Search for ReCQL4 mutations in 39 patients genotyped for suspected Rothmund-Thomson/Baller-Gerold syndromes

Three overlapping conditions, namely Rothmund-Thomson (RTS), Baller-Gerold (BGS) and RAPADILINO syndromes, have been attributed to RECQL4 mutations. Differential diagnoses depend on the clinical presentation, but the numbers of known genes remain low, leading to the widespread prescription of RECQL4 sequencing. The aim of our study was therefore to determine the best clinical indicators for the presence of RECQL4 mutations in a series of 39 patients referred for RECQL4 molecular analysis and belonging to the RTS (27 cases) and BGS (12 cases) spectrum. One or two deleterious RECQL4 mutations were found in 10/27 patients referred for RTS diagnosis. Clinical and molecular reevaluation led to a different diagnosis in 7/17 negative cases, including Clericuzio-type poikiloderma with neutropenia, hereditary sclerosing poikiloderma, and craniosynostosis/anal anomalies/porokeratosis. No RECQL4 mutations were found in the BGS group without poikiloderma, confirming that RECQL4 sequencing was not indicated in this phenotype. One chromosomal abnormality and one TWIST mutation was found in this cohort. This study highlights the search for differential diagnoses before the prescription of RECQL4 sequencing in this clinically heterogeneous group. The combination of clinically defined subgroups and next-generation sequencing will hopefully bring to light new molecular bases of syndromes with poikiloderma, as well as BGS without poikiloderma.

Molecular findings and clinical data in a cohort of 150 patients with anophthalmia/microphthalmia

Anophthalmia and microphthalmia (AM) are the most severe malformations of the eye, corresponding respectively to reduced size or absent ocular globe. Wide genetic heterogeneity has been reported and different genes have been demonstrated to be causative of syndromic and non-syndromic forms of AM. We screened seven AM genes [GDF6 (growth differentiation factor 6), FOXE3 (forkhead box E3), OTX2 (orthodenticle protein homolog 2), PAX6 (paired box 6), RAX (retina and anterior neural fold homeobox), SOX2 (SRY sex determining region Y-box 2), and VSX2 (visual system homeobox 2 gene)] in a cohort of 150 patients with isolated or syndromic AM. The causative genetic defect was identified in 21% of the patients (32/150). Point mutations were identified by direct sequencing of these genes in 25 patients (13 in SOX2, 4 in RAX, 3 in OTX2, 2 in FOXE3, 1 in VSX2, 1 in PAX6, and 1 in GDF6). In addition eight gene deletions (five SOX2, two OTX2 and one RAX) were identified using a semi-quantitative multiplex polymerase chain reaction (PCR) [quantitative multiplex PCR amplification of short fluorescent fragments (QMPSF)]. The causative genetic defect was identified in 21% of the patients. This result contributes to our knowledge of the molecular basis of AM, and will facilitate accurate genetic counselling.

Nager syndrome: confirmation of SF3B4 haploinsufficiency as the major cause

Nager syndrome belongs to the group of acrofacial dysostosis, which are characterized by the association of craniofacial and limb malformations. Recently, exome sequencing studies identified the SF3B4 gene as the cause of this condition in most patients. SF3B4 encodes a highly conserved protein implicated in mRNA splicing and bone morphogenic protein (BMP) signaling. We performed SF3B4 sequencing in 14 families (18 patients) whose features were suggestive of Nager syndrome and found nine mutations predicted to result in loss-of-function. SF3B4 is the major gene responsible for autosomal dominant Nager syndrome. All mutations reported predict null alleles, therefore precluding genotype-phenotype correlations. Most mutation-negative patients were phenotypically indistinguishable from patients with mutations, suggesting genetic heterogeneity.

Split hand/foot malformation with long-bone deficiency and BHLHA9 duplication: report of 13 new families

Split hand/foot malformation (SHFM) with long-bone deficiency (SHFLD, MIM#119100) is a rare condition characterized by SHFM associated with long-bone malformation usually involving the tibia. Previous published data reported several unrelated patients with 17p13.3 duplication and SHFLD. Recently, the minimal critical region had been reduced, suggesting that BHLHA9 copy number gains are associated with this limb defect. Here, we report on 13 new families presenting with ectrodactyly and harboring a BHLHA9 duplication.

Hippocampal dysgenesis and variable neuropsychiatric phenotypes in patients with Bardet-Biedl syndrome underline complex CNS impact of primary cilia

The Bardet-Biedl syndrome (BBS) is a rare ciliopathy clinically defined by the association of retinitis pigmentosa, polydactyly, obesity, kidney disease and cognitive impairment. The cognitive functioning, behavioral phenotype, prevalence of psychiatric diseases and memory performances of a cohort of 34 patients with BBS were evaluated and a systemic brain magnetic resonance imaging (MRI) was performed. The patients' cognitive functioning was of marked variable efficiency ranging from normal to disabling performances. Neuropsychological disorders such as slow thought process, attention difficulties and obsessive-compulsive traits were observed. Our main finding was hippocampal dysgenesis, diagnosed by MRI, found in 42.31% of the patients in this cohort. Moreover, we show that BBS proteins are expressed in the human hippocampus and in the human brain in the normal subject. Recent literature in the murine model shows that hippocampal neurogenesis, in particular in the adult mouse, requires an intact primary cilia. These results encourage us to further investigate the possible role of BBS proteins in the hippocampus and related central nervous system structures.

IRF6 Screening of Syndromic and a priori Non-Syndromic Cleft Lip and Palate Patients: Identification of a New Type of Minor VWS Sign

Van der Woude syndrome (VWS), caused by dominant IRF6 mutation, is the most common cleft syndrome. In 15% of the patients, lip pits are absent and the phenotype mimics isolated clefts. Therefore, we hypothesized that some of the families classified as having non-syndromic inherited cleft lip and palate could have an IRF6 mutation. We screened in total 170 patients with cleft lip with or without cleft palate (CL/P): 75 were syndromic and 95 were a priori part of multiplex non-syndromic families. A mutation was identified in 62.7 and 3.3% of the patients, respectively. In one of the 95 a priori non-syndromic families with an autosomal dominant inheritance (family B), new insights into the family history revealed the presence, at birth, of lower lip pits in two members and the diagnosis was revised as VWS. A novel lower lip sign was observed in one individual in this family. Interestingly, a similar lower lip sign was also observed in one individual from a 2nd family (family A). This consists of 2 nodules below the lower lip on the external side. In a 3rd multiplex family (family C), a de novo mutation was identified in an a priori non-syndromic CL/P patient. Re-examination after mutation screening revealed the presence of a tiny pit-looking lesion on the inner side of the lower lip leading to a revised diagnosis of VWS. On the basis of this data, we conclude that IRF6 should be screened when any doubt rises about the normality of the lower lip and also if a non-syndromic cleft lip patient (with or without cleft palate) has a family history suggestive of autosomal dominant inheritance.

MEF2C haploinsufficiency caused by either microdeletion of the 5q14.3 region or mutation is responsible for severe mental retardation with stereotypic movements, epilepsy and/or cerebral malformations

BACKGROUND

Over the last few years, array-comparative genomic hybridisation (CGH) has considerably improved our ability to detect cryptic unbalanced rearrangements in patients with syndromic mental retardation.

METHOD

Molecular karyotyping of six patients with syndromic mental retardation was carried out using whole-genome oligonucleotide array-CGH.

RESULTS

5q14.3 microdeletions ranging from 216 kb to 8.8 Mb were detected in five unrelated patients with the following phenotypic similarities: severe mental retardation with absent speech, hypotonia and stereotypic movements. Facial dysmorphic features, epilepsy and/or cerebral malformations were also present in most of these patients. The minimal common deleted region of these 5q14 microdeletions encompassed only MEF2C, the gene for a protein known to act in brain as a neurogenesis effector, which regulates excitatory synapse number. In a patient with a similar phenotype, an MEF2C nonsense mutation was subsequently identified.

CONCLUSION

Taken together, these results strongly suggest that haploinsufficiency of MEF2C is responsible for severe mental retardation with stereotypic movements, seizures and/or cerebral malformations.

Mutational spectrum of COH1 and clinical heterogeneity in Cohen syndrome

Cohen syndrome (CS) is an autosomal recessive disorder with variability in the clinical manifestations, characterised by mental retardation, postnatal microcephaly, facial dysmorphism, pigmentary retinopathy, myopia, and intermittent neutropenia. Mutations in the gene COH1 have been found in an ethnically diverse series of patients. Brief clinical descriptions of 24 patients with CS are provided. The patients were from 16 families of different ethnic backgrounds and between 2.5 and 60 years of age at assessment. DNA samples from all patients were analysed for mutations in COH1 by direct sequencing. Splice site mutations were characterised using reverse transcriptase PCR analysis from total RNA samples. In this series, we detected 25 different COH1 mutations; 19 of these were novel, including 9 nonsense mutations, 8 frameshift mutations, 4 verified splice site mutations, 3 larger in frame deletions, and 1 missense mutation. We observed marked variability of developmental and growth parameters. The typical facial gestalt was seen in 23/24 patients. Early onset progressive myopia was present in all the patients older than 5 years. Widespread pigmentary retinopathy was found in 12/14 patients assessed over 5 years of age. We present evidence for extended allelic heterogeneity of CS, with the vast majority of mutations leading to premature termination codons in COH1. Our data confirm the broad clinical spectrum of CS with some patients lacking even the characteristic facial gestalt and pigmentary retinopathy at school age.

Adams-Oliver syndrome: clinical description of a four-generation family and exclusion of five candidate genes

We present a Belgian Adams-Oliver syndrome (AOS) family with 10 affected individuals over four generations, of which six were available for this study. Clinical symptoms observed in these patients were very variable as previously reported in other families and included large areas of alopecia on the vertex of the skull and serious limb reduction defects with agenesis of all toes of one foot. To identify the disease-causing gene, we sequenced the MSX1, CART1, P63 (P73L), RUNX2, and HOXD13 genes in this family and nine previously reported families, but no disease-causing mutations were found. Further investigation is ongoing in these families in order to identify the genetic cause of AOS.

Société Française d’Orthopédie Pédiatrique

Limb malformations are frequent. These malformations are isolated or associated with anomalies of other developmental fields and accurate diagnostic is essential for prognosis evaluation, treatment and genetic counseling. Animal embryology and molecular biology techniques, have given us a better understanding of the processes of growth and patterning of the limb buds. The key genes that are involved in these processes have been identified and their interactions recognized. Human genetics has been able to identify, or at least localize, several genes implicated in limb development. We here review the present knowledge on these genes and their mutations responsible for limb anomalies.

Familial syndromic duodenal atresia: Feingold syndrome

Familial duodenal atresia occurs as part of Feingold syndrome. Other features of this variable autosomal dominant condition include tracheo-oesophageal fistula and oesophageal atresia, microcephaly, hand and foot anomalies, facial dysmorphism, and developmental delay. We report a father and two sons with Feingold syndrome. One has bilateral dysplastic kidneys which have not been reported previously.

Absent lacrimal ducts, distichiasis, dysmorphic features, and brachydactyly: a case report

We report a male patient presenting with the association of absent lacrimal ducts, distichiasis, dysmorphic facial features and limb abnormalities. Extensive chromosomal studies showed normal chromosomes. We discuss differential diagnoses such as Setleis, Char and Lacrimo-Auriculo-Dento-Digital (LADD) syndromes. This may represent a novel entity for which parental consanguinity would support an autosomal recessive mode of inheritance.

Pierre Robin sequence: a series of 117 consecutive cases

A series of 117 cases of Pierre Robin Sequence are classified as isolated (48%), syndromic (35%), and with associated anomalies (17%); the latter group had a poor long-term prognosis. In isolated Pierre Robin Sequence, familial cases and a high incidence of twins were noted. Among syndromic Pierre Robin Sequence, 4 syndromes represent more than 50% of the diagnoses.

Genetics of limb anomalies in humans

The limbs have an essential function in all vertebrates. In animals, the key genes that are involved in the growth and patterning of the limb buds, and of the development of the complex extremities, have been identified and their interactions recognized. Aided by these discoveries, human genetics has also been able to identify, or at least localize, certain genes responsible for anomalies of the limbs. These malformations are isolated or associated with anomalies of other developmental fields, according to the expression domain of the gene involved. Increasing knowledge of the embryology and genes involved has lead to a regrouping of malformation manifestations in genetics terms. Clear genotype-phenotype correlations are difficult to establish owing to the interlinking network of genetic signals underlying limb development.