Romano Tenconi

Gain-of-function RAF1 mutations cause Noonan and LEOPARD syndromes with hypertrophic cardiomyopathy

Noonan and LEOPARD syndromes are developmental disorders with overlapping features, including cardiac abnormalities, short stature and facial dysmorphia. Increased RAS signaling owing to PTPN11, SOS1 and KRAS mutations causes ∼60% of Noonan syndrome cases, and PTPN11 mutations cause 90% of LEOPARD syndrome cases. Here, we report that 18 of 231 individuals with Noonan syndrome without known mutations (corresponding to 3% of all affected individuals) and two of six individuals with LEOPARD syndrome without PTPN11 mutations have missense mutations in RAF1, which encodes a serine-threonine kinase that activates MEK1 and MEK2. Most mutations altered a motif flanking Ser259, a residue critical for autoinhibition of RAF1 through 14-3-3 binding. Of 19 subjects with a RAF1 mutation in two hotspots, 18 (or 95%) showed hypertrophic cardiomyopathy (HCM), compared with the 18% prevalence of HCM among individuals with Noonan syndrome in general. Ectopically expressed RAF1 mutants from the two HCM hotspots had increased kinase activity and enhanced ERK activation, whereas non–HCM-associated mutants were kinase impaired. Our findings further implicate increased RAS signaling in pathological cardiomyocyte hypertrophy.

Geographical and ethnic variation of the 677C>T allele of 5,10 methylenetetrahydrofolate reductase ( MTHFR ): findings from over 7000 newborns from 16 areas world wide

Since its biochemical characterisation in 19911 and its genetic identification in 1995,2 677C>T allele (T allele) of the 5,10 methylenetetrahydrofolate reductase ( MTHFR ) gene has been a focus of increasing interest from researchers world wide. The expanding spectrum of common conditions linked with the 677C>T allele now includes certain adverse birth outcomes (including birth defects), pregnancy complications, cancers, adult cardiovascular diseases, and psychiatric disorders.3–8 Although several of these associations remain unconfirmed or controversial,4 their scope is such that it becomes of interest to explore the geographical and ethnic distribution of the allele and associated genotypes.9 Accurate information on such distribution can contribute to studies of gene-disease associations (by providing reference population data) and population genetics (by highlighting geographical and ethnic variations suggestive of evolutionary pressures),10 as well as help to evaluate health impact (by allowing estimates of population attributable fraction). Current population data, however, show gaps and even for some ethnic groups or large geographical areas (for example, China) few data are available.3 Our aim was to supplement the available data by collecting a large and diverse sample of newborns from different geographical areas and ethnic groups, and to examine international variations in the distribution of the 677C>T allele. We present findings relating to more than 7000 newborns from 16 areas around the world. The study was conducted under the auspices of the International Clearinghouse for Birth Defect Monitoring Systems (ICBDMS) and was coordinated through its head office, the International Center on Birth Defects (ICBD). ### Sample selection Participating programmes, in consultation with the coordinating group, identified a population sampling approach that would be simple yet minimise sampling bias with respect to the MTHFR genotype. We made an explicit attempt to sample systematically the newborn population. Details of each programme’s approach are listed below, and further …

Mutation of SHOC2 promotes aberrant protein N-myristoylation and causes Noonan-like syndrome with loose anagen hair

N-myristoylation is a common form of co-translational protein fatty acylation resulting from the attachment of myristate to a required N-terminal glycine residue. We show that aberrantly acquired N-myristoylation of SHOC2, a leucine-rich repeat–containing protein that positively modulates RAS-MAPK signal flow, underlies a clinically distinctive condition of the neuro-cardio-facial-cutaneous disorders family. Twenty-five subjects with a relatively consistent phenotype previously termed Noonan-like syndrome with loose anagen hair (MIM607721) shared the 4A>G missense change in SHOC2 (producing an S2G amino acid substitution) that introduces an N-myristoylation site, resulting in aberrant targeting of SHOC2 to the plasma membrane and impaired translocation to the nucleus upon growth factor stimulation. Expression of SHOC2S2G in vitro enhanced MAPK activation in a cell type–specific fashion. Induction of SHOC2S2G in Caenorhabditis elegans engendered protruding vulva, a neomorphic phenotype previously associated with aberrant signaling. These results document the first example of an acquired N-terminal lipid modification of a protein causing human disease.

Methimazole embryopathy: Delineation of the phenotype

We report on a further case of congenital anomalies in a child exposed to methimazole during the first trimester of pregnancy (from first to seventh gestational week), and define a specific malformation pattern related to prenatal methimazole exposure and consisting of choanal and esophageal atresia, scalp defects, minor facial anomalies and psychomotor delay.

Evaluation of prenatal diagnosis of cleft lip with or without cleft palate and cleft palate by ultrasound: experience from 20 European registries

Ultrasound scans in the mid‐trimester of pregnancy are now a routine part of antenatal care in most European countries. Using data from registries of congenital anomalies a study was undertaken in Europe. The objective of the study was to evaluate prenatal detection of cleft lip with or without cleft palate (CL(P)) and cleft palate (CP). All CL(P) and CPs suspected prenatally and identified at birth in the period 1996–98 were registered from 20 Congenital Malformation Registers from the following European countries: Austria, Croatia, Denmark, France, Germany, Italy, Lithuania, Spain, Switzerland, The Netherlands, UK, Ukraine. These registries followed the same methodology. A total of 709 027 births were covered; 7758 cases with congenital malformations were registered. Included in the study were 751 cases reported with facial clefts: 553 CL(P) and 198 CP. The prenatal diagnosis by transabdominal ultrasound of CL(P) was made in 65/366 cases with an isolated malformation, in 32/62 cases with chromosomal anomaly, in 30/89 cases with multiple malformations and in 21/36 syndromic cases. The prenatal diagnosis of CP was made in 13/198 cases. One hundred pregnancies were terminated (13%); in 97 of these the cleft was associated with other malformations. Copyright

The “Cat Eye syndrome”: Dicentric small marker chromosome probably derived from a No. 22 (Tetrasomy 22pter→q11) associated with a characteristic phenotype

Eleven patients with the so-called Cat Eye syndrome are reported including a more detailed description of the original cases reported by Schmid and Fraccaro. All cases had, in addition to a normal karyotype, a small extra G-like chromosome which appeared to be an isochromosome for the juxtacentromeric region (pter to q11) of an acrocentric chromosome. None were mosaics. Clinical findings and further cytogenetic studies in a few cases suggest that these markers probably derive from a No. 22 chromosome. Characteristic features of the Cat Eye syndrome in these 11 patients and those reviewed from the literature are: ocular coloboma which may involve the iris, choroid and/or optic nerve, preauricular skin tags and/or pits which are probably the most consistent feature, congenital heart defect, anal atresia with a fistula, renal malformations such as unilateral absence, unilateral or bilateral hypoplasia, and cystic dysplasia, and antimongoloid position of eyes. Intelligence is usually low-normal, although moderate retardation is also seen. There is great variability in the clinical findings ranging from near normal to lethal malformations. Less frequent, but also characteristic findings are: microphthalmia, microtia with atresia of the external auditory canal, intrahepatic or extrahepatic biliary atresia and malrotation of the gut. Direct transmission of the marker from one generation to the other was observed in both sexes. In those families, there was considerable variability in the clinical findings between affected family members. These cases show that there is a bias of ascertainment for patients who have the more striking malformations, especially those with ocular coloboma and anal atresia, a combination which appears to be present in only a minority of cases. Many mildly affected patients probably remain undetected. It is proposed that the term Cat Eye syndrome should be applied only to cases with trisomy or tetrasomy of not more than 22pter to q11 and without additional duplication or deletion of another autosomal segment.SummaryEleven patients with the so-called Cat Eye syndrome are reported including a more detailed description of the original cases reported by Schnid and Fraccaro. All cases had, in addition to a normal karyotype, a small extra G-like chromosome which appeared to be an isochromosome for the juxtacentromeric region (pter→q11) of an acrocentric chromosome. None were mosaics. Clinical findings and further cytogenetic studies in a few cases suggest that these markers probably derive from a No. 22 chromosome.Characteristic features of the Cat Eye syndrome in these 11 patients and those reviewed from the literature are: ocular coloboma which may involve the iris, choroid and/or optic nerve, preauricular skin tags and/or pits which are probably the most consistent feature, congenital heart defect, anal atresia with a fistula, renal malformations such as unilateral absence, unilateral or bilateral hypoplasia, and cystic dysplasia, and antimongoloid position of eyes. Intelligence is usually low-normal, although moderate retardation is also seen. There is great variability in the clinical findings ranging from near normal to lethal malformations. Less frequent, but also characteristic findings are: microphthalmia, microtia with atresia of the external auditory canal, intrahepatic or extrahepatic biliary atresia and malrotation of the gut.Direct transmission of the marker from one generation to the other was observed in both sexes. In those families, there was considerable variability in the clinical findings between affected family members. Theses cases show that there is a bias of ascertainment for patients who have the more striking malformation, especially those with ocular coloboma and anal atresia, a combination which appears to be present in only a minority of cases. Many mildly affected patients probably remain undetected.It is proposed that the term Cat Eye syndrome should be applied only to cases with trisomy or tetrasomy of not more than 22pter→q11 and without additional duplication or deletion of another autosomal segment.

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. …

International trends of Down syndrome 1993-2004: Births in relation to maternal age and terminations of pregnancies

BACKGROUND The aim of this study was to examine trends of Down syndrome (DS) in relation to maternal age and termination of pregnancies (ToP) in 20 registries of the International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR). METHODS Trends of births with DS (live-born and stillborn), ToP with DS, and maternal age (percentage of mothers older than 35 years) were examined by year over a 12-year period (1993-2004). The total mean number of births covered was 1550,000 annually. RESULTS The mean percentage of mothers older than 35 years of age increased from 10.9% in 1993 to 18.8% in 2004. However, a variation among the different registers from 4-8% to 20-25% of mothers >35 years of age was found. The total mean prevalence of DS (still births, live births, and ToP) increased from 13.1 to 18.2/10,000 births between 1993 and 2004. The total mean prevalence of DS births remained stable at 8.3/10,000 births, balanced by a great increase of ToP. In the registers from France, Italy, and the Czech Republic, a decrease of DS births and a great increase of ToP was observed. The number of DS births remained high or even increased in Canada Alberta, and Norway during the study period. CONCLUSIONS Although an increase in older mothers was observed in most registers, the prevalence of DS births remained stable in most registers as a result of increasing use of prenatal diagnostic procedures and ToP with DS.

Familial congenital bicuspid aortic valve: A disorder of uncertain inheritance

Congenital bicuspid aortic valve (BAV) is one of the most frequent heart defects detected by echocardiographic investigation and necropsy (0.9-1% of the general population), but only 16 families with familial congenital BAV have been described up to now. We report on a family in which 4 members of two generations (2 brothers, 1 sister, and her son) are affected with BAV. The BAV mode of inheritance is discussed.

NF1 Microdeletion Syndrome: Refined FISH Characterization of Sporadic and Familial Deletions with Locus-Specific Probes

Two familial and seven sporadic patients with neurofibromatosis 1-who showed dysmorphism, learning disabilities/mental retardation, and additional signs and carried deletions of the NF1 gene-were investigated by use of a two-step FISH approach to characterize the deletions. With FISH of YAC clones belonging to a 7-Mb 17q11.2 contig, we estimated the extension of all of the deletions and identified the genomic regions harboring the breakpoints. Mosaicism accounted for the mild phenotype in two patients. In subsequent FISH experiments, performed with locus-specific probes generated from the same YACs by means of a novel procedure, we identified the smallest region of overlapping (SRO), mapped the deletion breakpoints, and identified the genes that map to each deletion interval. From centromere to telomere, the approximately 0.8-Mb SRO includes sequence-tagged site 64381, the SUPT6H gene (encoding a transcription factor involved in chromatin structure), and NF1. Extending telomerically from the SRO, two additional genes-BLMH, encoding a hydrolase involved in bleomycin resistance, and ACCN1, encoding an amiloride-sensitive cation channel expressed in the CNS-were located in the deleted intervals of seven and three patients, respectively. An apparently common centromeric deletion breakpoint was shared by all of the patients, whereas a different telomeric breakpoint defined a deletion interval of 0.8-3 Mb. There was no apparent correlation between the extent of the deletion and the phenotype. This characterization of gross NF1 deletions provides the premise for addressing correctly any genotype-phenotype correlation in the subset of patients with NF1 deletions.