Central ray deficiency with extensive syndactyly: a dilemma for classification

Split Hand Foot Malformation (SHFM) (cleft hand/foot, central ray deficiency) is a complex, highly variable anomaly involving the hands and/or feet. A clinical epidemiologic study of split hand/foot (central ray deficiency) of the Manitoba population identified a subset of patients who did not present with either typical or atypical split hand. Clinically, some patients presented with "mitten hand" syndactyly; the deficiency was not recognized before imaging. In this paper, we identify additional similarly affected literature cases, review existing classifications of split hand and syndactyly and attempt to classify these patients. This group presents a challenge for classification and genetic counseling. General classifications permit inclusion of patients with diverse phenotypes; however, details are overlooked. Osseous fusions and disorganization of osseous components complicate classification. Many of these patients had findings that overlapped different subtypes within existing classifications. This cohort highlights the importance of imaging patients with distal limb anomalies. An effective classification scheme should include relevant clinical and radiographic findings in order to assist clinicians following these patients.

Double outlet right ventricle and aortopulmonary window in a patient with Cornelia de Lange syndrome: a novel association

We report a patient with Cornelia de Lange syndrome with congenital cardiac malformation; double outlet right ventricle and aortopulmonary window. This is the first report describing this combination of findings for Cornelia de Lange syndrome. Behalf of this report, the pathogenesis of congenital heart disease in Cornelia de Lange syndrome was also revisited.

[Genetic background of isolated forms of congenital malformations of the hand]

Congenital hand malformations comprise a clinically and etiologically heterogeneous group of developmental anomalies. They may occur as an isolated trait or be a part of a syndrome. In recent years, enormous progress in revealing the molecular background of congenital hand anomalies has been made. It proved helpful for better understanding of function of the genes responsible for embroynic limb development in humans. This review presents a classification of hand malformations, which takes into account not only differences of anatomic and morphological origin, but also distinct genetic background. Since there is an abundance of syndromes with congenital hand anomalies, the paper is focused mainly on the non-syndromic hand malformations and their genetic etiology.

A familial case of popliteal pterygium syndrome

Popliteal pterygium syndrome (PPS) is a rare malformation disorder characterized by autosomal dominant inheritance, highly variable expressivity and incomplete penetrance. The disorder is caused by the mutation of the IRF6 gene and the respective protein, which belongs to a family of nine transcription factors and is involved in the differentiation and proliferation of keratinocytes. Mutations in the IRF6 gene give rise to popliteal pterygium syndrome, Van Der Woude syndrome and nonsyndromic orofacial clefts. The anomalies from which affected patients suffer can be subdivided into alterations of the orofacial region, the musculoskeletal system and the genitals. Diagnosis is difficult, as is differential diagnosis, due to the variability of the manifestations. Prenatal diagnosis is possible by means of sequence analysis of the IRF6 gene in DNA extracted from the chorionic villus or amniotic fluid, or by means of intrauterine ultrasound. The prognosis is generally good, with normal mental development and the possibility to correct most of the alterations through targeted surgery. The case presented in this study involves two patients: a father and daughter who suffer from PPS, of whom the former was not diagnosed at birth. The two patients have undergone numerous operations over the years on various parts of the body and sequence analysis of the IRF6 gene, which revealed the presence of a mutation in the target site.

Ectopic acanthosis nigricans occurring in a child after syndactyly repair

Skin grafts from the groin area were used to repair syndactyly of the fourth and fifth fingers in an 8-month-old infant with oculodentodigital dysplasia (ODD). At 12 years of age, he developed hyperpigmented velvety plaques at the repair sites. This patient is the first reported case of acanthosis nigricans (AN) occurring in a graft site after syndactyly repair. We propose the term ectopic acanthosis nigricans to describe the phenomenon of AN occurring in transplanted skin away from the original donor site.

Synpolydactyly and HOXD13 polyalanine repeat: addition of 2 alanine residues is without clinical consequences

BACKGROUND

Type II syndactyly or synpolydactyly (SPD) is clinically very heterogeneous, and genetically three distinct SPD conditions are known and have been designated as SPD1, SPD2 and SPD3, respectively. SPD1 type is associated with expansion mutations in HOXD13, resulting in an addition of > or = 7 alanine residues to the polyalanine repeat. It has been suggested that expansions < or = 6 alanine residues go without medical attention, as no such expansion has ever been reported with the SPD1 phenotype.

METHODS

We describe a large Pakistani and an Indian family with SPD. We perform detailed clinical and molecular analyses to identify the genetic basis of this malformation.

RESULTS

We have identified four distinct clinical categories for the SPD1 phenotype observed in the affected subjects in both families. Next, we show that a milder foot phenotype, previously described as a separate entity, is in fact a part of the SPD1 phenotypic spectrum. Then, we demonstrate that the phenotype in both families segregates with an identical expansion mutation of 21 bp in HOXD13. Finally, we show that the HOXD13 polyalanine repeat is polymorphic, and the expansion of 2 alanine residues, evident in unaffected subjects of both families, is without clinical consequences.

CONCLUSION

It is the first molecular evidence supporting the hypothesis that expansion of < or = 6 alanine residues in the HOXD13 polyalanine repeat is not associated with the SPD1 phenotype.

Fraser syndrome: recurrence in a family

Fraser syndrome is a rare, autosomal recessive condition with classical features of cryptophthalmos, syndactyly, ambiguous genitalia, genitourinary mal-formations and mental retardation. We report a family with affected child where the pregnant woman was referred at 24 weeks of gestation for termination of pregnancy. The aborted fetus showed typical findings suggestive of Fraser syndrome.

Genetic heterogeneity of synpolydactyly: a novel locus SPD3 maps to chromosome 14q11.2-q12

Syndactyly type II or synpolydactyly (SPD) is the second most frequent syndactyly type and is inherited in an autosomal dominant fashion. The cardinal features of this malformation are the cutaneous or bony fusion of third and fourth fingers, and fourth and fifth toes associated with additional digital elements within the web. It shows incomplete penetrance and high inter- and intrafamilial phenotypic variability. Two loci are known for SPD (MIM 186000, MIM 608180) associated with mutations in HOXD13 and FBLN1, respectively. Here, we report further genetic heterogeneity for SDP. Employing a whole genomic screen, we demonstrate, in a large Pakistani kindred, that the classical phenotype of SPD maps on a new locus at chromosome 14q11.2-q12. The highest LOD score (Z(max) = 4.06) was obtained with microsatellite marker D14S264, and the multipoint LOD score reached a maximum of 5.01. Haplotype analysis revealed that the disease interval is flanked by microsatellite markers D14S283 and D14S1060, encompassing a physical distance of 10.72 Mb. We propose to allocate to this locus the symbol SPD3 (synpolydactyly 3), and to name the loci associated with HOXD13 or FBLN1 mutations SPD1 and SPD2, respectively.

A novel mutation of p63 in a Chinese family with inherited syndactyly and adactylism

p63 is a transcription factor homologous to p53 and p73; mutations in this gene have been identified in individuals with several types of developmental abnormalities, including EEC (ectrodactyly, ectodermal dysplasia, facial clefts) syndrome and split-hand/split-foot malformation (SHFM). Several mutations in the p63 gene have previously been shown to be related to SHFM. In this study, we report on a Chinese family with intrafamilial clinical variability of SHFM that have a novel heterozygous mutation in all four affected individuals. The mutation is in exon 8 of p63, 1046G --> A, which predicts an amino acid substitution G310E. SSCP analysis of the segregation pattern of the mutation strongly suggests a causal relationship to the SHFM phenotype in p63. This mutation has not been observed in other countries in the world.

Some oculodentodigital dysplasia-associated Cx43 mutations cause increased hemichannel activity in addition to deficient gap junction channels

Oculodentodigital dysplasia (ODDD) is a dominantly inherited human disorder associated with different symptoms like craniofacial anomalies, syndactyly and heart dysfunction. ODDD is caused by mutations in the GJA1 gene encoding the gap junction protein connexin43 (Cx43). Here, we have characterized four Cx43 mutations (I31M, G138R, G143S and H194P) after stable expression in HeLa cells. In patients, the I31M and G138R mutations showed all phenotypic characteristics of ODDD, whereas G143S did not result in facial abnormalities and H194P mutated patients exhibited no syndactylies. In transfected HeLa cells, these mutations led to lack of the P2 phosphorylation state of the Cx43 protein, complete inhibition of gap junctional coupling measured by neurobiotin transfer and increased hemichannel activity. In addition, altered trafficking and delayed degradation were found in these mutants by immunofluorescence and pulse-chase analyses. In G138R and G143S mutants, the increased hemichannel activity correlated with an increased half-time of the Cx43 protein. However, the I31M mutated protein showed no extended half-time. Thus, the increased hemichannel activity may be directly caused by an altered conformation of the mutated channel forming protein. We hypothesize that increased hemichannel activity may aggravate the phenotypic abnormalities in ODDD patients who are deficient in Cx43 gap junction channels.

Oculodentodigital dysplasia with mandibular retrognathism and absence of syndactyly: a case report with a novel mutation in the connexin 43 gene

Oculodentodigital dysplasia (ODDD) is a rare, autosomal dominant pleiotropic disorder, caused by mutations in the Connexin 43 (Cx43 or GJA1) gene. Described here is the case of a 10-year-old girl with enamel hypoplasia, typical facies and mental delay, initially thought to be related to an unknown metabolic disorder. Careful clinical re-evaluation revealed a type of ODDD, characterised by the predominance of facial and ophthalmological involvement with mandibular retrognathism, and by the absence of cutaneous hand or foot syndactyly. A novel single-sequence variation (Nt460A>G) in exon 2, resulting in the substitution of alanine for threonine at amino acid 154, was found. These findings confirm once again the highly variable phenotypic expression caused by Cx43 mutations.

A syndactyly type IV locus maps to 7q36

Syndactyly occurs as an isolated abnormality or a part of a malformation syndrome. Syndactyly types I, II, III and V have been mapped to chromosomal regions 2q34-q36, 2q31-q32, 6q21-q23.2 and 2q31-q32, respectively, whereas syndactyly type IV (SD4) is extremely rare, and its gene localization has not yet been assigned. The SD4 manifests complete syndactyly of all fingers accompanied with polydactyly, and flexion of the fingers gives the hand a cup-shaped appearance. We performed a linkage and haplotype analysis of a Chinese pedigree with autosomal dominant, non-syndromic SD4 using a set of 406 microsatellite markers. The analysis gave the maximum two-point LOD score of 1.613 at recombination fraction of 0.00 and penetrance of 1.00. Thus, the SD4 locus in the family was likely assigned to a 17.39-cM region at a segment between markers D7S3070 and D7S559 at 7q36, although the LOD score obtained was not high enough to conclude the localization. Analysis of three candidate genes, LMBR1, SHH and ZRS, failed to identify any pathogenic mutations. Our gene mapping may give a clue to identify the putative SD4 gene and provide a better understanding of normal human limb development.

A t(4;6)(q12;p23) translocation disrupts a membrane-associated O-acetyl transferase gene (MBOAT1) in a patient with a novel brachydactyly-syndactyly syndrome

Here, we report a patient with a novel brachydactyly-syndactyly syndrome and a de novo translocation 46,XY,t(4;6)(q12;p23). We mapped the breakpoint and identified genes in the breakpoint region. One of the genes on chromosome 6, the membrane-associated O-acetyl transferase gene 1 (MBOAT1), was disrupted by the breakpoint. This gene consists of 13 exons and encodes a protein of 495 amino acids. MBOAT1 is predicted to be a transmembrane protein and belongs to the superfamily of membrane-bound O-acyltransferases. These proteins transfer organic compounds, usually fatty acids, onto hydroxyl groups of membrane-embedded targets. Identification of the transferred acyl group and the target may reveal the signaling pathways altered in this novel brachydactyly-syndactyly syndrome.

Skin changes in oculo-dento-digital dysplasia are correlated with C-terminal truncations of connexin 43

Oculo-dento-digital dysplasia (ODDD, OMIM no.164210) is a pleiotropic disorder caused by mutations in the GJA1 gene that codes for the gap junction protein connexin 43. While the gene is highly expressed in skin, ODDD is usually not associated with skin symptoms. We recently described a family with ODDD and palmoplantar keratoderma. Interestingly, mutation carriers had a novel dinucleotide deletion in the GJA1 gene that resulted in truncation of part of the C-terminus. We speculated, that truncation of the C-terminus may be uniquely associated with skin disease in ODDD. Here, we describe a patient with ODDD and palmar hyperkeratosis caused by a novel dinucleotide deletion that truncates most of the connexin 43 C-terminus. Thus, our findings support the notion that such mutations are associated with the occurrence of skin symptoms in ODDD and provide the first evidence for the existence of a genotype-phenotype correlation.

Congenital syndactyly in cattle: four novel mutations in the low density lipoprotein receptor-related protein 4 gene (LRP4)

Background

Isolated syndactyly in cattle, also known as mulefoot, is inherited as an autosomal recessive trait with variable penetrance in different cattle breeds. Recently, two independent mutations in the bovine LRP4 gene have been reported as the primary cause of syndactyly in the Holstein and Angus cattle breeds.

Results

We confirmed the previously described LRP4 exon 33 two nucleotide substitution in most of the affected Holstein calves and revealed additional evidence for allelic heterogeneity by the identification of four new LRP4 non-synonymous point mutations co-segregating in Holstein, German Simmental and Simmental-Charolais families.

Conclusion

We confirmed a significant role of LRP4 mutations in the pathogenesis of congenital syndactyly in cattle. The newly detected missense mutations in the LRP4 gene represent independent mutations affecting different conserved protein domains. However, the four newly described LRP4 mutations do still not explain all analyzed cases of syndactyly.

A single C to T transition in intron 5 of LMBR1 gene is associated with triphalangeal thumb-polysyndactyly syndrome in a Chinese family

Triphalangeal thumb-polysyndactyly syndrome (TPT-PS) is a type of human hand-foot malformation. In this study, we collected data from a Chinese family with TPT-PS and mapped the disease region to chromosome 7q36. By using a fine mapping study and a haplotype analysis, we narrowed the affected region to 1.7cM between markers D7S2465 and D7S2423, which contains four candidate genes: HLXB9, LMBR1, NOM1, and RNF32. By sequence analysis, we found no sequence alterations, which are specific to the patients in the transcribed regions and in the intron-exon boundaries among the four genes. After closely examining intron 5 of the LMBR1 gene, we discovered a single C to T transition in the affected TPT-PS individuals of the Chinese subject family. The position of this C to T transition is located close to other sequence alterations involved in several preaxial polydactyly (PPD) families, supporting the notion that intron 5 of LMBR1 contains a cis-acting regulator of limb-specific Sonic Hedgehog (SHH). We postulate that the disruption of this cis-regulator via a single C to T transition results in the dysregulation of SHH, which leads to the TPT-PS found in this case.

Mutations in HOXD13 underlie syndactyly type V and a novel brachydactyly-syndactyly syndrome

HOXD13, the homeobox-containing gene located at the most 5' end of the HOXD cluster, plays a critical role in limb development. It has been shown that mutations in human HOXD13 can give rise to limb malformations, with variable expressivity and a wide spectrum of clinical manifestations. Polyalanine expansions in HOXD13 cause synpolydactyly, whereas amino acid substitutions in the homeodomain are associated with brachydactyly types D and E. We describe two large Han Chinese families with different limb malformations, one with syndactyly type V and the other with limb features overlapping brachydactyly types A4, D, and E and mild syndactyly of toes 2 and 3. Two-point linkage analysis showed LOD scores >3 (theta =0) for markers within and/or flanking the HOXD13 locus in both families. In the family with syndactyly type V, we identified a missense mutation in the HOXD13 homeodomain, c.950A-->G (p.Q317R), which leads to substitution of the highly conserved glutamine that is important for DNA-binding specificity and affinity. In the family with complex brachydactyly and syndactyly, we detected a deletion of 21 bp in the imperfect GCN (where N denotes A, C, G, or T) triplet-containing exon 1 of HOXD13, which results in a polyalanine contraction of seven residues. Moreover, we found that the mutant HOXD13 with the p.Q317R substitution was unable to transactivate the human EPHA7 promoter. Molecular modeling data supported these experimental results. The calculated interactions energies were in agreement with the measured changes of the activity. Our data established the link between HOXD13 and two additional limb phenotypes--syndactyly type V and brachydactyly type A4--and demonstrated that a polyalanine contraction in HOXD13, most likely, led to other digital anomalies but not to synpolydactyly. We suggest the term "HOXD13 limb morphopathies" for the spectrum of limb disorders caused by HOXD13 mutations.

Intrafamilial variability in Fraser syndrome

Fraser syndrome (OMIM 219000) is a rare, autosomal recessive disorder characterized by cryptophthalmos, cutanaeous syndactyly, malformations of the larynx and genitourinary tract, craniofacial dysmorphism, orofacial clefting, mental retardation and musculoskeletal anomalies. There is marked interfamilial clinical heterogeneity. However, there is strong phenotypic similarity and concordance of the degree of severity of the disease within a family. We report a family with two cases of Fraser syndrome with marked clinical heterogeneity. One case had lethal phenotype with bilateral renal agenesis, while the other had mild phenotype with normal kidneys. It has not been reported before and highlights the importance of careful screening of pregnancies in families with Fraser syndrome.

Duplication 18q21.31-q22.2

We report on three siblings with mild mental retardation and minor dysmorphic features carrying an interstitial duplication of the long arm of chromosome 18 inherited from a healthy mosaic carrier mother. The duplicated region spanned between 18q21.31 and 18q22.2 for about 12 Mb. The distal duplications of 18q are rare and only a small number of subjects, manifesting quite different clinical outcomes, have been described. However, in most of these cases, molecular characterization was not available. We have reviewed nine patients, including three familial cases, displaying overlapping duplicated regions, and compared them with the present individuals in an attempt to delineate karyotype-phenotype correlation.