Syndromes presenting adducted thumb with/without clubfoot and Dundar syndrome.

Congenital adducted thumb has been called variously as congenital clasped thumb, thumb in palm deformity or flexion adduction deformity of the thumb. This condition can be an isolated anomaly or associated with several genetic disorders. The syndromes that include adducted thumb as a cardinal feature such as Dundar Syndrome are few in the literature. This syndrome is an autosomal-recessive very rare disorder characterized by typical facial appearance with dysmorphic features that includes wasted build, hyperextensible, thin and translucent skin with atrophic scarring, severe congenital contractures of fingers and thumbs, club feet, severe kyphoscoliosis, joint instability, muscular hypotonia, and ocular involvement. Heart, kidney, and/or intestinal defects can also be observed. Up to date the syndrome is described in few families in the literature. Here we discuss the syndromes that include adducted thumb as a cardinal feature and also the differential diagnosis of the Dundar Syndrome according to the literature.

Identification of dosage-sensitive genes in fetuses referred with severe isolated congenital diaphragmatic hernia.

OBJECTIVE: Congenital diaphragmatic hernia (CDH) is a fetal abnormality affecting diaphragm and lung development with a high mortality rate despite advances in fetal and neonatal therapy. CDH may occur either as an isolated defect or in syndromic form for which the prognosis is worse. Although conventional karyotyping and, more recently, chromosomal microarrays support a substantial role for genetic factors, causal genes responsible for isolated CDH remain elusive. We propose that chromosomal microarray analysis will identify copy number variations (CNVs) associated with isolated CDH. METHODS: We perform a prospective genome-wide screen for CNVs using chromosomal microarrays on 75 fetuses referred with apparently isolated CDH, six of which were later reclassified as non-isolated CDH. RESULTS: The results pinpoint haploinsufficiency of NR2F2 as a cause of CDH and cardiovascular malformations. In addition, the 15q25.2 and 16p11.2 recurrent microdeletions are associated with isolated CDH. By using gene prioritisation and network analysis, we provide strong evidence for several novel dosage-sensitive candidate genes associated with CDH. CONCLUSIONS: Chromosomal microarray analysis detects submicroscopic CNVs associated with isolated CDH or CDH with cardiovascular malformations.

Congenital High Airway Obstruction Syndrome (CHAOS) as part of Fraser syndrome: ultrasound and autopsy findings.

Congenital High Airway Obstruction Syndrome (CHAOS) is a potential lethal condition. We describe a case report of CHAOS, with additional malformations diagnosed at 20 weeks. Autopsy findings are suggestive for Fraser syndrome (cryptophthalmos-syndactyly syndrome; OMIM 219000). The diagnosis was confirmed by mutation analysis of FRAS1.

A comparative study on culture conditions and routine expansion of amniotic fluid-derived mesenchymal progenitor cells.

BACKGROUND: Amniotic fluid (AF) cell populations will be applied in perinatology. We aimed to test the feasibility of large-scale cell expansion. STUDY METHODS: We determined the best out of three published expansion protocols for mesenchymal progenitors (AF samples, n = 4) in terms of self-renewal ability. Characterization was performed based on morphology, surface marker analysis, cytogenetic stability, and differentiation potential. The conditions for the best self-renewal ability were further determined in a consecutive series (n = 159). RESULTS: The medium containing fetal bovine serum (FBS), epidermal growth factor, insulin, transferrin, and tri-iodothyronine, combined with seeding on gelatin-coated wells, best stimulated the growth of cells with mesenchymal features, as demonstrated by flow cytometry; however, only osteogenic differentiation was possible. Large-scale testing (n = 44) failed to confirm a robust self-renewal ability. Better results were obtained (n = 88) using optimized FBS or an increased initial cell density. Eventually over 81% of cultures continued growing after the initial medium change and had mesenchymal features but failed differentiation assays. DISCUSSION: Routine in vitro expansion of AF-derived mesenchymal cells remains problematic. Despite an increase in successful cell cultures from 40 up to 80% using optimized serum and an increased cell density, eventually cells failed to demonstrate differentiation abilities. Routine isolation and expansion from unselected AF samples remains a challenge.

Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome.

Keutel syndrome (KS, MIM 245150) is an autosomal recessive disorder characterized by abnormal cartilage calcification, peripheral pulmonary stenosis and midfacial hypoplasia. A genome search using homozygosity mapping provided evidence of linkage to chromosome 12p12.3-13.1 (maximum multipoint lod score, 4.06). MGP was a candidate on the basis of its localization to this chromosomal region and the known function of its protein. MGP maps to chromosome 12p near D12S363. Human MGP is a 10-kD skeletal extracellular matrix (ECM) protein that consists of an 84-aa mature protein and a 19-aa transmembrane signal peptide. It is a member of the Gla protein family, which includes osteocalcin, another skeletal ECM protein, and a number of coagulation factors (factors II, VII, IX, X and proteins S and C). All members of this family have glutamic acid residues modified to gamma-carboxyglutamic acids (Gla) by a specific gamma-carboxylase using vitamin K as a cofactor. The modified glutamic acid residues of Gla proteins confer a high affinity for mineral ions such as calcium, phosphate and hydroxyapatite crystals, the mineral components of the skeletal ECM. The pattern and tissue distribution of Mgp expression in mice suggest a role for Mgp in regulating ECM calcification. Mglap-deficient mice (Mglap-/-) have been reported to have inappropriate calcification of cartilage. Mutational analysis of MGP in three unrelated probands identified three different mutations: c.69delG, IVS1-2A-->G and c.113T-->A. All three mutations predict a non-functional MGP. Our data indicate that mutations in MGP are responsible for KS and confirm its role in the regulation of extracellular matrix calcification.

Constitutively activating mutation in WASP causes X-linked severe congenital neutropenia.

The Wiskott-Aldrich syndrome protein (WASP; encoded by the gene WAS) and its homologs are important regulators of the actin cytoskeleton, mediating communication between Rho-family GTPases and the actin nucleation/crosslinking factor, the Arp2/3 complex. Many WAS mutations impair cytoskeletal control in hematopoietic tissues, resulting in functional and developmental defects that define the X-linked Wiskott-Aldrich syndrome (WAS) and the related X-linked thrombocytopenia (XLT). These diseases seem to result from reduced WASP signaling, often through decreased transcription or translation of the gene. Here we describe a new disease, X-linked severe congenital neutropenia (XLN), caused by a novel L270P mutation in the region of WAS encoding the conserved GTPase binding domain (GBD). In vitro, the mutant protein is constitutively activated through disruption of an autoinhibitory domain in the wild-type protein, indicating that loss of WASP autoinhibition is a key event in XLN. Our findings highlight the importance of precise regulation of WASP in hematopoietic development and function, as impairment versus enhancement of its activity give rise to distinct spectra of cellular defects and clinical phenotypes.

Mutations in ARHGEF6, encoding a guanine nucleotide exchange factor for Rho GTPases, in patients with X-linked mental retardation.

X-linked forms of mental retardation (XLMR) include a variety of different disorders and may account for up to 25% of all inherited cases of mental retardation. So far, seven X-chromosomal genes mutated in nonspecific mental retardation (MRX) have been identified: FMR2, GDI1, RPS6KA3, IL1RAPL, TM4SF2, OPHN1 and PAK3 (refs 2-9). The products of the latter two have been implicated in regulation of neural plasticity by controlling the activity of small GTPases of the Rho family. Here we report the identification of a new MRX gene, ARHGEF6 (also known as alphaPIX or Cool-2), encoding a protein with homology to guanine nucleotide exchange factors for Rho GTPases (Rho GEF). Molecular analysis of a reciprocal X/21 translocation in a male with mental retardation showed that this gene in Xq26 was disrupted by the rearrangement. Mutation screening of 119 patients with nonspecific mental retardation revealed a mutation in the first intron of ARHGEF6 (IVS1-11T-->C) in all affected males in a large Dutch family. The mutation resulted in preferential skipping of exon 2, predicting a protein lacking 28 amino acids. ARHGEF6 is the eighth MRX gene identified so far and the third such gene to encode a protein that interacts with Rho GTPases.

A new gene involved in X-linked mental retardation identified by analysis of an X;2 balanced translocation.

X-linked forms of mental retardation (MR) affect approximately 1 in 600 males and are likely to be highly heterogeneous. They can be categorized into syndromic (MRXS) and nonspecific (MRX) forms. In MRX forms, affected patients have no distinctive clinical or biochemical features. At least five MRX genes have been identified by positional cloning, but each accounts for only 0.5%-1.0% of MRX cases. Here we show that the gene TM4SF2 at Xp11.4 is inactivated by the X breakpoint of an X;2 balanced translocation in a patient with MR. Further investigation led to identification of TM4SF2 mutations in 2 of 33 other MRX families. RNA in situ hybridization showed that TM4SF2 is highly expressed in the central nervous system, including the cerebral cortex and hippocampus. TM4SF2 encodes a member of the tetraspanin family of proteins, which are known to contribute in molecular complexes including beta-1 integrins. We speculate that through this interaction, TM4SF2 might have a role in the control of neurite outgrowth.

A new member of the IL-1 receptor family highly expressed in hippocampus and involved in X-linked mental retardation.

We demonstrate here the importance of interleukin signalling pathways in cognitive function and the normal physiology of the CNS. Thorough investigation of an MRX critical region in Xp22.1-21.3 enabled us to identify a new gene expressed in brain that is responsible for a non-specific form of X-linked mental retardation. This gene encodes a 696 amino acid protein that has homology to IL-1 receptor accessory proteins. Non-overlapping deletions and a nonsense mutation in this gene were identified in patients with cognitive impairment only. Its high level of expression in post-natal brain structures involved in the hippocampal memory system suggests a specialized role for this new gene in the physiological processes underlying memory and learning abilities.

Holoprosencephaly and ZIC2 microdeletions: novel clinical and epidemiological specificities delineated.

Holoprosencephaly (HPE), the most common malformation of the human brain results from abnormal cleavage of the forebrain during the early embryonic developmental stages. The spectrum of malformations in HPE is wide, ranging from the classical cyclopia/proboscis to fairly asymptomatic forms [i.e. a single maxillary central incisor (SMCI)]. HPE may be caused by environmental or genetic factors. ZIC2 (13q32) was the second gene identified in which mutations cause HPE and recently a specific phenotype was ascribed to ZIC2-mutation HPE. Earlier, we reported a boy presenting HPE and deafness. Cytogenetic analyses were normal. Using array-comparative genomic hybridization (aCGH), we found a de novo 129 kb del(13)(q32) encompassing ZIC2 and ZIC5. There is no evidence for the involvement of ZIC5 in human diseases. We reviewed the literature for ZIC2-ZIC5 deletions and their involvement in neural tube defects (NTDs). Interestingly, we found evidence for a specific facial phenotype for ZIC2 gene deletion patients distinct from those with point mutations. In addition, based on the clinical data together with pathology, imaging and functional studies, we suggest an outline for a model explaining the genetic heterogeneity of ZIC2-ZIC5-associated NTDs and propose further studies for validation.

A new syndrome: multiple congenital abnormalities and mental retardation in two brothers.

In this report we present two brothers with abnormal neurological development, hypotonia, short stature, pylorus stenosis, pectus excavatum, brachycephaly due to craniosynostosis, frontal bossing, depressed nasal bridge, high arched-wide palate, downslant palpebral fissures, low-set, large ears, thin upper lip and bilateral cryptorchidism. The brothers were born to a couple of second cousins and were the third and fourth pregnancies of the mother. The father, the mother and the eldest sibling were phenotypically and chromosomally normal. The clinical findings of the brothers were found to be similar. These clinical findings were compared with syndromes showing some of the symptoms, namely Apert, FG, Floating-Harbor, Shprintzen-Goldberg and Rett Syndromes. However, when the findings were detailed, we observed that they did not match completely any of the syndromes in a discernable way. The MECP2 gene mutation was analysed because of mental retardation, poor neurological evolution and large ears, but no mutation was found. So these cases are presented as a new syndrome with apparent autosomal recessive inheritance.

Fetal hydrometrocolpos, uterus didelphys with low vaginal and anal atresia: difficulties in differentiation from a complex cloacal malformation: a case report.

Hydrometrocolpos, occurring in approximately 1/6000 newborn girls, can be caused by a stenotic urogenital sinus, a severe cloacal malformation, but also by other conditions such as an imperforate hymen, a midline vaginal septum and vaginal atresia. The prenatal differential diagnosis of this wide spectrum of conditions is not easy and requires a multidisciplinary approach with follow-up scans and MRI to access the severity of the condition. A non-consanguineous couple was referred in the first pregnancy at 30 weeks. The father, 30 years of age, of Kaukasian origin, and the mother of Asian origin, 26 years of age. Ultrasound at 30 weeks revealed ambiguous genitalia (with suspicion of clitoral hypertrophy), a septated structure located behind the bladder compatible with hydrometrocolpos with a uterine malformation (uterus didelphys), a single umbilical artery, mild ascites and growth on the tenth centile. The differential diagnosis included a vaginal atresia, a urogenital sinus and a more severe cloacal malformation. After serial scans, MRI and counselling by an experienced surgeon the preferential diagnosis of a cloacal malformation was made and a late pregnancy termination was performed. Pathological examination revealed: low vaginal atresia with uterus didelphys, anal atresia with rectovaginal fistula and a normal urinary tractus. The differential diagnosis between hydrometrocolpos due to vaginal atresia or due to a more severe cloacal malformation is not straightforward. Care should be taken in decision making and counselling patients with these complex prenatal malformations.

Mutations of the UPF3B gene, which encodes a protein widely expressed in neurons, are associated with nonspecific mental retardation with or without autism.

Mutations in the UPF3B gene, which encodes a protein involved in nonsense-mediated mRNA decay, have recently been described in four families with specific (Lujan-Fryns and FG syndromes), nonspecific X-linked mental retardation (XLMR) and autism. To further elucidate the contribution of UPF3B to mental retardation (MR), we screened its coding sequence in 397 families collected by the EuroMRX consortium. We identified one nonsense mutation, c.1081C>T/p.Arg361(*), in a family with nonspecific MR (MRX62) and two amino-acid substitutions in two other, unrelated families with MR and/or autism (c.1136G>A/p.Arg379His and c.1103G>A/p.Arg368Gln). Functional studies using lymphoblastoid cell lines from affected patients revealed that c.1081C>T mutation resulted in UPF3B mRNA degradation and consequent absence of the UPF3B protein. We also studied the subcellular localization of the wild-type and mutated UPF3B proteins in mouse primary hippocampal neurons. We did not detect any obvious difference in the localization between the wild-type UPF3B and the proteins carrying the two missense changes identified. However, we show that UPF3B is widely expressed in neurons and also presents in dendritic spines, which are essential structures for proper neurotransmission and thus learning and memory processes. Our results demonstrate that in addition to Lujan-Fryns and FG syndromes, UPF3B protein truncation mutations can cause also nonspecific XLMR. We also identify comorbidity of MR and autism in another family with UPF3B mutation. The neuronal localization pattern of the UPF3B protein and its function in mRNA surveillance suggests a potential function in the regulation of the expression and degradation of various mRNAs present at the synapse.

Oculocerebral hypopigmentation syndrome maps to chromosome 3q27.1q29.

BACKGROUND: In 1967, Cross et al. [J Pediatr 1967;70:398-406] reported four siblings with intellectual disability, microcephaly, neurologic and ocular disorders, and hypopigmentation involving skin and hair. This novel entity, known as oculocerebral hypopigmentation syndrome (OCHS) or Cross syndrome (OMIM 257800), is assumed to be autosomal recessive. However, its genetic cause is still unknown. CASE REPORT: A 4-year-old girl is reported with OCHS, a history of recurrent infections and vertebral fusion of L4-L5. Central nervous system and cardiac imaging as well as metabolic screening were normal. Microscopic hair investigations did not show any melanin deposit defects. RESULTS: Using molecular cytogenetics, we detected a de novo interstitial del(3)(q27.1q29) of the paternal chromosome. To our knowledge, this is the first molecular genetics finding in a patient with OCHS. Here we discuss the genotype-phenotype correlations and suggest candidate genes for this disorder. CONCLUSION: Investigating further patients would enable fine-mapping the OCHS locus and identifying its putative gene.

Distal limb deficiencies, micrognathia syndrome, and syndromic forms of split hand foot malformation (SHFM) are caused by chromosome 10q genomic rearrangements.

BACKGROUND: The 10q24 chromosomal region has previously been implicated in split hand foot malformation (SHFM). SHFM3 was mapped to a large interval on chromosome 10q. The corresponding dactylaplasia mouse model was linked to the syntenic locus on chromosome 19. It was shown that the two existing Dac alleles result from MusD-insertions upstream of or within Dactylin (Fbxw4). However, all efforts to find the underlying cause for the human SHFM3 have failed on the analysis of all the genes within the linkage region. Intriguingly a submicroscopic duplication within the critical locus on chromosome 10q24 was associated with the phenotype. METHODS AND RESULTS: As a part of screening for genomic rearrangements in cases with unexplained syndromic limb defects, a cohort of patients was analysed by array comparative genomic hybridisation (CGH). A 10q24 microduplication was detected in two individuals with distal limb deficiencies associated with micrognathia, hearing problems and renal hypoplasia. In addition, in a family with two affected siblings, a somatic/gonadal mosaicism for the microduplication was detected in the apparently healthy mother. Using a high resolution oligoarray further delineation of the duplication size was performed. CONCLUSIONS: The detected 10q24 genomic imbalance in our syndromic patients has a similar size to the duplication in the previously reported individuals with an isolated form of SHFM, thus extending the clinical spectrum of SHFM3. These findings clearly demonstrate the importance of array CGH in the detection of the aetiology of complex, clinically heterogeneous entities.

A boy with classical Rubinstein-Taybi syndrome but no detectable mutation in the CREBBP and EP300 genes.

Rubinstein-Taybi syndrome (RTS) is a rare autosomal dominant genetic disorder and is characterized by mental retardation, distinctive facial features, broad and often angulated thumbs and great toes. We report on a 7 year old boy with classical Rubinstein-Taybi syndrome. His facial and clinical features were very typical, including broad thumbs with radial angulation and broad great toes. Rigorous genetic analysis of the CREBBP and EP300 genes using DNA sequencing and multiple ligation-dependent probe amplification (MLPA) revealed no causative mutation in this boy, only a hitherto unreported but paternally inherited heterozygous sequence alteration, c.506 1+9C>T in IVS 30-31, which most likely represents a normal variant (NetGene 2 splice prediction software). We question if this boy could have a hitherto undetectable mutation type.

Lethal evolution of a newborn with consistent features of hydrolethalus syndrome--Romanian patient.

Hydrolethalus syndrome is a severe lethal disorder most commonly found in Finland. We present a lethal case of complex congenital malformation in a Romanian family who showed multiple signs described in hydrolethalus syndrome. Our case presented the specific characteristics: macrocephaly, midline cleft-lip, cleft palate, polydactyly of both hands and feet but without occipitoschisis, considered as the pathognomonic sign of the syndrome. Sequencing analysis of HYLS1 did not identify the point mutation present in the Finnish cases or other mutations in this gene.

DISC1 duplication in two brothers with autism and mild mental retardation.

We describe the identification and delineation of an inherited 2.07 Mb microduplication in 1q42.2 in two brothers with autism and mild mental retardation. Since this duplication was not present in 1577 Belgian persons, we consider this as an extremely rare variant which has the potential to provide further insight into the genetics of autism. The duplication contains seven genes including the DISC1 gene, an interesting candidate gene that has been associated to schizophrenia, bipolar disorder, autism and Asperger syndrome. In this report we describe additional analyses undertaken to investigate the causal relationship of the duplication to the autism phenotype. We conclude that the 1q42.2 microduplication probably confers susceptibility to autism in the current family. This study is a typical illustration of the difficult interpretation of causality of a very rare variant in neuropsychiatric disease and the challenge of genetic counselling in a particular family.

17q21.31 microduplication patients are characterised by behavioural problems and poor social interaction.

BACKGROUND: Microdeletions at 17q21.31 have recently been shown to cause a novel syndrome. Here we identify the reciprocal 17q21.31 duplication syndrome in 4 patients. METHOD: Patients with the 17q21.31 duplication were identified by screening a large cohort of patients (n = 13,070) with mental retardation and congenital malformation by comparative genomic hybridisation microarray. Parental origin was investigated in 3 patients by quantitative polymerase chain reaction and microsatellite genotyping. RESULTS: In three cases it was possible to show that duplication arose de novo. Intellectual skills range from normal to mild mental retardation. Patients are characterised by poor social interaction, with relationship difficulties, reminiscent of autistic spectrum disorders. Other features are rather variable with no striking common phenotypic features. Parental origin was investigated for 3 patients. In all cases duplication was of maternal origin either through interchromosomal (2 cases) or interchromatid (1 case) rearrangement. The 3 mothers are all carriers of the inverted H2 haplotype, emphasising the role of local genomic architecture alteration as a predisposing factor for this duplication. CONCLUSION: Autistic features observed in our patients suggest that genes in the duplicated interval should be considered as candidates for disorders in the autistic spectrum. Other phenotypic observations are rather variable or aspecific. This adds 17q21.31 duplications to a growing group of recently identified genomic disorders with variable penetrance and expressivity.

Recurrent reciprocal deletions and duplications of 16p13.11: the deletion is a risk factor for MR/MCA while the duplication may be a rare benign variant.

BACKGROUND: Genomic disorders are often caused by non-allelic homologous recombination between segmental duplications. Chromosome 16 is especially rich in a chromosome-specific low copy repeat, termed LCR16. METHODS AND RESULTS: A bacterial artificial chromosome (BAC) array comparative genome hybridisation (CGH) screen of 1027 patients with mental retardation and/or multiple congenital anomalies (MR/MCA) was performed. The BAC array CGH screen identified five patients with deletions and five with apparently reciprocal duplications of 16p13 covering 1.65 Mb, including 15 RefSeq genes. In addition, three atypical rearrangements overlapping or flanking this region were found. Fine mapping by high-resolution oligonucleotide arrays suggests that these deletions and duplications result from non-allelic homologous recombination (NAHR) between distinct LCR16 subunits with >99% sequence identity. Deletions and duplications were either de novo or inherited from unaffected parents. To determine whether these imbalances are associated with the MR/MCA phenotype or whether they might be benign variants, a population of 2014 normal controls was screened. The absence of deletions in the control population showed that 16p13.11 deletions are significantly associated with MR/MCA (p = 0.0048). Despite phenotypic variability, common features were identified: three patients with deletions presented with MR, microcephaly and epilepsy (two of these had also short stature), and two other deletion carriers ascertained prenatally presented with cleft lip and midline defects. In contrast to its previous association with autism, the duplication seems to be a common variant in the population (5/1682, 0.29%). CONCLUSION: These findings indicate that deletions inherited from clinically normal parents are likely to be causal for the patients' phenotype whereas the role of duplications (de novo or inherited) in the phenotype remains uncertain. This difference in knowledge regarding the clinical relevance of the deletion and the duplication causes a paradigm shift in (cyto)genetic counselling.