Emanuela Conti

Grouping of Multiple-Lentigines/LEOPARD and Noonan Syndromes on the PTPN11 Gene

Multiple-lentigines (ML)/LEOPARD (multiple lentigines, electrocardiographic-conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth, and sensorineural deafness) syndrome is an autosomal dominant condition--characterized by lentigines and café au lait spots, facial anomalies, cardiac defects--that shares several clinical features with Noonan syndrome (NS). We screened nine patients with ML/LEOPARD syndrome (including a mother-daughter pair) and two children with NS who had multiple café au lait spots, for mutations in the NS gene, PTPN11, and found, in 10 of 11 patients, one of two new missense mutations, in exon 7 or exon 12. Both mutations affect the PTPN11 phosphotyrosine phosphatase domain, which is involved in <30% of the NS PTPN11 mutations. The study demonstrates that ML/LEOPARD syndrome and NS are allelic disorders. The detected mutations suggest that distinct molecular and pathogenetic mechanisms cause the peculiar cutaneous manifestations of the ML/LEOPARD-syndrome subtype of NS.

Correlation between PTPN11 gene mutations and congenital heart defects in Noonan and LEOPARD syndromes

Noonan syndrome (MIM 163950), an autosomal dominant disorder with an estimated prevalence of 1/1000–2500 at birth, is characterised by short stature, facial anomalies, pterygium colli, and congenital heart disease.1,2 Although pulmonary valve stenosis with dysplastic leaflets, hypertrophic cardiomyopathy, and atrial septal defects (ASD) are the most common congenital heart defects in Noonan syndrome,3 a broad spectrum of cardiac phenotypes has been recognised.2–6 About half the affected individuals have PTPN11 gene mutations.7–9 This gene, which maps to chromosome 12q22-qter,10 encodes for the human SH2 domain containing protein tyrosine phosphatase (SHP2).11 PTPN11 gene mutations have also been detected in multiple lentigines/LEOPARD syndrome (multiple lentigines, ECG conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth and sensorineural deafness; ML/LS, MIM 151100),12,13 in Noonan-like/multiple giant cell lesion syndrome (MIM 163955),8 in two families presumably affected by cardio-facio-cutaneous syndrome (CFCS, MIM 115150),14 but not in sporadic CFCS.15 The clinical and genetic heterogeneity of these disorders suggests a possible relation between different PTPN11 gene mutations and distinct clinical features. A genotype–phenotype correlation study in Noonan syndrome found an association between pulmonary stenosis and PTPN11 mutations.8 Our aim in this study was to screen a large cohort of patients with Noonan syndrome and ML/LS in order to expand the genotype–phenotype correlation analysis, with particular emphasis on cardiac diseases.nn### Key points

Spectrum of atrial septal defects associated with mutations of NKX2.5 and GATA4 transcription factors

Atrial septal defect (ASD) is a common cardiovascular malformation, affecting over 1 in 1000 live births, accounting for 10% of congenital heart defects (CHD).1 ASD refers to a communication between the right and left atria, anatomically classified into the deficient atrial septum structure. ASD ostium secundum (ASDos) is the prevalent defect, representing 85% of all ASDs.2 ASD may be isolated or associated with other CHDs, such as pulmonary valve stenosis (PVS), ventricular septal defect (VSD), or conduction defects. In addition, persistent left to right blood shunt may result in atrial and ventricular dysfunctions and atrial arrhythmias, in the absence of surgical or catheter based repair.nnThe atrial septum is one of the cardiac structures most sensitive to environmental or genetic factors. Several lines of evidence have highlighted a role for different proteins and transcription factors in the septogenesis process;3 however, only two genes, encoding for the transcription factors NKX2.5 and GATA4, have been implicated so far in non-syndromic ASDs.4,5 Clinical and molecular analyses have shown that mutations in these two genes are responsible for ASDs in association with distinct cardiac features.4–15 Mutations in NKX2.5 , a member of the NK-2 class of homeobox genes, have been described in autosomal dominant ASDos with progressive atrioventricular (AV) block, and in 1–4% of sporadic ASD patients.4,6–12 Most of these mutations occur within the homeodomain, a critical protein domain that interacts specifically with DNA, and are associated with conduction anomalies. Low penetrance NKX2.5 gene mutations, mainly outside the homeodomain, have been found in 5% of patients with tetralogy of Fallot, and in a number of individuals with other CHDs and normal conduction.4,6,9–13 Recently, heterozygous mutations in the GATA4 zinc finger transcription factor gene have been identified in three families with …

Clinical and molecular analysis of 30 patients with multiple lentigines LEOPARD syndrome

Multiple lentigines LEOPARD syndrome (MIM 151100) is an autosomal dominant multiple congenital anomaly syndrome, with high penetrance and markedly variable expression.1 The acronym LEOPARD was coined by Gorlin et al. in 1971 as a mnemonic of the major features of this disorder: multiple l entigines, E CG conduction abnormalities, o cular hypertelorism, p ulmonic stenosis, a bnormal genitalia, r etardation of growth, and sensorineural d eafness.2 It is also known as cardiocutaneous syndrome, Moynahan syndrome, lentiginosis profuse, and progressive cardiomyopathic lentiginosis.3,4 Voron et al. proposed some diagnostic criteria for multiple lentigines LEOPARD syndrome.5 More than 100 cases have been described, and one review has been published.5,6nnMultiple lentigines LEOPARD syndrome shares many features with Noonan syndrome (MIM 163950),7–9 in which lentigines and deafness usually are not present. About 40% of patients with Noonan syndrome have missense mutations in the PTPN11 gene, which encodes for the protein tyrosine phosphatase SHP2.10–14 Multiple lentigines LEOPARD syndrome has proved to be allelic to Noonan syndrome,15,16 with two recurrent PTPN11 mutations in exons 7 (Tyr279Cys) and 12 (Thr468Met). Recently, we reported a novel PTPN11 mutation (Gln506Pro) in a unique patient with multiple lentigines LEOPARD syndrome, which suggests that mutations other than Tyr279Cys and Thr468Met could be found in these patients.17 As PTPN11 mutations in multiple lentigines LEOPARD syndrome and Noonan syndrome are exclusive to these conditions, the distinctive manifestations of these disorders likely result from different molecular mechanisms. For instance, as commented in a recent report, the cardiac phenotypes in patients with Noonan syndrome and those with multiple lentigines LEOPARD syndrome with PTPN11 mutations are rather dissimilar, with pulmonary valve stenosis prevailing in the former and hypertrophic cardiomyopathy in the latter.18nnWe examined the PTPN11 gene in a consecutive series …

DiGeorge subtypes of nonsyndromic conotruncal defects: Evidence against a major role of TBX1 gene

The role of the 22q11 region genes, and among them TBX1, in nonsyndromic conotruncal defects (CTDs) is still unclear. Mice hemizygous at the Tbx1 locus show a remarkable incidence of heart outflow tract anomalies, of the same type commonly found in DiGeorge/Velo-cardio-facial syndrome (DGS/VCFS). Mutation analysis of the TBX1 gene in isolated, nonsyndromic CTDs has not demonstrated any functional pathogenetic variation so far. We screened the TBX1 gene in 41 patients affected by nonsyndromic CTDs of the DGS/VCFS subtype, principally ‘atypical’ tetralogy of Fallot. Besides a few polymorphisms, we did not find any pathogenetic variation. These results do not support a major role of the TBX1 gene as responsible for human nonsyndromic CTDs.

A novel PTPN11 gene mutation bridges Noonan syndrome, multiple lentigines/LEOPARD syndrome and Noonan-like/multiple giant cell lesion syndrome

Noonan (NS) and multiple lentigines/LEOPARD syndromes (LS) have proved to be associated with distinct PTPN11 mutations. Noonan-like/multiple giant cell lesion syndrome (NLS) is a rare disease, characterised by short stature, facial dysmorphisms, congenital heart defect (CHD) and central giant cell lesions. PTPN11 gene mutations have been reported in a single NLS family and two sporadic patients. Here we report a patient with a complex phenotype progressing throughout the years from NS at birth towards LS and NLS. PTPN11 gene analysis disclosed a novel missense mutation (Ala461Thr) in exon 12, affecting the consensus sequence of the SHP2-active site. This observation joins together NS and LS to NLS into a unique genetic defect, broadening the clinical and molecular spectrum of PTPN11-related disorders.

ZFPM2/FOG2 and HEY2 genes analysis in nonsyndromic tricuspid atresia.

Tricuspid atresia (TriAt), the third most common cyanotic congenital heart defect (CHD), consists of complete lack of tricuspid valve formation, with no connection between the right atrium and the right ventricle. To date, the genetic mechanism responsible of TriAt is still obscure. However, animal models have suggested a role of cardiogenic Zfpm2/Fog2 and Hey2 genes in the pathogenesis of TriAt. Therefore, we screened 40 individuals affected by nonsyndromic TriAt for ZFPM2/FOG2 and HEY2 gene mutations. No pathogenetic mutation has been identified, thus failing to demonstrate a major role of ZFPM2/FOG2 and HEY2 genes in the pathogenesis of human TriAt.

Erratum: Mutations of ZFPM2/FOG2 Gene in Sporadic Cases of Tetralogy of Fallot (Human Mutation (2003) 22 (372-377))

The original article to which this Erratum refers was published in Human Mutation 22:372–377 Human Mutation (2003) 22(5) 372–377