Choroidal abnormalities in café-au-lait syndromes: a new differential diagnostic tool?

The best known café-au-lait syndrome is neurofibromatosis type 1 (NF1). Legius syndrome (LS) is another, rarer syndrome with café-au-lait macules (CALMs). In young patients their clinical picture is often indistinguishable. We investigated the presence of choroidal abnormalities in syndromes with CALMs as a candidate tool for a more efficient diagnosis. Thirty-four patients with NF1 (14 with a truncating mutation, 14 with a non-truncating mutation and 6 with unknown mutation) and 11 patients with LS. All patients underwent an ophthalmological examination. Infrared images were performed. Choroidal nodules were diagnosed in 65% of the NF1 group. About 71% of NF1 patients with a truncating mutation and 50% of patients with a non-truncating mutation were found to have nodules. Choroidal nodules were seen in 18% of the LS patients, never more than one nodule/eye was detected in this group. Choroidal nodules are more abundantly present in NF1 genotypes with truncating mutations. In contrast, the number of choroidal nodules in LS is comparable with their presence in healthy individuals. Especially at an early age, when the clinical picture is incomplete, the detection of choroidal nodules is of diagnostic value, and helps in an appropriate genetic counselling and follow-up. These results support the suggestion to include choroidal nodules to the diagnostic criteria for NF1.

Clinical implementation of NIPT - technical and biological challenges.

Non-invasive prenatal testing (NIPT) for fetal aneuploidy detection is increasingly being offered in the clinical setting. Whereas the majority of tests only report fetal trisomies 21, 18 and 13, genome-wide analyses have the potential to detect other fetal, as well as maternal, aneuploidies. In this review, we discuss the technical and clinical advantages and challenges associated with genome-wide cell-free fetal DNA profiling.

Hypotrichosis-lymphedema-telangiectasia-renal defect associated with a truncating mutation in the SOX18 gene.

SOX18 mutations in humans are associated with both recessive and dominant hypotrichosis-lymphedema-telangiectasia syndrome (HLTS). We report two families with affected children carrying a SOX18 mutation: a living patient and his stillborn brother from Canada and a Belgian patient. The two living patients were diagnosed with HLTS and DNA analysis for the SOX18 gene showed that both had the identical heterozygous C > A transversion, resulting in a pre-mature truncation of the protein, lacking the transactivation domain. Both living patients developed renal failure with severe hypertension in childhood for which both underwent renal transplantation. To our best knowledge this is the first report of renal failure associated with heterozygous mutations in the SOX18 gene. We conclude that this specific mutation results in a new, autosomal dominant condition and propose the acronym HLT-renal defect syndrome for HLTRS.

Role of visual evoked potentials in the assessment and management of optic pathway gliomas in children.

OBJECTIVE: The aim of this study is to investigate the role of pattern reversal visual evoked potentials (pVEPs) in the screening and monitoring of optic pathway gliomas (OPGs) in children with and without neurofibromatosis type 1. METHODS: A review of the English literature published between 1980 and 2012 was performed, with comparison of results of retro- and prospective studies. RESULTS: Pattern reversal VEPs have a high sensitivity (85.7-100 %) for the diagnosis of OPGs, moreover they are safe and cost-effective. Conversely, they have a low specificity (43-83 %) and are not widely available. Besides, pattern reversal VEP results can be unreliable in young children, because of the need for a good cooperation. The studies that were analyzed have drawbacks, including the small sample size, the retrospective design, the differences in gold standard for diagnosis, the different interpretation of small changes in VEP results and the lack of control groups. CONCLUSION: There is still debate about the gold standard for the screening and follow-up of OPGs. The added value of pVEPs to the ophthalmic examination is controversial. Randomized controlled trials or prospective multicentre studies are necessary to assess with sufficient accuracy the sensitivity and specificity of pattern reversal VEPs in the screening for OPGs and its follow-up.

Neuropsychological profile in adults with neurofibromatosis type 1 compared to a control group.

BACKGROUND: Neurofibromatosis type 1 (NF1) is a common inherited autosomal dominant condition, characterised by multiple café-au-lait macules, axillary and/or inguinal freckling, iris Lisch nodules and tumours of the nervous system such as neurofibromas and optic pathway gliomas. At the same time, NF1 is frequently associated with intellectual disabilities across several neuropsychological domains. Existing neuropsychological data in NF1 adults are limited and sometimes contradictory. Moreover, most studies use a non-IQ-controlled norm group for comparison. This study sought to investigate specific neuropsychological characteristics in intellectual abilities unrelated to the global intellectual capacity. METHOD: Twenty NF1 adults and an IQ-, age- and gender-matched control group completed a comprehensive neuropsychological test battery composed of specific cognitive tests investigating visual-spatial abilities and memory, auditory memory, selective and sustained attention and executive functioning. A short version of the Wechsler Adult Intelligence Scale - III was also administered to both groups. RESULTS: Norm comparison showed that both groups perform poorly on most neuropsychological functions, except for sustained attention. However, comparison with the IQ-matched control group showed significantly lower scores on visual-spatial abilities and memory, on auditory working memory and on tests for cognitive flexibility in NF1 adults. Nevertheless, as the significant difference in average estimated IQ score between the NF1 group and the selected control group almost reaches the 5% significance level, further analysis is needed to include IQ as a covariate. Eventually, problems in visual-spatial skills and auditory long-term memory seem to be specific NF1-related deficits, while problems in attention and executive functioning are particularly related to their general lowered intellectual abilities. CONCLUSION: Taking into account that primary visual perception problems could be part of a more general central coherence deficit while interpreting auditory memory problems as possibly related to deficits in language use and comprehension, this idea also fits with the observation of several problems in social information processing and functioning of NF1 persons.

Somatic deletion of the neurofibromatosis type 1 gene in a neurofibrosarcoma supports a tumour suppressor gene hypothesis.

Individuals with neurofibromatosis type 1 (NF1) have an increased risk of developing benign and malignant tumours. The NF1 gene is thought to be a tumour suppressor gene, yet no direct proof at the molecular level exists to support this hypothesis. Here we describe a neurofibrosarcoma from a patient with NF1 with loss of heterozygosity for all chromosome 17 polymorphisms tested. On the remaining chromosome 17 homologue, a 200 kilobase (kb) tumour specific deletion of NF1 was demonstrated. This is the first example of a homozygous inactivation of NF1 at the molecular level in a malignant tumour from an NF1 patient and the results strongly support the tumour suppressor gene hypothesis for this disease.

Mutations in the CCN gene family member WISP3 cause progressive pseudorheumatoid dysplasia.

Members of the CCN (for CTGF, cyr61/cef10, nov) gene family encode cysteine-rich secreted proteins with roles in cell growth and differentiation. Cell-specific and tissue-specific differences in the expression and function of different CCN family members suggest they have non-redundant roles. Using a positional-candidate approach, we found that mutations in the CCN family member WISP3 are associated with the autosomal recessive skeletal disorder progressive pseudorheumatoid dysplasia (PPD; MIM 208230). PPD is an autosomal recessive disorder that may be initially misdiagnosed as juvenile rheumatoid arthritis. Its population incidence has been estimated at 1 per million in the United Kingdom, but it is likely to be higher in the Middle East and Gulf States. Affected individuals are asymptomatic in early childhood. Signs and symptoms of disease typically develop between three and eight years of age. Clinically and radiographically, patients experience continued cartilage loss and destructive bone changes as they age, in several instances necessitating joint replacement surgery by the third decade of life. Extraskeletal manifestations have not been reported in PPD. Cartilage appears to be the primary affected tissue, and in one patient, a biopsy of the iliac crest revealed abnormal nests of chondrocytes and loss of normal cell columnar organization in growth zones. We have identified nine different WISP3 mutations in unrelated, affected individuals, indicating that the gene is essential for normal post-natal skeletal growth and cartilage homeostasis.

SOX10 mutations in patients with Waardenburg-Hirschsprung disease.

Waardenburg syndrome (WS; deafness with pigmentary abnormalities) and Hirschsprung's disease (HSCR; aganglionic megacolon) are congenital disorders caused by defective function of the embryonic neural crest. WS and HSCR are associated in patients with Waardenburg-Shah syndrome (WS4), whose symptoms are reminiscent of the white coat-spotting and aganglionic megacolon displayed by the mouse mutants Dom (Dominant megacolon), piebald-lethal (sl) and lethal spotting (ls). The sl and ls phenotypes are caused by mutations in the genes encoding the Endothelin-B receptor (Ednrb) and Endothelin 3 (Edn3), respectively. The identification of Sox10 as the gene mutated in Dom mice (B.H. et al., manuscript submitted) prompted us to analyse the role of its human homologue SOX10 in neural crest defects. Here we show that patients from four families with WS4 have mutations in SOX10, whereas no mutation could be detected in patients with HSCR alone. These mutations are likely to result in haploinsufficiency of the SOX10 product. Our findings further define the locus heterogeneity of Waardenburg-Hirschsprung syndromes, and point to an essential role of SOX10 in the development of two neural crest-derived human cell lineages.

Mutation analysis of RAD51D in non-BRCA1/2 ovarian and breast cancer families.

BACKGROUND: Recent data show that mutations in RAD51D have an aetiological role in ovarian carcinoma, yet mutations do not appear to be associated with an increased risk for breast cancer. We studied ovarian and breast cancer families having at least one woman affected by ovarian carcinoma, to assess the importance of RAD51D mutations in such families. METHODS: The coding region of the RAD51D gene was analysed in 175 BRCA1/2-negative families with family histories of both ovarian and breast cancer ascertained from two Canadian and two Belgian institutions. RESULTS: We identified one previously reported deleterious mutation, p.Arg186(*) (c.556C>T), and two novel variants; missense substitution p.Cys119Arg and an intronic variant c.83-26A>G. p.Arg186(*) segregated with the disease in the family and two ovarian carcinomas available for analysis showed loss of the wild-type allele, but the novel variants are likely neutral. CONCLUSION: RAD51D should be included in genetic screening of ovarian cancer families that do not have BRCA1/BRCA2 mutations. We show that mutations are more likely to be found in families with two or more ovarian cancers, or in probands with first-degree relatives with ovarian cancer, and we feel testing should be preferentially offered to affected women from such families.

Evaluation of RAD51C as cancer susceptibility gene in a large breast-ovarian cancer patient population referred for genetic testing.

Despite extensive analysis of the BRCA1 and BRCA2 genes, germline mutations are detected in <20% of families with a presumed genetic predisposition for breast and ovarian cancer. Recent literature reported RAD51C as a new breast cancer susceptibility gene. In this study, we report the analysis of 410 patients from 351 unrelated pedigrees. All were referred for genetic testing and we selected families with at least one reported case of ovarian cancer in which BRCA1&2 mutations were previously ruled out. We analyzed the coding exons, intron-exons boundaries, and UTRs of RAD51C. Our mutation analysis did not reveal any unequivocal deleterious mutation. In total 12 unique sequence variations were identified of which two were novel. Our study and others suggest a low prevalence of RAD51C mutations with an exception for some founder populations. This observation is in favor of the rare allele hypothesis in the debate over the nature of the genetic contribution to individual susceptibility to breast and ovarian cancer and further genome-wide studies in high risk families are warranted.

PGD for a complex chromosomal rearrangement by array comparative genomic hybridization.

Patients carrying a chromosomal rearrangement (CR) have an increased risk for chromosomally unbalanced conceptions. Preimplantation genetic diagnosis (PGD) may avoid the transfer of embryos carrying unbalanced rearrangements, therefore increasing the chance of pregnancy. Only 7-12 loci can be screened by fluorescence in situ hybridization whereas microarray technology can detect genome-wide imbalances at the single cell level. We performed PGD for a CR carrier with karyotype 46,XY,ins(3;2)(p23;q23q14.2),t(6;14)(p12.2;q13) using array comparative genomic hybridization. Selection of embryos for transfer was only based on copy number status of the chromosomes involved in both rearrangements. In two ICSI-PGD cycles, nine and seven embryos were analysed by array, leaving three and one embryo(s) suitable for transfer, respectively. The sensitivity and specificity of single cell arrays was 100 and 88.8%, respectively. In both cycles a single embryo was transferred, resulting in pregnancy following the second cycle. The embryo giving rise to the pregnancy was normal/balanced for the insertion and translocation but carried a trisomy 8 and nullisomy 9 in one of the two biopsied blastomeres. After 7 weeks of pregnancy the couple miscarried. Genetic analysis following hystero-embryoscopy showed a diploid (90%)/tetraploid (10%) mosaic chorion, while the gestational sac was empty. No chromosome 8 aneuploidy was detected in the chorion, while 8% of the cells carried a monosomy for chromosome 9. In summary, we demonstrate the feasibility and determine the accuracy of single cell array technology to test against transmission of the unbalanced meiotic products that can derive from CRs. Our findings also demonstrate that the genomic constitution of extra-embryonic tissue cannot necessarily be predicted from the copy number status of a single blastomere.

Preimplantation genetic diagnosis using fluorescent in situ hybridization for cancer predisposition syndromes caused by microdeletions.

BACKGROUND: Neurofibromatosis type 1 (NF1) and Von Hippel-Lindau (VHL) are dominantly inherited late onset cancer predisposition syndromes caused by mutations in the respective tumor suppressor genes (TSGs) NF1 and VHL. Less frequently TSGs are partially or fully deleted. Preimplantation genetic diagnosis (PGD) for cancer predisposition can be applied to select against the mutant allele in carrier couples. However, microdeletions within a single cell can, at present, not be detected by molecular diagnostic methods usually applied for PGD of monogenic disorders. METHODS: We performed PGD using interphase fluorescent in situ hybridization (FISH) on single blastomeres for three couples of which the women carried a microdeletion. One patient had the recurrent 1.4 Mb microdeletion covering NF1, a second suffered from an intragenic NF1 deletion and the last had a deletion of VHL. RESULTS: In total, seven PGD cycles were carried out for these couples, which resulted in the delivery of a healthy twin for the VHL microdeletion carrier. CONCLUSIONS: FISH-based PGD is a straightforward approach to detect (micro)deletions in single blastomeres. It seems likely that the number of conditions for which PGD-FISH is beneficial will increase rapidly with the advent of high-resolution arrays.

Clinical and molecular aspects of RAS related disorders.

RAS proteins play key roles in normal cell growth, malignant transformation and learning and memory. Somatic mutations in RAS genes and several of their upstream and downstream molecules result in different human malignancies. In recent years germline mutations in genes coding for components of the RAS signalling cascade have been recognised in a group of phenotypically overlapping disorders, referred to as the neuro-cardio-facial-cutaneous syndromes. These present with variable degrees of psychomotor delay, cardiac abnormalities, facial dysmorphism, short stature, skin defects and increased cancer risk. These findings point to important roles for this evolutionary conserved pathway not only in oncogenesis, but also in cognition, growth and development. Other constitutional disorders caused by mutated RAS pathway genes point to involvement of the RAS-MAPK pathway in immune modulation and vascular development.

BRCA1/2 predictive testing and gender: uptake, motivation and psychological characteristics.

BRCA1/2 predictive testing and gender: Uptake, motivation and psychological characteristics: Data on male uptake of BRCA1/2 predictive testing and psychological characteristics of males in comparison to females are scarce. We investigated gender differences in the cohort tested at the Center for Human Genetics in Leuven during a 10-year period (1998-2007). Males were significantly older than females. Breast cancer related distress (IES) was significantly lower in men and was not associated with BRCA1 or BRCA2. The groups of both males and females were psychologically stronger than average (SCL-90, UCL) and self-selected. Men were unanimously motivated (personal relevance of 12 motives rated on a Likert scale) by concern for their daughters, and significantly more so than women. One third of them (versus 12% women) referred to child-bearing decisions. Considering all unaffected siblings in the family of origin, uptake of predictive testing was significantly higher in females. Moreover, uptake was significantly higher in women belonging to a BRCA2 than to a BRCA1 family. In the descendants of identified carriers, uptake was predicted by gender and age, but not by the parent's gender or by BRCA1 or BRCA2 status.

Unilateral Coats'-like disease and an intragenic deletion in the TERC gene: A case report.

We report a case of a 25-year-old woman with unilateral Coats'-like disease. Her brother was previously diagnosed with an autosomal dominant form of dyskeratosis congenita. Genetic testing was performed by screening the TERC gene for mutations and identified heterozygosity for the n.68_124del mutation. Our case demonstrates that the exudative retinopathy seen in Coats'-like disease can be caused by mutations in a telomere-capping gene TERC as a part of the dyskeratosis congenita spectrum without other systemic involvement. This is an interesting case that illustrates that retinal Coats'-like involvement can be the first manifestation of dyskeratosis congenita.

Mutations in LZTR1 drive human disease by dysregulating RAS ubiquitination.

The leucine zipper-like transcriptional regulator 1 (LZTR1) protein, an adaptor for cullin 3 (CUL3) ubiquitin ligase complex, is implicated in human disease, yet its mechanism of action remains unknown. We found that Lztr1 haploinsufficiency in mice recapitulates Noonan syndrome phenotypes, whereas LZTR1 loss in Schwann cells drives dedifferentiation and proliferation. By trapping LZTR1 complexes from intact mammalian cells, we identified the guanosine triphosphatase RAS as a substrate for the LZTR1-CUL3 complex. Ubiquitome analysis showed that loss of Lztr1 abrogated Ras ubiquitination at lysine-170. LZTR1-mediated ubiquitination inhibited RAS signaling by attenuating its association with the membrane. Disease-associated LZTR1 mutations disrupted either LZTR1-CUL3 complex formation or its interaction with RAS proteins. RAS regulation by LZTR1-mediated ubiquitination provides an explanation for the role of LZTR1 in human disease.