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.

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.

Erratum: Capturing the wide variety of impaired fracture healing phenotypes in Neurofibromatosis Type 1 with eight key factors: a computational study.

This corrects the article DOI: 10.1038/srep20010.

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.

Capturing the wide variety of impaired fracture healing phenotypes in Neurofibromatosis Type 1 with eight key factors: a computational study.

Congenital pseudarthrosis of the tibia (CPT) is a rare disease which normally presents itself during early childhood by anterolateral bowing of the tibia and spontaneous tibial fractures. Although the exact etiology of CPT is highly debated, 40-80% of CPT patients are carriers of a mutation in the Neurofibromatosis Type 1 (NF1) gene, which can potentially result in an altered phenotype of the skeletal cells and impaired bone healing. In this study we use a computational model of bone regeneration to examine the effect of the Nf1 mutation on bone fracture healing by altering the parameter values of eight key factors which describe the aberrant cellular behaviour of Nf1 haploinsufficient and Nf1 bi-allelically inactivated cells. We show that the computational model is able to predict the formation of a hamartoma as well as a wide variety of CPT phenotypes through different combinations of altered parameter values. A sensitivity analysis by "Design of Experiments" identified the impaired endochondral ossification process and increased infiltration of fibroblastic cells as key contributors to the degree of severity of CPT. Hence, the computational model results have added credibility to the experimental hypothesis of a genetic cause (i.e. Nf1 mutation) for CPT.

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.

Comparative study of the ophthalmological examinations in neurofibromatosis type 1. Proposal for a new screening algorithm.

PURPOSE: Efforts are made to unify the protocol concerning the ophthalmological screening, monitoring and treatment of Optic Pathway Gliomas (OPGs) in children with neurofibromatosis type 1 (NF1). The aim of this study is to compare the most recent recommendations published in 2007 with the screening strategies in NF1 centres. The integration of these data resulted into a recommendation for an improved screening strategy. METHODS: A literature search on PubMed between 1984 and 2013 was performed. A questionnaire on the ophthalmological screening in NF1 was sent to centres of expertise in the field of NF1. Literature and questionnaire data were analysed. Also, findings of a round table discussion on the ophthalmological screening of NF1 patients at the European Paediatric Ophthalmological Society (EPOS) meeting in 2013 were summarized. RESULTS: In most centres ophthalmological screening in NF1 patients is well organized, but is performed longer and at more regular intervals than is mentioned in the recommendations. Visual acuity testing, fundoscopy and pupillary reflexes are carried out unanimously. CONCLUSIONS: There is no uniformity of the ophthalmological screening in NF1 patients. The present recommendation advises to screen annually until the age of 8. Because OPGs are likely to develop before the age of 6 and children do not usually complain of visual problems, OPGs can be missed or detection can be delayed if screening is only yearly performed at this young age. Based on these arguments, about half of our responders screen more frequently and until a later age. Therefore, we suggest performing a six monthly screening until the age of 6 and a yearly examination from 6 years until adulthood. This examination should include visual acuity assessment, pupillary reflexes and a fundoscopy.

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.

NRAS Mutations in Noonan Syndrome.

Noonan syndrome is a genetically heterogeneous disorder caused by mutations in PTPN11, SOS1, RAF1 and less frequently in KRAS, NRAS or SHOC2. Here, we performed mutation analysis of NRAS and SHOC2 in 115 PTPN11, SOS1, RAF1, and KRAS mutation-negative individuals. No SHOC2 mutations were found, but we identified 3 NRAS mutations in 3 probands. One NRAS mutation was novel. The phenotype associated with germline NRAS mutations is variable. Our results confirm that a small proportion of Noonan syndrome patients carry germline NRAS mutations.

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.