Paget disease, and McCune-Albright syndrome (and polyostotic fibrous dysplasia). Because our patient shared some features in common with juvenile Paget disease, we thought that mutational analysis of TNFRSF11B was indicated, even though our patient had some manifestations not found in juvenile Paget disease. Direct sequencing failed to identify a TNFRSF11B mutation. Because the parents of our propositus were first cousins suggests that polyosteolysis/hyperostosis syndrome may possibly have autosomal recessive inheritance.

A newly recognized syndrome involving limbs, pelvis, and genital organs or a variant of Al-Awadi/Raas-Rothschild syndrome?

We report on a 3-year-old Thai boy with limb, pelvic, and genital malformations. The combination of findings found in this patient is similar to that of Al-Awadi/Raas-Rothchild syndrome (AARRS) or limb/pelvis hypoplasia/aplasia syndrome. The upper limbs are more severely affected than the lower ones. Unlike that of AARRS, the radial ray is more severely affected than the ulnar ray. The presence of humeroulnar synostosis and humero-ulnar-radial synostosis and the absence of a radius distinguishes it from AARRS. The similarities and dissimilarities between the features in the present patient and other limb-pelvic hypoplasia/aplasia syndromes are discussed. The findings in this group of patients appear to demonstrate limb-pelvis-genital organ developmental field defects.

Microcephalic osteodysplastic primordial dwarfism with severe microdontia and skin anomalies: confirmation of a new syndrome.

We report two related Thai children having a new syndrome of microcephalic osteodysplastic primordial dwarfism (MOPD). The findings which classify them as having MOPD include IUGR, microcephaly, prominent nose and nasal bridge, small pinnae, short stature, cone-shaped and ivory-epiphyses, delayed bone age, slender long bones, and abnormal pelvis. The findings that distinguish them as having newly recognized syndrome consist of severe microdontia, malformed teeth, single-rooted or rootless teeth, severely hypoplastic alveolar bone, café au lait spots, acanthosis nigricans, and areas of hypo- and hyperpigmented skin. The reported patients appear to have the same condition as the family reported by Kantaputra [2002: Am J Med Genet 111:420-428]. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299/suppmat/index.html.

A new syndrome of symphalangism, multiple frenula, postaxial polydactyly, dysplastic ears, dental anomalies, and exclusion of NOG and GDF5.

A Thai girl with a unique combination of limb and craniofacial anomalies is reported. Manifestations include blepharoptosis; prominent nose; hypodontia; multiple, hyperplastic frenula; and dysplastic ears. Limb anomalies include short stature, postaxial polydactyly of both hands and the left foot, proximal and distal symphalangism of fingers, and congenital absence of the distal phalanges of toes 2-5. Mutation analyses of NOG and GDF5, the genes responsible for symphalangism-related syndromes, were negative.

Apparently new osteodysplastic and primordial short stature with severe microdontia, opalescent teeth, and rootless molars in two siblings.

A Thai man and his sister affected with a newly recognized syndrome of proportionate primordial short stature are reported. The patients had severe intrauterine and postnatal growth retardation, prominent nose and nasal bridge, small pinnae, large sella turcica, areas of hypo- and hyperpigmentation of skin, dry and thin scalp hair, and long and straight clavicles. Ivory epiphyses and cone-shaped epiphyses of the hands were found when they were young, but most of them disappeared as they grew up. Scaphoid and trapezium had angular appearance. The second toes were unusually long. Distal symphalangism of toes and barchymesophalangy of fingers were noted. The findings that appear to distinguish this syndrome from the previously reported syndromes are long second toes, opalescent and rootless teeth, severe microdontia, severely hypoplastic alveolar process, and unerupted tooth. The mode of inheritance is suspected to be autosomal recessive.

A dominantly inherited malformation syndrome with short stature, upper limb anomaly, minor craniofacial anomalies, and absence of TBX5 mutations: report of a Thai family.

We report on a Thai family with dominantly inherited malformation syndrome with upper limb anomalies, short stature, quadricuspid aortic valve, and minor craniofacial anomalies. The affected individuals comprised a mildly affected mother, a moderately affected daughter, and a most severely affected son. The daughter and son had short stature. The craniofacial abnormalities comprised frontal bossing, hypoplastic nasal bones, depressed nasal bridge, and broad nasal alae. The upper limb defects varies among the patients, ranging from radial ray defects in the mother through radial and ulnar ray defects with unilateral humeral hypoplasia in the daughter to radial ray defects with severe oligodactyly and bilateral humeral hypoplasia in the son. All patients in this family had hypoplasia of the shoulder girdle and resembled what is observed in many families with Holt-Oram syndrome. Moreover, the son showed quadricuspid aortic valve with mild aortic regurgitation. However, the present family did not show any mutation of the TBX5 gene, a disease-causing gene of Holt-Oram syndrome. The present family deserves further investigation on other genes that play a role in the development of the upper limbs, particularly of radial rays.

A Thai mother and son with distal symphalangism, hypoplastic carpal bones, microdontia, dental pulp stones, and narrowing of the zygomatic arch: a new distal symphalangism syndrome?

A Thai mother and son with distal symphalangism and other associated abnormalities are reported. Distal and middle phalanges of fingers and toes 2-5 were either aplastic/hypoplastic or fused between the corresponding digits. The second fingers and fourth fingernails were most severely affected in both patients. The mother's hands were less severely affected; the middle and distal phalanges of her hands were malformed and fused. Besides the absence of fusion lines, the shape of the fused middle and distal phalanges was quite different from that of other types of fusion, i.e., fused bones in both patients did not maintain the normal configuration of bone, referring to as "middle-distal phalangeal complex". Distal symphalangism was observed in toes 2-5 of the mother and in toe 3 of the son. Both patients had additional clinical manifestations such as narrowing of the zygomatic arch, dental pulp stone, microdontia of a mandibular permanent central incisor, cone-shaped epiphyses of middle phalanges of fingers, and absence of scaphoid, trapezium, trapezoid, and pisiform bones. Mutation analysis of NOG and ROR2, the genes responsible for proximal symphalangism and brachydactyly type B, respectively, was negative.

A novel gene is disrupted at a 14q13 breakpoint of t(2;14) in a patient with mirror-image polydactyly of hands and feet.

Mirror-image polydactyly of hands and feet (MIP) is a very rare congenital anomaly characterized by mirror-image duplication of digits. To isolate the gene responsible for MIP, we performed translocation breakpoint cloning from an MIP patient with t(2;14)(p23.3;q13). We isolated a good candidate gene for MIP that was disrupted by the translocation of the patient. We had previously con structed a 1.2-megabase bacterial artificial chromosome (BAC)/P1-derived artificial chromosome (PAC) contig covering the 14q13 breakpoint of t(2;14)(p23.3;q13). From a 500-kb segment consisting of seven BAC/PAC clones in the contig, we isolated a novel gene (the mirror-image polydactyly 1 gene, designated as MIPOL1, GenBank Accession No. AY059470), in addition to the hepatocyte nuclear factor 3 alpha gene (HNF3A, GenBank Accession No. XM 007360). MIPOL1 spans about 350kb, comprises 15 exons, and encodes 442 amino acids. Northern blot analysis revealed that MIPOL1 expression is definite but very weak in adult heart, liver, skeletal muscle, kidney, and pancreas, and in fetal kidney. In view of the genome sequence and the contig map constructed, the 14q13 breakpoint of the patient was identified as located in intron 11 of MIPOL1, indicating that the gene was disrupted by the translocation, and that the breakage resulted in MIPOL1 protein truncation. Whole-mount in situ hybridization in mouse resulted in mouse Mipol1 signals all over E10.5-E13.5 mouse embryos. Two other unrelated patients with limb anomalies similar to MIP were subjected to mutation analysis of MIPOL1, but none had any mutations. We then isolated BAC clones from the other breakpoint, 2p23.3. A search for genes and expressed sequence tags in a more than 300-kb region around the 2p23.3 breakpoint found only the neuroblastoma-amplified protein gene (NAG, GenBank Accession No. NM 015909), which is located at least 50kb centromeric to the breakpoint and is not likely to be related to MIP. MIPOL1 is a good candidate gene for the MIP type of anomaly.