Federica Natacci

Mental retardation and cardiovascular malformations in NF1 microdeleted patients point to candidate genes in 17q11.2

Neurofibromatosis type 1 ( NF1 [MIM 162200]) is a common autosomal dominant disorder that affects 1/3500 individuals and is caused by deletion or point mutations of NF1 , a tumour suppressor gene mapping to 17q11.2. Its main features include cafe au lait spots, axillary and inguinal freckling, iris Lisch nodules, neurofibromas, and an increased risk of benign and malignant tumours, particularly optic glioma, neurofibrosarcoma, malignant peripheral nerve sheath tumours (MPNSTs),1 and childhood myeloid leukaemia.2 Over 70% of NF1 germline mutations cause truncation or loss of the encoded protein. Approximately 5–20% of all NF1 patients carry a heterozygous deletion of usually 1.5 Mb involving the NF1 gene and contiguous genes lying in its flanking regions,3,4 which is caused by unequal homologous recombination of NF1 repeats (REPs).5 Known as the “ NF1 microdeletion syndrome,” this condition is often characterised by a more severe phenotype than is observed in the general NF1 group. In particular, NF1 microdeleted patients often show variable facial dysmorphisms, mental retardation, developmental delay, and an excessive number of neurofibromas for age.3,6–12 The severe phenotype of microdeleted patients may be explained by variations in the expression of the genes involved in the rearrangement, which may be caused by different mechanisms, such as gene interruptions, position effects, and decreased gene dosages. Although NF1 microdeleted patients generally have different characteristics from those of classic NF1 patients, it remains difficult to foresee the presence of the deletion at an individual level on the basis of clinical observations. Various studies have reported the clinical characterisation of NF1 deleted patients and the precise extent of the deletion has been characterised in a subset.3–5,13,14 However, no study comparing the incidence of specific clinical signs in NF1 deleted and classical NF1 patients has yet been published. …

FISH characterisation of an identical (16)(p11.2p12.2) tandem duplication in two unrelated patients with autistic behaviour

Partial trisomy 16p is a rare chromosomal anomaly in newborns: of the fewer than 30 carrier patients so far reported, most were born to parents with a balanced translocation involving the p arm of chromosome 16.1 Pure partial trisomy 16p has been reported in seven patients,2–6 three of whom (all showing behavioural problems with autistic traits) carried a tandem duplication of the (16)(p11.2–p12) region4,6; minor dysmorphisms were reported in only one patient.4 Linkage studies indicated chromosome 16p as a major location for autism susceptibility genes,7 while association was reported between autistic traits and attention deficit or hyperactivity disorders mapping to the 16p13 band.8 In addition TSC2, one of the genes responsible for tuberous sclerosis, a syndrome often associated with autistic traits, maps to the same cytogenetic band.9 We report the clinical phenotype and refined molecular cytogenetic characterisation of a patient carrying a (16)(p11.2p12.2) duplication. By extending the FISH analysis to a previously described patient with an apparently similar chromosomal rearrangement,6 we found that low copy repeats map to the 16p11.2 and 16p12.2 duplication endpoints, suggesting non-allelic homologous recombination as the pathogenetic mechanism. This finding is consistent with the non-random occurrence of the observed chromosomal rearrangement and the high frequency of segmental duplications identified throughout chromosome 16.10–12 We also inferred from genotype-phenotype correlation studies that genes involved in autism susceptibility are located within the duplicated region. Patient 1 is a 25 year old man, the first son of unrelated parents. At the time of his birth, his mother was aged 30 and his father 29 years. He was born at term with a weight of 2.550 kg (3rd centile). The father suffered from alcohol misuse and left the family when the patient was 12 years old. Because of …

Developmental abnormalities and cancer predisposition in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a developmental and cancer predisposing syndrome resulting from haploinsufficiency or alteration in neurofibromin, a multifunctional protein that acts in various signaling pathways affecting morphogenetic processes and cell proliferation. Neurofibromin deficiency deregulates Ras/Raf/MEK/ERK and Ras/PI3K/AKT/PKB/mTOR signaling networks and intersected pathways including the cAMP-dependent protein kinase A (PKA) and the Rho-cofillin which acts on actin cytoskeleton reorganization, cell motility and adhesion. As the neurofibromin-mediated pathways are associated with biological effects depending on the cell lineage, deregulation induced by NF1 mutation clearly has cell type-specific effects. This review summarizes our increasing knowledge of NF1 as a disease rooted in defective developmental mechanisms that can also influence the potential for malignant growth. The cardinal features of NF1 patients, at birth and during life involve the cardiovascular, connective/skeletal and central nervous systems, as they reflect the NF1 mutation sensitivity of cell lineages committed to specifying these systems during embryonic development. A switch to neoplastic transformation may also occur in both the prenatal and postnatal life in cancer initiating cells of defined lineages, with the cooperation of a genetically and epigenetically modified tumor microenvironment. We emphasize how much of our current knowledge of the pathomechanisms of NF1 clinical signs and cancer has come from engineered mouse models and in vitro primary cells and cell lines exposed to inhibitors of signaling molecules. Advances in our knowledge of the developmental defects primed by the loss neurofibromin should reveal further associations between given NF1 mutations and tissue-specific symptoms, thus improving the clinical management of the patients.

Association of syndromic mental retardation with an Xq12q13.1 duplication encompassing the oligophrenin 1 gene

OPHN1 mutations cause a syndromic form of mental retardation (MR) characterized by cerebellar hypoplasia, early hypotonia, motor and speech delay, with occasional seizures and strabismus. Here we report on a familial chromosome duplication spanning about 800 Kb of Xq12q13.1, associated with MR and a distinctive phenotype in the affected male, but not in his heterozygous mother. The parents were healthy and non‐consanguineous with a history of three pregnancies. The first resulted in the birth of a boy with MR, motor impairment and seizures. The second pregnancy was terminated because of trisomy 18. At the time of the third, the first affected boy was analyzed by array‐CGH, which revealed a 800 Kb duplication at Xq12q13.1, encompassing three genes, including OPHN1. This mutation was inherited from his healthy mother and was not present in any of the three maternal brothers. To our knowledge this is the first report of a clinical phenotype associated with duplication of Xq12q13.

Discordant Prenatal Phenotype and Karyotype of Monozygotic Twins Characterized by the Unequal Distribution of Two Cell Lines Investigated by Different Methods: A Review

We present the case of a monozygotic twin pregnancy discordant for phenotype and karyotype. A chorionic villus sample was performed at the 11th week of gestation in a primigravida because of cystic hygroma detected by ultrasound in one twin of a monochorionic, biamniotic pregnancy. Rapid testing by means of quantitative fluorescence polymerase chain reaction and conventional karyotyping, obtained by both short- and long-term culture, revealed a homogeneous monosomy X (45,X). Amniocentesis was performed separately for both twins before termination and showed an homogeneous monosomy X in one sample and a 46,X,del(X)(p11.1) karyotype in the other one. Postmortem fetal tissues culture confirmed the discordant karyotype between the two embryos. Placental samples obtained after termination revealed the cell line which was not detected at chorionic villus sampling. Based on this and previous reports, we suggest that in cases of a phenotypic discordance detected at ultrasound in the first trimester, it is advisable to perform a karyotype analysis on amniocytes because it better reflects fetal constitution rather than chorionic villi or lymphocytes in case of heterokaryotipic monosomy X monochorionic twins.

Germline mosaicism in achondroplasia detected in sperm DNA of the father of three affected sibs

We describe a sib recurrence for achondroplasia with parents of average stature. The three sibs shared the paternal allele and all carried the same causal mutation in the fibroblast growth factor receptor 3 gene (FGFR3): G > A nt1138 (Gly380Arg). We were able to identify this mutation on sperm DNA confirming paternal germinal mosaicism. Our family shows that a more precise definition of the recurrence risk is feasible using this approach, based on a single DNA test, which could be offered in selected cases.

Clinical follow-up of young adults affected by Williams syndrome: Experience of 45 Italian patients†

Williams–Beuren syndrome (WBS) is a multisystem disorder that requires ongoing management by a primary care physician familiar with the natural history and specific medical problems associated with the condition. While the natural history of the disease during infancy is well known, data about the adult WBS population have been published only in the last few years, and show a wide range of medical, neurological, and psychiatric problems. We investigated 45 young adult WBS patients (mean age 23 years, range 17–39 years) using a well‐coordinated team which included a cardiologist, a nephrologist, an ophthalmologist, an endocrinologist, a gastroenterologist, orthodontist, and orthopedist. Here we describe the clinical features and medical complications in this cohort of patients. Most patients demonstrated a high frequency of multiple organ systems complications, in particular, abnormal body habitus; cardiovascular disease, and hypertension; sensorineural hearing loss; gastrointestinal symptoms including diverticular disease and abnormal glucose tolerance. We offer some suggestions for clinical monitoring which we propose will be useful in the overall care of adults with WBS.

Healthcare transition in patients with rare genetic disorders with and without developmental disability: neurofibromatosis 1 and Williams-Beuren syndrome.

There are between 5,000 and 8,000 distinct rare diseases (RDs) affecting 6–8% of the population, most of which are caused by genetic defects. Many are highly complex, childhood‐onset, multi‐system disorders that are often associated with developmental disability, and require lifelong, highly specialized care and support. As larger numbers of children with previously fatal RDs survive into adulthood, they encounter significant challenges in transitioning from family‐centered, developmentally focused, multidisciplinary pediatric care to a less supportive adult healthcare system that is often unfamiliar with these conditions. This paper discusses the challenges of the transition from pediatric to adult health care in two groups of patients with multisystem genetic RDs (neurofibromatosis 1 [NF1] and Williams–Beuren syndrome [WBS]), and analyzes strategies for making the process easier for patients with and without developmental disabilities. Our findings show that there are still no guidelines in national healthcare programs on how to transition RD adolescents with and without developmental disabilities, and only a few pediatric centers have implemented the elements of transition in their general practice. Evidence regarding programs to facilitate transition is inconclusive and the transition from pediatric medicine to adult medicine for RDs remains a major challenge. However, transition requires both time and personnel, which are difficult to find in periods of fiscal austerity. Nevertheless, we should strongly advocate for governments investing more into transition infrastructure or they will face increased long‐term social and economic costs due to poor treatment compliance, disengagement from services, increased genetic risks, and higher rates of disease‐related complications.

126 novel mutations in Italian patients with neurofibromatosis type 1.

Genetic analysis of Neurofibromatosis type 1 (NF1) may facilitate the identification of patients in early phases of the disease. Here, we present an overview of our diagnostic research spanning the last 11 years, with a focus on the description of 225 NF1 mutations, 126 of which are novel, found in a series of 607 patients (513 unrelated) in Italy. Between 2003 and 2013, 443 unrelated patients were profiled by denaturing high pressure liquid chromatography (DHPLC) analysis of 60 amplicons derived from genomic NF1 DNA and subsequent sequencing of heterozygotic PCR products. In addition, a subset of patients was studied by multiplex ligation‐dependent probe amplification (MLPA) to identify any duplications, large deletions or microdeletions present at the locus. Over the last year, 70 unrelated patients were investigated by MLPA and sequencing of 22 amplicons spanning the entire NF1 cDNA. Mutations were found in 70% of the 293 patients studied by DHPLC, thereby fulfilling the NIH criterion for the clinical diagnosis of NF1 (detection rate: 70%); furthermore, 87% of the patients studied by RNA sequencing were genetically characterized. Mutations were also found in 36 of the 159 patients not fulfilling the NIH clinical criteria. We confirmed a higher incidence of intellectual disability in patients harboring microdeletion type 1 and observed a correlation between a mild phenotype and the small deletion c.2970_2972delAAT or the missense alteration in amino acid residue 1809 (p.Arg1809Cys). These data support the use of RNA‐based methods for genetic analysis and provide novel information for improving the management of symptoms in oligosymptomatic patients.

Neurofibromatosis type 1 and pregnancy: Maternal complications and attitudes about prenatal diagnosis

Neurofibromatosis type 1 (NF1) is one of the most commoninherited genetic disorders with an incidence of 1/2,500 to 1/3,300 live births. The disease is caused by a mutation in NF1,atumorsuppressorgeneon17q11.2codingforneurofibromin,orbyamicrodeletioninvolvingtheNF1anditssurroundingregion.NF1is an autosomal dominant condition with complete penetranceafter childhood. Almost half the cases result from a de novomutation,whiletheothersinheritthealteredgenefromanaffectedparent.Thediseaseismarkedbypoorgenotype–phenotypecorre-lation and high inter- and intra-familial variability. Thereforegenetic counseling for affected individuals is hampered by thedifficulty in forecasting the clinical outcome for future offspring.Prenatal testing can be carried out if the parental mutation isknown, or if there are multiple affected family members, andlinkagehasbeenestablishedwithinthefamily;suchtestingisusefulfor establishing the presence of the parental mutation in the fetalDNA, but, as noted, cannot make any prediction about diseaseseverity [Origone et al., 2000; Terzi et al., 2009].Pregnancyhasalwaysbeenconsideredacriticaltimeforwomenwith NF1 because of reports of increased complications duringgestationarisingfrompre-eclampsia,pretermlabor,IUGR,hyper-tension, oligohydramnios, and spontaneous abortion and/or still-birth [Blickstein and Lancet, 1987; Sharma et al.,1991;Segalet al.,1999].Furthermore,casereportsdescribedtheassociationbetweenpregnancy and HELLP syndrome [Hagymasy et al., 1998; Agarwaletal.,2003],diagnosisofmalignantperipheralnervesheathtumor(MPNST)[Posmaaetal.,2003;KelloggandWatson,2010;Nelsonet al., 2010] and the occurrence of pheochromocytoma [Liu et al.,1996]. Although Dugoff and Sujansky [1996] presented a largestudy of pregnancy in 105 women, including data from 247gestations and noted a greater cesarean rate than in thegeneral population, they did not find an increased incidence ofany of these complications. However they did describe thegrowth of new neurofibromas and the enlargement ofexistingneurofibromasinmorethanthehalf.Althoughthemajor-ity of NF1 pregnant women did not report complications, someinvestigators proposed special monitoring in specific situations[Chetty et al., 2011].Here we describe our experience in the management of preg-nancies in women with NF1, and their attitude towards prenataldiagnosis. We included 43 women with a total of 79 pregnancies.Eightofthewomen(18.6%)werereferredforcareduringtheentiregestationalperiod,whiletheother35womenhadtheirpregnanciesdetected before joining our program; for them we obtained datafrom a review of their medical records and through personalinterviews. Among these 79 pregnancies, 65 were carried to termwhile the other 14 resulted in five first trimester spontaneousabortions, seven elective terminations (not related to concernsaboutNF1),andtwotherapeuticabortionsafterprenataldiagnosisthrough chorionic villus sampling (CVS). Two of the 65 full termpregnancies were twins, for a total of 67 live births.Forwomenvisitingourcenterbeforeandduringtheirpregnan-cies, we set up a model based on a set of preconceptional multi-specializedevaluationsthatwefeltwereaprerequisiteforaproperpersonalized management of pregnancy in women with NF1. The