Syndactyly in Apert syndrome. Utility of a prognostic classification

The authors report a series of 36 patients of Apert's Syndrome in whom a genetic analysis was performed. 2 major types of mutation were found (S252W and P253R). The correlation between the type of mutation and certain clinical abnormalities allowed validation of Upton's modification of Blauth's classification and also helped add a prognostic indicator for the intellectual development of the child. Thus, global treatment of the child should take into account not just the clinical abnormalities but also its intellectual prospects.

Mutation analysis and description of sixteen RSH/Smith-Lemli-Opitz syndrome patients: polymerase chain reaction-based assays to simplify genotyping

We report the clinical and molecular data of 16 patients with RSH/Smith-Lemli-Opitz syndrome (RSH/SLOS) with varying phenotypic severity, for which we have identified mutations in both alleles. RSH/SLOS is an autosomal recessive malformation syndrome caused by mutations in the gene encoding the sterol Delta(7)-reductase. This protein catalyzes the reduction of 7-dehydrocholesterol to cholesterol in the last step of cholesterol biosynthesis via the Kandutsch-Russell pathway. In addition to previously reported mutations (T93M, L109P, G147D, W151X, T154M, R242C, A247V, T289I, IVS8-1G-->C, Y408H, and E448K), we have identified six previously undescribed mutations (321G-->C, W177R, R242H, Y318N, L341P, and C444Y). We also report rapid polymerase chain reaction (PCR)-based assays developed to detect four of the recurring mutations (T93M, W151X, V326L, and R404C) and six other RSH/SLOS mutations (321G-->C, L109P, T154M, T289I, Y318N, and L341P). The purpose of this article is to correlate detailed clinical information with molecular data in order to improve our understanding of the genotype-phenotype correlation of RSH/SLOS and to report the development of PCR-based assays that will allow more rapid mutation analysis.

Physical mapping of the t(12;22) translocation breakpoints in a family with a complex type of 3/3'/4 synpolydactyly

We previously reported clinical and radiological findings in a Belgian family with a complex type of synpolydactyly associated with metacarpal and metatarsal synostoses, cosegregating with a balanced t(12;22). Recently, expansions of a polyalanine stretch within the first exon of the HOXD13 gene, which resides on chromosome 2q31, have been shown to cause synpolydactyly (SPD). Using exon amplification followed by direct sequencing, we were able to exclude the direct involvement of the HOXD13 gene in this family. As a first step toward the positional cloning of a candidate disease gene on chromosome 12 and/or 22 responsible for the type of complex synpolydactyly observed in this family, we report here the construction of a somatic cell hybrid retaining only the der(22) of the t(12;22)(p11.3;q13.3). STS content mapping and FISH experiments allowed us to position the chromosomal breakpoints between markers D12S1596 and D12S1034 on chromosome 12 and markers N73F4 and D22S158 on chromosome 22.

Variable expression of isolated familial long-ring-little syndactyly

A family with isolated long-ring-little syndactyly is reported to demonstrate that the responsible autosomal gene may cause either simple or complex syndactyly.

Localization of a gene for syndactyly type 1 to chromosome 2q34-q36

Syndactyly type 1 (SD1) is an autosomal dominant limb malformation characterized in its classical form by complete or partial webbing between the third and fourth fingers and/or the second and third toes. After exclusion of a candidate region previously identified for syndactyly type 2 (synpolydactyly), we performed a genomewide linkage analysis in a large German pedigree. We found evidence for linkage of SD1 to polymorphic markers on chromosome 2q34-q36, with a maximum LOD score of 12.40 for marker D2S301. Key recombination events in affected individuals defined a 9.4-cM region between markers D2S2319 and D2S344. The identification of the responsible gene will give further insights into the molecular basis of limb development.

Physical map of a 1.5 mb region on 12p11.2 harbouring a synpolydactyly associated chromosomal breakpoint

Synpolydactyly (SPD) is a rare malformation of the distal limbs known to be caused by mutations in HOXD13. We have previously described a complex form of SPD associated with synostoses in three members of a Belgian family, which co-segregates with a t(12;22)(p11.2;q13.3) chromosomal translocation. The chromosome 12 breakpoint of this translocation maps to 12p11.2 between markers D12S1034 and D12S1596. Here we show that a mutation in the HOXD13 gene is not responsible for the phenotype, and present a physical map of the region around the 12p11.2 breakpoint. Starting from D12S1034 and D12S1596, we have established a contig approximately 1.5 Mb in length, containing 13 YAC clones, 16 BAC clones, and 11 cosmid clones. FISH analysis shows that cosmid LL12NCO1-149H4 maps across the breakpoint, and Southern blot experiments using fragments of this cosmid as probes identify a rearranged BamHI fragment in the patients carrying the translocation. A search for expressed sequences within the contig have so far revealed one CpG island, seven anonymous ESTs and three previously characterised genes, DAD-R, KRAG and HT21, all of which were found not to be directly disrupted by the translocation. The gene represented by EST R72964 was found to be disrupted by the translocation. These findings lay the groundwork for further efforts to characterise a gene critical for normal distal limb development that is perturbed by this translocation.

Are triphalangeal thumb-polysyndactyly syndrome (TPTPS) and tibial hemimelia-polysyndactyly-triphalangeal thumb syndrome (THPTTS) identical? A father with TPTPS and his daughter with THPTTS in a Thai family

We report on a Thai man who had triphalangeal thumb-polysyndactyly syndrome (TPTPS, MIM *190605) and his daughter who had tibial hemimelia-polysyndactyly-triphalangeal thumb syndrome (THPTTS, MIM *188770). The father had polysyndactyly of triphalangeal thumbs, syndactyly of fingers, duplicated distal phalanx of the left great toe, brachymesophalangy of toes, and the absence of middle phalanges of some toes. He was diagnosed as having TPTPS. His daughter was more severely affected, having complete syndactyly of five-fingered hands in rosebud fashion (Haas-type syndactyly), hypoplastic tibiae, absent patellae, thick and displaced fibulae, preaxial polysyndactyly of triphalangeal toes, and cutaneous syndactyly of some toes, the manifestations being consistent with THPTTS. Having two different syndromes in the same family suggests that they are actually the same disorder. A literature survey showed that there have been several families where THPTTS occurred with TPTPS or Haas-type syndactyly (and/or preaxial polydactyly type 2, PPD2). In addition, all loci for TPTPS, THPTTS, and PPD2 (and/or PPD3) have been assigned to chromosome band 7q36. These findings support our conclusion that TPTPS, PPD2 (and/or PPD3), and Haas-type syndactyly are a single genetic en-tity (THPTTS). We propose to call the condition "tibial hemimelia-polysyndactyly-triphalangeal thumbs syndrome."

Imperforate anus in Feingold syndrome

A father and daughter had the characteristic findings of Feingold syndrome including microcephaly, short palpebral fissures, brachydactyly with clinodactyly of fifth fingers, and bilateral syndactyly of second to third and fourth to fifth toes. The infant presented with long-gap esophageal atresia without fistula (type A). Her father, who had short stature and learning disabilities, had congenital imperforate anus with a recto-vesical fistula. This is the first report of distal intestinal atresia in Feingold syndrome.

Popliteal pterygium syndrome in a Swedish family--clinical findings and genetic analysis with the van der Woude syndrome locus at 1q32-q41

The present study describes a Swedish family in which the mother and her son were affected with signs of popliteal pterygium syndrome (PPS, OMIM 119500). Both individuals had bilateral complete cleft lip and palate, oral synechiae, paramedian pits on the lower lip, toe syndactyly and a piece of triangular skin overgrowth on the great toes. The son also presented with soft tissue syndactyly of the 2nd and 3rd fingers. Although popliteal pterygium was not found, the above clinical features were diagnostic for PPS. Chromosomal abnormalities were not revealed in either case by cytogenetic analyses. A test for microdeletion in the VWS region at 1q32-q41 was performed in the family using 5 polymorphic microsatellite markers from the region. The affected son was found to be heterozygous for all 5 markers, suggesting that microdeletion at the VWS region was unlikely. The VWS locus, however, was not excluded by haplotype analysis of the family.

Symbrachydactyly involving hands and feet

Two patients are described with a symbrachydactyly of the hand and foot. This is a rare combination which cannot be explained by the subclavian artery supply disruption sequence.

Genotype-phenotype analysis in Apert syndrome suggests opposite effects of the two recurrent mutations on syndactyly and outcome of craniofacial surgery

Apert syndrome is an autosomal dominant condition characterized by craniosynostosis and severe syndactyly, caused by two recurrent mutations in the fibroblast growth factor receptor 2 gene (FGFR2). The genotype-phenotype correlations of 21 patients with Apert syndrome were analysed as to the craniofacial appearance following surgery and the degree of syndactlyly. The craniofacial appearance following craniofacial surgery was better in patients with the P253R mutation, whereas these patients showed a more pronounced severity of the syndactyly.

Phenotypic variability of triphalangeal thumb-polysyndactyly syndrome linked to chromosome 7q36

Triphalangeal thumb-polysyndactyly (TPT-PS) is an isolated limb malformation consisting of pre- and postaxial polysyndactyly of hands and feet. The only family reported so far is of Dutch origin, and the genetic mapping study localized the TPT-PS locus at chromosome region 7q36 where the isolated triphalangeal thumb (TPT) anomaly has also been mapped. It was suggested that TPT-PS is a phenotypic variation of isolated TPT, and the same ancestral mutation may produce both phenotypes. Here we report on the second family with this malformation from the Turkish population. The characteristic findings in this family are triphalangeal thumb, webbing between 3rd, 4th, and 5th fingers associated with bony synostosis in the distal phalanges of the same fingers, and pre- and postaxial polysyndactyly of feet. Some individuals show a more severe phenotype with a complete syndactyly of all fingers giving a "cup-like" appearance to the hands. Genetic linkage study with DNA markers D7S1823, D7S550, D7S559, and D7S2423 demonstrated that this family is also linked to chromosome band 7q36. Identification of a second family from a distinct ethnic background suggests that TPT-PS and isolated TPT are not caused by the same ancestral mutation as it was originally anticipated.

Filippi syndrome: report of three additional cases

Filippi syndrome is an autosomal recessive condition characterized by variable soft tissue syndactyly of the fingers and toes, microcephaly, pre- and postnatal growth retardation, mildly abnormal craniofacial appearance, and mental retardation. We report on three unrelated individuals with Filippi syndrome. All have microcephaly, minor facial anomalies, variable syndactyly of digits, growth impairment, and developmental delay. One patient also has polydactyly, which has not been reported previously in the Filippi syndrome.

Syndactyly of Ft/+ mice correlates with an imbalance in bmp4 and fgf8 expression

The most obvious phenotype of Ft/+ mice is a syndactyly of fore limbs characterised by a fusion of the tips of digits 1 to 4. The tempospatial expression of genes involved in limb development revealed that patterning of Ft/+ limb buds is not affected by the mutation. However, an upregulation of Bmp4 in the anterior-distal region of the limb bud at d12.0 of embryonic development is accompanied by a loss of Fgf8 expression in the distal part of the AER. Downstream target genes of Bmp action such as Msx1 and 2 are upregulated. This induction of the signalling cascade indicates ectopic expression of functional Bmp4. Nevertheless, analysis of physical parameters of bones from adult mice revealed a reduction of the bone mass of the autopod. The data suggest a negative effect of Bmp4 on Fgf8 expression and a positive influence on the induction of bone elements.

Mutation of the Na-K-Cl co-transporter gene Slc12a2 results in deafness in mice

Hearing impairment is a common human condition, but we know little about the molecular basis of cochlear function. Shaker-with-syndactylism (sy) is a classic deaf mouse mutant and we show here that a second allele, sy(ns), is associated with abnormal production of endolymph, the fluid bathing sensory hair cells. Using a positional candidate approach, we demonstrate that mutations in the gene encoding the basolateral Na-K-Cl co-transporter Slc12a2 (Nkcc1, mBSC2) cause the deafness observed in sy and sy(ns) mice. This finding provides the molecular basis of another link in the chain of K+recycling in the cochlea, a process essential for normal cochlear function.

Unknown syndrome in two male sibs with hypotonia, ptosis, hand malformations, 2/3 toes syndactyly, and mental retardation

We report two brothers from nonconsanguineous parents who share hypotonia, ptosis, high arched palate, camptodactyly, fifth fingers clinodactyly, 2/3 toes syndactyly and psychomotor retardation. Differential diagnosis, such as the Ohdo syndrome, the Morillo-Cucci syndrome, the Marden-Walker-like syndrome, and the Frydman syndrome and discussed.

Anterior chamber eye anomalies, redundant skin and syndactyly--a new syndrome associated with breakpoints at 2q37.2 and 7q36.3

We report a 34-year-old female with a de novo balanced reciprocal translocation involving 2q37.2 and 7q36.3. She has a unique combination of multiple congenital malformations that include redundant skin, complete tissue syndactyly of the hands and feet, hirsutism, polycystic ovaries and bilateral anterior chamber eye anomalies. Her son has inherited the unbalanced product (46,XY,der(2) t(2;7)(q37.2;q36.3). He has a similar clinical picture with additional features including complex congenital heart disease, post axial polydactyly, hypotonia and global developmental delay. The breakpoints may indicate the location of the gene(s) responsible for this unique combination of features.

Two sibs with microcephaly, hygroma colli, renal dysplasia, and cutaneous syndactyly: a new lethal MCA syndrome?

We report two sibs of Turkish descent with multiple congenital anomalies including severe microcephaly, hygroma colli, cystic renal dysplasia, and bilateral cutaneous syndactyly of toes IV-V. In addition, the second sib presented with bilateral fusion of the eyelids, a bicornuate uterus, and clitoromegaly. The parents are first cousins, which suggests autosomal recessive inheritance. In reviewing previously published reports, several cases were found with cerebral, renal, and digital anomalies as the main features. Several of the additional symptoms present in the second sib were suggestive of Fraser syndrome, but the severe microcephaly in both sibs is unusual. The differential diagnosis is discussed, including the possibility of an entirely new entity in the broad spectrum of syndromes with cerebral, renal, and digital anomalies.

Abnormalities of developmental cell death in Dad1-deficient mice

BACKGROUND

Dad1, the defender against apoptotic cell death, comprises the oligosaccharyltransferase complex and is well conserved among eukaryotes. In hamster BHK21-derived tsBN7 cells, loss of Dad1 causes apoptosis which cannot be prevented by Bcl-2.

RESULTS

To determine the role of Dad1 function in vivo, we prepared by gene targeting, mice harbouring a disrupted Dad1 gene. Homozygous mutants died shortly after they were implanted with the characteristic features of apoptosis. In an in vitro blastocyst culture system, Dad1-null cells displayed abnormalities which were comparable to those obtained in vivo. However, oligosaccharyltransferase activity was apparently retained even after the Dad1-null cells were destined to die. Some live-born heterozygous mutants displayed soft-tissue syndactyly. Mild thymic hypoplasia was also indicated in heterozygotes.

CONCLUSION

These results suggest the involvement of the Dad1 gene in the acquisition of a common syndactyly phenotype, as well as in the control of programmed cell death during development.

Mutchinick syndrome in a Japanese girl

We report on a 7-year-old Japanese girl with Mutchinick syndrome, a rare congenital malformation syndrome described in a pair of Argentinean sisters and a pair of German brothers; both originating from the same geographic region in the former East Prussia. The girl we describe had most of the clinical manifestations of the syndrome, including growth and developmental retardation, and craniofacial anomalies with microcephaly, hypertelorism, a broad straight nose, low-set malformed ears, and a wide, tented mouth. She also had the following hitherto undescribed manifestations: ventricular septal defect, palmoplantar hyperkeratosis, bilateral partial soft-tissue syndactyly of second and third toes, and megaloureters. The occurrence of the syndrome in a Japanese girl indicates that the syndrome is not restricted to the descendants of individuals from a confined region in northeastern Europe.

Roles for laminin in embryogenesis: exencephaly, syndactyly, and placentopathy in mice lacking the laminin alpha5 chain

Laminins are the major noncollagenous glycoproteins of all basal laminae (BLs). They are alpha/beta/gamma heterotrimers assembled from 10 known chains, and they subserve both structural and signaling roles. Previously described mutations in laminin chain genes result in diverse disorders that are manifested postnatally and therefore provide little insight into laminin's roles in embryonic development. Here, we show that the laminin alpha5 chain is required during embryogenesis. The alpha5 chain is present in virtually all BLs of early somite stage embryos and then becomes restricted to specific BLs as development proceeds, including those of the surface ectoderm and placental vasculature. BLs that lose alpha5 retain or acquire other alpha chains. Embryos lacking laminin alpha5 die late in embryogenesis. They exhibit multiple developmental defects, including failure of anterior neural tube closure (exencephaly), failure of digit septation (syndactyly), and dysmorphogenesis of the placental labyrinth. These defects are all attributable to defects in BLs that are alpha5 positive in controls and that appear ultrastructurally abnormal in its absence. Other laminin alpha chains accumulate in these BLs, but this compensation is apparently functionally inadequate. Our results identify new roles for laminins and BLs in diverse developmental processes.

Thanatophoric dysplasia type I with syndactyly

We report on a case of thanatophoric dysplasia type 1 (TD1) due to a Tyr373Cys mutation in the fibroblast growth factor receptor 3 (FGFR3) gene with soft tissue syndactyly of the fingers and toes. Syndactyly has not been previously described in TD or other conditions with FGFR3 mutations, but occurs in several craniosynostosis syndromes due to mutations in FGFR2. We conclude that mutations in FGFR3 may also be associated with developmental abnormalities due to interference with programmed cell death.

The original shaker-with-syndactylism mutation (sy) is a contiguous gene deletion syndrome

Tests for allelism among mice with four different mutant alleles at the shaker-with-syndactylism locus on mouse Chromosome (Chr) 18 provide evidence that the original radiation-induced mutation, sy, is a deletion including at least two genes associated with distinct phenotypes. Mice homozygous for sy have syndactylous feet and other skeletal malformations, are deaf, and exhibit abnormal behavior characteristic of vestibular dysfunction. Two less severe spontaneous mutations, shown to be allelic with sy, cause syndactylism when homozygous (hence named fused phalanges, sy(fp) and sy(fp-2J)), but do not affect hearing and behavior. Here we describe a third spontaneous mutation allelic with sy that does not affect foot morphology (hence named no syndactylism, sy(ns)), but that does cause deafness and balance defects when homozygous. Complementation test results indicate that sy(fp) and sy(fp-2J) are alleles of the same gene, but that sy(ns) is an allele of a different gene. The original sy mutation, therefore, includes both of the genes defined by these three spontaneous mutations. Typing of DNA markers in sy/sy mice revealed a deletion of approximately 1 cM in the sy region of Chr 18, including D18Mit52, D18Mit124, D18Mit181, and D18Mit205. The genetic relationships described here will aid in positional cloning efforts to identify the genes responsible for the disparate phenotypes associated with the sy locus.

Mesoaxial complete syndactyly and synostosis with hypoplastic thumbs: an unusual combination or homozygous expression of syndactyly type I?

Syndactyly type I is an autosomal dominant condition with complete or partial webbing between the third and fourth fingers or the second and third toes or both. We report here a previously undescribed phenotype of severe mesoaxial syndactyly and synostosis in patients born to affected parents. The characteristic features of these severe cases are (1) complete syndactyly and synostosis of the third and fourth fingers; (2) severe bone reduction in the proximal phalanges of the same fingers; (3) hypoplasia of the thumbs and halluces; (4) aplasia/hypoplasia of the middle phalanges of the second and fifth fingers; and (5) complete or partial soft tissue syndactyly of the toes. We report on three offspring with this phenotype from two different branches of a syndactyly type I family, suggesting that they may be homozygous for this condition. SSCP and linkage analysis indicated that neither HOXD13 nor other relevant genes in the chromosome 2q31 region was responsible for this phenotype.