Duplication of 10q24 locus: broadening the clinical and radiological spectrum.

Split-hand-split-foot malformation (SHFM) is a rare condition that occurs in 1 in 8500-25,000 newborns and accounts for 15% of all limb reduction defects. SHFM is heterogeneous and can be isolated, associated with other malformations, or syndromic. The mode of inheritance is mostly autosomal dominant with incomplete penetrance, but can be X-linked or autosomal recessive. Seven loci are currently known: SHFM1 at 7q21.2q22.1 (DLX5 gene), SHFM2 at Xq26, SHFM3 at 10q24q25, SHFM4 at 3q27 (TP63 gene), SHFM5 at 2q31 and SHFM6 as a result of variants in WNT10B (chromosome 12q13). Duplications at 17p13.3 are seen in SHFM when isolated or associated with long bone deficiency. Tandem genomic duplications at chromosome 10q24 involving at least the DACTYLIN gene are associated with SHFM3. No point variant in any of the genes residing within the region has been identified so far, but duplication of exon 1 of the BTRC gene may explain the phenotype, with likely complex alterations of gene regulation mechanisms that would impair limb morphogenesis. We report on 32 new index cases identified by array-CGH and/or by qPCR, including some prenatal ones, leading to termination for the most severe. Twenty-two cases were presenting with SHFM and 7 with monodactyly only. Three had an overlapping phenotype. Additional findings were identified in 5 (renal dysplasia, cutis aplasia, hypogonadism and agenesis of corpus callosum with hydrocephalus). We present their clinical and radiological findings and review the literature on this rearrangement that seems to be one of the most frequent cause of SHFM.

CFTR p.Arg117His associated with CBAVD and other CFTR-related disorders.

BACKGROUND: The high frequency of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene mutation p.Arg117His in patients with congenital bilateral absence of the vas deferens (CBAVD) and in newborns screened for CF has created a dilemma. METHODS: Phenotypic and genotypic data were retrospectively collected in 179 non-newborn French individuals carrying p.Arg117His and a second CFTR mutation referred for symptoms or family history, by all French molecular genetics laboratories, referring physicians, CF care centres and infertility clinics. RESULTS: 97% of the patients had the intronic T7 normal variant in cis with p.Arg117His. 89% patients were male, with CBAVD being the reason for referral in 76%. In 166/179 patients with available detailed clinical features, final diagnoses were: four late-onset marked pulmonary disease, 83 isolated CBAVD, 67 other CFTR-related phenotypes, including 44 CBAVD with pulmonary and/or pancreatic symptoms and 12 asymptomatic cases. Respiratory symptoms were observed in 30% of the patients, but the overall phenotype was mild. No correlation was observed between sweat chloride concentrations and disease severity. Five couples at risk of CF offspring were identified and four benefited from prenatal or preimplantation genetic diagnoses (PND or PGD). Eight children were born, including four who were compound heterozygous for p.Arg117His and one with a severe CF mutation. CONCLUSIONS: Patients with CBAVD carrying p.Arg117His and a severe CF mutation should benefit from a clinical evaluation and follow-up. Depending on the CBAVD patients' genotype, a CFTR analysis should be considered in their partners in order to identify CF carrier couples and offer PND or PGD.

A SUMOylation-defective MITF germline mutation predisposes to melanoma and renal carcinoma.

So far, no common environmental and/or phenotypic factor has been associated with melanoma and renal cell carcinoma (RCC). The known risk factors for melanoma include sun exposure, pigmentation and nevus phenotypes; risk factors associated with RCC include smoking, obesity and hypertension. A recent study of coexisting melanoma and RCC in the same patients supports a genetic predisposition underlying the association between these two cancers. The microphthalmia-associated transcription factor (MITF) has been proposed to act as a melanoma oncogene; it also stimulates the transcription of hypoxia inducible factor (HIF1A), the pathway of which is targeted by kidney cancer susceptibility genes. We therefore proposed that MITF might have a role in conferring a genetic predisposition to co-occurring melanoma and RCC. Here we identify a germline missense substitution in MITF (Mi-E318K) that occurred at a significantly higher frequency in genetically enriched patients affected with melanoma, RCC or both cancers, when compared with controls. Overall, Mi-E318K carriers had a higher than fivefold increased risk of developing melanoma, RCC or both cancers. Codon 318 is located in a small-ubiquitin-like modifier (SUMO) consensus site (ΨKXE) and Mi-E318K severely impaired SUMOylation of MITF. Mi-E318K enhanced MITF protein binding to the HIF1A promoter and increased its transcriptional activity compared to wild-type MITF. Further, we observed a global increase in Mi-E318K-occupied loci. In an RCC cell line, gene expression profiling identified a Mi-E318K signature related to cell growth, proliferation and inflammation. Lastly, the mutant protein enhanced melanocytic and renal cell clonogenicity, migration and invasion, consistent with a gain-of-function role in tumorigenesis. Our data provide insights into the link between SUMOylation, transcription and cancer.

Comparison of clinical presentations and outcomes between patients with TGFBR2 and FBN1 mutations in Marfan syndrome and related disorders.

BACKGROUND: TGFBR2 mutations were recognized recently among patients with a Marfan-like phenotype. The associated clinical and prognostic spectra remain unclear. METHODS AND RESULTS: Clinical features and outcomes of 71 patients with a TGFBR2 mutation (TGFBR2 group) were compared with 50 age- and sex-matched unaffected family members (control subjects) and 243 patients harboring FBN1 mutations (FBN1 group). Aortic dilatation was present in a similar proportion of patients in both the TGFBR2 and FBN1 groups (78% versus 79%, respectively) but was highly variable. The incidence and average age for thoracic aortic surgery (31% versus 27% and 35+/-16 versus 39+/-13 years, respectively) and aortic dissection (14% versus 10% and 38+/-12 versus 39+/-9 years) were also similar in the 2 groups. Mitral valve involvement (myxomatous, prolapse, mitral regurgitation) was less frequent in the TGFBR2 than in the FBN1 group (all P<0.05). Aortic dilatation, dissection, or sudden death was the index event leading to genetic diagnosis in 65% of families with TGFBR2 mutations, versus 32% with FBN1 mutations (P=0.002). The rate of death was greater in TGFBR2 families before diagnosis but similar once the disease had been recognized. Most pregnancies were uneventful (without death or aortic dissection) in both TGFBR2 and FBN1 families (38 of 39 versus 213 of 217; P=1). Seven patients (10%) with a TGFBR2 mutation fulfilled international criteria for Marfan syndrome, 3 of whom presented with features specific for Loeys-Dietz syndrome. CONCLUSIONS: Clinical outcomes appear similar between treated patients with TGFBR2 mutations and individuals with FBN1 mutations. Prognosis depends on clinical disease expression and treatment rather than simply the presence of a TGFBR2 gene mutation.

Null mutations causing depletion of the type 1 ryanodine receptor (RYR1) are commonly associated with recessive structural congenital myopathies with cores.

Mutations of the ryanodine receptor cause dominant and recessive forms of congenital myopathies with cores. Quantitative defects of RYR1 have been reported in families presenting with recessive forms of the disease and epigenic regulation has been recently proposed to explain potential maternal monoallelic silencing of the RYR1 gene. We investigated nine families presenting with a recessive form of the disease and showing a quantitative defect of RYR1 expression. Genetic analysis allowed the identification of a mutation on both alleles of the RYR1 gene for all patients, 15 being novel variants. We evidenced for all patients an alteration of the expression of the RYR1 gene caused by amorphic mutations responsible either for mRNA or protein instability. In seven families the variant present on the second allele was a missense mutation. In the remaining two families the second variant led to a hypomorphic expression of the RYR1 gene and was associated with a severe neonatal phenotype, pointing out the minimal amount of RYR1 needed for skeletal muscle function. Noticeably, a novel additional exon 3b was characterized in the most severely affected cases. This study showed that all cases presenting with a quantitative defect of RYR1 expression in our panel of patients affected by recessive core myopathies were caused by the presence of one recessive null allele and that variability of the phenotype depended on the nature of the mutation present on the second allele. Our study also indicated that presence of a second mutation must be investigated in sporadic cases or in dominant cases presenting with a familial clinical variability.

Identification of four new PITX2 gene mutations in patients with Axenfeld-Rieger syndrome.

PURPOSE: Axenfeld Rieger syndrome (ARS) is an autosomal dominant inherited disorder affecting development of the ocular anterior chamber, abdomen, teeth and facial structures. The PITX2 gene is a major gene encoding a major transcription factor associated with ARS. METHODS: ARS patients were collected from six unrelated families. Patients and their families were ophthalmologically phenotyped and their blood was collected for DNA extraction. We screened the coding region of human PITX2 gene by direct sequencing. The consequences of the mutations described were investigated by generating crystallographic representations of the amino acid changes. In order to better understand the occurrence of glaucoma in ARS patients, we studied the PITX2 gene expression in human embryonic and fetal ocular tissue sections. RESULTS: We identified four novel PITX2 genetic alterations in four unrelated families with ARS. These mutations included two nonsense mutations (E55X and Y121X), an eight nucleotides insertion (1251 ins CGACTCCT) and a substitution (F58L), in familial and sporadic cases of ARS. We also showed for the first time that PITX2 is expressed at early stages of the human embryonic and fetal periocular mesenchyme, as well as at later stages of human development in the fetal ciliary body, ciliary processes, irido corneal angle and corneal endothelium. The human fetal eye PITX2 gene expression pattern reported here for the first time provides a strong basis for explaining the frequent occurrence of glaucoma in patients affected by PITX2 gene mutations. CONCLUSIONS: Two mutations identified affect the homeodomain (E55X and F58L). The E55X nonsense mutation is likely to alter dramatically the DNA-binding capabilities of the PITX2 homeodomain. Furthermore, there is a complete loss of the carboxy-terminal part of the PITX2 protein beyond the site of the mutation. The phenylalanine F58 is known to contribute to the hydrophobic network of the homeodomain. The crystallographic representations of the mutation F58L show that this mutation may change the conformation of the helical core. The F58L mutation is very likely to modify the homeodomain conformation and probably alters the DNA binding properties of PITX2. The other mutations (Y121X and the eight-nucleotide insertion (1251 ins CGA CTC CT) CGA CTC CT, at position 224 in PITX2A) result in partial loss of the C-terminal domain of PITX2. Pitx2 synergistically transactivates the prolactin promoter in the presence of the POU homeodomain protein Pit-1. Pitx2 activity is regulated by its own C-terminal tail. This region contains a highly conserved 14-amino-acid element involved in protein-protein interactions. The C-terminal 39-amino-acid tail represses DNA binding activity and is required for Pitx2 interactions with other transcription factors, for Pitx2-Pit-1 interaction and Pit-1synergism. Pit-1 interaction with the Pitx2 C terminus masks the inhibitory effect and promotes increased DNA binding activity. Thus, the partial or complete loss of the C terminus tail can lead to decreased or absent DNA binding activity and trigger severe ARS phenotypes. Our in situ hybridization results obtained on human embryonic and fetal ocular tissue sections constitute the first molecular histological data providing an explanation for the occurrence of precocious glaucoma in human patients affected by ARS caused by PITX2 mutations. Further structural and biochemical studies are needed for understanding the wide spectrum of clinical phenotypes caused by the increasing number of new PITX2 mutations found in ARS affected patients.

Simple detection of genomic microdeletions and microduplications using QMPSF in patients with idiopathic mental retardation.

In contrast to the numerous well-known microdeletion syndromes, only a few microduplications have been described, and this discrepancy may be due in part to methodological bias. In order to facilitate the detection of genomic microdeletions and microduplications, we developed a new assay based on QMPSF (Quantitative Multiplex PCR of Short fluorescent Fragments) able to explore simultaneously 12 candidate loci involved in mental retardation (MR) and known to be the target of genomic rearrangements. We first screened 153 patients with MR and facial dysmorphism associated with malformations, or growth anomalies, or familial history, with cytogenetically normal chromosomes, and the absence of FRAXA mutation and subtelomeric rearrangements. In this series, we found a 5q35 deletion removing the NSD1 gene in a patient with severe epilepsy, profound MR and, retrospectively, craniofacial features of Sotos syndrome. In a second series, we screened 140 patients with MR and behaviour disturbance who did not fulfil the de Vries criteria for subtelomeric rearrangements and who had a normal karyotype and no detectable FRAXA mutation. We detected a 22q11 deletion in a patient with moderate MR, obesity, and facial dysmorphism and a 4 Mb 17p11 duplication in a patient with moderate MR, behaviour disturbance, strabismus, and aspecific facial features. This new QMPSF assay can be gradually upgraded to include additional loci involved in newly recognised microduplication/microdeletion syndromes, and should facilitate wide screenings of patients with idiopathic MR and provide better estimates of the microduplication frequency in the MR population.

Molecular characterization of a 14q deletion in a boy with features of Holt-Oram syndrome.

Holt-Oram syndrome, the major "heart-hand" syndrome is defined by the association of radial defects or triphalangeal thumbs and septal heart defects. The transmission is autosomal dominant and the causative gene has been shown to be TBX5, located on 12q24.1, which encodes a transcription factor. Genetic heterogeneity has been suggested by several reports. We identified a 14(q23.3 approximately 24.2q31.1) deletion in a boy presenting severe bilateral asymmetrical radial aplasia, congenital heart defects, and developmental delay. This deletion, whose size could be estimated to be 9.6-13.7 Mb, was shown to be inherited via his mother's interchromosomal insertion. This is the second report of a chromosome 14 interstitial deletion associated with clinical features of Holt-Oram syndrome. These observations suggest the existence of a new "heart-hand" locus on chromosome 14q.

Atlastin1 mutations are frequent in young-onset autosomal dominant spastic paraplegia.

BACKGROUND: Hereditary spastic paraplegias are disorders that are very heterogeneous, both clinically and genetically. The atlastin1 gene has recently been implicated in SPG3A, a form of autosomal dominant pure spastic paraplegia. Atlastin1 mutations have been identified in 8 families so far. OBJECTIVES: To determine the relative frequency, phenotype, and mutation spectrum of SPG3A in patients with pure autosomal dominant spastic paraplegia and onset before age 20 years. PATIENTS AND METHODS: We sequenced the atlastin1 gene in a large series of patients (31 families) in which mutations in the spastin gene, corresponding to the frequent SPG4 locus, had previously been excluded. The phenotype was compared with 126 SPG4 patients. RESULTS: We identified 12 families (39%) including 34 patients with 9 different missense atlastin1 mutations, 7 of which are newly described. The main clinical characteristic of these SPG3A patients was pure spasticity with very young onset of symptoms (mean age, 4.6 +/- 3.9 years) and slow progression. However, additional signs such as decreased vibration sense and wasting in lower limbs, sphincter disturbances, and scoliosis were found in a minority of patients. In addition, several gene carriers were clinically affected but still asymptomatic (n = 5) or had no clinical signs (n = 2), indicating incomplete penetrance. Compared with patients from other families meeting the same diagnostic criteria (43 patients) and families with SPG4 (126 patients), the major form of autosomal dominant spastic paraplegia, SPG3A patients had earlier symptom onset, less frequently increased reflexes in the upper limbs, decreased vibration sense in the lower limbs, and fewer sphincter disturbances, but more frequently observed wasting in the lower limbs and scoliosis. These particularities, as well as frequent abnormal motor evoked potentials, could help identify patients to be screened for atlastin1 gene mutations. CONCLUSIONS: This study enables us to estimate the frequency of the SPG3A mutations in France at 39% in families with young-onset autosomal dominant spastic paraplegia after exclusion of SPG4 cases. So far, most mutations have been private, although they were all found in exons 7, 8, 12, and 13. These exons should be given priority when performing molecular diagnoses for SPG3A.

Complete germline deletion of the STK11 gene in a family with Peutz-Jeghers syndrome.

Peutz-Jeghers syndrome (PJS, MIM175200) is an autosomal-dominant inherited disorder characterised by multiple gastrointestinal hamartomatous polyps, melanin spots of the oral mucosa and digits, and an increased risk for various neoplasms. The PJS results from germline alterations of the STK11/LKB1 tumour suppressor gene, located on 19p13.3, and encoding a serine/threonine kinase. The detection of STK11 germline mutations, in only 50-70% of PJS families, has suggested a genetic heterogeneity of the disease. We report the case of a family with typical features of PJS, including gastrointestinal hamartomatous, breast cancers and melanin spots of the oral mucosa. Quantitative multiplex PCR of short fluorescent fragments (QMPSF) of the 19p13 region allowed us to identify an approximately 250 kb heterozygous deletion removing entirely the STK11 locus. This report, which constitutes the first description of a complete germline deletion of STK11, shows that the presence of such large genomic deletions should be considered in PJS families without detectable point mutations of STK11.

Fetal capillary haemangioblastoma: an exceptional tumour. A review of the literature.

We report a case of a fetal haemangioblastoma located in the cerebellopontine angle. On prenatal ultrasonographic examination a hyperechogenic and heterogeneous mass with a major vascularization on colour Doppler imaging was observed. It increased progressively and laminated the cerebellum. A neoplastic tumour was suspected but its extent into the cerebral peduncle was unclear. Diagnosis was made at autopsy using histological, immunohistochemical and flow cytometric evaluation. Haemangioblastoma is an exceptional congenital tumour, which is either sporadic or integrated in von Hippel-Lindau disease (VHLD). We discuss the obstetrical management of prenatal brain tumours and the genetic counselling of haemangioblastoma.

Significant contribution of large BRCA1 gene rearrangements in 120 French breast and ovarian cancer families.

Genetic linkage data have shown that alterations of the BRCA1 gene are responsible for the majority of hereditary breast-ovarian cancers. However, BRCA1 germline mutations are found much less frequently than expected, especially as standard PCR-based mutation detection approaches focus on point and small gene alterations. In order to estimate the contribution of large gene rearrangements to the BRCA1 mutation spectrum, we have extensively analysed a series of 120 French breast-ovarian cancer cases. Thirty-eight were previously found carrier of a BRCA1 point mutation, 14 of a BRCA2 point mutation and one case has previously been reported as carrier of a large BRCA1 deletion. The remaining 67 cases were studied using the BRCA1 bar code approach on combed DNA which allows a panoramic view of the BRCA1 region. Three additional rearrangements were detected: a recurrent 23.8 kb deletion of exons 8-13, a 17.2 kb duplication of exons 3-8 and a 8.6 kb duplication of exons 18-20. Thus, in our series, BRCA1 large rearrangements accounted for 3.3% (4/120) of breast-ovarian cancer cases and 9.5% (4/42) of the BRCA1 gene mutation spectrum, suggesting that their screening is an important step that should be now systematically included in genetic testing surveys.

Refinement of the NHS locus on chromosome Xp22.13 and analysis of five candidate genes.

Nance-Horan syndrome (NHS) is an X-linked condition characterised by congenital cataracts, dental abnormalities, dysmorphic features, and mental retardation in some cases. Previous studies have mapped the disease gene to a 2 cM interval on Xp22.2 between DXS43 and DXS999. We report additional linkage data resulting from the analysis of eleven independent NHS families. A maximum lod score of 9.94 (theta=0.00) was obtained at the RS1 locus and a recombination with locus DXS1195 on the telomeric side was observed in two families, thus refining the location of the gene to an interval of around 1 Mb on Xp22.13. Direct sequencing or SSCP analysis of the coding exons of five genes (SCML1, SCML2, STK9, RS1 and PPEF1), considered as candidate genes on the basis of their location in the critical interval, failed to detect any mutation in 12 unrelated NHS patients, thus making it highly unlikely that these genes are implicated in NHS.